Obstetric Anesthesia This Page Intentionally Left Blank Obstetric Anesthesia

Obstetric Anesthesia This page intentionally left blank Obstetric Anesthesia

Craig M. Palmer, MD Professor of Anesthesiology University of Arizona Tucson, Arizona Robert D’Angelo, MD Professor, Obstetric and Gynecologic Anesthesia Wake Forest University School of Medicine Winston-Salem, North Carolina Michael J. Paech, FANZCA Winthrop Professor and Chair of Obstetric Anaesthesia School of Medicine and Pharmacology The University of Western Australia Perth, Australia

1 1

Oxford University Press, Inc., publishes works that further Oxford University's objective of excellence in research, scholarship, and education. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With ofﬁ ces in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Copyright © 2011 by Oxford University Press, Inc. Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 www.oup.com Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Palmer, Craig M., author. Obstetric anesthesia / Craig M. Palmer, Robert D'Angelo, Michael J. Paech p. ; cm. Includes bibliographical references and index. ISBN 978-0-19-973380-4 1. Anesthesia in obstetrics. 2. Analgesia. I. D'Angelo, Robert, author. II. Paech, Michael J., author. III. Title. [DNLM: 1. Anesthesia, Obstetrical. 2. Analgesia, Obstetrical. 3. Gynecologic Surgical Procedures—methods. WO 450] RG732.P36 2011 617.9'682—dc22 2010050965

This material is not intended to be, and should not be considered, a substitute for medical or other professional advice. Treatment for the conditions described in this material is highly dependent on the individual circumstances. And, while this material is designed to offer accurate information with respect to the subject matter covered and to be current as of the time it was written, research and knowledge about medical and health issues is constantly evolving and dose schedules for medications are being revised continually, with new side effects recognized and accounted for regularly. Readers must therefore always check the product information and clinical procedures with the most up-to-date published product information and data sheets provided by the manufacturers and the most recent codes of conduct and safety regulation. The publisher and the authors make no representations or warranties to readers, express or implied, as to the accuracy or completeness of this material. Without limiting the foregoing, the publisher and the authors make no representations or warranties as to the accuracy or efﬁ cacy of the drug dosages mentioned in the material. The authors and the publisher do not accept, and expressly disclaim, any responsibility for any liability, loss or risk that may be claimed or incurred as a consequence of the use and/or application of any of the contents of this material.

9 8 7 6 5 4 3 2 1 Printed in the United States of America on acid-free paper Contents

Preface vii Contributors ix Abbreviations xi 1. Neuroanatomy and Neurophysiology 1 2. Anatomic and Physiologic Changes of Pregnancy 19 3. Pain Relief for Labor and Delivery 31 4. Anesthesia for Cesarean Delivery 79 5. Post-Cesarean Analgesia 156 6. Anesthesia for Surgery During and After Pregnancy 182 7. Pregnancy Induced Hypertension and Preeclampsia 199 8. Obstetric Hemorrhage 213 9. Obesity 242 10. Coexisting Disease and Other Issues 265 11. Complications of Labor and Delivery 314 12. Fetal Assessment and Care 342 13. Management of Later Complications of Obstetric Anesthesia and Analgesia 361 14. Critical Care of the Obstetric Patient 392 15. Neonatal Resuscitation 402

Index 415 This page intentionally left blank lished the objectives, butinoneareafellfarbelowourvision.In2002wepub- thetists, bothintrainingandpractice,withthatpracticalreference. different. Ourgoalhasbeentoprovideanesthesiologistsandanes- to giveit,howmuchgive,andwhenstoptrysomething manage specific patientsinspecifi c situations. Whatdrugtogive,how outline aconcretecourseofclinicalmanagement,coveringhowto management—one thatcouldbeconsultedquickly(andoften)to some yearsagowesawaneedforpracticalguidetopatientcareand Obstetricanesthesiaisarapidlyexpanding,constantlyevolvingfi approaches. present each,withtheadvantages anddisadvantagesofalternative advocated it.Wherethereareequally viableoptions,we’vetriedto where ourexperiencehasshownoneapproachworksbest,we’ve provide additionalbackgroundandthebasisforfurtherstudy. although thereadingsandreferencesatendofeachchapterdo making. Thisisnotintendedtobeanexhaustivereferencetextbook, essential background,rationale,andsciencebehindclinicaldecision used bulletpointstohighlightkeyofmanagement,andthe and fl owcharts thatcanbequicklyaccessedandapplied.Wehave have triedtodistillessentialinformationintotables,charts,diagrams, diligently tomaketheinformationeasyuse—whenpossible,we last achievedwhatwesetouttodo10yearsago.Wehaveworked anesthesia cart. home onabookshelfthaninthepocketofscrubsuitoran it wasalarger,hardcovertext.Whilevisuallyappealing,moreat not. Ratherthanbeingapocket-sized,inexpensive,“readyreference,” style ofthe who hadtheirownvisionforthetext,andwhileinformation Ourfi rst attempttoprovidesuchareferencemetmanyofthese Ofcourse,thereisusuallymorethanonemeanstoanend,but WithournewpartnershipwithOxfordUniversityPress,wehaveat Preface Handbook ofObstetricAnesthesia Handbook werewhatweenvisioned,itsphysicalformwas withadifferentpublisher, eld;

vii viii PREFACE do it,andwhy. draws onourexperienceandstudytotellyouwhatwedo,how patients anddealwiththeseproblemseveryday. of obstetricpatients,ashaveourcontributors.Wecareforthese Allthreeofushavededicatedourcareerstotheanestheticcare MichaelJ.Paech,FANZCA RobertD’Angelo,MD CraigM.Palmer,MD Obstetric Anesthesia

Winston-Salem,NC WakeForestUniversitySchoolofMedicine AssociateProfessor,Obstetric&GynecologicAnesthesia JohnA.Thomas,MD Winston-Salem,NC WakeForestUniversitySchoolofMedicine Professor,Obstetric&GynecologicAnesthesia MedgeD.Owen,MD Winston-Salem,NC WakeForestUniversitySchoolofMedicine AssociateProfessor,Obstetric&GynecologicAnesthesia KennethE.Nelson,MD Winston-Salem,NC WakeForestUniversitySchoolofMedicine AssistantProfessor,Obstetric&GynecologicAnesthesia LauraS.Dean,MD Philadelphia,PA UniversityofPennsylvaniaSchoolMedicine AssistantProfessorofClinicalAnesthesiologyandCriticalCare EmilyBaird,MD,PhD Philadelphia,PA UniversityofPennsylvaniaSchoolMedicine ProfessorofClinicalObstetricsandGynecology ProfessorofClinicalAnesthesiologyandCriticalCare ValerieA.Arkoosh,MD,MPH Contributors

ix This page intentionally left blank CSF CSEA CS CPD CNS bpm BP ASA AMPA ACOG Ach IVH IVC IV IUGR IU IM ICP HOCM GA FRC FHR EGA ECV ECG EBP EA DIC

Abbreviations cerebrospinal ﬂ combined spinal-epiduralanesthesia cesarean section cephalopelvic disproportion central nervoussystem beats perminute blood pressure American SocietyofAnesthesiologists α -amino-3-hydroxy-5-4-isoxazolepropionicacid American CollegeofObstetriciansandGynecologists acetylcholine intraventricular hemorrhage inferior venacava intravenous intrauterine growthretardation international units intramuscular intracranial pressure hypertrophic obstructivecardiomyopathy general anesthesia functional residualcapacity fetal heartrate estimated gestationalage external cephalicversion electrocardiogram epidural bloodpatch epidural anesthesia disseminated intravascularcoagulation uid

xi xii ABBREVIATIONS WDR UPP UFH TPA SVR SVC SA RDS PVR PTL PPV ppm PIH PE PDPH PCIA PCEA NYHA NSAIDs NMDA MMR MLK mcg MAC LOR LMWH LMA LBW LA wide dynamicrange uterine perfusionpressure unfractionated heparin tissue plasminogenactivator systemic vascularresistance superior venacava spinal anesthesia respiratory distresssyndrome pulmonary vascularresistance preterm labor positive-pressure ventilation parts permillion pregnancy-induced hypertension pulmonary embolism post-dural punctureheadache patient-controlled intravenousanalgesia patient-controlled epiduralanesthesia New YorkHeartAssociation nonsteroidal anti-inﬂ N -methyl-D-asparate maternal mortalityratio myosin light-chainkinase microgram minimum alveolarconcentration loss ofresistance low molecularweightheparin laryngeal maskairway low birthweight local anesthetic ammatory drugs ammatory

and Bonica,clariﬁ ﬁ Theperipheralneuralpathwaysassociated withlaborsensationwere Peripheral Pathways Afferent NeuralPathways population. is centraltooptimizinguseofregionalanesthetictechniquesinthis understanding thebasicsofneuroanatomyandneurophysiology pregnancy isessentialtoprovidingcareduringtheperipartuminterval, been advancingrapidly.Justasunderstandingthephysiologyof at everylevel(particularlythecellularandmolecularlevel),has understanding ofthestructureandfunctionnervoussystem, sia techniques,primarilyneuraxialblockade.Inrecentdecades,our area withincurrentanestheticpractice,isrootedinregionalanesthe- Thepracticeofobstetricanesthesia,morethananyothersubspecialty • rst describedbyHead in1893;morerecentwork,notablybyCleland

Introduction Neuroanatomy onset ofcontractionsthroughcomplete cervicaldilation)travel Neuronscarryingsensationfromthe ﬁ rst stageoflabor(i.e.,the Neuropharmacology Neuroanatomy Introduction Craig M. Neurophysiology Palmer , MD Neuroanatomyand Chapter 1 edourunderstanding. 1 1 8

1 2 Neuroanatomy and Neurophysiology • Chestnut DH, and caudalanesthesia:anatomy,physiology, andtechnique,pp.181–201.In: the pudendalnerve.Reprintedwithpermission fromBrownDL.Spinal,epidural • lumbar sympatheticplexusandenterthe spinalcordbetweenlevelsT Sensation fromtheﬁ rst stageoflaboriscarried byneuronsthattravelwiththe Figure1.1 labor) entersthespinalcordbetweenS Sensation fromdistentionoftheperineum (largelyduringthesecondstageof

pudendal nerveandentersthespinalcordatS dilation throughdeliveryoftheinfant)travelsperipherallyvia Sensationfromthesecondstageoflabor(fromcompletecervical through thedorsalrootentryzone. root ganglion,andsendtheirprojectionsintothespinalcord Thecellbodiesoftheseprimaryafferentneuronslieinthedorsal levels. the T with thelumbarsympatheticsandenterspinalcordbetween 10 andL

S S Peripheral neural pathways associated with labor sensation. Peripheral neuralpathwaysassociatedwith laborsensation. 3 S 2 T T T 4 Obstetric Anesthesia 12 11 10 L 1 1 levels(Figure1.1). 1994, Elsevier. , PrinciplesandPractice. 1994,Elsevier. 2

throughS

4 , traveling peripherally via ,travelingperipherallyvia 2 throughS 10

toL 1 . 4 • • ing rapidly.Generally speaking,however,sensations traveling viathe station (thelevelofthefetalheadwithin thematernalpelvis)ischang- stage maybesignifi cant during thefi rst stageoflaborifthefetal gression ofawoman’slabor,sensation typicallyascribedtothesecond perineum duetodescentofthefetal head.Dependentonthepro- but itisoftensupersededbypain resultingfromdistentionofthe not stopmiraculouslywiththeentry intothesecondstageoflabor, mutually exclusive:painassociatedwiththefi rst stageoflabordoes on thebasisoftheirsizeanddegreemyelination(Table also morphologicallydistinct.Peripheralneuronscanbecharacterized second stagesoflabor,theperipheralneuronsthesepathwaysare Inadditiontotheanatomicseparationofpathwaysfi

push” andtoknowwhendeliveryisimminent. sensation givesrisetotheparturient’sabilitysense“theurge their perineumratherthaninabdomen.Thismorediscrete the sacralpathways.Parturientstendtofeelthissensationin of synapticconnectionsandthefasterconductionvelocityin neal distentionandismorelocalized,duemainlytolessbranching localized. Sensationofthesecondstageisprimarilyduetoperi- dilation; itiscrampingandvisceralinnature,diffusepoorly stage laborpainresultsfromuterinecontractionsandcervical second-stage neuralpathwayshaveclearclinicalcorrelates.First- Theanatomicandmorphologicdistinctionsbetweentheﬁ Itisimportanttorealizethatthesetwotypesofsensationarenot and havemorerapidconductionvelocities. larger indiameterandbettermyelinated,donotbranchaswidely, larger typeA Duringthesecondstageoflabor(distentionperineum), • quite slow. small ﬁ bers arepoorlymyelinated,andtheirconductionvelocityis TypeCfiberspredominateinthefirststageoflabor;these

sensation associatedwiththeﬁ diffuse branchingcontributestothepoorlylocalizednatureof also oneortwolevelsaboveandbelowthelevelofentry.This tic connections single secondaryneuron,butbranchwidelywithmultiplesynap- Theseprimaryafferentssynapsenotatonesinglepointorona

δ ﬁ bers dominate.Theseneurons aresigniﬁ cantly — not onlyatthelevelofentrytocord,but rststage.

1.1 ). rst- and rst and

3 Obstetric Anesthesia 4 Neuroanatomy and Neurophysiology

Table 1.1 Classifi cation of Peripheral Nerve Fibers Fiber Myelinated Fiber diameter Conduction Function Resistance to (microns) velocity (m/sec) local anesthetic blockade A-alpha Yes 12–20 70–120 Innervation of skeletal muscles + + + + Proprioception -beta Yes 5–12 30–70 Tactile sensory receptors (touch, pressure) + + + -gamma Yes 3–6 15–30 Skeleton muscle tone + + + -delta Yes 2–5 12–30 Stabbing pain + + Touch Temperature B Yes <3 3–15 Preganglionic autonomic fi bers + C No 0.3–1.3 0.5–2 Burning and aching pain + Touch Temperature Pruritus Adapted from: Voulgaropoulos, D. and Palmer, C.M. (1996) Local Anesthetic Pharmacology. In: Prys-Roberts C, Brown BR Jr. and Nunn JF (eds). International Practice of Anaesthesia . Butterworth-Heinemann, Oxford. • Watson C. Basic Human Neuroanatomy. 1995, Lippincott Williams & Wilkins. Watson C.BasicHuman Neuroanatomy.1995,LippincottWilliams &Wilkins. ventral laminaareassociatedprimarilywith motorneurons.Modifi way occursinthedorsalgraymatterofspinalcord. central nervoussystem;thefi afferent fi Laborsensationalsofollowswell-defi ned pathways Central Pathways advanced. sacral nerverootsdonotbecomesignificantuntillaboriswell to asthe sensation synapseinitiallybetweenlaminas IIthroughV.Laminaisalsoreferred lamina ofthegraymatter.Mostprimaryafferent neuronsassociatedwithlabor Figure1.2 • and V. V, butcurrentunderstandingofthesepathwaysfocusesonlaminaeII TheinitialsynapsemaybelocatedinanyofthelaminabetweenIand of cord) enlargements and lumbar (cervical of limbs Motor neurons

matter, commonlyreferredtoas Histologically,several(ten)distinctzonesarefoundinthegray • • and function. tions withineach,reﬂ ecting differences ininformationprocessing distinct becauseofvariationsinthecelltypeandneuronalconnec- superﬁ Mostoftheprimaryafferentneuronssynapseinitiallyinmore

sensory informationassociatedwithlabor(Figure LaminaeIthroughVaremostimportantindiscussionofafferent spinal cord. LaminaIisthemostsuperﬁ cial anddorsaloftheselaminainthe

bersenteringattheT substantia gelatinosa ciallamina(IandII).

Diagrammatic cross section of the spinal cord illustrating Rexed’s Diagrammatic crosssectionofthespinalcord illustratingRexed’s Proximal partoflimb Distal partoflimb Extensors Flexors

and neck(C Motor neuronsoftrunk (lamina II) Substantia gelatinosa , and is the primary synaptic site of most sensory , andistheprimarysynapticsiteofmostsensory 10 toL 1 rstsynapseintheafferentsensorypath- –S

4 ) 1 levels(i.e.,theﬁ Rexed’s lamina rst stage of labor). The rststageoflabor).The X . Thesezonesare after IX VIII 1.2 ). ed from edfrom

VI VII V IV entrytothe III IX II IX I

5 Obstetric Anesthesia 6 Neuroanatomy and Neurophysiology the widerangein they receivefromthesemultiplesynapses;theirnamederives TheWDRneuronsplayoneoftheinitialrolesinprocessinginput • • neurons. • spinothalamictract(Figure ventral whitematterofthecord,andthentravelcephaladvia Projectionsfromthedorsalgraymattercrosstocontralateral processing ofnociceptiveinformation (Figure pathways withinthecentralnervous systemplayanactiveroleinthe Inadditiontotheafferentpathways describedabove,descending Descending Pathways • ately enough,inthethalamus. • • • • the primarysensorycortex. sensation, second-orhigher-orderneuronsmustprojectcephaladto Inorderforprimaryafferentinputtoreachthelevelofconscious

modulate inputtohigherlevelsoftheCNS. Throughthisvariabilityinfi ring rate,thesespinalWDRneurons (Figure input, theyarecapableoffi ring actionpotentialsingreatbursts Withminimalinput,theirrateoffi ring isverylow;withgreater periaquaductal graymatter. and projectcaudallytothemidbrain, synapsingonneuronsinthe Thesedescendingpathwaysoriginate intheprimarysensorycortex, contraction. sensory cortex,andtheparturientbecomesawaresheishavinga Neuronslocatedinthethalamusprojectatlasttoprimary distances betweenafewlamina,orlevelswithinthegraymatter. but canalsobefromlocal“interneurons,”whichprojectshort Theseafferentprojectionsmaybefromprimaryneurons, numbers ofotherneuronsatthesameandnearbylevelscord. input. TheseWDRneuronsreceiveafferentprojectionsfromlarge neurons playanimportantroleintheinitialprocessingofafferent NeuronswithinlaminaVknownas“widedynamicrange”(orWDR) LaminaIIisalsoreferredtoasthe also onetotwolevelshigherandlower. secondary neuronsnotonlyatthelevelofentrytocord,but Primaryafferentneuronsbranchwidely,synapsingonmultiple T primary synapticsiteformostsensoryafferentfibers enteringatthe 10 toL 1.3 ). 1 levels.

rate ofdepolarizationcharacteristicthese

1.4

).Thenextsynapseoccurs,appropri- substantia gelatinosa

1.5 ).

,andisa

• • possible. A widevarietyofbothexcitatoryandinhibitorysynapticconnectionsare tract. Interneuronsprojectbetweenlaminaandlevelsofthegraymatter. to spinallevelsaboveandbelowtheirlevelofentrythecordviaLissauer’s carries adescendingpathway.Primaryafferentneuronsmaysendbranches from manyotherneuronsandprojectingcentrally.Thedorsolateralfuniculus deeper levelsofthegraymatter,receivingsynapticconnectionsandinput of thespinalcord.Widedynamicrange(WDR)neuronsarelocatedin Figure 1.3 To higherCNScenters

V (WDR)neuronsintheafferent(ascending) pathway. (implied bybehavioralcriteria),but alsoinhibitsoutputoflamina the rostralventralnucleinotonly produces analgesiainanimals that electricalstimulationoftheperiaquaductal graymatterand pathway Itisnotclearatpresentexactlywhat activatesthisdescending matter ofthespinalcord. cord viathedorsilateralfuniculustosynapsewithindorsalgray Neuronswithcellbodieslyinginthesenucleiprojecttothespinal nuclei. Theseneuronsinturnprojecttothemedulla,rostralventral Primary sensoryafferents in vivo,butitiseffective.Studiesanimals haveshown Diagrammatic crosssectionofthedorsalnerverootentryzone WDR

V IV III c Lissauer tract Substantia gelatinosa c Aδ II ( ) I Dorsolateral funiculus Dorsal root

ganglion root Dorsal

7 Obstetric Anesthesia 8 Neuroanatomy and Neurophysiology Medicine and Pain. Vol. 19, No. 1., 2000, Elsevier. Medicine andPain.Vol.19,No.1.,2000,Elsevier. Neuroanatomy andNeuropharmacology.In:SeminarsinAnesthesia,Perioperative projection totheprimarysensorycortex.Modiﬁ spinothalamic tracttothethalamus.Anothersynapseoccursinpathwaybefore whose cellbodieslieinthedorsalgraymatterofspinalcordprojectvia Figure1.4 rics for decades, and will likely continue in this role for decades to come. rics fordecades,and willlikelycontinueinthisrolefordecades tocome. Localanestheticshavebeenthemainstay ofregionalanesthesiainobstet- Local Anesthetics Neuraxial Medications Neuropharmacology

Low-medulla Mid-medulla Mid-pons Midbrain capsule internal limb of Posterior gyrus postcentral cortex Cerebral Cephalad extension of labor sensory pathways. Secondary neurons Cephalad extensionoflaborsensorypathways.Secondaryneurons C T 7 12 tract Spinothalamic ed from Palmer C. Spinal edfromPalmerC.Spinal

of thalamus VPL nucleus afferents sensory labor Primary receptors pressure touch and Light

• positive chargeandallowthemolecule tobecomepolar(Figure • the aminegroupmayreversiblybind afreeproton(H Thearomaticringandhydrocarbon chainarenonpolar,but Alllocalanestheticssharecertainstructuralcharacteristics. Structural Characteristics Perioperative Medicine and Pain. Vol. 19, No. 1., 2000, Elsevier. Perioperative MedicineandPain.Vol.19,No.1.,2000,Elsevier. Spinal NeuroanatomyandNeuropharmacology.In:SeminarsinAnesthesia, in thegraymatterofdorsallumbarspinalcord.Modiﬁ midbrain. Anothersynapseoccursinthemedullabeforepathwayterminates sensory cortexprojectcaudally,synapsingintheperiaqueductalgraymatterof Figure1.5

can bedescribedin termsofpK Theprotonationoflocalanesthetics isaphysicalcharacteristicthat amine group(-NH of varyinglengthandcomposition in themiddle;andallhavean Allhaveanaromaticringatoneend;allahydrocarbonchain Ascending sensory pathway (spinothalamic tract) Mid-medulla Midbrain Cerebrum

Lumbar Descending inhibitory pathway. Neurons with cell bodies in the Descending inhibitorypathway.Neuronswithcellbodiesinthe spinal cord nuclei Raphe 2 )attheotherend. a ; when local anesthetics are placed in ;whenlocalanesthetics areplacedin

matter Periaqueductal gray ed from Palmer C. edfromPalmerC.

ventral medulla Nuclei inrostral neurons Dorsal horn cortex Somatic sensory Hypothalamus + )toacquirea

1.6 ).

9 Obstetric Anesthesia 10 Neuroanatomy and Neurophysiology The intermediatelinkagemaybeeitheranester(-COO)oramide(-NH). intermediate hydrocarbonchainlinkage,andanaminegroupattheotherend. anesthetics. Alllocalanestheticshaveanaromaticringatoneend, Figure 1.6 • uncharged (nonpolar)formsarepresent atequalconcentrations. aqueous solution,thepK •

DecreasingthepH(increasing freeH necessary forthe clinical effectsoflocalanesthetics. Boththechargedanduncharged forms ofthemoleculeare will havetheoppositeeffect. state; increasingthepH(decreasing thefreeH increase theproportionofmolecules inthechargedorpolar Esters Amides Representative chemicalstructuresofcommonlyusedlocal Chloroprocaine Bupivacaine Lidocaine Ropivacaine H 2 N CH CH CH a CH CH CH is the pH at which the charged (polar) and isthepHatwhichcharged(polar)and NHCO Cl 3 NHCO 3 3 HOCH NHCO 3 3 3 COOCH

H 2 CH C 2 C N N 4 3 H H 2 N 9 7 +

C C concentration)will N 2 2 H H + 5 5 C CH concentration) 2 H

2 H 5 5

• • least twononpolarbarriers(Figure The sodiumchanneloftheneuronalcellmembrane Site ofAction more poorlymyelinated theneuron,moresusceptible itistolocal Ithaslongbeenmaintainedthatthe smallerthediameterand Clinical Use • • • • four repeating“domains.” neuron. Thesodiumchannelisalargetransmembraneproteinwith altering theionpermeabilityanddecreasingexcitabilityof reversibly bindtosodiumchannelsintheneuronalcellmembrane,

to speedtheiraction. basis fortheadditionofbicarbonate toepidurallocalanesthetics speeds theclinicalonsetofblock.Thisisphysiochemical the pHshiftsequilibriumtofavorunchargedstate,and of themolecule,slowingpenetrationtositeaction.Raising pH of7.4;invivo,equilibriumfavorstheprotonated,chargedform pK more readilyintheirnonpolar,unchargedform.However,the Localanestheticsdiffuseacrossthesenonpolarmembranesmuch progress beenmadeintheareaofreceptorpharmacology. was ﬁ Theideathatcellmembranereceptorscanmediatedrugeffects Toreachitssiteofaction,thelocalanestheticmustdiffuseacrossat Theoverlyingepineurium Thelipid-bilayeroftheneuronalmembrane that isabletobindthechannel. Itisthepolar,protonatedformoflocalanestheticmolecule channel initsrestingstateandpreventtheconformationalchange. Localanestheticsreversiblybindtotheintracellularsurfaceofsodium and allowsthepassageofsodiumions. channel undergoesaconformationalchangethatopensthepore Inresponsetodepolarizationoftheneuronalmembrane, the restingstate,poreisclosedandchannelinactive. Invivo a sofalltheclinicallyusedlocalanestheticsareabovephysiologic rstpostulatedinthe1800s,butonlyrecentlyhassubstantial , thechannelformsadonut-shapedringwithcentralpore.In

1.7 ):

Local anesthetics

11 Obstetric Anesthesia 12 Neuroanatomy and Neurophysiology • • anesthetics. susceptible toeffectiveblockatverylowconcentrationsoflocal clear clinicallyisthatnerveﬁ bers transmittinglaborsensationare into questionthistraditionalunderstanding.Whatisstillquite anesthetic block.Somerecent 1994, Elsevier. Obstetric Anesthesia,PrinciplesandPractice(ed.ChestnutDH)p.202-228, Modiﬁ ed fromSantosAC,PedersonH,andFinsterM.Localanesthetics.In: membrane. “B”representsthelocalanestheticmolecule(i.e.,bupivacaine). action atthesodiumchannelonintracellularsurfaceofneuronalcell Figure 1.7 • Axoplasm

Interstitium Epineurium Thefi bers innervatingtheperineum,mainlytypeA effect. drug distributionandbinding ent propertiesoftheneuron,orresultotherfactorsaffecting local anesthetics.Whetherthissusceptibilityistheresultofinher- fibers, arereadilyblockedwithverylowconcentrationsof Thefibers transmittingfi the pelvicfl to notonlythelowerextremities, but alsotothemusculatureof anesthetics, whichshouldhaveminimal effectonlargemotorfi Bothtypescanbereadilyblocked withconcentrationsoflocal blockade andpainrelief. ally requireahigherlocalanesthetic concentrationforeffective

Local anestheticdiffusionfromepiduralspacetositeof oor.

B +H B +H B +H rst-stage sensation,felttobemainlytypeC

BB + + + in vivo,islessimportantthanclinical in vitroinvestigationshavecalled BH BH BH H + + + + δ ﬁ Na bers, gener- bers, membrane Neuronal cell + channel bers the neuralpathwaysdescribedabove. appear toexerttheireffectsthroughspeciﬁ c receptorpopulationsin Otheradjunctsthatcanbeusedforneuraxialregionalanesthesia Other Adjuncts • • • •

via largerA sation of“pressure”associatedwithcontractionsiscarriedmainly (pain) withoutcompletelyeliminatingawarenessoflabor;thesen- “differential blockade”explainstheabilitytoeliminatenociception and rotationofthefetalheadasittraversespelvicoutlet.This important roleintheprogressoflaborbyguidingdescent Maintainingmusculartoneofthepelvicmusclesmayplayan neurons intheprimaryafferentpathway. jecting interneuronstoactonsecond- orhigher-order(WDR) indicates thatacetylcholineismost likely releasedbylocallypro- stitial fl uid, atthesametimeas itproducesanalgesia.Evidence cord increasesthelevelofacetylcholine (Ach)inspinalcordinter- Applicationorreleaseofnorepinephrine atthislevelofthespinal Ourcurrentunderstandingofneurotransmissionindicates: amino acidneurotransmitter,probably neurons andsecond-orderappearstobeanexcitatory Theprimaryneurotransmitterbetweenfi rst-order typeCafferent the graymatterofdorsalhornspinalcord. inhibitory pathway.Muscarinic(cholinergic)receptorsarefoundin Acetylcholine it appearstofunctiononlyaugmentthepostsynapticresponse. synaptically bytheseneuronsasafacilitativeneurotransmitter,but acting primarilyonneurokininreceptors.Itmayalsobereleased SubstancePappearstobeanotherrelevantneurotransmitter, terminating inthedorsalgreymatterofspinalcord(Figure1.8). tors. Norepinephrineisreleasedbydescendinginhibitorypathways Asecondmajorneurotransmitterappearstobe acid, orAMPA)receptorsonthepostsynapticmembrane. catecholamine (monoamine)withanaffinity for primarily at non-NMDA ( β fi bers, whicharerelativelyresistanttoblockade. isalsoimportant,apparentlyinthedescending α -amino-3-hydroxy-5-4-isoxazolepropionic -amino-3-hydroxy-5-4-isoxazolepropionic glutamate

α norepinephrine -2adrenergicrecep- . Glutamate acts . Glutamateacts

, a , a

13 Obstetric Anesthesia 14 Neuroanatomy and Neurophysiology fi labor occursinthesubstantiagelatinosa (laminaII),particularlyforthe Theinitialsynapseofmanythe primary afferentsassociatedwith the humancentralnervoussystem:mu,kappa,anddelta. receptor populations.Thereareatleast3typesofopioidreceptorsin Likelocalanesthetics,opioidsalsoexerttheirinfl uence viaspecifi c Site ofAction Almostallneuraxiallyadministeredopioidsareanalgesic. Opioids Figure1.8 pp. 10–17, Copyright (2000), with permission from Elsevier. pp. 10–17,Copyright(2000),withpermissionfromElsevier. Neuroanatomy andNeuropharmacology:AnObstetricAnesthesiaPerspective, Anesthesia, PerioperativeMedicineandPain,Vol.19Issueno.1 afferent neuronsincludeglutamateandsubstanceP. cephalad viathespinothalamictract.Neurotransmittersreleasedbyprimary inhibitory, atsynapseswithneuronsoftheafferentsensorypathwayprojecting neurons inthegraymatter.Theseturnreleaseacetylcholine,whichis release norepinephrine,whichisexcitatoryandactsprimarilyonlocallyprojecting rststageoflabor. periaquaductal graymatterofthemidbrain. stantia gelatinosa(laminaII)of thespinalcordand tion. Highconcentrationsofmureceptorswerefoundinthesub- the centralnervoussystemhadrevealedopioidreceptordistribu- and characterized. In1975,enkephalins,aformofendogenousopioid,wereisolated

Neurotransmitters in the dorsal horn. Descending inhibitory pathways Neurotransmitters inthedorsalhorn.Descendinginhibitorypathways

Bythelate1970s,autoradiographicmappingof V IV (norepinephrine) Descending fibers transmission cell Spinothalamic III To spinothalamic II I gelatinosa Substantia Reprinted from tract

(glutamate, substanceP) Aδ andCfibers,pain

, Palmer C, , PalmerC,

Seminars in Seminars in activation decreasesexcitabilityofthepostsynapticmembrane. neurotransmitters bytheprimaryafferent.Postsynaptically,receptor Presynaptically,opioidagonistsresultindecreasedreleaseof • • • Copyright (2000),with permissionfromElsevier. Neuropharmacology: AnObstetricAnesthesia Perspective,pp.10–17, Medicine andPain,Vol.19Issueno.1, PalmerC,Neuroanatomyand Type A-deltaﬁ on TypeCﬁ bers andonpostsynapticmembranes, butnotonpresynaptic (the smallsquaresintheneuralcellmembranes) arelocatedpresynaptically Figure 1.9

lack ofpresynapticinhibitionontheA Though notcompletelyineffectiveduringthesecondstage, during thefi rst stageoflabor,whereCfi ber inputpredominates. Spinalorepiduralopioidsaremuchmoreeffectiveanalgesics in themidbrainsubstantiallyinhibitsspinalnociceptiverefl cussed above.Inanimals,injectionofanopioidsuchasmorphine tant synapticjunctionofthedescendinginhibitorypathwaydis- has averyhighconcentrationofopiatereceptors,andisanimpor- stantia gelatinosa,theperiacquaductalgraymatterofmidbrain second stage,signifi cantly reducesopioideffi cacy. Likethesub- terminals. About75 synaptic second-orderneurons. Toalesserextent,theyarealsofoundonthesurfaceofpost- not A OpioidreceptorsareconcentratedontheterminalsoftypeC,but δ C-fiber terminal neurons(Figure Primary synapsesintheafferentpathway. Opioidreceptors % bers. ofopioidreceptorsareonthepresynapticCfi ber Reprinted from C A 1.9 ) . Seminars inAnesthesia,Perioperative

δ ﬁ bers, whichdominatethe A-fiber terminal exes.

15 Obstetric Anesthesia 16 Neuroanatomy and Neurophysiology • • differences induration,speedofonset,andpotency. Specifi spinal possibly moreplausibleexplanation isepinephrine’sabilitytoactivate ulations inthesuperfi cial laminaofthe spinalcord,analternativeand ties ofvirtuallyallopioidsprovidesignifi Wheninjectedintheepiduralorintrathecalspace,verysmallquanti- Clinical Use • • • • α anesthetic. Withthecharacterization of strictor, slowingtheuptake(andthereforemetabolism)oflocal this prolongationhasbeenepinephrine’sactionasalocalvasocon- prolong thedurationofblock.Thereasonusuallyadvancedfor surgical anesthesia,viaboththeepiduralandintrathecalroutes,to and fordecadesepinephrinehasbeenusedwithlocalanesthetics Theanalgesiceffectsofspinalepinephrinehavelongbeenknown, Fentanyl Meperidine Sufentanil Morphine Opioid Table 1.2

-2 AdrenergicAgonists:Epinephrine inversely proportionaltowatersolubility. Speedofonsetisusuallyproportionaltolipidsolubility,and tion ofaction. solubility; highlylipid-solubleopioidstendtohaveashorterdura- Durationofanopioidisusuallyinverselyproportionaltolipid lamina IIofthedorsalgraymatter, substantiagelatinosa. Thedescendinginhibitorypathway describedaboveterminatesin increases theincidenceofsideeffects. Exceedingthenecessarydoserequiredforanalgesiausuallyonly low doses. with localanesthetics,andsigniﬁ cantly augmentanalgesiaatvery Whileopioidscanbeinjectedalone,theyareusuallycombined result fromanincreaseinK Botheffectsaremediatedbymembrane-boundGprotein,and c clinicalapplicationofindividualopioidsisgenerally drivenby α -2 adrenergicreceptorsonafferent neurons. Comparative PropertiesofNeuraxialOpioids

High eyHg eyfs Very short Very fast Moderate Very High Low ii ouiiy Sedo ne Duration Speed ofOnset Lipid Solubility

+ permeability. Fast Intermediate Slow cantanalgesia. α

-2 adrenergicreceptorpop-

Short Intermediate Long

• • Other • • • an unacceptablesideeffectproﬁ clonidine,itseffectivenessasananalgesic hasbeenovershadowedby tory pathway,preventingthebreakdown ofacetylcholine.Like Presumably, neostigmineexertsitseffect withinthedescendinginhibi- cally investigatedasaneuraxiallabor analgesicinhumanstodate. Neostigmineistheonlyanticholinesterase thathasbeensystemati- Anticholinergics: Neostigmine ments the resulting block, not only in terms of duration but also intensity. ments theresultingblock,notonlyintermsofdurationbutalsointensity. Epinephrineaddedtobothintrathecalandepidurallocalanestheticsaug- Clinical Use • • • • investigated andusedasalaboranalgesicinhumans. Amongother

routine clinicaluseinobstetrics. widespread clinicalutilization.Itisnotcurrentlyrecommendedfor labor analgesiaisapparent,thesesideeffectshavesofarprevented Whiletheeffectivenessofintrathecalandepiduralclonidinefor pressure, decreasedheartrate,andsedation. It causesmajordose-relatedsideeffects,notablydecreasedblood acting localanesthetics. Theeffectofepinephrineismostapparentwhenusedwithshort- greater mechanismofactionviavasoconstriction. greater (thoughstillusually5mcg/mlorless),whichmayindicate Whenusedwithepidurallocalanesthetics,epinephrinedoseis augment someintrathecallocalanesthetics. Verysmalldoses( in theWDRneuronsoflaminaV. TheresultisselectiveinhibitionofCandA- postsynaptic effect. inhibitory effectoccurswithinthesubstantiagelatinosa,indicatinga cells, whichsuggeststhepresynapticaction,most Likeepinephrine,neuraxialclonidineresultsinsigniﬁ Whilesigniﬁ transmission intheprimaryafferentpathway. Norepinephrinereleasefromthedescendingneuronsinhibits neurons, respectively. and postsynapticallyonprimaryafferentneuronssecondary Receptorsfornorepinephrinearelocatedbothpresynaptically α -2 AdrenergicAgonists:Clonidine cant α -2 adrenergics,onlyclonidinehasbeensystematically α + -2agonistbindingoccursondorsalroot

/– 10mcg)ofepinephrinehavebeenshownto

le:

ﬁ ber evokedactivity

cant analgesia. cant profound ganglion

17 Obstetric Anesthesia 18 Neuroanatomy and Neurophysiology 13. 12. 11. 10.

Further Reading to havefewersideeffectsandbesafeforuseinhumans. Itisnotclearwhetherotheranticholinesteraseswilleventuallyprove •

9. 8. 7. 6. 5. 4. 3. 2. 1.

unacceptable. local anesthetics,theincidenceofnauseaandvomitinghasproven Evenwhenusedinverylowdosescombinationwithopioidsand

lidocaine . increases theintensityofsensoryblockduring epiduralanesthesiawith Sukara S Anesthesia. , Philadelphia Sumi : Elsevier M ; , Strichartz 2005 : GR 573 Morimoto , - 603 N Stamford . , Berde JA Manage CB Saito . . Y 1990 Descending controlofpain . ; . Local anesthetics 5 . In . : Sabbe The additionofepinephrine 191 - Miller MB 203 , . RD Yaksh , ed. TL . Pharmacology ofspinalopioids . MA : Sinauer Associates ; 1997 . Purves D , Anesth PainMed analgesia inlabor:theadditionofclonidinetobupivacaine-fentanyl . Paech MJ , 2001 ; 94 Pavy : TJG , Lui SS Orlikowski , 1997 CEP ; , 87 McDonald etal : . dorsal horninsheep.Anvivomicrodialysisstudy. 110 SB Patient-controlled epidural - 116 . . Current issuesinspinalanesthesia stimulate acetylcholineandnorepinephrinereleasefromthespinalcord . Klimscha ActaAnaesthiolScand . 1989 ; and cholinergicmechanismsinvolvedinspinalnociceptiveprocessing 33 . : 39 - 47 . Gordh T Ther Jr . , 1993 ; 2 adrenoreceptormediatedantinociceptioninsheep 265 Jansson . : 536 I - , 542 . Hartvig P , Detweiler dorsal hornofthespinalcord . epinephrine suppressesnoxiouslyevokedactivityofWDRneuronsinthe Collins JG , 57 ; 51 Kitahata - 62 LM . , Matsumoto M , Cleland , JGP 1998 : 915 - Anesthesia andManagementofPain 941 . . Philadelphia : options Lippincott-Raven . In: ; Cousins MJ Carr , DB , Bridenbaugh PO Cousins MJ , eds. . Spinal routeofanalgesia:opioidsandfuture 888 - 906 . W Reg AnesthPainMed . 1999 ; 24 : 541 - 546 .

Augustine GJ , DJ . Paravertebral anesthesiainobstetrics . , Tong C , Eisenach JC . Intrathecal α2-adrenergicagonists , Eisenach . 2000 ; 25 : 34 - 40

JC Fitzpatrick D , , Tong . Anesthesiology . 1984 ; 60 : 269 - 275 .

et al . Interactions betweennoradrenergic C , etal et al. eds. et al . Spinally administered . A cholinergicinteractioninalpha Br JAnaesth. 1995 ; 75 : 217 - 227 . Neural BlockadeinClinical Neuroscience . Sunderland, 1933; SurgGynecolObstet.1933; Anesthesiology . J PainSymptom J PharmacolExp Anesthesiology .

Miller’s Reg

• Hemodynamics pregnancy inwomenofchildbearing ageimperative. adaptations occurduringtheﬁ rst trimester,makingrecognitionof puerperium, aswellduringnon-obstetricsurgery.Manyphysiologic this alteredphysiologyinordertocareforpatientsthroughoutthe Anesthesia providersmustrecognizetheanestheticimplicationsof prepare theparturientfordemandsoflaboranddelivery. Unique alterationsallowforthedevelopmentofagrowingfetus,and Profoundphysiologicandmechanicalchangesoccurduringpregnancy.

Introduction Cardiovascular pregnancy (Table Cardiovascularparameters arealteredprogressively throughout Uterus Neurologic Hematologic Thyroid Glucose Metabolism Hepatic andGallbladder Renal Gastrointestinal Pulmonary Cardiovascular Introduction Robert D Laura ’Angelo S. , MD Changes ofPregnancy Dean , MD AnatomicandPhysiologic Chapter 2 25 28 27 23 28 2.1 ). 19 27 19 25 27 26

19 20 Anatomic and Physiologic Changes • • • • • • • vrl nraeDrn rgac 1.5–2 liters/min Overall IncreaseDuringPregnancy Breasts Renal Skin Uterus Organ Table 2.2 † ∗ Cardiac Output Parameter Table 2.1 vascular resistancedespitetheincreaseincardiacoutput. throughout labor.

StrokeVolume Plasma Volume Heart Rate Oxygen Consumption Systemic VascularResistance Mean ArterialPressure

Cardiacoxygenconsumptionincreasesinparallelwithcardiacoutput ∗ contractility isprobablyunchanged. accommodate theelevatedcardiacoutput.Despiteremodeling, Increasedleftventricularwallthicknessandcavity of thegrowingfetusandalteredmaternalphysiology(Table Theincreasedcardiacoutputisredistributedtomeetthedemands volume andheartrate. Cardiacoutputincreases,withcontributionsfrombothstroke aldosterone toelevatebloodvolume. Volumerestoringmechanismscausereleaseofangiotensinand preload, triggeringareﬂex increaseinheartrate. Thisdecreaseinsystemictoneresultsreducedafterloadand circulatingestrogenandprogesterone. Systemicvascularresistancedecreasesasaresultofincreased worsens beyond20weeksgestation. changes intheparturient’sposition,asaortocavalcompression 16–24 weeks,thesealterationsbecomefurtherdependenton Beginningasearly4–8weeksgestationandplateauingbetween Meanarterialbloodpressure willfallasaresultofdecreaseinsystemic

Redistribution ofBloodFlowDuringPregnancy Cardiovascular AdaptationsatTermGestation †

∗

200 ml/min 400 ml/min 300–400 ml/min 800 ml/min Increase inBlood Flow Change ↑ 50 ↑ 20 ↓ 20 ↑ 30 ↑ 10–50 ↑ 20 ↓ 30 % % –50 % % % %

% % 2.2 ). • • • • decreased venousreturninthesupineposition. from hemorrhageatdelivery,andthedeleteriouseffectsof relative hypervolemiaiscrucialforprotectingthemotherandfetus metabolic demandsoftheenlarginguterusandgrowingfetus.This A40 Blood Volume ﬁ general, hemodynamicsreturntoprepregnancybaselineduringthe should beatimeofvigilanceinpatientswithcardiacvalvularlesions.In pregnancy valuesuntilamonthorsoafterdelivery(Table labor, peaksimmediatelyafterdelivery,anddoesnotreturntopre- causing asurgeinstrokevolume.Cardiacoutputincreasesduring fused intothesystemiccirculationfromintervillouscirculation, ated. Duringuterinecontractions,300–500mlofbloodisautotrans- Atthetimeofdelivery,hemodynamicalterationsarefurtherexagger- • rst6monthspostpartum. • • isoelectric Twavesand STchangesontheelectrocardiogram. the alterationincardiacoutput.Apericardial effusion(9 ∗ Table 2.3 • •

• •

Flowmurmurscorrelatewiththeincreaseinbloodvolumerather than

In contrast,responsetonorepinephrineinfusionsisunchanged. diminish thepressorresponsetoangiotensinduringpregnancy. Asearlyastheﬁ rst trimester,increasedreninandangiotensin the increaseintotalbodywater. tion ofaldosterone.Theresultantretentionsodiumallowsfor increase inhepaticreninproduction,whichtriggersenhancedsecre- Estrogenandprogesteronearealsothoughttodirectlymediatean response toﬁ venous capacitance.Theincreaseinbloodvolumemaybea Progesteronerelaxesvenoussmoothmuscle,thusincreasing multifactorial. Themechanismsaccountingfortheincreaseinbloodvolumeare that occurduringpregnancy(Table Itiscrucialtorecognizethenormalchangesincardiacexam Accentuated andSplitS Occasional S 20 80 90 Normal S % % haveS % haveDiastolicFlowMurmur % haveSystolicEjectionMurmur –50 % 2 Cardiac ExamDuringPregnancy

increaseinbloodvolumeduringpregnancymeetsthe 3 HeartSound 4

llthisincreasedvascularcapacity. 1

2.3 ).

∗

% ) maycause 2.4 ).This

21 Obstetric Anesthesia 22 Anatomic and Physiologic Changes occurs inupto15 Asymptomaticreductionincardiacoutputthesupineposition Aortocaval Compression that isvitalforthe obstetricpatientmaynotbeadequate torelieve Itisimportantto recognizethatthestandard15-degree lateraltilt • sion canoccurbeforethistime. described beyond20weeksgestation,partialorcompletecompres- hypotensive syndrome • adequate venousreturnareparamount. these hemodynamiceffects.Alleviatingthecompressionandrestoring resist separation.Neuraxialorgeneralanesthesiawillexaggerate pressed inferiorvenacavamayactliketwopiecesofwetglassthat caval compressionissuspectedinahypotensivepatient,thecom- aortic compressionfurthercompromisesuterinebloodﬂow. Ifaorto- venous returnandcanresultinprofoundhypotension.Abdominal Compressionoftheinferiorvenacavabyenlargeduterusreduces • • • • • • • • Term Prepregnancy CO Stage Puerperium Table 2.4 Stage 1Labor Stage 2Labor Immediately FollowingDelivery 1 HourAfterDelivery 2 DaysAfterDelivery 2 WeeksAfterDelivery

Manifestationsofsupinehypotensivesyndromeinclude: Treatmentconsistsof: Shortnessofbreath Ensuringleftuterinedisplacement Fetaldistress Tachycardia Maternalhypotension Nausea Dizziness Elevationofthelegs(notTrendelenburg positioning) Vasopressoradministration Fluidadministration

Percent ChangeinCardiacOutputDuring

% ofparturients,andisreferredtoasthe

.Althoughsupinehypotensionisclassically

Change fromBaseline ↑ 50 Baseline ↑ 75 ↑ 110 ↑ 160 ↑ 90 ↑ 45 ↑ 10 % % % % % % %

supine during pregnancy,assummarizedinTable Numerousphysiologicandmechanicalpulmonaryadaptationsoccur maternal hypotensionorfetalheartratedecelerations. tion, oreventhekneechestposition,maybenecessarytoalleviate aortocaval compressioninallparturients.Thelateraldecubitusposi- • during generalanesthesiaandattemptedtrachealintubation)include: the airwayandchestwallwithanestheticimplications(especially Tidal Volume O Basal MetabolicRate Total LungCapacity Minute Ventilation

Vital Capacity in thesupineposition. airway closureduringtidalbreathinginasmany50 consumption sotheAVO progesterone-mediated hypersensitivityofrespiratorycenterstoCO FEV1 andFEV1/FVC Respiratory Rate Parameter Gestation Table 2.5 ‡ † ∗ ∗ ∗ Expiratory ReserveVolume diameter. change invitalcapacitybecauseofthesimultaneous increaseinchestwall Diaphragm Excursion Residual Volume Functional ResidualCapacity uterus furtherincreasesO As cardiacoutputplateausandthemetabolism ofthefetusandgrowing pre-pregnancy levels.

Pulmonary Therearenodocumented changesinairwayﬂ ow ordiffusioncapacity. Theincreaseincardiacoutputisgreater thantheincreaseinoxygen ∗ ∗ Earlyintheﬁ rst trimester,hyperventilation isstimulatedbya and larynx Venousengorgementandedemaoftheoropharynx,nasopharynx ∗ ThedecreaseinFRCresultsfromreducedERVandRVmayresult 2 Despiteelevationofthediaphragmbyenlarginguterusthereis no Consumption Pulmonary PhysiologicChangesatTerm

2 2 differenceinearlypregnancyisdecreased. consumptiontheAVO ↑ 40 Very minimaltonochange ↑ 14 ↑ 40 ↑ 40 No change Change DuringPregnancy No change Increased ↑ 10 ↓ 20 ↓ 20 ↓ 12 % % % % –50 % % % % –25 ∗ †

2.5 2 % % ∗ ‡ differenceapproaches .Anatomicchangesin

∗ ∗ ∗ % oftermparturients ∗

2 .

23 Obstetric Anesthesia 24 Anatomic and Physiologic Changes • Acid–Base PhysiologyinPregnancy • • • • • • • • • • pH PaO Supine PaO PaCO Parameter Table 2.6 HCO

• • RenalcompensationdecreasesplasmaHCO Hyperventilationinducesaslightrespiratoryalkalosis. DecreaseinPaCO Vocalcordedemaresultinginhoarseness are listedinTable Arterialbloodgasvaluesseeninnonpregnantandpregnantpatients Redundantsofttissueinthemouth,neckandchest Enlargedbreasttissue and transversediameters Increasedchestcircumference5–7cminbothanteriorposterior arterial toendtidalCO along withafallinalveolardeadspace,contributetonegligible Theincreaseinminuteventilation,cardiacoutputandbloodvolume, fetus. P50isincreasedfrom26.7to30.4,aidingoxygendeliverythe nant levelsandshiftsthecurvebacktoright. Althoughrespiratoryalkalosisshiftstheoxyhemoglobin normal pH. curve totheleft,2,3-DPGproductionrises30

the left,decreasingreleaseofO Alkalosis willalsoshifthemoglobinoxygendissociationcurveto uterine vasoconstrictionanddecreasedplacentalbloodﬂ ow. Hyperventilationshouldbeavoided,ashypocarbiacanleadto (see alsoChapter4). parturient undergoinggeneralanesthesiaforcesareandelivery Thesepulmonarychangeshaveimportantimplicationsforthe 2

3 2

Arterial BloodGasResultsinNormalPregnancy

2 2.6 . leadstoslightlyincreasedPaO

62 e/ 24 meq/l 16–21 meq/l 7.405–7.44 Pregnant 63 mg 40 mmHg 26–32 mmHg 216mH 100 mmHg 92–106 mmHg 101→94 mmHg

2 differenceatterm.

2 tofetus.

Nonpregnant 7.40 100 mmHg 3 allowingforanear % 2

in early pregnancy. inearlypregnancy. abovenonpreg-

dissociation

• • • • • during pregnancy,labor,anddelivery. Anumberofphysiologicchangesimpactthegastrointestinalsystem kidneys. Thepelvis,calycesandureters aredilatedbythesmooth Increasedvascularandinterstitialvolumes resultinslightlyenlarged

Gastrointestinal Renal pneumonitis should be strongly considered (see Chapter 4). pneumonitis shouldbestronglyconsidered(seeChapter4). more likelytooccur.Aspirationprophylaxisreducethechanceof intubation ishigherthannormalatatimewhenaspirationalso eral anesthesia:thelikelihoodofdifﬁ cult maskventilationandfailed Theobstetricpatientposesuniquechallengesfortheconductofgen- • • Gastricacidsecretionisprobablynotalteredinpregnancy. the routeofadministration. during labor.Opioidanalgesicsfurtherdelayemptying,regardlessof Gastricemptyingisnotalteredduringgestationbutlikelyslowed geal reﬂ parturients experiencepyrosis,orheartburn,duetogastroesopha- esophagus intothethoraxinmanywomen.Consequently, Thegraviduterusincreasesgastricpressureandelevatesthelower ing smoothmuscle. Progesteronediminishesloweresophagealsphinctertonebyrelax- gravid uterus. Thestomachisdisplacedandrotatedcephaladbytheincreasingly

during labor. support onlytheoralintakeofmodestamountsclearliquids Gynecologists andtheAmericanSocietyofAnesthesiologists cies. BoththeAmericanCollegeofObstetriciansand labor, despitecallsbysomegroupsformoreliberalizedpoli- Oralintakeofsolidsshouldbestronglydiscouragedduring emptying duringlabor. achs regardlessofNPOstatus,secondarytodelayedstomach Allpregnantwomenshouldbeconsideredtohavefullstom- ux.

25 Obstetric Anesthesia 26 Anatomic and Physiologic Changes • • • • • • • • normal changesthatoccurinliverfunctionstudiesduringgestation. Thediagnosisofliverdiseaseinpregnancyisconfoundedbythe mechanical effectsofthegraviduterus. muscle relaxationeffectsofprogesteroneandprobablybythe Creatinine RPF/GFR Filtration Fraction – BUN GFR RPF Parameter (Listed asChangefromPrepregnancyValues) Table2.7

Hepatic andGallbladder Additionalchangesassociatedwithpregnancyinclude: prompting fluid intaketocontributethedeclineinosmolality. in excessofsodium.Theosmoticthresholdforthirstdeclines, Plasmaosmolalitydecreasesearlyinpregnancyaswaterisretained concentration increasesinthethirdtrimester. Uricacidtubularreabsorptiondeclines,sothatplasmauric increased fi ltered loadofglucoseaccompanyingtheincreaseinGFR. after conception.Therenaltubulesarelikelyunabletoacceptthe Glucosuria,independentofbloodsugarconcentration,isnotedsoon investigated forevidenceofrenaldisease. increase (Table BUNandcreatinineareloweredasGFRrenalplasmafl ow volume, suggestinghormonalmechanisms. fi rst trimester.Thesechangesprecedetheincreaseinplasma Renalplasmafl ow andglomerularfi ltration increaseearlyinthe Bilirubin,AST,ALTandLDHallincreasetohighnormal. Plasmacholinesteraselevelsdecline20 production. Alkalinephosphataseincreases2–4timesnormalduetoplacental blockade fromsuccinylcholine. counters anyclinicallysignifi cant prolongationofneuromuscular However, thesimultaneousincreaseinvolumeofdistributionlikely

Renal HemodynamicsAssociatedwithPregnancy 2.7 ). Evenmildelevationsinplasmalevelsshouldbe ↓ WNL 8–9 mg/dl ↑ 50 ↑ 75 is rmse Third Trimester First Trimester

% % –85

% –30

bytermpregnancy. ↔ ↓ 0.4–0.6mg/dl ↑ 50 7–8 mg/dl ↑ 50

% %

• • • ance, decreasingperipheralsensitivitytoinsulin. human placentallactogen,orHPL)likelymediatethisinsulinresist- relative insulinresistance.Circulatingplacentalhormones(particularly Althoughinsulinsecretionrisesduringgestation,parturientsexhibita gallstone formation. progesterone levels,leadingtoasluggishmilieuwithpropensityfor contractile response.Thischangeisprobablymediatedbyincreased Cholecystokinin releaseisdecreased,whichleadstoareduced Theincidenceofgallbladderdiseaseincreaseswithpregnancy. tional anemia(Table than theredcellvolumeincreases, resultinginarelativehemodilu- volume. However,plasmavolumeincrease isproportionatelygreater Enhancedrenalerythropoietinproduction increasesredbloodcell clinical stateismaintainedthroughoutpregnancy. tion, andthethyroidglandisoftennotedtobeenlarged,aeuthyroid Althoughthereisanelevationoftotalserumthyroxinduringgesta-

Thyroid Glucose Metabolism Hematologic has elevatedcirculatinglevelsofinsulin. after deliverywhenitnolongerreceivesaglucoseload,butstill a hyperglycemicmothermaybecomeprofoundlyhypoglycemic secreting itsowninsulininresponsetoglucoseloads.Thefetusof Insulindoesnotcrosstheplacenta,sofetusisresponsiblefor of thepropensityforhypoglycemiaimmediatelypostpartum. Insulinshouldbeadministeredcautiouslypriortodeliverybecause returns tobaseline. Shortlyafterdeliveryofthefetusandplacenta,insulinsensitivity the fetus. nonpregnant patients,allowingforplacentaltransferofglucoseto Carbohydrateloadsresultinhigherplasmaglucoselevelsthan

2.8 ).

27 Obstetric Anesthesia 28 Anatomic and Physiologic Changes • endogenous enkephalinsandendorphins. Parturientsingeneralhaveanelevatedpainthresholdduetoincreased 25 cmx30by term gestation. Thenongraviduterusisabout5cm x6cminsizeandincreasesto • • • Blood Volume Parameter Table 2.8 Plasma Volume Hematocrit Red CellVolume Hemoglobin

Neurologic Uterus Otherbloodelementsaresimilarlyaffectedbypregnancy. sensitivity tolocalanestheticshavebeensuggested(Table thetic forregionalanesthesia.Severalexplanationsthisincreased Pregnantpatientsrequireapproximatelyone-thirdlesslocalanes- requirements. favor thisasthemostlikelyexplanationforreducedanesthetic and allowsforanenhancedlocalanestheticeffect.Mostexperts gesterone levelsandthiselevationlikelyaltersneuronalstructure is welldocumentedthatpregnantwomenhaveelevatedCSFpro- during gestation,contributingtoincreasedriskofinfection. clear leukocytes(PMNL).However,PMNLfunctionislikelyimpaired Leukocytosispeakspostpartum,withanincreaseinpolymorphonu- leading causeofmorbidityandmortalityduringpregnancy. to allowhemostasisafterdelivery,emboliccomplicationsremaina Although thishypercoagulablestatemaybeaprotective tration ofﬁ brinogen andallclottingfactorsexcept XIandXIII. Clottingmechanismsareactivated,withanelevatedserumconcen- apparentclinicaleffect. but plateletcountremainsunchangedorfallsslightlywithno Plateletaggregationandturnoverareacceleratedduringgestation,

Physiologic AnemiaofPregnancy

Level DuringPregnancy 33.5 mg/dl ↑ 45 ↑ 55 11.6 mg/dl ↑ 30

% % %

mechanism

2.9 ).It •

• Further Reading Progesterone-enhanced sensitivity ofnervestolocalanesthetics anesthetic Exaggerated lumbarlordosis allowingincreasedcephaladspreadoflocal anesthetics Increased abdominalpressure enhancingtransduralspreadoflocal Decreased epiduralspacesecondarytovenousengorgement Sensitivity duringPregnancy Table 2.9 4. 3. 2. 1. 8. 7. 6. 5.

cardiac outputtotheuterusincreasesfrom3 term. Uterinevesselsaremaximallyvasodilated.Thefractionof Uterinebloodflow increasesfrom50ml/minto500–800at nant stateto12 and canleadtofetalcompromise. fl systemicbloodpressurewillresultinimpaireduteroplacental Uterineperfusionisnotautoregulated;asignifi cant decreasein

ow. Uterinecontractionsresultin decreasedplacentalperfusion pathophysiology . Dafnis E , 1469 - 1473 Sabatini . after thefiS rst andsubsequentpregnancies . . Effect ofpregnancyonrenalfunction . Physiology and Clapp JF III , 1988 ; 159 Capeless : adaptations toearlyhumanpregnancy 1456 E . - 1460 . . Cardiovascular functionbefore,duringand Clapp JF 1993 3rd ; , 36 : 3 Seaward - Blechner 12 BL . , JN Sleamaker . Maternal–fetal acid-basephysiology RH . , etal . Maternal physiologic 2009 : 15 - Principles andPractice 36 (4th Ed.) . Philadelphia, PA : Mosby Elsevier Polley ; LS , Gaiser Tsen R LC , 394 - 403 Wong . of plasmaandredcellvolumes CA . , eds. Lund CJ , 1993 ; 169 Donovan : triggered byaprimaryfallinsystemicvasculartone 1382 JC . - 1392 . . Blood volumeduringpregnancy:Signifi hemodynamics andvolumehomeostasisareconsecutiveadjustments Duvekot JJ Analg. , 1986 Cheriex ; progesterone concentrationinpregnantandnonpregnantwomen 65 EC . : , 950 - 954 Pieters . FA , Datta S , Hurley RJ , Naulty JS , . Physiologic ChangesofPregnancy . In Chestnut DH , Theories forIncreasedLocalAnesthetic % Am JMedSci . 1992 ; 303 ormoreatterm. et al Am JObstetGynecol. 1967 ; 98 : . Plasma andcerebrospinalfl Chestnut’s ObstetricAnesthesia et al

Am JObstetGynecol. : 184 - 205 . . Early pregnancychangesin Am JCardiology. 1997 ; 80 : % –4 Clin ObstetGynecol. Am JObstetGynecol. % inthenonpreg- cance uid Anesth

29 Obstetric Anesthesia 30 Anatomic and Physiologic Changes

10. 9.

Weinberger SE , Weiss ST , Cohen Wong CA , McCarthy RJ , Fitzgerald PC , 751 - 755 . water inobesepregnantwomenatterm . Rev RespirDis. 1980 ; 121 : 559 - 581 . WR , et al . Pregnancy andthelung . et al . Gastric emptyingof Anesth Analg. 2007 ; 105 : Am prolonged periods oftime;thepresencecatheter alsoallows Continuousepidural techniquesallowanalgesiatobe maintainedfor Advantages use ofregionalanalgesiaforlaborincreasedfromlessthan20 mortality hasdecreaseddramatically.U.S.statisticssuggestthatthe the pastthreedecades,incidenceofanesthesiarelatedmaternal Paralleling theincreaseinuseofregionalanesthesiaduring complete analgesiawhileminimizingrisktothemotherandfetus. Contemporaryregionalanalgesictechniquesproviderapid,almost 1981 tomorethan65 Introduction Epidural Analgesia Systemic andAlternativeAnalgesiaforLabor Epidural AnalgesiaandtheProgressofLabor Improving AnestheticEfﬁ ciency inObstetrics Alternative RegionalAnestheticTechniques Anesthesia forVaginalDelivery Continuous SpinalAnalgesia Combined SpinalEpidural(CSE)Analgesia Medications Epidural Analgesia Introduction Michael J. John Paech A. , Robert D’Angelo , FANZCA Thomas MD , MD and Delivery PainReliefforLabor Chapter 3 43 31 % today. 31

60 62

53 64 68 69 66 % in

31 32 Pain Relief for Labor and Delivery beneﬁ exist, theriskofacomplicationoccurring mustbeweighedagainstthe analgesia forlabor,afocusedhistory andphysicalexamshould Priortoplacementoftheepidural catheter orinductionofepidural Preparation of regionalanesthesia(Table number ofrelativecontraindicationsoccurthatmayprecludetheuse Althoughabsolutecontraindicationstoneuraxialblockadearerare,a Contraindications contraindications toregionalanesthesia. an epiduralserviceexistsatthatinstitution,andthepatienthasno of cervicaldilatation,isacandidateforepiduralanalgesia.Thisassumes rient requestingpainreliefduringanyphaseoflabor,andirrespective intervention, whileunderaphysician’scare.” acceptable forapersontoexperienceseverepain,amenablesafe Gynecologists, “Thereisnoothercircumstancewhenitconsidered Anesthesiologists andtheAmericanCollegeofObstetricians AsnotedinajointstatementbytheAmericanSocietyof Indications these goals. based approachtoprovidinglaboranalgesiawhileaccomplishing patient safetyandsatisfaction.Thischapterfocusesonanevidence- Anesthesiaservicesmustbalanceefﬁ cient useof manpower with • • • • obstetrics isrelativelylaborintensive: increased manpowerrequirements.Providingepiduralanalgesiain Themajordisadvantageofepiduralanalgesiaisprimarilyrelatedto Disadvantages general anesthesiainhigh-riskpatients. analgesia hasalowincidenceofsideeffectsandreducestheneedfor instrumental oroperativedeliveryberequired.Inaddition,epidural the qualityofanalgesiatobevariedshouldconditionschange,or

Contemporaryobstetricanesthesiapracticedictatesthatanypartu- Mostlaborsuitesarenotsituatednearthemainoperatingsuite. Ittakesapproximately20minutestoinduceeachanesthetic. Nearly10 intravenous cannulationorinadequateanalgesia. Asmanyas30 tsoftheregionalanesthetic,onacase-by-case basis.

% ofepiduralcatheterswillrequirereplacement. % ofepiduralcathetersrequiremanipulationfor 3.1 ).Whenrelativecontraindications

• Other essentialstepsinclude: of theprocedure,andinformedconsentobtained(verbalorwritten). be performed.Thisshouldincludeanexplanationofrisksandbeneﬁ • • • • • catheter. Inaddition,recommended equipmentincludes: epidural needle,asyringeforlossofresistance,saline,andan tions, anestheticandneedlesforlocalinﬁ ltration, asteriledrape,an Disposableepiduralkitsgenerallyincludesterilepreparatorysolu- Equipment in Obstetrics(Table of AnesthesiologistshaspublishedGuidelinesforRegionalAnesthesia to treathypotension,seizures,orcardiacarrest.TheAmericanSociety Drugsandequipmentforresuscitationshouldbeimmediately of theregionalanestheticonacase-by-casebasis. UcretdHpvlma Severe FetalDepression Uncorrected Hypovolemia ∗ Severe Coagulopathy Septic shock Site Localized InfectionattheInsertion Cooperate Patient RefusalortheInability to Absolute Table 3.1

Theriskofacomplicationoccurring mustbeweighedagainstthebeneﬁ Obtaininglaboratorytestswhenappropriate:forexample,a To assure that an obstetrician is available for an obstetric emergency. Toassurethatanobstetricianisavailableforobstetricemergency. boplastin timeforapatientonIVheparin(seealsoChapter6). count ifapatientispreeclamptic(seeChapter7)orpartialthrom- Intravenousaccessshouldbeestablished. 1 cmincrements,toassistwithdetermining theamountofcatheter Anepiduralcatheterthatisclearlymarked alongthedistal20cmin depth fromthepatient’sskinto epiduralspace. increments forcatheterinsertion;the markingshelpdeterminethe AwingedTuohytypeneedle,witha 9cmbarrelmarkedinto1 solution beforeepiduralplacement,iftimeallows. Administer250–500mlofanon-dextrosecontainingbalancedsalt Contraindications toRegionalAnesthesia 3.2 ).

Relative Biﬁ Neurologic Disease(e.g.,Spina Aortic Stenosis such as Eisenmenger Syndromeor Severe MaternalCardiacDisease Mild Coagulopathy da)

∗

available platelet

ts ts

33 Obstetric Anesthesia 34 Pain Relief for Labor and Delivery • is outlinedinTable Arecommendedtechniqueforcontinuous lumbarepiduralanalgesia Technique ∗ 10. Obstetrics Table 3.2 Oct 12,1988andamendedon17,2007.

AdaptedfromtheguidelinesapprovedbyASAHouseofDelegateson 9. 8. 7. 6. 5. 4. 3. 2. 1. A clearsteriledrapetoassistwithlandmarkandmidlineidentiﬁ • needle. that remainswithintheepiduralspaceafterremovalof tion, especiallyduringdifﬁ

CPR forpatientsreceivingpost-anesthesiacare. A physicianshouldbeavailabletomanagecomplicationsandprovide The StandardsforPost-AnesthesiaCareshouldbeapplied. post-anesthesia conditionisstable. regional anesthetictomanagecomplicationsuntilthe The anesthesiacareprovidershouldremainreadilyavailableduringthe be immediatelyavailablefornewbornresuscitation. Qualifi ed personnel,otherthantheattendinganesthesiologist,should be immediatelyavailable. for BasicAnestheticMonitoringbeapplied,andthattheobstetrician Regional anesthesiaforcesareansectionrequiresthattheStandards The parturient’svitalsignsandfetalheartrateshouldbemonitored. throughout theregionalanesthetic. An intravenousinfusionshouldbeestablishedandmaintained any complicationsthatmayarise. labor anestheticandisreadilyavailabletosupervisemanage maternal andfetalstatustheprogressoflaborapproves by aqualifi ed individual,andtheobstetricianwithknowledgeof Regional anesthesiashouldnotbeinitiateduntilthepatientisexamined direction of,aphysicianwithappropriateprivileges. Regional anesthesiashouldbeinitiatedby,orunderthemedical support. pressure ventilation,andabilitytoperformadvancedcardiaclife and performendotrachealintubation,abilitytoprovidepositive available including:oxygen,suction,equipmenttomaintainanairway Appropriate resuscitationequipmentanddrugsmustbeimmediately cannulation. forced epiduralcathetersreducethe incidenceofintravenous analgesia comparedtosingle-orifice catheters.Flexiblewire-rein- and 1.5cmfromthedistaltip)reduceincidenceofinadequate Multiportcatheters(closedtipandwith3lateralholesat0.5,1.0, Guidelines forRegionalAnesthesiain ∗

3.3 . cultepiduralplacement.

ca- the latephasesof labor. position maybemorecomfortable forthepatient,especiallyduring midline, especiallyinobesepatients. Incontrast,thelateraldecubitus The primaryadvantageofthesitting positioniseasieridentiﬁ necessitate lateralpositioningshould aregionalanestheticberequired. because emergencyclinicalscenarios suchasaprolapsedcordmay at epiduralcatheterinsertionwith the patientinlateralposition, will developapersonalpreference;however,theymustbecomeadept position duringepiduralcatheterplacement.Eachanesthesiaprovider Thepatientmaybepositionedineitherthelateraldecubitusorsitting Positioning andChoiceofInterspace • • • • • • • • • • LOR =lossofresistance;PCEApatientcontrolledepiduralanalgesia. section. of theepiduralcatheterinpatientsathighriskrequiringacesarean ∗ Epidural Analgesia Table 3.3 • ThedoubleLidocainetestdoseisrecommendedtotheadequacy

Adequate analgesia:Begininfusionof0.0625 maintenance asabove Persistent inadequateanalgesia:Ifpainpersistsafter5min,remove and • replace epiduralcatheter. additional localanesthetic(2 pull catheterso3–4cmremainswithintheepiduralspaceandadminister Inadequateanalgesia:Ifpainpersists15minafterLidocaineadministration, • For continuousinfusionanalgesia,beginat10to14ml/h or L • • with eithersingleordoubleLidocainetestdose: If aspirationnegative,testcatheterforspinalorintravenousplacement Once theepiduralspaceisidentiﬁ ed, inserttheepiduralcatheter4–6cm Midline approach LOR withsaline,cephalad-directedneedlebevel • Sitting position:Cross-legged,orwithfeetsupportedandkneesbent, to allowasmuchﬂSterile prepanddrapeanyinterspacebetweenL exion of the lumbarspineaspossible. Fentanyl 2mcg/mlformaintenance For PCEA,usethefollowinginitialsettings: •

by 2 negative by2 H ul ii 20–30ml Hourly limit B slrt 6–12ml/h Basal rate B lsds 5–6ml Bolus dose Lockout8–12 min

Single testdose: 1.5 If negative,administer15ml(5 Bupivacaine double testdose: 5 –S % Lidocaine60mg(3mltototal 200mg) 1 preferred) Recommended TechniqueforLumbar + Fentanyl2mcg/mltoinitiate laboranalgesia % Lidocaine100mg(5ml)followed in1minifnegative ∗ 2 % Lidocaine45mg % Lidocaine40mg(2ml)followed in5minif

% Lidocaine100mg);ifpainrelieved,begin

+ 5 + 5ml)0.0625 + Epi15mcg(3ml). % –0.125 2 andS % –0.125 % Bupivacaine 1 (L 3–4 % , L cation of 4–5 , +

35 Obstetric Anesthesia 36 Pain Relief for Labor and Delivery • • • • Recommendations thatFacilitatePlacement learning theLORtechnique. Saline isalsoincompressibleandmaybepreferentialwhenteaching/ the incidenceofintravenouscannulationandinadequateanalgesia. epidural space,facilitatingcatheterinsertion,andtheoreticallyreduces cians currentlyadvocatetheuseofsaline:salinebetterexpands safely andeffectivelyforLORtoidentifytheepiduralspace.Mostclini- is avoided(i.e.,inject1–4mlorless),eitherairsalinecanbeused As longasinjectionofsigniﬁcant volumesofairintotheepiduralspace epidural space;theuseofairorsalineforLORremainscontroversial. Alossofresistance(LOR)techniqueisrecommendedtolocatethe Loss ofResistanceandNeedleAdvancement nique (Figure ment, anintermittentLORtechniqueandacontinuoustech- theoretically preventsdiffusionoflocalanesthetictoallnerveroots. causes analmostimmediateheadacheifinjectedintrathecally,and step ofopeningavialsalineisavoided.Incontrasttosaline,air of accidentalduralpuncture(clearﬂ Intermittent Technique • •

AdvantagesofairLORincludea“betterfeel,”easieridentifi Therearetwocommontechniquesforepiduralneedleadvance- to palpate,betweentheL Althoughtextbooksoftenrecommendtheinterspacethatiseasiest reasonable alternative. with kneesraisedandfl exed, ratherthandanglingoffthebed,isa Ifthepatientcannotassumethisposition,placingherfeetonastool facilitates theelbowonkneeposition. Sitting“IndianStyle”(anklescrossedandthekneesfullyabducted) over theabdomen;bothmaneuverswillreducelumbar knees whilereachingaroundherabdomen,oroverapillowplaced Witheitherposition,askthepatienttoplaceherelbowson cord damage.ThespinalendsatL best toavoidtheL predicted. and upto25 A“winged”epiduralneedleisrecommended. insertion sitetoprevent excessmovement. ing themiddlefingers ofeachhandagainsttheneedle shaft nearthe Graspthewingsbetweenthumbs andindexfingers whilepress- 3.1a % and ofproceduresoccuroneinterspacehigherthan 2 –L 3.1b ). 3

interspacetoreducethelikelihoodofspinal 2 spinousprocessandthesacrum,itis uid isidentiﬁ ed), andtheextra

2 in4

% ofthepopulation lordosis. lordosis. cation with resistancewhile theepiduralneedleisineither the interspinous Witheithertechnique,depression oftheplungerwillbemet • • is slowlyandcontinuouslyadvanced. pressure isthenappliedtothesyringewithdominanthandasneedle placed againstthepatient’sbacktopreventexcessmovement.Continuous the epiduralneedlenearinsertionsite,whilebackofhandis picture. Thethumbandindexfi nger ofthenondominanthandfi either hand.(b)The“ContinuousLORTechnique”isdemonstratedinthis distance (1–2mm),thenLORisascertainedbydepressingtheplungerwith insertion sitetopreventexcessmovement.Theneedleisadvancedashort hand, whilethemiddlefi ngers arepressedagainsttheneedleshaftnear epidural needlearegraspedbetweenthethumbandindexfi nger ofeach epidural catheterplacementispictured.Withthistechnique,thewingsof Figure 3.1 • • Continuous Technique •

(a) LOR isachieved. nant handastheneedleisslowlybut continuouslyadvanceduntil Applycontinuouspressuretothe syringe plungerwiththedomi- RepeatuntilLORisachieved. securing theneedlewithotherhand. for LORbydepressingthesyringeplungerwithonehandwhile Advancetheneedleashortdistance(1–2mm),stop,andcheck and indexﬁ Securetheepiduralneedlenearpatient’sbackwiththumb to preventexcessmovement. Ensurethatthebackofhandispressedontopatient’s (a) The“IntermittentLossofResistance(LOR)Technique”for ngerofthenondominanthand.

(b)

rmly secure rmly

37 Obstetric Anesthesia 38 Pain Relief for Labor and Delivery Inserttheepiduralcatheter5–6cmintospaceifpossible. Epidural CatheterInsertion(Table 3.3 tended duralpuncture. ) a horizontal,cephaladorientationminimizestheincidenceofunin- approaching theepiduralspaceandinsertingneedleusing mended toavoidtheextrastepofneedle itself increasethelikelihoodofdural dural catheterinsertion.Sincerotationoftheepiduralneedlemayin epiduralneedleisusuallyrotatedcephaladtofacilitatemidlineepi- accidental duralpuncture.However,afterverticalinsertionthe the back)signifi cantly reducestheincidenceofheadacheincases facing vertically,ratherthanhorizontally(inrelationtothelongaxisof Ithasbeensuggestedthatinsertingtheepiduralneedlewithbevel Bevel Direction resistance.” gentle pressurewilleasilydepresstheplunger,whichdefi nes “lossof passes throughtheligamentumflavumintoepiduralspace, ligament ortheligamentumfl avum. Whentheepiduralneedlebevel • • • • • •

there arepersistentneurologicalsymptoms. inform thepatient.Surgicalremoval israrelywarrantedunless Shouldaportionofepiduralcatheter shearduringremoval, needle canshearthecathetertip. unit, sincepullingtheepiduralcatheter throughtheepidural the procedure,removeepiduralcatheterandneedleasone Whenwithdrawinganepiduralcatheterforanyreasonduring sistent paresthesia(seealsointravenouscannulationsection). Removeandreplaceepiduralcathetersassociatedwithaper- insertion. rotational forcewhichcouldtheoreticallyfacilitatelateral during insertionsothatthecoilsdonotgeneraterightorleft Ifusingacatheterreinforcedwithwirecoil,holdthe during prolongedlabors,especiallyinobesepatients. Cathetersinserted<5cmaremorelikelytobecomedislodged cannulation. Cathetersinserted

> 6cmincreasetheriskofintravenous

puncture, itisgenerallyrecom- rotation. Cautiously

• • or intravenousplacement. the cathetershouldbefurthertestedtoruleoutaccidentalintrathecal epidural catheter.Ifnegativeforcerebrospinalﬂ position toavoidaortocavalcompression,andcarefullyaspiratethe Aftersecuringthecatheter,placepatientinsemilateral Epidural CatheterTesting patients athighriskofurgentoperativedelivery. pitfalls associatedwithepinephrine.Itisparticularlysuitedforusein Thedoubletestdoseisanattractivealternative,becauseitavoidsthe • test dose,itisimportantto: both intrathecalandintravenouscatheterplacement.Regardlessof lidocaine 45mgplusepinephrine15mcg,asasingletesttoruleout Table Severalepiduraltestsolutionshavebeenproposedandareoutlinedin • • • DopplerDetectionofAir1–2 ml Fentanyl100mcg Isoproterenol5mg Others: 2 1.5 Single TestDoses: 2 2 Double TestDose: Table 3.4 0.25

Monitormaternalheartrateafteradministration Waitatleast5minutesbeforeassessingmotorblock tions increasematernalheartrate Administertestdosesbetweencontractions,sincepainfulcontrac- intravenous injection. will notbeabletocommunicateeffectivelyfor2–3minutesafteran Inaddition,somepatientsmaydevelopa“glassy-eyedlook”and intravenous placement). ment) andsymptomssuchastinnitusorperioralnumbness(signsof should bemonitoredformotorblock(signsofintrathecalplace- Ifatestdosecontaininglocalanestheticisadministered,thepatient arrest. but notproduceahighspinalblock,seizuresorcardiopulmonary Thepurposeofatestdoseistoproduceearlysignstoxicity % Chloroprocaine60mg % Lidocaine100mg(5ml)IVTest % Lidocaine40mg(2ml)ITtestfollowedin3–5minutes,ifnegative,by % Lidocaine45mg 3.4 % Bupivacaine7.5mg . Themostcommonlyusedtestdoseisa3mlsolution1.5 Epidural TestDoses + Epi15mcg(3ml)

+ Epi15mcg(3ml) + Epi15mcg(3ml)

uid (CSF)orblood,

39 Obstetric Anesthesia 40 Pain Relief for Labor and Delivery duced in venous cannulations),adequateanalgesiawillstillbesuccessfullypro- administered incrementallytoobtainaT Onceanegativetestdoseisconfi rmed, localanestheticshouldbe Establishing aBlock blood cannolongerbeaspirated,shouldremovedandreplaced. that have<3cmremainingwithintheepiduralspaceatpoint • • 3 cmormorewithintheepiduralspace(whichislikelyin50 ing untilbloodcannolongerbeaspirated.Ifthecathetertiprests dose, withdrawthecatheterin1cmincrementswhilegentlyaspirat- Ifanintravenouscatheterisdetectedbyeitheraspirationorthetest Intravenous Catheter analgesia). or leftinplaceandusedasaspinalcatheter(seecontinuous catheter caneitherberemovedandreplacedatanotherinterspace, test dosesuggestanintrathecalcannulation.Shouldthisoccur,the Signifi Intrathecal Catheter recommended. dural cathetermayreducematernalandfetalrisk,istherefore Regardlessofthespecifi Approximately20 Epidural CatheterManagement • • • possible explanation,andmayhave a varietyofcauses. analgesia. Maldistributionoflocalanesthetic hasbeenpostulatedasa

Whenusingthedoubletestdose,2 gesia within7–10minwhenthecatheterissitedproperly. Theprimarybeneﬁ t isthat lidocainecanproducegoodlaboranal- dose toruleoutintravenouscannulation. serves asanintrathecaltest,followedin5minbyaml(100mg) some degreeofmotorblock. lidocaine tototal200mgwillproduceadensesensoryblockand Ifthedoubletestdosewasadministered,anadditional3mlof2 administered. whether ornotthelidocaineplusepinephrinetestdosewas 10–15mlofdilutelocalanestheticplusopioidisusuallyrequired, a maldistributionof localanestheticwithintheepidural space. Thecathetermaydeviatefrommidline duringinsertion,leadingto cant motorblockandcompletepainreliefwithin5minofthe > 90 %

ofcases.Theremaining50 % –30 ctestdosechosen,carefullytestingeachepi- % ofpatientsexperienceinadequateepidural

% 10 plainlidocaine2ml(40mg) % –T

ofintravenouscatheters, 8 sensoryblock.

ofintra-

% • • • of localanesthetic(mostcommonlybupivacaine0.0625 Whenpatientsdevelopadequateanalgesia,administeradilute • • that epiduralanesthesiawillproduceadequatesurgicalanalgesia. Thisapproachimprovesoverallefﬁciency andincreasesthelikelihood • • replaced: insertion thepatientiseithercomfortableorepiduralcatheter catheter management,sothatwithin20minutesofepidural technique isrecommendedasanaggressiveapproachtoepidural until adequateanalgesiaisestablished,orreplaced.Thefollowing Regardlessofthecause,theseepiduralcathetersshouldbewithdrawn ultra-dilute solutionsofbupivacaine(<0.0625 plus opioid(usuallyfentanyl2mcg/ml)formaintenance.Although evidence suggeststhatapproximately50 fentanyl andepinephrinehavebeenrecommendedintheliterature, infusion, andpatient-controlled epiduralanalgesia(PCEA) techniques. Laboranalgesiacanbemaintained by intermittentbolus,continuous Maintenance Techniques need forfurtherinterventions,arerecommended. solutions notedabove,whichproduce betteranalgesiaandreducethe inadequate analgesiaduringlabor.Therefore,themoreconcentrated

spread ofthelocalanesthetic. scar tissueorothermechanicalobstructionsthatinhibitcomplete Previoussurgery,orevenpreviousepiduralanesthetics,maycreate impede completespreadoflocalanesthetic. Theuseofairforlossresistancemayintroducebubblesthat local anesthetic. Septawithintheepiduralspacemaypreventuniformdistributionof tually requirecathetermanipulation. it wastestimeandthepatientremainsuncomfortablebutwilleven- drawing theepiduralcatheter(91%v.74 Evidencesuggeststhistechniqueislesseffectivethanﬁ rst with- local anestheticbeforewithdrawingtheepiduralcatheter. analgesia intothedependentposition,andadministersadditional Analternativerecommendationplacesthepatientwithinadequate epiduralcatheter. Ifnotcomfortablewithin5minutes,removeandreplacethe additional localanesthetic. so that3–4cmremainswithintheepiduralspace,andadminister Ifpainpersists15minafterthetestdose,withdrawcatheter

% % successrate);further, ofpatientsexperience

% concentration), % –0.125 solution % )

41 Obstetric Anesthesia 42 Pain Relief for Labor and Delivery bradycardia afterepiduralplacement shouldbetreatedpromptlyby artery bloodﬂ ow andfetaloxygenation. Hypotensionand/orfetal which, ifuntreated,canleadtofetal bradycardiabyreducinguterine and ambulation.Hypotensionresults fromsympatheticblockade, Back painisusuallyself-limitedand treatedwithoralanalgesics (Table Epiduralanalgesiaisassociatedwithsideeffectsandrarecomplications Complications can bemanipulatedaspreviouslydescribed. 5–10 mlisrecommended.Ifdiscomfortpersists,epiduralcatheters The administrationofadditionalbolusesbupivacaineorlidocaine experience breakthroughpainorperinealpressureaslaborprogresses. ments varythroughoutlaboranddeliveryand,occasionally,patients nique foreachmethodisdescribedTable interventions andPCEAtechniquestheleast.Arecommendedtech- In general,intermittentbolustechniquesrequirethemostanesthetic (re-boluses) requiredduringlabor. efﬁ the basalinfusionsignificantlyreducesworkloadandimproves epidural analgesiawithabackgroundinfusionisrecommended,since bolus Intermittent Technique Maintenance Table 3.5 infusion Continuous basal infusion PCEA with basal infusion PCEAwithouta Regardlessofthemaintenancetechniqueused,analgesicrequire- ciency bylimitingthenumberofanesthesiaproviderinterventions 3.6 ).Fortunately,themostcommonof theseareeasilytreated. Recommended SolutionsforEpiduralAnalgesia Concentration andDosingSchedule 0.125 1:200,000 10ml(5 0.0625 8–16 ml/h 0.0625 following settings: 0.0625 following settings: Hourly limit:20–30ml Lockout: 8–12min Bolus dose:5–6ml Basal rate:6–12ml/h Hourly limit:30–40ml Lockout: 8–12min Bolus dose:6–8ml % –0.25 % –0.125 % –0.125 % –0.125 % Bupivacaine % Bupivacaine % Bupivacaine % Bupivacaine + 5ml)boluses,repeatasneeded

+ Fentanyl3–5mcg/ml

+ Fentanyl2mcg/mlat + Fentanyl2mcg/mlatthe + Fentanyl2mcg/mlatthe 3.5 .Patient-controlled + Epi common localanestheticsusedinobstetricsarelistedTable and delivery,aswellanesthesiaforcesareandelivery.Themost anesthesia; theyareusedtoprovideregionalanalgesiaforlabor Localanestheticsaretheprimarypharmacologicdrugsusedinobstetric needed (seealsoChapter12). ephedrine 5–10mgorphenylephrine50–100mcgintravenouslyas ensuring leftuterinedisplacement,givingintravenousﬂ toxicity. that followrepresentanoverview of localanestheticpropertiesand for instrumentalandoperativedeliveries. Thebulletedsections maintain laboranalgesia,andchloroprocaine toprovideanesthesia cathetersforlocationandestablish laboranalgesia,bupivacaineto the author’sinstitution,lidocaineis primarilyusedtotestepidural Require replacement Urinary retention Motor block Hypotension Inadequate laboranalgesia Fetal bradycardia value obtainedfrommultiplesourceswithintheliterature. ∗ Backache atinsertionsite Epidural Analgesia Table 3.6 Intravenous cannulation opiaino ieEfc Incidence Complication orSideEffect Inadvertent duralpuncture(Wet Tap) Post duralpunctureheadache Inadvertent spinalcatheter Death Epidural abscess Epidural hematoma Permanent neurologicinjury High spinalblock Subdural catheter Medications Thelistedincidenceforeach complicationorsideeffectisanaverage Complications andSideEffectsAssociatedwith ∗

8 Varies withdose Varies withdose Varies withdose 15 8 75 1 1 1 <1 Extremely rare(<1:100,000) Extremely rare(<1:100,000) Extremely rare(<1:100,000) Extremely rare(<1:10,000) Rare (1:10,000) Rare (1:1000) % –10 % % –6 % –2 % % –25 % –90 % % % % % % uid andeither 3.7 . At

43 Obstetric Anesthesia 44 Pain Relief for Labor and Delivery

Table 3.7 Commonly Administered Local Anesthetics in Obstetrics Drug Class Concentration Dose∗ Onset Duration of pka Protein Labor Bound Analgesia∗ ∗ Chloroprocaine Ester 2 % –3 % 10–30 ml Rapid 30 min 8.7 0 Lidocaine Amide 1 % –2 % 10–30 ml Intermediate 45 min 7.9 70 Bupivacaine Amide 0.04 % –0.5 % 10–30 ml Slow 60 min 8.1 95 Levobupivacaine Amide 0.04 % –0.5 % 10–30 ml Slow 60 min 8.1 97 Ropivacaine Amide 0.04 % –0.5 % 10–30 ml Slow 60 min 8.1 94 ∗ Local anesthetics should be administered incrementally rather than as a bolus (5 ml aliquots) ∗ ∗ Duration of labor analgesia from a single 15 ml epidural dose administered incrementally. • Esters: amine. the alkylchainlinkinglipophiliccarbonringandtertiary Localanestheticsareclassiﬁed aseitherestersoramides,accordingto Local Anesthetics(seealsoChapter1) • • • • Amides: • • cross cellmembranes. ionized formbutonlyunionizedmoleculesdiffusethroughtissuesand At physiologicpH,mostofthelocalanestheticmoleculesexistin AlllocalanestheticsareweakbaseswithpKavaluesapproximating8.0. • administered. Usinglidocaineasanexample: vasoconstrictors, metabolism,andthevascularityofsitewhere of drugadministered,itsphysiochemicalproperties,theaddition Bloodlevelsoflocalanestheticsareinﬂ uenced bythetotaldose • •

tions andprolongsthedurationof block. Theadditionofepinephrine1:200,000 lowersplasmaconcentra- Includecocaine,tetracaine,procaine,andchloroprocaine ciﬁ Aredegradedintheplasmabypseudocholinesteraseandnonspe- gives themgreaterallergicpotentialthantheamides Arehydrolyzedtoproducepara-aminobenzoicacid(PABA),which Aremetabolizedintheliver ropivacaine, andlevobupivacaine Includelidocaine,etidocaine,mepivacaine,prilocaine,bupivacaine, vascularityofeachsiteinthefollowing order:intercostal producesvaryingplasmalevelsthat directlycorrelatewiththe Asimilardoseadministeredinto thefollowingcompartments produce aseizure. ered safe,20mginjecteddirectlyintothecarotidarterywilllikely Although5mg/kgadministeredwithintheepiduralspaceisconsid- ized molecules. anesthetics withlowerpKavalueshaveahigherfractionofunion- SpeedofonsetisgenerallyinverselyrelatedtopKa,sincelocal action. ics, includingvariabilityinspeedofonset,potency,andduration binding determinetheclinicalpropertiesofvariouslocalanesthet- PhysiochemicalpropertiessuchaspKa,lipidsolubility,andprotein epidural cesterases > brachialplexus=femoral.

caudal >

45 Obstetric Anesthesia 46 Pain Relief for Labor and Delivery • intravenously cancausecardiacarrest. large bolus(intendedfortheepiduralspace)inadvertentlyinjected will produceaseizurebutposesnoriskofcardiacarrest,while dose oflocalanestheticadministereddirectlyintothecarotidartery tered andthelocalanestheticconcentrationinblood.Asmall arrest (Table followed byCNSdepression,respiratoryarrest,andeventualcardiac rologic symptoms,suchastinnitus,perioralnumbnessandseizures, As bloodlevelsincrease,localanestheticsfi rst causeexcitatoryneu- Alllocalanestheticsaretoxicifadministeredinhighenoughdoses. Local AnestheticToxicity • • • • artery bloodflow atclinicallyrelativedoses. Localanestheticshavenoadverseeffectsonuterineorumbilical ∗ 6.Cardiac arrest 5.Respiratory arrest 4.Seizure Lossofconsciousness 3. Inabilitytocommunicateappropriately(glassy-eyedlook) 2. Toxicity Tinnitus,perioralnumbness 1. Table 3.8 fractionated doses(5mlaliquots). severe toxicreactions,localanesthetics should alwaysbeadministeredin not lossofconsciousness,seizures,orcardiopulmonary arrest.Toprevent dose containinglocalanestheticshouldproducethefi rst twosymptomsbut generally occurinthelistedorderasbloodconcentrationsincrease.Atest

Alllocalanestheticscanproducethesereactions.Thesignsandsymptoms Cardiotoxicity and forchloroprocaine is ics. Ifthedoseofbupivacainerequired toproducecardiactoxicity Bupivacaineisthemostcardiotoxic of clinicallyusedlocalanesthet- Unionizedlocalanestheticmoleculesfreelycrosstheplacenta. hypertonus athigherconcentrations. Theycanproduceinuterinearteryvasoconstrictionand distressed,acidoticfetus. This“iontrapping”effectmaybecomeclinicallysigniﬁ cant ina phenomenonknownas“iontrapping.” becomes ionizedandaccumulatesinthefetalcirculation,a SincefetalpHislowerthanthematernalpH,morelocalanesthetic 1 , theequivalentdoseofropivacaine is

∗

Signs andSymptomsofLocalAnesthetic 3.8 ).

isrelativetothespeciﬁ c drug,totaldoseadminis-

> 16.

2 ; forlidocaineitis 8–16

• • • • • • vigilance arethekeystopreventinglocalanesthetictoxicity. Testingepiduralcathetersafterplacement,fractionateddosing,and • • • many casesoflocalanesthetictoxicityinhumans. anesthetic toxicityinrodents,andhasbeenusedsuccessfullytotreat vasopressin incombinationwithepinephrineforresuscitationoflocal duced cardiacarrestindogs,issuperiortoeithervasopressinaloneor emulsion hasimprovedresuscitationsuccessafterbupivacaine-in- of bupivacaineneededtocauseasystoleinrats.Infusionalipid models haveshownthatinfusionofalipidemulsionincreasesthedose results inanimalmodelsandnumerouscasereports.Experimental ment modalityforlocalanesthetictoxicitythathasshownpromising Theterm“lipidrescue”wasﬁ rst coinedin2003andisanewtreat- Lipid TreatmentofLocalAnestheticToxicity intravascular orintrathecalinjection. seconds apart,whileobservingthepatientforsignsandsymptomsof Fractionateddosingentailsadministering5mlaliquotsatleast30–60

RecommendationsforUseofLipidRescue: Intralipid cessful afterLAoverdose,consider administrationofIntralipid Ifstandardadultcardiaclifesupport (ACLS)isnotimmediatelysuc- delivery unitsforeasyaccessinemergencies. due torapidmetabolism. Chloroprocainehastheleastpotentialforinducingcardiotoxicity, The but nothighspinalblock. intended tobelargeenoughproducepainreliefandmotorblock The (Table 30 ml)canbeadministeredover3–4minutesin5mlincrements. Eveninurgentsituations,largevolumesoflocalanesthetic(i.e., intrathecally. epidural catheter,sincecatheterscanmigrateintoveinsor be injectedasasinglerapidbolus,evenwithfunctioning Largebolusesofconcentratedlocalanestheticshouldnever catastrophic toxicevent. Therelativelysmalldosesandslowinjectionwilllessenriskofa arrest. toxicity, butnotsolargeastoproduceseizuresorcardiopulmonary and isintendedtobelargeenoughproduceearlysignsofCNS Atpresent,nostandardprotocolexists spinal testdose intravenous testdose 3.9 ). ® (lipidemulsion)solutionshouldbe stocked onlaborand willruleoutanintrathecalcatheter,andis

willdetectanintravenouscatheter,

47 Obstetric Anesthesia 48 Pain Relief for Labor and Delivery concentrations, several factors have slowed their clinical acceptance. concentrations, severalfactorshaveslowedtheirclinicalacceptance. newer agentsresultinslightlylessmotorblockthanbupivacaineatequal administered whenusedasalternativestobupivacaine.Whilethese tions anddosingregimensofropivacaineorlevobupivacaineshouldbe produce clinicallyindistinguishablelaboranalgesia.Similarconcentra- levobupivacaine, atthesameconcentration;however,threedrugs four-carbon sidechains. three-carbon sidechain,whilebupivacaineandlevobupivacainehave pipecoloxylidide familyandarestructuralanalogs.Ropivacainehasa Bupivacaine, levobupivacaine,andropivacainebelongtothesame to bupivacaine,andarepreparationsofnearlypureL-isomers. Levobupivacaine andropivacaineweredevelopedasalternatives tightly thantheL-isomer,andisconsequentlymorecardiotoxic. L-isomers. TheD-isomerbindscardiacsodiumchannelsmore Bupivacaineispreparedasa50/50 Ropivacaine andLevobupivacaine • • • • labor analgesiaforanumberofreasons: Bupivacaineisthemostcommonlyusedlocalanesthetictomaintain Bupivacaine Speciﬁc DrugsUsedinObstetricAnesthesia Local AnestheticInducedCardiac Arrest Table 3.9 • • • •

Ropivacaineproduceslessmotorblockthaneitherbupivacaineor minimal sideeffects. of 10–15ml/h,withorwithoutopioids,providelaboranalgesia Continuousinfusionsofdilutebupivacaine0.04 60 minbeforethepatientrequestsadditionalanalgesia. 10–15 mlproducesanalgesiainminthatlastsapproximately Plain0.25 bound. Bupivacainehaslimitedplacentaltransfersinceitishighlyprotein- block thanmotorblock. Diluteconcentrationsproduceproportionallygreatersensory Increase infusionrate by 0.25ml/kg/minifthebloodpressuredeclines Repeat bolus 1–2timesforpersistentasystole 0.25–0.5 ml/kg/minfor 30–120minutes 20 % Intralipidsolution:1.5ml/kgasaninitialbolus,followedby Recommended LipidRescueProtocol for % bupivacaineor0.125

% % racemicmixtureofD-and

bupoivacainewithopioid % –0.125

% atrates

requests additionalanalgesia.Alkalinizationwith8.4 minutes thatlastsapproximately45beforethepatient • • • Plain1 Lidocaine for instrumentaloroperativedeliveries. management diffi as amaintenanceagentbecauseitsshortdurationofactionmakes requests additionalanalgesia.Chloroprocaineisnotroutinelyused 3–6 minutesthatlastsapproximately30beforethepatient Plain2 Chloroprocaine motor blockandhasgreaterplacentaltransferthanbupivacaine. routinely usedasamaintenanceagentbecauseitproducesmore produce anesthesiaforinstrumentaloroperativedeliveries.Itisnot epidural catheters,initiatelaboranalgesia,treatbreakthroughpain,or approximately 3–6minutes.Lidocaineiscommonlyusedtotest bonate 1meq/10mloflocalanestheticdecreasesonsettimeto • • • • with boththepH ofthesolutionanduse preservative tically significant, thiseffectdoes notappeartobeclinicallysignifi morphine analgesia,evenaftertheblock hasreceded.Althoughstatis- exact mechanismisunknown,chloroprocaine reducesfentanyland opioid effectisinconsistentinboth quality andduration.Althoughthe back pain,andwhenadministeredtogether withepiduralopioids,the cally. Insomepatients,itmayproducetransientbutuncomfortable been associatedwithneurologicinjurywhenadministeredintrathe- Despitethesebenefi ts, chloroprocainehasseveraldrawbacks.It

Chloroprocaine-inducedneurotoxicity 3 Ropivacaineandlevobupivacainecostmorethanbupivacaine. anesthesia practiceisexceedinglyrare. Theincidenceoflocalanestheticinducedcardiacarrestinobstetric remains unproven. Thebeneﬁ t ofthereducedmotorblockinlaboringparturients Ithasaveryrapidonsetofaction. Itproducesdensesensoryandmotorblock. Ithasashortdurationofaction. making itoneoftheleasttoxiclocalanesthetics. esterases, resultinginaplasmahalf-lifeofapproximately30 Ithasaveryfavorablesafetyproﬁ le; itismetabolizedbyplasma % chloroprocaineiswellsuitedforproducingsurgicalanesthesia % % –2 chloroprocaine10–15mlproduceslaboranalgesiain % lidocaine10–15mlproduceslaboranalgesiain5–10 cult.

hasbeenassociated

% sodiumbicar- seconds,

cant.

49 Obstetric Anesthesia 50 Pain Relief for Labor and Delivery to producelaboranalgesia). commonly usedopioidsinobstetrics (combinedwithlocalanesthetic Fentanyl(2–4mcg/ml)andsufentanil(0.3–0.5arethemost Lipid SolubleOpioids often co-administeredwithlocalanesthetics. Sinceopioidsdonotproducecompletelaboranalgesia,theyaremost • • are lesseffectiveduringthelaterphasesoflaborandfor tors). Althoughopioidsreliablyproduceanalgesiainearlylabor,they spinal cord(spinalreceptors)andwithinthebrain(supraspinalrecep- Opioidsproduceanalgesiabybindingtoopioidreceptorsbothinthe Opioids (SeealsoChapter5) mal psuedocholinesterase(1:3,000patients). of theserarecomplications. opinion thatthebeneﬁ ts ofchloroprocaineclearlyoutweightherisks using EDTAarenolongeravailable. usuallyafterepiduralanalgesiahasreceded.Commercialpreparations the upperbackfollowinglargedoses( binds calciumions).Patientshavedevelopedseveremusclespasmsof muscle hypocalcemiainducedfromthepreservativeEDTA(which • • avoiding chloroprocaineseemsprudent. in casesofunintentionalduralpuncturewiththeepiduralneedle there havebeennofurtherreportsofneurotoxicity.Nevertheless, the preparation’spHwasincreasedfrom3.0to7.0severalyearsago, preparation ofchloroprocainehasbeenmarketed.Inaddition,since sodium metabisulﬁ te. Becauseoftheseconcerns,apreservative-free

Chloroprocaineshouldbeavoidedinpatientswithknownabnor- Whenconsideringarisk/benefit ratioforthisdrug,itistheauthor’s Chloroprocaineinducedbackpain receptors. deeply withinthespinalcordandhavefewerassociatedopioid Somaticpainfi bers (latelaboranddeliverypain)arelocatedmore modulation. opioid receptors,makingthemmoreamenabletoopioid-induced the peripheryofspinalcordandhavealargerpopulation Visceralpainfi bers (earlylaborpain)areprimarilylocatedin 100 Pruritusisthemostfrequentlyencountered sideeffect(60 equipotentdoses. Sideeffectsproducedbyfentanyl andsufentanilaresimilarat % incidence),butrarelyrequires treatment. Ifnecessary,

hasbeenrelatedtolocalized > 50ml)ofchloroprocaine;

delivery. % – reduces localanestheticuseby25 • • • • • • • • tory depression.” Epidural morphineisassociatedwithbiphasic“earlyandlaterespira- gesia fromneuraxialadministrationofmorphineisslow(upto1hour). but muchlesscommonlythanlipidsolubleopioids.Theonsetofanal- Morphineandmeperidine(pethidine)havebeenusedinobstetrics, Hydrophilic Opioids anesthetic (typicallybupivacaine0.0625 Theadditionoffentanyl2mcg/mltodiluteconcentrationslocal Overview ofFentanylMechanismActioninObstetrics nous administrationtotreatpostoperativepain. Incontrast,epiduralfentanylaloneofferslittleadvantageoverintrave- •

and activatesbothspinalsupraspinalopioidreceptors. Atthesehigherdoses,epiduralfentanylisabsorbedsystemically naloxone (40 mcg boluses titrated to effect are recommended). naloxone (40mcgbolusestitratedtoeffectarerecommended). Allsideeffects,includingrespiratorydepression,canbereversedwith doses. central nervoussystemand,maybemorelikelyfollowingrepeat to rapidsystemicuptakeorcephaladdistributionwithinthe sion,” whichoccurswithin30minofadministration.Itislikelydue Lipidsolubleopioidsareassociatedwith“earlyrespiratorydepres- phoria andrespiratorydepression. Lesscommonsideeffectsincludenausea,urinaryretention,dys- phine 5mg. pruritus isreadilytreatedwithanagonist-antagonistsuchasnalbu- fentanyl ( Treatmentofpostoperativepainrequiresrelativelylargedoses effects aresimilar. Fentanylrequirements,bloodconcentrations,analgesiaandside stem depressionofrespiration. and issecondarytorostralspreadwithin theCSFleadingtobrain- Laterespiratorydepressionoccurs 6–18 hoursafteradministration uptake, andoccurswithin1hourof administration. Earlyrespiratorydepressionisprobably duetorapidsystemic effect. in laboringwomen,whichindirectlyindicatesaspinalanalgesic contrast tointravenousfentanyl,reducesepiduralbupivacaineuse Epiduralfentanylat20mcg/h,atypicalobstetricdose,andin > 100 mcg/h).

% –30

% –0.125 % . %

) forlaboranalgesia

51 Obstetric Anesthesia 52 Pain Relief for Labor and Delivery • • • epidural adjunct. mary ofthreeadjunctsstudiedtodate. routine useisprecludedintheUnitedStates.Thefollowingasum- produced undesirablesideeffectsor,asisthecasewithclonidine,its Unfortunately, eachadjunctstudied(e.g.,epinephrine,neostigmine) prolong laboranalgesiawhileminimizingsideeffects(Table and spinaladjunctshavebeenstudiedinanattempttoimproveor Since allcurrentmedicationsproducesideeffects,avarietyofepidural that produceslong-lasting,completepainreliefwithoutsideeffects. Theholygrailofanalgesiainobstetricsisamedicationorcombination Adjuncts and safetyforlaboranalgesiacannotbemadeatthistime. erties, butclinicaldataarelacking,sorecommendationsaboutitsuse Neuraxialmeperidinehaslocalanesthetic-likeaswellopioidprop- prolongs blockduration. reduces bloodlevelsoflocalanesthetics,increasesonsettimes,and • • • Clonidine

• wards. all anesthetics,andareusuallysenttounmonitoredpostpartum tive delivery.Additionally,parturientsaremoresensitivetonearly rience lesspostpartumpainthanparturientsrequiringanopera- risk ofmorphine-inducedrespiratorydepressionsincetheyexpe- Intheory,parturientsthatdelivervaginallymaybeatincreased Epinephrine Box Warning”against itsuseinobstetrics. ClonidineisexpensiveintheUnited States,andhasanFDA“Black sufentanil butproducesedationand hypotension. Spinaldosesof15–50mcgprolonglabor analgesiafrombupivacaine/ ing sideeffects. PCEA bupivacaine/fentanyluseinlaboring womenwithoutincreas- Atanepiduraldoseof4mcg/ml, clonidine signiﬁ cantly reduces Single-shotspinaldosesof200mcgorlesshavebeenreported. epidural analgesia. Epiduraldosesof1:200,000–600,000areoftenusedforcontinuous especially withcontinuousinfusions. Epinephrineincreasesthedegreeanddurationofmotorblock,

recommendedforvaginaldelivery. Forthesereasons,epiduralorintrathecalmorphineisnot , an α , an 2

adrenergicreceptoragonist,isthemostpromising

α -adrenergicreceptoragonist,enhancesanalgesia,

3.10

). • • likelihood ofsuccessfulduralpuncture,thespinalneedletipshould SpeciallydesignedCSEkitsarecommerciallyavailable.Toincreasethe Equipment to gainwidespreadacceptanceinobstetrics. ache andinadvertentspinalcatheterplacementhaveallowedCSEuse tip spinalneedlesthatminimizetheriskofpost-duralpuncturehead- of eachwhileminimizingrisks.Thedevelopmentsmallgaugepencil- epidural analgesia,asoneprocedurethatharnessestheadvantages ACSEanestheticcombinesasingle-shotspinalwithcontinuous indirectlyincreasingspinallevelsofacetylcholine. Neostigmine

Combined SpinalEpidural(CSE)Analgesia limits sideeffects,andincreasespatient satisfaction. true combinedspinal-epiduraltechnique thatincreaseseffi and nausea(Table produced sideeffectssuchasmotor block,hypotension,sedation nearly 3.5hours,therequiredcombination ofmedicationsalso the spinalanalgesia.Although analgesia canbeprolongedto dilatation and 40 tice, nearlyallpatientsadministeredCSEanalgesiainearlylabor, patients todeliverwithoutrequiringepiduralanalgesia.Inprac- tions byspeedingtheprogressoflaborandallowingmore late labor;itwasviewedasatooltoreduceanestheticinterven- believed tobeparticularlybeneficial forpatientsineither early or Whenfi rst introducedtoclinicalpractice,CSEanalgesiawas this time. under investigationandcannotberecommendedforroutineuseat it enhanceslaboranalgesiawithoutproducingnausea,butisstill Atepiduraldosesupto500mcg,preliminarystudiesindicatethat gesia butproducesseverenausea. Ataspinaldoseof10mcg,neostigminefailstoenhancelaboranal- EarlyCSEresearchoftenfocusedonprolongingthedurationof % ofmultiparouswomenadministeredCSEwithacervical

> isananticholinesterasethatenhancesanalgesiaby 7cm,requireepiduralanalgesiapriortodelivery. 3.10 ).Consequently,CSEhasevolved into a

ciency,

53 Obstetric Anesthesia 54 Pain Relief for Labor and Delivery extend 11–15mmpastthetipofepiduralneedle(Figure 3.2b • • • needle” approachisrecommended(Figure when theCSEistechnicallyeasy.Asaresult,“needlethrough Further studieshavefailedtodemonstrateanincreasedrisk,especially the riskofunintentionallyplacingaspinalcatheter,theyareexpensive. and epiduralcatheterlumensareavailable,totheoreticallyminimize lines forregionalanesthesiapreviouslydescribed( Tables Thecontraindicationstoregionalanalgesiaandanesthesiatheguide- Anesthetic Technique • Neostigmine Clonidine Clonidine ∗ Sufentanil Sufentanil Epinephrine Sufentanil Bupivacaine Sufentanil Sufentanil Bupivacaine Fentanyl Fentanyl Drugs CSE Solutions Table 3.10 although itrarelyrequires treatment. Bupivacaine Bupivacaine Bupivacaine

Nearlyallpatientsadministeredspinalopioidsexperiencepruritus Astandardepiduralneedleisusedtoidentifythespace. Theepiduralcatheterisinsertedasusual. intrathecal space,andthespinalneedleisremoved. Spinalmedicationsareadministeredviathespinalneedleinto needle. Alongspinalneedleisinsertedthroughthelumenofepidural ;Figure 3.3c Summary ofSpinalAnalgesiafromVarious ).Althoughepiduralneedleswithseparatespinal 0mg Nausea 10 mcg 50 mcg 50 mcg Dose c 5 mcg 5 mcg 200 mcg 10 mcg 150 2.5 mg 105 10 mcg 10 mcg 108 2.5 mg 90 25 mcg 25 mcg 2.5 mg 2.5 mg 2.5 mg Duration (min) 205 205 188 3.2b ).

Side Effects Sedation Sedation Motor block Hypotension Hypotension

3.1 and 3.2a ∗

and 3.2

) • • advantages. recommended forCSEplacement. The sittingpositionoffersseveral technique describedinTable niques aresimilar,withonlyafewexceptions(alsoseerecommended also applytoCSEtechniques.Procedurally,andepiduraltech- epidural needle. The tipofthespinalneedlepicturedextends11mmpast 11–15 mmpastthetipofepiduralneedletofacilitateduralpuncture. epidural needle.Itisrecommendedthatthespinalneedletipextend epidural needle,thespinalneedleisinsertedthroughlumenof technique arepictured.Oncetheepiduralspacehasbeenlocatedwith epidural andspinalneedleusingtherecommended“needlethroughneedle” needle, whichisa27g4 –11/16" Whitacreneedle.(b)Thetipsofthe 9 cmbarrel.Thehubisspeciallydesignedtoreceivethisparticularspinal CSE kitarepictured.Theepiduralneedleisa17gwingedwith Figure 3.2

(b) (a) Thesittingposition,ratherthanthelateraldecubitusis puncture. dura moretautandincreasingthe likelihood ofasuccessfuldural Thepositionincreaseslumbarintrathecal pressure,makingthe ful duralpuncture. Identiﬁ cationofthemidlineiseasier,which isessentialforsuccess- (a) Anepiduralneedleandaspinalfromstandard

3.11 ).

55 Obstetric Anesthesia 56 Pain Relief for Labor and Delivery • rate. aspiration andinjection,toreduceneedlemovementthefailure and epiduralneedlehubsbetweenthethumbindexﬁ the spinalneedle,secureneedlebypinchingboth Eitherairorsalinecanbeusedforlossofresistance.Afterplacing • spread. makes theinjectatemoreisobaric,andtheoreticallylimitscephalad SinceCSEsolutionsarehypobaric,aspirationofspinalﬂ uid 1ml be initiatedimmediately. may resultinanunnecessarilydense block.Theepiduralinfusioncan eter. Somecliniciansprefertoavoid theuseofthistestdose,feelingit Aspinaltestdosemaybeadministered toruleoutanintrathecalcath- Labor Analgesia Table 3.11 • • • • • • • • • • • • •

ligamentum flavum duringaone-shot spinaltechnique. Theduradoesnotholdthespinalneedlefirmly inplaceasdoesthe and securethecatheter. removed, havethepatientassume thelateraldecubitusposition Oncetheepiduralcatheterisinsertedandneedle Sitting position Sterile prepanddrape,anyinterspacebetweenL Firmly securespinalandepiduralneedlehubswithindexfi needle tip) Small gaugepenciltipspinalneedle(25–27g) CSE kit(spinalneedletipshouldextend11–15mmpastepidural LOR withairorsaline • thumb Spinal injectate: • • Test dose(ifdesired): remove epiduralneedle Have patientassumelateralposition Secure catheter Remove spinalneedle,insertmultiportepiduralcatheter5–6cm, If possible,aspirateCSFtototal2mlpriorinjection Begin epiduralmaintenanceinfusionasdescribedinTable 3.5

Bupivacaine (0.25 3 ml1.5 2 ml (0.3–0.4 ml) % lidocaine(40mg),or % lidocaine(45mg) Recommended TechniqueforCSE % ) 1.75–2.5mg(0.7–1ml)

+ epi15mcg + Fentanyl15–20mcg 2 andS 1

nger and nger

nger during nger • InitiationofCSEwiththespinalinjectionnotedinTable midline ( Figures the mostlikelyreasonforfailureto obtainCSFisdeviationfromthe Assumingtheuseofappropriately sized spinalandepiduralneedles, Reasons forCSEFailure • • • • • • When toConsiderAvoiding CSE sectionberequired. reduces theneedforgeneralanesthesiashouldurgentcesarean patients isrecommended,sinceawell-functioningepiduralcatheter recommended.Inducingtraditionalepiduralanalgesiainhigh-risk thetics inparturientsathighriskforoperativedeliveryisnot after thespinalinjection.Asaresult,routineuseofCSEanes- epidural catheterplacementremainsunprovenforsometime TheprimarydrawbackoftheCSEtechniqueisthatcorrect • • • • analgesia. The onsetofanalgesiaisapproximately5–7minutesfasterthanepidural ( • • bupivacaine/fentanyl) willproduceabout90–120minutesof

the spinalanalgesiarecedes. and increasesthelikelihoodofpatientremainingpainfreewhen mately 45minafterspinalinjection;thisaugmentstheepiduraldose IfusingPCEA,askthepatienttopressdemandbuttonapproxi- Abnormalfetalheartratetracing Fetalmacrosomia Multiplegestation Historyofpreviaorabruption Severepreeclampsia Morbidobesity quate analgesia. Lessthan20 nates theneedforindependentdosingofepiduralcatheter. Initiatingtheepiduralinfusionsoonafterspinalinjectionelimi- hypotension. Thelowdrugdosesminimizesideeffectssuchasmotorblockand compared toepiduraltechniques. Therapidonsetofprofoundanalgesiaimprovespatientsatisfaction Anticipateddifﬁ Abnormalpresentation % 3.3 ). ofpatientsshouldrequireinterventionsforinade-

cultairway

analgesia. 3.11

57 Obstetric Anesthesia 58 Pain Relief for Labor and Delivery following stepscanbeperformed: • needle. and epiduralneedletips,causinganaccidental“wettap”withthe epidural needlemayresultinthedurareboundingoverbothspinal of thedurawitha“tooshort”spinalneedle.Furtheradvancement laterally, whichmayresultintheinabilitytoaspirateCSF.(f ) “Tenting” miss theduralsac.(e)Similarto(d)exceptthatduraispunctured (d) Lateraldeviationoftheepiduralneedlecausingspinalto rather thanpunctured.(c)Ashortspinalneedlefailstoreachthedura. spinal ﬂ uid. (a)Asuccessfuldural puncture,(b)Thedurais“tented” of possiblescenariosthatleadtoCSEfailureortheinabilityaspirate Figure 3.3 • • •

ShouldCSFfailtoreturnwhenthespinalneedleispassed, Removethespinalneedle. Withdrawtheepiduralneedle1–2cm. technique andproceedwithanepidural technique. Ifstillunsuccessfulfollowingthesecond attempt,abandontheCSE different position. right orleft,usingLORtore-enter theepiduralspaceinaslightly Reassesstheangleofepiduralneedle placementandredirecteither (d) (a) The ﬁ gure illustratesasuccessfulduralpuncture,andnumber

(b) (e)

above L nent neurologicinjury;spinalcord damagecanoccurifinterspaces be usedduringCSEplacement,to minimizetherisksofperma- above). lateral penetrationofthedura. IfCSFisobservedbutcannotbeaspirated,thismostlikelydueto • • • • spinal needles. from standardepiduraltechniqueswiththeuseofverysmallgauge post-dural punctureheadacheshouldnotbesigniﬁ cantly different tions hasnotincreasedsincetheadventofCSE.Theincidence complications ofthetechnique,incidencethesecomplica- introducedintothespinalspacehavebeensuggestedaspossible permanent neurologicinjury,hematoma,andmetallicfragments are similar.Althoughconcernsofmeningitis,highspinalblock,abscess, Ingeneral,therisksassociatedwithCSEandepiduralanalgesia Complications • • Itisimperativethatinterspaces below theL nal epinephrineasaconsequenceofrapidonsetanalgesia. hypertonicity, inducedbyaprecipitousdecreaseincirculatingmater- speculationthatfetalheartratechangeswererelatedtouterine InitialreportsoffetalbradycardiaassociatedwithCSEledto

Attempttoaspiratewhilerotatingthespinalneedle. rapidlyapparent),dosetheepiduralcatheter. Ifthepatientfailstodevelopspinalanalgesia(whichshouldbe catheter placement. ommended toinjectthespinalsolutionandproceedwithepidural Ifstillunsuccessfulbutthereisnopersistentparesthesia,itrec- epiduralneedleplacement. using thespinalneedleasa“ﬁ nder needle”toconﬁ rm correct avoids inadvertentduralpunctureswiththeepiduralneedleby SomeserieshaveindicatedthatuseoftheCSEtechniqueactually pressure, ifnecessary,arerecommended. placement, administeringoxygenandsupportingmaternalblood and generallypersistsonlyafewminutes.Ensuringleftuterinedis- Fetalbradycardiafollowingeithertechniqueisusuallyself-limiting imates 10 cardia issimilarwithbothCSEandepiduralanesthetics,approx- Clinicalstudies,however,suggestthattheincidenceoffetalbrady- 2 –L 3 % . areused(seealsoPositioningand Choice ofInterspace

2 spinousprocess

59 Obstetric Anesthesia 60 Pain Relief for Labor and Delivery anestheticposestechnicalchallenges. a prolongedduration.Despitethesebeneﬁ ts, acontinuousspinal reliable analgesiathatcanbetitratedtovaryinglaborconditionsover spinal orthecontinuousepiduraltechniquesincluderapid-onset, Theadvantagesofcontinuousspinalanalgesiaovereitherone-shot Continuous Spinal Analgesia • • • investigated inarecentseries,butthe catheterisnot anesthetic withintheCSF.Safeuse ofa24gspinalcatheterwas These injuriesarebelievedtoresult frommaldistributionoflocal United Statesfollowingreportsofpermanent neurologicinjuries. however, thesecatheterswerewithdrawn formthemarketin gauge spinalcatheters(<24g)were introducedinthelate1980s; Toreducetheincidenceofpost-duralpunctureheadache,small

patient satisfaction. bedside, withonlyminimalnursingassistance,mayenhance ing parturientswhoareabletodosositinachairatthe CSE placementisnotrecommended.Ontheotherhand,allow- Forthesereasons,allowingpatientstoambulatefollowing should shesustainaninjuryduringaccidentalfall. ambulating, theanestheticwouldmostlikelybeimplicated risk. Evenifthepatientcanperformadeepkneebendpriorto late afterinducinganyregionalanestheticincursmedicolegal form subsequentre-dosing.Further,allowingpatientstoambu- place andinitiallydosewithlocalanesthetic,butalsotoper- multiple anestheticinterventions.Timeisrequiredtonotonly the workload,sincemanywalkingepiduralprotocolsrequire Inmanyrespects,havingpatientsambulatetendstoincrease studies havefailedtosupportthishypothesis. incidence ofinstrumentaloroperativedeliveries,prospective ambulation duringactivelaborshortensandreducesthe ambulate. Althoughtheconceptisbasedontheorythat nique thatproducesanalgesiawithoutinhibitingtheabilityto A“ walking epidural

” issimplyanyepiduralorspinaltech-

commercially

• include: decision tousethecatheterviaspinalroute.Suchscenariosmight sia isaconsequenceofdifﬁ culty placinganepidural catheter,andthe Mostoften,theuseofacontinuousspinaltechniqueforlaboranalge- Recommended ClinicalScenariosforSpinalAnalgesia should bepersonallynotiﬁ the anesthesiarecord,andall providersinthelaborsuite stand outfromaregularepiduralcatheter, properlydocumentedon level. careful titrationoftheanesthetictoadesiredsensorydermatomal spinal blockfromaone-shottechnique,byallowingforthe Continuousspinalanesthesiacanreducethelikelihoodofahigh • • • • clinical scenarios: Planneduseofacontinuousspinaltechniquecanbeusefulin •

puncture headache. niques andthesecathetersincreasethelikelihoodofapost-dural gauge epiduralcathetersmustbeusedforcontinuousspinaltech- available intheUnitedStates.Asaconsequence,relativelylarge Inallcasesthe“spinalcatheter”should beboldlymarkedtoclearly the CSForinaccuratedosinginto spinalcatheterincreasesthe Thepotentialforaccidentaladministration ofepiduraldosesinto Unintentionalduralpunctureinparturientsthatarenearing Unintentionalduralpunctureinapatientwithananticipateddiffi scoliosis surgery). attempts inamorbidlyobesepatientorwithprevious Unintentionalduralpunctureduringdiffi cult placement(multiple (multiparous womenpresentinginlatephaselabor). be required. ing theriskoflosingairwayshouldemergentoperativedelivery continuous spinalanestheticinthesepatientsisameansofminimiz- to intubate,secondarydeformityorairwayanomaly.Aplanned Thepatientconsideredlikelytobeextremelydifficult orimpossible thetic maybeinadequate,resultinginanunacceptableblock. catheter canbeplacedinsuchpatients,thespreadoflocalanes- for labor,oranesthesiasurgicaldelivery.Evenifanepidural Thepatientwithpriorbacksurgerywhodesiresregionalanalgesia cult airway.

ed.

delivery several

61 Obstetric Anesthesia 62 Pain Relief for Labor and Delivery RecommendeddosingregimensareoutlinedinTable to 1mlofdeadspace. with a2mlbolus,sincetheepiduralcatheterandﬁlter maycontainup bolus technique,thecathetershouldbeﬂ increase theriskofrespiratorydepression.Withintermittent must beusedwhenadministeringopioids,asrepeatdosesmay thetic toanesthetizethanthoracicorlumbarnerveroots. relatively large,andmayrequirehigherconcentrationsoflocalanes- input entersthespinalcordatT Painduringearlylaborisprimarilyvisceralinnature,andnociceptive Vaginal Delivery pain (sacralsparing)aslaborprogresses.TheS mon forpatientstoexperienceincreasingrectalpressureorperineal ments overthecourseoflaborandduringdelivery.Itisnotuncom- nerve). Thesedualpainpathwaysresultinvaryinganalgesicrequire- pain arisesduetostimulationofspinalcordatS

Anesthesia: Surgical ∗ Analgesia: Labor Technique Spinal CatheterAnalgesia Table 3.12 bolus dose. continuous spinalcathetershouldbeﬂ ushed with2mlofsalineafter each Anesthesia forVaginalDelivery Theepiduralcatheterandﬁ lter has catastrophic lossofairway. trolled settingofalaborroompotentiallyincreasestherisks likelihood ofahighspinalblock.Ablockintheuncon- Infusion: Continuous Bolus: Intermittent Recommended SolutionsforMaintenanceof 0.5–3.0 ml/hrandtitratedtoaT 0.05 needed (CSEdosesevery1–2hours) height bupivacaine doseasneededtomaintain the desiredblock desired blockheightisobtained.Repeat the0.5ml boluses of0.5 Fentanyl 15mcgfortheinitialdosefollowed by0.5ml

Preservative free0.5 0.25 Solution % –0.125 % Bupivacaine1.75–2.5mg

∗

% Bupivacaine % bupivacaine(2.5mg)every5minuntilthe

> 1 mlofdeadspace;therefore,a % Bupivacaine5.0mg(1ml) 10 –L 1 + Fentanyl2–5mcg/ml@ levels.Aslaborprogresses, ushed aftereachinjection + Fentanyl15–20mcgas 10 block 2 –S 2 –S 4 nerverootsare 4 (thepudendal 3.12

.Caution + • a denseT are usuallyinsufﬁ cient forforcepsdelivery.Foroutletorlowforceps, Thedilutelocalanestheticsolutionsusedtoprovidelaboranalgesia Anesthesia RequirementsforForcepsorVacuumDelivery anesthetic requirements. turn increasestheriskoffetalandmaternalcomplications,aswell head requiremoreforcebytheobstetricianfordelivery,whichin attempted. Ingeneral,higherfetalstationsandrotationofthe Anestheticrequirementsvarywiththetypeofforcepsdelivery fetal distress,arrestedrotationandabnormalposition. cardiovascular orneurologicdisordersthatprecludematernal Indicationsforassistedvaginaldeliveryincludematernalexhaustion, Forceps orVacuumAssistedDelivery • • • • Treatment forBreakthroughPainduringLabor for amid-forcepstrial. vaginal deliveries,whileadenseT T ∗ Agent Vaginal orAssistedDelivery Table 3.13 Lidocaine Chloroprocaine Bupivacaine

Volume shouldbevariedtoindividualpatientrequirements.Adense 10 spines, although high forceps deliveries are almost never indicated. spines, althoughhighforcepsdeliveriesarealmostneverindicated. depending ontherelationoffetalheadtointroitusandischial Forcepsdeliveriesareclassiﬁ ed aseitheroutlet,low,mid,orhigh 5–15 mlofeither2 Forvaginaldelivery,perinealanalgesiacanusuallybeproducedwith anesthetic. remains withintheepiduralspaceandadministeradditionallocal Ifdiscomfortpersists,withdrawtheepiduralcathetersothat3–4cm 25 mcg. Ifineffective,administer5–10mlof2 fentanyl 25mcg. Administer5–10mlofepidural0.125 sensoryblockisdesirableforvaginaldeliveriesorlow-riskassisted 10

sensoryblockwillusuallysufﬁ Recommended EpiduralLocalAnestheticsfor

% Solution Perineal (Sitting) 2 2 0.25 %

lidocaineor2

6 sensoryandmotorblockisdesirable % Forceps Outlet % 2 2 0.25–0.5 chloroprocaine(Table

ce. % % –0.25 lidocainewithfentanyl % Forceps Mid 2 3 0.5 % bupivacainewith (ml) Volume Initial 10–15 10–15 10–15

pushing, 3.13 ). ∗

63 Obstetric Anesthesia 64 Pain Relief for Labor and Delivery • • • hours ofanalgesia. is administerednearthelumbarsympatheticchaintoprovide2–3 originating intheloweruterinesegmentsandcervix.Localanesthetic Thistechniqueproducesanalgesiaforearlylaborbyblockingpain Lumbar SympatheticBlock have contraindicationstoregionalanesthesia. who arenotcandidatesforepiduralorCSEanalgesiaanddo epidural orCSEtechniques.Nevertheless,theycanbeusedinpatients difﬁ analgesia.Ingeneral,alternativetechniquesaretechnicallymore in obstetrics,theydonotaffordtheﬂ exibility ofepiduralorCSE Althoughalternativeregionalanesthetictechniquescanbeused • • • of lowandoutletforceps. Vacuumdeliveriesgenerallyrequireanestheticlevelssimilartothose •

Alternative RegionalAnestheticTechniques

requires adenseT Mid-forcepsdeliverywithheadrotation(mid-forcepstrial)typically treatment. Becauseoftheserisks,and thefactthatthistechniqueis Approximately20 puncture headache. retroperitoneal hematomas,Horner’s Syndrome,andpost-dural as accidentalintravascular,subarachnoid orepiduralinjection, sticks, andoccasionallyproduces signifi cant complications,such fetus, itistechnicallydiffi cult toperform,requiresmultipleneedle Although alumbarsympatheticblockhasminimaleffectsonthe Thetechniqueisineffectiveforlaterphasesoflaborordelivery. 3 the laborroom. preparedforanoperativedelivery(doubleset-up)ratherthanin Considerattemptingamid-forcepstrialintheoperatingroom ing cesareansection. Mid-forcepstrialscanresultinprolongedfetalbradycardia,requir- emergent cesareansectionberequired. for theforcepstrial,andalowerabdominalincisionshouldan anesthetic titratedtoeffect. Eachpatientshouldbeevaluatedindividually,andthedoseoflocal cult toperform,andproducemorefrequentcomplications,than % chloroprocaine15–20mlshouldproducesuffi

% 6 sensoryblock.

ofpatientsdevelophypotensionthat requires

cient anesthesia cient • • • • Technique • • • Technique blocks arerarelyusedinobstetrics. abscesses havebeenreported.Becauseoftheserisks,paracervical hematomas ofthebroadligamentandretropsoalorsubgluteal injection oflocalanestheticintothefetalpresentingpart.Inaddition, absorption, vasoconstrictionofuterinearteriesorfromaccidental intravascular injection,whilefetalbradycardiaresultsfromdirect effects. Maternaltoxicityresultsfromsystemicabsorptionordirect this techniqueproducesahighincidenceofmaternalandfetalside typically occurswithin5minutesandlasts45–120minutes.However, paracervical blockprovidesanalgesiaonlyforearlylabor.Analgesia (Frankenhauser’s) ganglion.Similartoalumbarsympatheticblock, cervix, anduppervaginalcanalbyanesthetizingtheparacervical Thistechniqueproducesanalgesiaoftheloweruterinesegment, Paracervical Block • • • •

Redirecttheneedlemediallybelowtransverseprocess 22 gneedle Followinganegativeaspiration,administer10ml0.5 passed beyondthepsoasfasciaandnearsympathetictrunk Usealossofresistancetechniquetoidentifywhentheneedlehas attachment ofthepsoasmuscle) vertebral column(tipoftheneedleliesjustanteriortomedial Advanceapproximately5cmintotheanterolateralsurfaceof Thepatientisplacedinthesittingposition obstetrics. ineffective fordelivery,lumbarsympatheticblocksarerarelyusedin IdentifythetransverseprocessofL Repeattheprocedureonoppositeside or ropivacaine/1:200,000epinephrinesolution Acontinuouscathetermethodhasalsobeendescribed Thepatientisplacedintothelithotomy position 9 o’clockpositions Approximately10mloflocalanesthetic isinjectedatboththe3and cervix 2–3 cmunderthemucosaof vaginal fornixadjacenttothe Aspecial12–14cm22gneedlewith adepthguardisintroduced

2 vertebrausinga10cm,

% bupivacaine

65 Obstetric Anesthesia 66 Pain Relief for Labor and Delivery ThistechniqueblockstheS Pudendal NerveBlock • catheters, fentanyl, andPCEA. four factorsthataccomplishthisgoal: CSEanalgesia,multiport able goalforanylaborepiduralservice. Thisdiscussionfocuseson Maximizingefficiency withoutcompromisingpatientsafetyisa reason- Technique produce analgesia.Thisblockisalsorarelyusednow. effective analgesiauntilafterdelivery,sinceittakes6–15minutesto unless theblockistimedcorrectly,manypatentsdonotdevelop wall hematomas,andretropsoasorsubglutealabscesses.Inaddition, pudendal arteryortothefetalpresentingpart,formationofvaginal temic toxicityfromintravascularinjection,potentialtraumatothe for late-phaselaboranddelivery.Disadvantagesincluderiskofsys- from theperineum,lowervaginalwall,andvulva.Itismosteffective • • • • during delivery. sia. Anestheticrequirementsvarywiththeamountofinjurysustained must beinjectedsubcutaneouslyandsubmucosallytoprovideanesthe- dural analgesia.Sincetheperineumlacksmajornerves,localanesthetic otomy, andmayalsobeusedtosupplementpoorlyfunctioningepi- analgesia.Itprovidesanesthesiaforrepairoflacerationsoranepisi- technique inpatientsthatdeliverwithoutpreexistingepidural Perinealinfi ltration isthemostcommonlyusedregionalanesthetic Perineal Infi • •

Improving AnestheticEfﬁ and fetalbradycardia Diluteconcentrationsreducetheriskofintravascularabsorption Thepatientisplacedinthelithotomyposition Dilutelocalanesthetic10mlisadministered a lossofresistancetechnique Theneedleisadvancedthroughthesacrospinousligamentbyusing mucosa slightlymedialandposteriortotheischialspine Aspecialneedlewithdepthguardisinsertedintothevaginal Theprocedureisrepeatedontheoppositeside the pudendalartery Aspirationpriortoinjectioniscriticalbecauseoftheproximity ltration

2 –S

nerverootsandthepainoriginating ciencyinObstetrics

epidural

• • pared touniportepiduralcatheters. gesia andthenumberofcathetersthatrequiremanipulationcom- Multiportepiduralcathetersreducetheincidenceofinadequateanal- Epidural Catheters • • Fentanyl • • intermittent bolusandcontinuousinfusion techniques. PCEAreducesanalgesicrequirementsandmotorblockcomparedto PCEA • • 600 manhours/yearat5,000vaginaldeliveriesperyear). be considerablyimprovedinabusylaborservice(estimatedsavingsof Although minimaltimeissavedinanyindividualpatient,efﬁ CSEtechniquesproduceanalgesiafasterthanepiduraltechniques. CSE • • •

Ifanalgesiaisinadequate15minafterinitialdosing: dislodgement. reduce theriskofintravenouscannulationandsubsequentcatheter Insertmultiportcatheters5–6cmintotheepiduralspaceto dence ofvenouscannulation. Flexiblewire-reinforcedepiduralcathetersalsoreducetheinci- • • • sia reduceslocalanestheticusebyapproximately25 Fentanyl2mcg/mladdedtodilutelocalanestheticforlaboranalge- RecommendedPCEAsettingsare 6–12ml/hbasalrate,5–6ml doses. Thepatientself-administersmostof therequiredsupplementary interventions (breakthroughpain). Useofabasalinfusionsigniﬁ cantly reducesanesthesiaprovider Thismaytranslateintofewersideeffects,thusreducingworkload. UseCSEforallpatientsatlowriskofurgentcesareansection. Initiateepiduralinfusionimmediatelyfollowingthespinalinjection. usually 6–7minutes),converttoepiduralanalgesia. following epiduralspacelocationbylossofresistance(timerequired IfCSFisnotobtainedafter2attemptsatspinalneedleplacement bolus, 8–12minlockout, 20–30mlhourlylimit.

Administeradditionallocalanesthetic dural space Withdrawthecathetersothat3–4cmremainswithinepi- patient isnotcomfortablewithin5minutes. Removethecatheterandreplaceit(considerusingCSE)if

% –30

ciency can % .

67 Obstetric Anesthesia 68 Pain Relief for Labor and Delivery cesarean section clinically signifi service, forexample)studiessuggestthatepiduralanalgesiahasno sentinel eventor“catastrophe”model(suddenofferingofanepidural analgesia. delivery, butalsotheprobabilityparturientwillrequestepidural and increasesnotonlythelikelihoodofinstrumentaloroperative mal ordysfunctionallabor,whichinitselfresultslongerlabors do not(Table ing epiduralanalgesiamaybeinherentlydifferentfromthosewho issues relatedtowithholdingtreatment.Inaddition,womenrequest- omization, theinabilitytoblindparticipants,crossover,andethical complicated byretrospectiveanalysis,selectionbias,alackofrand- The majorityofstudiesover10yearsoldaddressingthisissueare and anestheticfactorsinfluenceobstetricoutcome,however. operative deliveries.Numerousindependentmaternal,fetal,obstetric that itprolongslaborandincreasestheincidenceofinstrumental Forseveraldecades,epiduralanalgesiasufferedfromtheperception group. CSE patientshadmuchlowerpainscoresthanthesystemicanalgesia ence betweengroupsincesareandeliveryrateand,ofcourse,the had labor (<4cmcervicaldilatation)foundthatpatientsintheCSEgroup to eitherCSElaboranalgesiaorsystemicIVopioidinearly 8. 7. 6. 5. 4. 3. 2. 1. Epidural Analgesia Table 3.14 Epidural AnalgesiaandtheProgressofLabor Despitelimitationswithanystudydesign,thevastmajorityof disease) Higher riskofoperativedelivery(poorfetal statusormaternal Greater painoflabor(dysfunctionallabor) Have smallerpelvicoutlets Deliver largerbabies More likelytobereceivingoxytocin Slower cervicaldilatationpriortorequesting analgesia Earlier stagesoflaborandwithhigherfetalstation Frequently nulliparous shorter fi rst and secondstagesoflabor.Therewasnodiffer- Characteristics ofParturientsRequesting canteffectontheprogressoflabororincidence 3.14 . Arecentseriesof750parturientsrandomized ). Intensepainmayactuallybeamarkerforabnor- • • • electrical nervestimulation(TENS;Figure and localinfluences(Table Thepopularityofnon-epiduralmethodsvarieswithcultural,regional • via amouthpieceorfacemask. solubility. Theparturientinhalesinconjunctionwitheachcontraction ally uniqueandindividual-specifi gists forepiduralanalgesia,painduringlaboranddeliveryiscontextu- diverse. Despitethejustifi able enthusiasmofobstetricanesthesiolo- Attitudestowardanalgesiaforlaborandanalgesicmethodsare General ConsiderationsandAlternatives 50:50 mixwithoxygen(Figure self-inhalation ofmixtureswithair.ThiswasfollowedbyEntonox,a became popularafterthemanufactureofMinnittapparatusfor Nitrousoxidewasdescribedasananalgesicforlaborpainin1880,and Nitrous Oxide opioids inmuchofEurope. nitrous oxideinhalationintheUKandAustralia;intramuscular (Figure • • •

Systemic andAlternativeAnalgesiaforLabor Nitrousoxidehasveryrapidonsetandoffsetduetolowblood-gas among staffworking intheunit. This raisesconcernsaboutabortion andbonemarroweffects measured, andisbeyondtherecommended limitsof25–100ppm. Atmosphericpollutioninthedelivery unitto300ppmhasbeen more likelyafteropioidanalgesiaor intheobeseparturient. contractions thatleadstomaternal andfetalhypoxemia.Thisis hypocarbia andtetany,compensatory hypoventilationbetween Risksincludeoversedation,dizziness,hyperventilation-induced ally nausea. Sideeffectsincludedrowsiness,reducedawareness,andoccasion- 10 women willuseit. Concentrationsof30 Ifreadyaccesstoepiduralanalgesiaisavailable,50 epidural analgesiabutmostrequestsomemethodofpainrelief. Indevelopedcountries,manyparturientsmanageverywellwithout epidural analgesia(oranyformofpharmacologicalpainrelief). Globally,thevastmajorityofpregnantwomenhavenoaccessto % –40 3.5 ) appearmorewidelyusedinScandinavia;ketamineIndia; % ofparturients.

–70 3.6 ).

3.15 c. %

providemodestanalgesiafor ).Forexample,transcutaneous 3.4 )and“waterblocks” % –90

69 Obstetric Anesthesia 70 Pain Relief for Labor and Delivery Figure 3.4 • • • • Water block • • Transcutaneous electricalnerve stimulation(TENS)/acupuncture • Learned relaxationtechniques/biofeedback/hypnosis • Water baths/massage Speciﬁ • Excellent safetyrecord • Popular andwidelyavailable • High levelsofmaternalsatisfaction • Aid relaxationandabilityto copewithpain In general Labor Analgesia Table 3.15

Otherinhalationalagentscanalsobeused. with 50 anesthetic drugs(e.g.,0.25 Inhalationalofsubhypnoticconcentrationsvariousinhalational drug delivery. Suchtechniquesarenotpopularbecauseofpracticalproblemswith modest efﬁ cacy andshortduration painful injectionmayneedrepetition safe, butmaylimitmobility mainly aplaceboanalgesiceffect motivation orinvestmentoftimemoneyessential readily available;noantenatalpreparationrequired compromised avoid hyperventilationduringbreathingexercisesifthefetusis useful aloneorasadjunctstoothermethods especially ifpatient-controlled no orminimalpainreduction c techniques c % Position ofTENSelectrodes forlabor. nitrousoxideandoxygen)hasshownmodestefﬁ Features ofNonpharmacologicalMethods

% isoﬂ urane or1

% –4.5 % desﬂ urane cacy.

• • promoted ashavingminimalrespiratorydepressanteffects. 1953. Meperidine(pethidine)wasintroducedinthe1940sand attempted untilVirginiaApgardevelopedhersimplescoringsystemin in 1902,butlittlesystematicevaluationofneonataleffectswas Morphineandscopolamineinjectionwereintroducedforlaborpain Opioid Analgesia Int.JObstetAnesth. 1994;3(4):196. blocks, pethidine,nitrousoxide,paracervicalandepiduralblocksinlabour. permission fromRantaP,Jouppilaetal.Parturient’sassessmentofwater (25th) quartile,median,upper(75th)maximum. Reprinted with in theﬁ rst stageoflaborinthevariouspainreliefgroups.Minimum,lower Figure 3.5

and tramadol(amixed agonists (e.g.,meptazinol,pentazocine, nalbuphine,butorphanol) InEuropeandtheUnitedStates,partial shorter, andplasmalevelsremainlow orundetectable. Morphinehasmorefavorablekinetics,theneonatalhalf-lifeis Australia. midwives ispermittedinsomecountries, includingtheUKand agonist) arealsoavailable.Administration ofsomeopioidsby Mean visual analog pain score 10 0 2 4 6 8 Visual painscores(0–10)beforeandaftermanagement Water block Nitrous oxide μ -opioid,serotonergicand Meperidine ( I.M. ) Paracervical μ -or block κ -opioidreceptor α

Epidural -adrenergic

block

71 Obstetric Anesthesia 72 Pain Relief for Labor and Delivery two injections. opioids (morphineormeperidine)areusuallyrestrictedtoone Overthecourseofalabor,intramuscular[IM]orintravenous[IV] Conventional SystemicOpioidAdministration • and PracticeofObstetricAnaesthesia5 th ed . 1984,Wiley-Blackwell. (British oxygen). Reprinted withpermissionfromCrawfordJS, Figure 3.6 • • •

Opioidsdelaygastricemptying. imental promise. are moresensitivetotheireffect,sothesedrugsshowsomeexper- nociceptors sensitizedbychemicalorthermalstimuli,andfemales κ Normeperidine,ametaboliteofmeperidine, isproconvulsant. fetal heartratevariability. their lowmolecularweightsandlipid solubility.Thismaydiminish Bothmeperidineandmorphinecross theplacentarapidlydueto -opioidagonistsareparticularlyeffectiveatpolymodalvisceral diaphragm Sensing (atmosphere) pressure reduction 2nd stage Corrugated hose The Entonoxnitrousoxide/oxygenanalgesicapparatus Face mask

valve (tilting type) 2nd stage

valve 1st stage valve Exhalation

Filter Diaphragm Spring Safety valve 1st stagereduction Gas cylinder and yoke cylinder valve interchangeable Non- Principles

• pg. 1011,CopyrightElsevier(1964). Shnider SMandMoyaF,Effectsofmeperidineonthenewborninfant, published intheAmericanJournalofObstetricsandGynecology,Vol.89, of intramuscularmeperidineadministrationbeforedelivery. This articlewas Figure 3.7 Opioidsgenerallyresultinpoor pain relief,withonly25 • satisfaction. reduced awarenessandnausea, areassociatedwithlowmaternal phoria andrelaxation.Opioidsalso commonlycauseconfusion, or onlyasmallreduction,ofpain scores,butbenefitfromeu- of womenreportingbeneﬁ t. Mostwomen reportnoreduction,

natal respiratorydepression(Figure Althoughdose-related,evenasingledoseofopioidcancauseneo- up to4days. normeperidine (60hours)depressnewbornsuckingbehaviorfor of bothmeperidine(13–23hours)anditsactivemetabolite, Thelongeliminationhalf-livesinnewborns(comparedwithadults) after IMadministration.

Percent 0 – 6 scores Percentage oflowneonatalApgarscoresinrelationtotiming 15 20 25 30 35 10 0 5

89 1234 Hour ofadministrationbeforebirth 177

68 153 75–100 mg 50 mg Meperidine 3.7 25 ); thisismaximal2–3hours 74 453 cases 197 cases 15 49 % –40 %

73 Obstetric Anesthesia 74 Pain Relief for Labor and Delivery cause neonatal depression and require reversal at birth with naloxone. cause neonataldepressionandrequire reversalatbirthwithnaloxone. nyl resultsinmodestanalgesiabuttotal doses remifentanil. Patient-controlledintravenous analgesia(PCIA)withfenta- • • countries becausethedrugischeapandreadilyavailable. (Figure Contractionpainscoresdiminish very littleaftersystemicopioids Patient-Controlled Intravenous Analgesia(PCIA) • labour pain. analgesic effectofsystemicallyadministeredmorphineorpethidineon (pethidine). Reprinted withpermissionfromOlofssonC,etal.Lackof signiﬁ cant effectwasfoundaftereachdose._,morphine;_,meperidine Values arepresentedinboxplot(medianwithinterquartilerange).No (dose 0.05mg/kgbodyweight)ormeperidine0.5weight). Figure 3.8

Non-opioidsystemicanalgesiawithketamineisemployedinsome Maternalamnesiaandaspirationarerecognizedhazards. labor oratdelivery. Smallintravenousdosesresultin3–5minutesofanalgesialate after abolusof0.25mg/kg,reduceslaborpainscores. Intravenousorsubcutaneousketamineinfusion(250mcg/kg/h), 3.8 Mean visual analog pain score ),withtheexceptionofpotent Br JObstetGyenaecol . 1996;103:969. Pain intensitybeforeandfollowingintravenousmorphine 10 20 30 40 50 0 Before

First dose μ -opioid receptor agonist -opioidreceptoragonist > 600 mcg are likely to 600mcgarelikelyto Second dose

ing oxygentherapyinapproximately15 Remifentailoftencausesmaternaldrowsinessandhypoxemia,requir- • • • • should beconsidered. Whenusing“alternativetechniques” forlaboranalgesia,severalpoints Alternative Techniques use duringlaborbeing“off-label.” opioid remifentanilisbeingusedforPCIAinmanycountries,despite dication torequestedepiduralanalgesia),thepotentultra-shortacting Althoughusuallyreservedforspeciﬁ c indications(suchasacontrain- (Table is avalidoptionwhenepiduraltechniquescannotbeemployed lines areessential(Table of drug,soprotocol-basedmonitoringandapplicationsafetyguide- emia afterarapidbolusoraccidentalinjectionofverysmallvolumes profound respiratorydepression,musclerigidityandseverehypox- • •

Remifentanil— RemifentanilPCIAisnotaseffectiveepiduralanalgesia,but labor. the fetus;neonatesrarelyappearaffectedafterremifentanilin Showsveryrapidplacentaltransfer,butisrapidlymetabolizedby to tissueandbloodesterasemetabolism. during druginfusion),independentofthedurationinfusion,due depression orfetalheartrateeffects werereported. remifentanil PCIA.Mildsedationoccurred in4%butnorespiratory labor, butlowerpainscoresthanthosereportedinmostseriesof resulted inanalgesiathatwasnotasgoodneuraxialfor 0.025–0.15 mcg/kg/min(meaninfusionrate0.075–0.1mcg/kg/min) tinuous infusionoranalone.Inonestudy,of Alternativeregimensprovideﬁ xed bolusdosesbutatitrated con- occurring afterthecontraction. repeated dosing,despitepeakeffectsiteconcentrationsusually Shortlockoutintervals(1–3minutes)areusedtoallowfrequent quently requiredtooptimizeoutcomes. (0.1–0.5 mcg/kg)over1minute,oradjustmentofinfusion,isfre- Theoptimumdosingregimenisunclear,buttitrationofbolusdoses for plasmaconcentrationtofallby50 Hasaveryshort,3-minute,context-sensitivehalf-life(i.e.,thetime IV administration. Reachespeakeffectsiteconcentrationwithin2–3minutesof 3.17 forapotentialregimen).

3.16 ).

% % ofparturients.Itcancause

fromasteady-statelevel

75 Obstetric Anesthesia 76 Pain Relief for Labor and Delivery • • • • • • • during Labor Table 3.17 Potential DosingRegimenforRemifentanilPCIA Labor Analgesia Table 3.16 • • • • • • • • •

with the experience of childbirth is largely determined by perception with theexperienceofchildbirthislargelydeterminedbyperception nous, inhaledorepidural,shouldbeencouraged.Maternalsatisfaction Patient-controlledtechniques,whethernon-pharmacological,intrave- express thatlaborwasapositiveexperience. experience modestreductionsinpainandaremorelikelyto pies suchaswaterbathsorcounter-irritationbybackrubbing, tion, breathingexercises,psychologicalsupportandphysicalthera- Womenaccompaniedbyaduola(supportperson)orusingrelaxa- ologists aswellmidwivescanplayanimportantrole. labor isimportant.Patienteducationveryhelpful,andanesthesi- Forsomepatients,useofaholisticapproachtopreparationfor remains <90 Encourage thewomantobreatheifSpO patient-controlled analgesiavariables Give naloxone200mcgIVandstopremifentaniladministration ifSpO • Continuous infusion(either routineorasanextraifmaximumbolus doses proveinadequate) • Lockout interval 1minute(1–3mindependingonpumpused) Dosing regimenmustbeprotocol-based dead space Demand bolus0.4mcg/kg (maximumdose40mcg) intravenous infusionlineorlimbwithananti-reﬂ ux valveandminimal (e.g., 20mcg/ml) Administer remifentanilusingadedicatedpumpvia Choose aﬁ xed concentrationofremifentanilfortheprotocol monitoring ofarterialoxyhemoglobinsaturation(SpO depression Use continuousorregular,frequentintermittentpulseoximetry or intravenouscannula Provide continuousobservationforsedationandrespiratory Use adedicatedadministrationlineandavoiddeadspacewithintubing Use dedicatedequipment,clearlylabeled Give supplementaloxygenifSpO

titrate down to0.1mcg/kgifsideeffectsexcessive 0.05 mcg/kg/min,titrated tomaximum0.15mcg/kg/min Safety GuidelineswhenUsingRemifentanilfor % 2 remains<95 2 <95 % but % onair&modifythe

> 90 2 ) % onair

especiallyinScandinaviancountries. 12. 11. 10. used indevelopedcountries,andarenotofprovenefﬁ neous electricalnervestimulation(TENS).Thesemethodsarerarely Non-pharmacologicalternativesincludeacupunctureandtranscuta-

Further Reading • •

5. 4. 3. 2. 9. 1. 8. 7. 6.

Atechniqueknownas“waterblock”issometimesemployed, decision making. decision making. of personalcontrol,rapportwithsupportstaff,andparticipationin to 60minutes. This istransientlypainful butreducesbackpainduringlaborforup corresponding tothesacralborders. Sterilewater0.1mLisinjectedintra-orsubcutaneouslyat4points

relief: Anopenstudyof205parturients continuous intravenousadministrationofremifentanilforbirthpain D’Onofrio P , Novelli AM , Mecacci F , ClinObstetGynecol. 2003 ; 46 : D’Angelo 623 - R 632 . 2005 ; . 103 New Techniquesforlaboranalgesia:PCEAand CSE : . anesthesia workforcesurvey:twenty-yearupdate 645 . - 653 . Bucklin BA A systematicreview , . Hawkins JL , Bricker L Anderson , JR , Lavender etal. T Obstetric . Parenteral opioidsforlaborpainrelief: AnesthAnalg. 2008 ; 106 : Rowlington 1,333 - JC 336 AmJObstetGynecol. . . 2002 Lipid rescue:a stepforwardinpatientsafety?Likelyso! ; 186 : Rosen S110 - M 126 AnesthAnalg . . . 2010 Nitrous oxideforrelief oflaborpain:Asystematicreview ; . 111 : Palmer 1476 - CM 1479 . . Continuous spinalanesthesiaandanalgesiainobstetrics . 2008 ; 17 : should beroutinelyavailableforuseinlabour 336 . - 342 . Hill D 103 , - 105 . Van deVelde M . Remifentanil patient-controlledanalgesia and delivery . Bloom SL , McIntire DD , Kelly MA , etal. Lack ofeffectwalkingon labor for obstetricanesthesia:update2006 . Hawkins JL 1998 ; . 280 American SocietyofAnesthesiologists’practiceguidelines : opioid analgesiaontheprogressoflabor:ameta-analysis 2105 . - 2110 . Halpern SH AnesthAnalg. , 2009 Leighton ; 108 BL : , Halpern 921 - SH 929 Ohlsson , . 1922 A - , 1924 Carvalho . B . Patient-controlled epiduralanalgesiaforlabor . N EnglJMed.

Am JObstetGynecol. 2002 ; 186 : S94 - 109 . 1998 ; 339 : 76 - 79 .

et al . The efﬁ et al . Effect ofepiduralvsparenteral Int JObstetAnesth. 2007 ; 16 : .

Anesth. Analg. 2009 ; 109 : Int JObstetAnesth. Anesthesiology. cacy andsafetyof cacy. JAMA.

77 Obstetric Anesthesia 78 Pain Relief for Labor and Delivery 14. 13.

Wong CA Delivery. Chapter23:429-92 . In: , eds. Chestnut DH Wong , CA Med. Polley . LS 2005 Epidural andSpinalAnalgesia/AnesthesiaforLaborVaginal , ; delivery withneuraxialanalgesiagivenearlyversuslateinlabor 352 . : Tsen 655 - LC 665 , . Wong CA , Scavone BM , Peaceman AM , ( 4 th

Ed . ) Philadelphia, PA : Mosby Elsevier ; 2009 . Chestnut’s ObstetricAnesthesiaPrinciplesandPractice et al . The riskofcesarean N EnglJ to developamutuallyagreeableplan fortheanesthetic. sary toexplaintheprocedurethoroughly, andworkwiththepatient possible, theanesthesiologistshould takethetimeandeffortneces- numerous questionsabouttheirimpending anesthesia.Whenever circumstances oftenresultinwomen (andtheirspouses)having their anxietyabouthavingamajoroperationwhilewideawake,these concern manywomenhaveaboutanestheticeffectsonthebaby,and not most,itisalsotheﬁ rst time theywillhavesurgery.Giventhe ishing. Formostwomentheprocedureisnoturgentandformany,if operation indevelopedcountriestoday,andshowsnosignofdimin- Cesareandeliveryisprobablythemostfrequentlyperformedsurgical What toTelltheWoman Management ofComplicationsGeneralAnesthesia General Anesthesia Management ofEarlyComplicationsRegionalAnesthesia Dealing withFailedRegionalAnesthesia Continuous SpinalAnesthesia Combined Spinal-EpiduralAnesthesia(CSEA) Epidural Anesthesia Spinal Anesthesia Monitoring Patient Preparation Obtaining ConsentforAnesthesia What toTelltheWoman Michael J. Delivery Paech , FANZCA AnesthesiaforCesarean Chapter 4 97 100 89 132 106 79 114 80 116 110

144 120

79 80 Anesthesia for Cesarean Delivery • • • while facingthepossiblelossofachildorseriouspersonalrisks. ronment, whensurroundedbyalargenumberofunfamiliarstaff,and options. Inurgentcases,consentisoftengiveninabusy,noisyenvi- while inseverepainorundergreatstress,withlittletimetorefl surgery whilefullyalertandpotentiallyconsentingtomajor Elements uniquetocesareandeliveryincludehavingmajor parents, butsometimesgeneratesconsiderablepsychologicalstress. Cesareandeliveryrepresentsanoccasionofgreatsignifi cance tothe • • • • • There arethreemainreasonsforthisemphasisonregional Consequently thepublichascometoexpectaregionalanesthetic. Thekeyelementsdefi ning adequateconsent(alsoseeChapter13)are: nonelectivecesareandeliveries(80 anesthesia, whichisnowusedinthevastmajorityofelectiveand Deaths intheUnitedKingdomrecommendedgreateruseofregional The1982–1984reportoftheConfi dential EnquiriesintoMaternal Reasons forRecommendingRegionalAnesthesia

Obtaining ConsentforAnesthesia Generalprinciplestonoteare: explanationofrisks,beneﬁ answeringanyquestionsthepatientmayhave Greatermaternalsafetycomparedwithgeneralanesthesia • • disclosure ofcomplications. anesthesia (andanalgesia)andare not mademoreanxiousbyfull Mostwomenwanttomaximizethe informationtheyreceiveabout may contributetoavoidinglitigation shouldcomplicationsarise. Spendingtimeobtaininginformedconsent establishesrapportand Enhancedparentalsatisfaction(Table Lessneonataldepressionatbirth. explanationoftheprocedure

cate farfewerdeathsfromregionalanesthesia. Enquiries intoMaternalandChildHealth(CEMACH),alsoindi- Maternal DeathsintheUnitedKingdom,andConﬁ dential ThematernalmortalitydatafromtheConﬁdential Enquiriesinto anesthesia, especiallygeneralhavefallen. those ofregionalanesthesia,althoughratesforalltypes 1997–2002 indicatecasefatalityratesforgeneralanesthesiatwice EpidemiologicaldatafromtheUnitedStatesduringperiod tsandalternativeoptions

–95 4.1 ). % )indevelopedcountries.

techniques. techniques.

ect on

• • • • particularinclude: Someofthedifficultiesfacingobstetricanesthesiologistin • Anesthesia cannotbeestablishedasquicklygeneralanesthesia Potential forpost-duralpuncture headache symptoms, andfetalcompromise Potential forhypotension,leading tomaternalsyncope,nauseaorvomiting Disadvantages • • • Consumer satisfaction • • • • • Desirable postoperativeoutcomes • Neonatal outcome • • Maternal safety Advantages Anesthesia forCesareanDelivery Table 4.1

Providing an opportunity for the woman to ask questions is important. Providinganopportunityforthewomantoaskquestionsisimportant. the timeofsurgery. preadmission clinics,improvesopportunitiesforfrankdiscussionat education resourcesintheantenatalperiod,atanestheticor Theprovisionofinformationthroughpamphletsorotherpatient can beusedasachecklistoraid). Thedetailsofthediscussionshouldbedocumented(consentforms However, inveryfew(only20 anesthesia withinminutesofmeeting thepatientforfi Theanesthesiologistisoftenexpected toprovideeffectiveandsafe constrained.Nevertheless, eveninemergentsituations, itis Theamountoftimeforinformed discussion maybesignifi cantly intervention. was there Early attachmentofinfanttothebreast experience forparents Early skin-to-skincontactimprovesmaternal-infantbonding Presence ofmotherandfather/supportpersonatbirthenhances birth High qualityanalgesiaachievablebyseveralmeans Early resumptionoforalintake Early interactionwiththenewborn Delayed recoveryofconsciousnessanddrowsinessavoided Less riskofnauseaandvomiting general anesthesia Immediate resuscitationatbirthlesslikelytoberequiredthan after gastric contentorhypoxicorganinjury Less bloodloss No airwaymanagementdiffi culties withconsequentrisksofaspiration Advantages andDisadvantagesofRegional no priorindicationofthepotentialneed foroperative

% ) ofunplannedcesareandeliveries

rst time. rst

81 Obstetric Anesthesia 82 Anesthesia for Cesarean Delivery and aboutconversiontogeneralanesthesia.Inaddition, demonstrate thattheyhadtakenreasonablestepstowarnaboutit, Ifpainleadstoacomplaint,theanesthesiologistshouldbeable • • • • • • sensations.Thepatientshouldbeawarethat. cesarean delivery,soitiscriticallyimportanttoexplaincommon from maternaldissatisfactionwiththemanagementofpainduring Closedclaimsandsimilarstudiesindicatethatlitigationoftenresults order drugtherapy,ifnecessary. has avaluableopportunitytoestablishrapport,assuageanxieties,and Whenobtainingconsentforaregionalanesthetic,theanesthesiologist Consent forRegionalAnesthesia • • • Manycontraindicationstoregionalanesthesia (Table Dealing withaPatientRefusingRegionalAnesthesia • of choice.Despite this,somewomenwillinitially refuse regional In mostinstances, regionalanesthesiawillremain theanesthetic

Moreseverepainwillnotbeignored. the situation). • Pressureandstretchingarenormalpartsoftheexperience. tion oftopicallocalanestheticcream,iftimeallows,maybehelpful. minimized byempatheticreassurance.Inrareinstances,theapplica- Thefearofpainduringneedleinsertionorsurgerycanbe ment planagreedupon(Table Theeffectsofregionalanesthesiashouldbeexplained,andatreat- or concernswhichmayremain. Alwaysvisitthewomanpostoperatively,toansweranyquestions ination ofvitalsignsandtheairway. while obtainingabriefhistoryandperformingbasicphysicalexam- importanttoexplainasmuchpossibleaboutwhatishappening, Mildintraoperativepainisnotuncommon(5 Theregionaltechniqueusedmusthavebeenreasonable. Painshouldhavebeentreatedwhen itwasreported. to surgery. Theblockshouldhavebeentestedandnotedtobeadequateprior Theanesthesiologistshouldhaveprovided follow-upandsupport.

amnesic effectsthatdetractfromthebirthexperience. affect neonataloutcomes,butshouldbetimedtoavoidmaternal 0.1–0.25 mcg/kg)maybeconsidered.Thesedrugsareunlikelyto midazolam 1–2mg,fentanyl0.5–1mcg/kgorremifentanil Althoughrarelynecessary,theuseoflightsedation(intravenous

4.2 ).

% –20 % 4.3 dependingon

) arerelative.

• • the surgery,orbecauseofculturalunfamiliarity.Inthissituation- anesthesia duetofearofpaineitherduringblockplacementor classiﬁ cation canbeuseful in determininganappropriate Cesareandeliveries canbeclassiﬁ ed bytheirdegreeofurgency,andthis Regional AnesthesiaforNonelectiveCesareanDelivery Death Extremely rarecomplications Neurological injury Highblock requiringintubation Neuraxial infection Rare complications Post-dural punctureheadache Infrequent complications to generalanesthesia) Pain (incidence/location/timing/severity/treatment planincludingconversion Abdominalstretchingandpressure Intraoperative events Insertionsitetenderness Itch Syncope Nauseaandvomiting Shaking Post-block effects Postoperativeanalgesicoptions(prosandcons,sideeffects) Intraoperative positioning Onsetandtestingofblock Positioningandneedleinsertion Procedural events Morealertneonateatbirth Possiblylowermortalityrate(extremelyrare) Fewerlife-threateningcomplications(high-block,localanesthetictoxicity) Enjoymentofthebirthexperience(includingfather) Advantages comparedwithgeneralanesthesia Anesthesia Table 4.2

any reasonedargument. attempts atinsertionorseverepain duringsurgery)andwillrefuse distressing experiencepreviously (forexample,multiplefailed Respectthepatient’sﬁ nal decision.Somewomenmayhavehada realistic discussion,pointingouttheadvantages. Attempttoallaythepatient’sconcernswithcompassionatebut

Discussion PointsatConsentforRegional

anesthetic

83 Obstetric Anesthesia 84 Anesthesia for Cesarean Delivery • anesthesia.Theseinclude: a numberofotherfactorshaveledtodecreasedusegeneral compromise(Table the parturient(5–15minutes)whenthereislife-threateningfetal of regionalanesthesiaorasthequickestmeansanesthetizing anesthesia isoccasionallypreferable,andmaybemandatedbyfailure spinal anesthesiacanbeestablished(within10–20minutes).General rapidly achieveasurgicalanestheticblock(within10–20minutes),or 2 and3),ifafunctioningepiduralcatheterisinplace,itcanbeusedto (Table • • such asearlyintravenous accessandplacementofanepidural orspinal antepartum consultationfromananesthesiologist” andthatstrategies suggests thatwhenriskfactorsareidentiﬁ ed, “theobstetrician obtain TheAmericanCollegeofObstetricians andGynecologists(ACOG) • • • • • Vertebral canalhematomarisk • Maternal hypovolemiawithcardiovascular instability • • • Exacerbation ofpreexisting disease states Severe immunocompromise inthepresenceofotherriskfactors • • Infection • Infection risk Anesthesia Table 4.3

Inadditiontotheadvantagesofregionalanesthesianotedabove, greateruseofepiduralanalgesiaduringlabor regional anesthesiaissafe liberalizationofthelimitstraditionallyappliedtodeﬁ ne when greaterexpertiseinrapidlyestablishing saferegionalanesthesia. anesthetic assessmentandpreparation foroperativedelivery betterinterdisciplinarycommunication,leadingtoearliermaternal vertebral canalvascularpathology anticoagulation coagulopathy severe thrombocytopenia obstetric ornon-obstetricmajorhemorrhage severe pulmonaryhypertension severe aorticstenosis raised intracranialpressure local skininfectionatinsertionsite septic shock bacteremia andsepsis 4.3 ). Foremergencyorurgentcesareandelivery(Categories1, Potential ContraindicationstoRegional 4.4 ).

• • document indetailhowherdecisionwasreached. Ifthepatient’srequestforgeneralanesthesiaappearsinadvisable, • number oftopicsneedtobediscussed(Table Whenobtainingconsentforgeneralanesthesiacesareandelivery,a Consent forGeneralAnesthesia hazardous”. tion ofgeneralanesthesiainwomenwhomthiswouldbeespecially catheter bedeveloped“tominimizetheneedforemergencyinduc- An uncooperativepatient Respiratory diseasewhenpostoperativeventilationwillberequired or semi-supineposition Cardiac orrespiratorydiseasewhenthepatientcannottoleratesupine resistance mayleadtoacriticalevent Cardiac diseasewhenreductioninsystemicorpulmonaryvascular uncontrolled byothermeans When intraoperativepainunderregionalanesthesiaissevereor mother isnotfullyalert,medicallystable,orhasfocalneurologicalsigns Following eclampsiaorotherseizurematernalcollapse,whenthe After twoattemptstoestablishregionalanesthesiahavefailed mother) Category 1cesareandelivery(immediatethreattothelifeoffetusor Regional, Anesthesia Table 4.5 ∗ mother andthemedicalteam Category 4:Electivecesarean deliveryscheduledatatimetosuitthe is nomaternalorfetalcompromise Category 3:Non-electivecesarean whereearlydeliveryisneededbutthere maternal orfetalcompromisethatisnotimmediatelylife-threatening Category 2:Non-electivecesarean wheredeliveryisindicatedbecauseof threat tothelifeofmotherorfetus Category 1:Non-electivecesareandeliverybecausethereisanimmediate Table 4.4 2000;93:346–350.

Adoptedbymanyhospitalsbased onLucasDN,etal. Commoneventsandsymptoms Beneﬁ Preparation,andpostoperativesequele tsandrisks When toConsiderGeneral,Ratherthan Categorization ofCesareanDelivery

4.6 ).Placeemphasison:

J RoyalSocMed. ∗

85 Obstetric Anesthesia 86 Anesthesia for Cesarean Delivery • • that neonatalumbilicalcordbloodpH andbasedeﬁ the methodofanesthesia. delivery,neonatalacidbasebalancecanbeimprovedirrespectiveof delivery ofhealthywomenandfetuses.Atemergencycesarean method ofanesthesiaispoorqualityandpertainsonlytoelective Muchoftheevidenceaboutneonataloutcomeanditsrelationto Factors AffectingNeonatalOutcome Explaining theEffectsof AnesthesiaontheBaby • • • • • • • • • Anesthesia Table 4.6 •

Meta-analysiscomparingregionaland generalanesthesiasuggests the durationof uterineincisiontodeliveryinterval affectedbytheseverityandduration ofmaternalhypotensionand (although themagnitudeofdifference issmall) worsewithspinalanesthesiacompared withgeneralanesthesia • • • Extremely rarecomplications • • • Rare complications • • • • Infrequent complications • Postoperative analgesia • Common postoperativesequelae Aspiration prophylaxis • Preoxygenation Greater riskoflife-threateningcomplications(hypoxemia,aspiration, • anaphylaxis) • Procedural events • Disadvantages comparedwithregionalanesthesia

Neurological injury Death Aspiration Dental injury Awareness Hypoxemia Failed intubation Coughing Nausea andvomiting Sore throat Drowsiness Cricoid pressure Monitoring Missing thebirthexperience(includingfather) Possibly highermortalityrate(extremelyrare) Assisted ventilationoftheneonatemorelikely Discussion PointsatConsentforGeneral

citis:

• • • Effects ofRegionalAnesthesia • • Maternal Elsevier. status ofnewborns,89–93,Copyright(1996), withpermissionfrom Anaesthetic techniqueforelectivecaesarean sectionandneurobehavioural from the Umbilical vein pH Elective CesareanDelivery1kPa=7.5mmHg Table 4.7 PO pH Umbilical artery PO pH Base defi Values aremean(SD). Base defi Base defi pO

when establishingregionalanesthesia). equate pelvictilt(indicatingthelateralpositionmaybepreferable possiblymadeworsebythearterialocclusionassociatedwithinad- OnlyaVenturitypefacemaskdeliveringatleast60 undetectable. Fetalandneonataleffectsoflocalanestheticoropioidareusually or metaraminol. artery pHandhigherbasedeﬁ cit thancontrolwithphenylephrine Controlofhypotensionwithephedrineresultsinlowerumbilical or profoundhypotensionareavoided(Table unaffected byregionalanesthesia,providedephedrineandsustained Thebiochemicalandmetabolicconditionofthehealthyfetusis ered ifthefetusisthoughttobehypoxemic. oxygen willimprovefetaloxygenation,butthisshouldbeconsid- 2 2 2 (kPa)

ct(mll (mmol/l) cit cit cit International JournalofObstetricAnesthesia et al. , Vol.2.MahajanJ, Anesthesia andNeonatalAcid-BaseStatusat

a P <0.01comparedwithothergroups. Reprinted 7.36 (0.04) .8(.4 .9(.7 7.28 (0.02) 7.29 (0.07) 7.28 (0.04) 7.34 (0.05) 7.34 (0.04) 7.33 (0.05) 3 .0(.7 17 15) 32.10 (1.50) 31.73 (1.56) 30.80 (1.37) .0(.2 .3(.3 3.21 (1.79) 2.43 (2.13) 5.10 (1.82) .0(.9 .1(.3 2.87 (0.23) 2.91 (0.23) 2.90 (0.19) 5.92 (0.51) 5.67 (0.36) 5.80 (0.33) .1(.9 .8(.9 4.53 (2.01) 4.58 (1.99) 4.31(1.79) 4.78 (2.23) 4.80 (1.81) 4.00(2.10) (n =30) General a

(n =30) Epidural .4(.6 7.42 (0.03) 7.44 (0.06)

4.7 ). (n =30) Spinal % inspired

87 Obstetric Anesthesia 88 Anesthesia for Cesarean Delivery • 1999, Elsevier. Anesthesia forcesareansection.In:Chestnut DH, BrJAnaesth. 56:1011. (1984) Fetal-neonatalstatusfollowingcesarean sectionforfetaldistress. Reprinted withpermissionfromReisnerLSandLinD, urgent cesareansectionforfetaldistress. DataderivedfromMarx,G.F.,etal. Figure 4.1 • • Effects ofGeneralAnesthesia •

Percentage 100 changes ininfantresponsivenessandsucking. Uncorrectedhypotensionmaycausesubtleneurobehavioral Fetaloxygenationisimprovedbygivingthewoman100 transfer. Fetaldrugexposureislimitedbyfactorsregulatingplacental after aprolongedinductiontodeliveryinterval( tory depressanteffectsofopioidmaybeevidentatbirth,especially Thesedativeeffectsoftheinhalationalanestheticsandrespira- shown. oxygen, butnoimprovementinneonatalclinicaloutcomehasbeen • • 20 40 60 80 0

anesthesia (Figure and neonatalintubationmaybemorelikelythanafterregional Incesareandeliveryforfetalcompromise,lowerApgarscores breaths). (although usuallyconfinedtoassistanceinestablishingfirst ble, becauseactiveresuscitationismorelikelytobenecessary Apersonexperiencedinneonatalresuscitationshouldbeavaila- eea Spinal General Inﬂ uence ofanesthetictechniqueonneonatalconditionafter Apgar 5–7 Apgar 1–4 Apgar 8–10 1 minscore 4.1 ). pdrlGnrlSpinal General Epidural Obstetric Anesthesia2 nd ed.

5 minscore > 15minutes). % inspired Epidural

• • including: Ideally,athoroughpre-anesthesiaassessmentshouldbecompleted, Preoperative Assessment • elective cesareandelivery. recommend afastingintervalofatleast6hoursforsolidspriorto TheAmericanSocietyofAnesthesiologist’s(ASA)practiceguidelines Fasting • • • • Spinal anatomy Placental location Relevant imaging Bloodgroupandholdorbloodcrossmatch Platelet Hemoglobinconcentration/hematocrit count Relevant investigationsandlaboratorytests Relevant surfacelandmarks,especiallyvertebralcolumn Fetalstatus duringpregnancyandcurrentfetalstatus Presence ofrupturedmembranesorlabor Pregnancy-related diseasesanddisorderstheirmanagement Gestational Indication forcesareandelivery age Current obstetrichistory Past obstetrichistory Pregnancy andCesareanDelivery Table 4.8

Patient Preparation fasting status.Inparturientswhohavenotbeen“nilperoris”(NPO), Inmanycases,theurgencyofdeliverywilltakeprecedenceover surgicaldelivery. alone, duetodifﬁ culty predictingwhichwomenareatriskof Inlaboringwomen,oralintakeshouldbelimitedtoclearﬂ uids Patientcharacteristics(age,weight,fastingstatus). Pastmedicalandsurgicalhistory. Systemsreview,medicationsandallergies. (Table Additionalelementsrelatedtopregnancyandcesareandelivery. systems, andtherelevantairwayinvestigationsimaging. Physicalexaminationfocusingonthecardiovascularandrespiratory 4.8 ) Pre-Anesthesia AssessmentRelatedto

89 Obstetric Anesthesia 90 Anesthesia for Cesarean Delivery of knownorsuspectedhighriskairway diffi based systemsofreferraltotheanesthesiologydepartmentwomen admission orasearlypossibleinlabor.Ideallytherearehospital- induced. ably housedbesidetheoperatingtablewhengeneralanesthesiais issue, andadiffi ment planning. Ahighfalsepositiverate(lowspecifi city) isnotan good airwayassessmentwillbepredictiveandcriticaltomanage- block areveryrareexceptindevelopingcountries). anesthesia indevelopedcountries(fatalcomplicationsofregional arrest, representsthemostcommonfatalcomplicationofobstetric dence 1in250–1500)leadingtohypoxemia,aspiration,andcardiac Diffi cult intubation(incidence1in30–60)orfailed(inci- Airway Assessment over thatofthefetus. preparation time.Thelifeofthemothermustalwaystakepriority Chapter 15)mayimprovethefetalconditionsignifi cantly andgain diate threattothelifeoffetus,intrauterineresuscitation(see and anesthesiologists.Evenifdeliveryappearsmandatedbyanimme- team includingobstetricians,obstetricphysicians,neonatologists careful consideration,preferablydecidedbyamultidisciplinary tate afatalevent. examples ofconditionsinwhichinductionanesthesiamayprecipi- Undiagnosed orinadequatelytreatedsepsisandcardiacfailureare the failureofstafftorecognizeseveritymaternalillness. urgency ofdelivery.RecentdatafromtheCEMACHdatabasenoted Preoperativeoptimizationisanimportantgoal,irrespectiveofthe Preoperative Optimization Risk FactorsforaDiffi (Table Riskfactorsmustbesoughtandacomprehensive evaluation ous itmaynotreflect thepatient’scurrentcondition. airway managementisvaluable,but unless reasonablycontemporane- Airwayassessmentshouldberoutineandperformedatpatient Althoughdifficultiesmayariseunexpectedly,inmanycases Thetimingofdeliveryincriticallyillpregnantwomenrequires ration. regional anesthesiaispreferableintermsofavoidingtheriskaspi- 4.9

andFigure cultairwaycartshouldbeavailableinallunits,prefer-

4.2 cult Airway ).Reviewofdocumentationprevious

culty.

performed performed intubation: aretrospectivestudy.Anaesthesia 1987;42:488. with permissionfromSamsoonGLTand YountJRB.Diffi Diffi cult intubationinobstetrics.Anaesthesia1994; 39:1105-1111.Reprinted J. 1985; 32: 429-434.Lowerpanelmodifi ed fromComarck RS andLehaneJ. clinical signtopredictdiffi cult intubation:aprospectivestudy.CanAnaesthSoc direct laryngoscopicview.Upperpanelmodifi ed fromMallampatiSR,etal.A pharyngeal structuresduringairwayassessment. Lowerpanel:Classifi Figure 4.2 History Table 4.9 • • • • • • • • • Examination andTests • • and multiplefactorsmultiplytherelativeriskofdiffi cult airwaymanagement. Combinations (e.g.,Mallampatitestandupper-lipbitetest)aremoreaccurate, Mostindividualtestsshowpoorspecifi city andpositivepredictivevalue. • •

Previous anesthesiaandairwaymanagementdetails(knowndiffi Height tothyromentaldistanceratio teeth ortobiteupperlip) Receding mandible (inter-incisor distance<3cm) Prominent upperincisors(inabilitytoprotrudelowerteethpast Temporomandibular jointdysfunctionorreducedmouthopening Small oralcavityorlargetongue(Grade34Mallampatiview) Reduced laryngoscopeaccess(e.g.,anteriorneckmassorlargebreasts) due tolargehairknotsorbuns) Short neck(thyromentaldistance<6cm) intubation) Limited cervicalspineoratlanto-occipitaljointextension(including Morbid obesity(associatedwithdiffi cult ventilationand preeclampsia) Breath sounds(stridorassociatedwithairwayinfectionorsevere Poor dentition(missing,loose,orprostheticteeth) Oral pathology Class I ClassIV ClassIII Class II Class I Airway assessment.Upperpanel:classifi cation of viewofthe Indicators ofPotentialDifficulty withtheAirway ls ICasIIClassIV ClassIII Class II > 21 cult tracheal cult culty) cation of cation

91 Obstetric Anesthesia 92 Anesthesia for Cesarean Delivery • woman liessupine. aorta (usuallyjustbelowthebifurcationofiliacarteries)when 20 weeksgestation)itmayobstructtheinferiorvenacavaand/or Oncethegraviduterusrisesfromwithinpelvis(atapproximately Physiology Minimization ofAortocavalCompression injury. Experiencedassistantsareessential. The patientshouldbewarnedaboutpossibledentalandsofttissue intubation, andbothsupraglottictranstrachealairwaydevices. with andhavepreparedarangeofequipmentforintubation,aidsto Ifdifficultyisanticipatedtheanesthesiologistshouldbefamiliar • • • • for theobstetricpopulation.Suchplansinclude: such asthoseendorsedbytheASA,withappropriatemodiﬁ cations • • aortocaval compressionhascontributed tocasefatalities. Incombinationwithotherevents, the hemodynamicdisturbanceof

Airwaymanagementplansarebestbasedonestablishedalgorithms, of venousfl ow viatheazygoussystem)and10 partial orcompleteinferiorvenacavalobstruction(withdiversion Atterm,imagingshowsthat90 management. appears necessaryinawomanathighriskofdifficultairway Useofawakefiberopticintubationwhengeneralanesthesia edema duetodeterioratingpreeclampsia). within theairway(e.g.,mucosalortongueswellinglaryngeal Repeatairwayassessmentinlaboringwomentoexcludechanges induction ofsurgicalanesthesiaifnecessary. known orsuspecteddiffi cult intubation).Thisallowsfor rapid increased riskofdiffi cultairwaymanagement (e.g.,morbidlyobese, Earlyplacementofanepiduralcatheterduringlaborinwomenat mucosa). epistaxis (duetoincreasedvascularityandedemaofthenasal Avoidingnasalinstrumentationifpossiblebecauseoftherisk Aorticobstructionandimpairedplacentalfl symptomatic (syncope,nausea)duetoreducedcerebralperfusion. tion, andreducedcardiacoutput. reduction inbloodpressure,impaired compensatoryvasoconstric- Theseeffectsareexaggeratedbyanesthesia, duetovenouspooling, cause fetalhypoxemiaandacidosis.

ofwomenlyingsupinehave

ow maybesilentbut

% –15

% become

• • • • fatal complicationofaspirationinpregnantwomen. Hallin1940,andMendelson1946,drewattentiontothepotentially Aspiration Risk Gastric Content Prophylaxis againstPulmonaryAspirationof aortic compressionmaypersistatupto30-degreetilt). safety, butuptoandatleast15-degreetiltisrecommended(although The degreeoftiltwillbelimitedbysurgicalconsiderationsandpatient devices canbeused,ortheoperatingtableinclinedlaterally. Inpractice,purpose-designedpelvicorlumbarwedgesinﬂ • • • compression. ple pregnancy),stepsshouldbetakentominimizeaortocaval surgery (evenmoresoinwomenwithpolyhydramniosormulti- Althoughimpossibletoprevententirelyduringtheperiodof Prevention

rate (estimatedas<5 Improvementsincriticalcarehave led toareductioninmortality • cesarean delivery. thetics inpregnancy)butoccurstwiceasfrequentlynonelective Aspirationpneumonitisisrare(estimated1in1,000generalanes- cesareandelivery. Regurgitationoccursin1100–200generalanestheticsfor in incidenceuntiltermgestation. regurgitation. Thesechangesoccurinearlypregnancyandincrease of thephysiologicalchanges(seeChapter2)thatpredisposeto Aspirationappearstobemorecommoninpregnancyasaresult displacement. ment (preferablytotheleft),increasetilt,orusemanualuterine Ifinitialstepsareunsuccessfulinincreasinguterinedisplace- (e.g., duringestablishmentofanesthesiaandsurgery). Maximizeleftpelvictiltifthefulllateralpositionisnotfeasible during transfertotheoperatingroomorpriorsurgery. lateral, tilted,semi-erectorsitting)wheneverpossible,including Placethewomaninleftlateralposition(preferabletoright

had aseizure). in theintensivecareunit,orwomen whohavecollapsedor ate perioperativeperiod(e.g.,insedated orunconsciouswomen Aspirationismorefrequentlyencountered outsidetheimmedi-

% ).

atable

93 Obstetric Anesthesia 94 Anesthesia for Cesarean Delivery • • • purposes. anesthetic sensoryandmotorblock(Table Earlyandregularassessmentdocumentationoftheregional Assessment ofRegionalBlock • • uted toseveralfactors.Theseinclude: Thecurrentlowincidenceofaspirationinobstetricshasbeenattrib- Aspiration Prophylaxis • Table they wish.Anexamplepolicyforaspirationprophylaxisisshownin units takeamorepragmaticapproachofallowingwomentoeatif containing clearfl uids; but,givenlackofevidenceharm,some argue thatwomeninlaborshouldconfi ne oralintaketoenergy- with solidsretainedformanyadditionalhours.Mostanesthesiologists treatment withopioidsresultsinprofounddelaygastricemptying, Eatingduringlaborhasnobenefits.Thepainofandits • pH and alkalinizinggastricsecretions(toachievesmallvolumes<30mlof to improveclinicaloutcome,butthephysiologicalbenefits ofreducing Theroleofdrugprophylaxisiscontroversial;ithasnotbeenproven • • •

H safe use. These causemildnauseainsomewomen,buthavealonghistoryof Nonparticulateantacids(e.g.,0.3molarsodiumcitrate30ml). thepredominantuseofregionalanesthesiaforoperativedelivery Itreassuresthepatientthatanesthetic willbeeffective. associated withalowriskofintraoperative pain. Itprovidesconfi rmation ofasuccessfulblockthatislikelytobe pharmacologicalprophylaxisagainstaspiration. general anesthesia theteachingthatrapidsequenceinductionshouldalwaysbepartof Itservesasasafetycheckforimpending highblock. antiemetic. limited effi cacy.Itincreasesloweresophageal sphinctertoneandis Metoclopramide(20mgIV).Metoclopromideisprokineticbuthas expensive proton-pumpinhibitors. These haveabenignsideeffectprofi of intraoperativepain. Itprovidesprotectionagainstacharge ofnegligenceifsuedbecause > 2 -receptor antagonists (e.g., ranitidine 150–300 mg PO or 50 mg IV). -receptorantagonists(e.g.,ranitidine150–300mgPOor50IV). 3.5)appearofhighbenefi 4.10 .

tversusrisk.Optionsare:

leandareaseffectivemore 4.11

)servesseveral

• and comfortableduringcesareandelivery. Aneffectivesensoryblockisrequiredifapatienttoremainawake Block Management (e.g., T Consider havingtheobstetriciantestlossofpainatlevelincision • • Prior tosurgeryconﬁ touch orpin-prick Test inacephaladdirectionusinglossoftemperaturetocoldand/orlight • • • • If thewomancomplainsoftingling inthearmsordyspnea: Check forlossofcoldortouchonouterborderthefoot(S and feet Initially conﬁ rm immediateparesthesiasensationsorwarmthinbuttocks Table 4.11 anesthesia atnon-electivecesareandelivery Consider passinganorogastric tubetoaspiratethestomachduringgeneral general anesthesiaplanned woman inlaborbycesareandeliveryandaddoralsodiumcitrateasaboveif Give IVranitidine50mg(or similar)atthetimeofdecisiontodelivera or women havingnon-electivesurgery Give oral0.3molarsodiumcitrate 30mlwithin45minutesofsurgerytoall • • Give anH2-receptorantagonist delivery Avoid intakeofsolidsbywomeninlaboratincreasedriskoperative Cesarean Delivery Table 4.10

wound (T Theblockshouldreducenociceptiveinputfromnotonlythe satisfactory bilateralcephaladsensoryblock(e.g.,lossofcoldtoT3–T4 and/or lossoflighttouchtoT5–T6) presence ofmotorblockinthelegs impaired consciousstate,severehypotension) further progressionofblock intervene ifclinicallyindicated (hypoxemia,respiratorydistress, reassure, monitorrespiration andmaternalsymptoms,observefor test gripstrength test sensationintheupperlimbs high risk Oral ranitidine150mg6hourlyregularlytowomeninlaborwhoareat Oral ranitidine300mg1–2hpriortoelectivesurgery 12 ) 12 Assessment ofRegionalBlock Suggested AspirationProphylaxisRegimenfor –L 1 forPfannenstielandT rm:

–T 12 forlowerabdominal 1 )

95 Obstetric Anesthesia 96 Anesthesia for Cesarean Delivery p. 74,Copyright(1995),withpermission fromElsevier. Anaesthesia andintraoperativepainatcaesarean sectionunderregionalblock, InternationalJournalofObstetricAnesthesia, Vol.4, subsequently experiencingpainwithinthat subgroup. Reprinted from the or anesthesiaafterspinalepiduralanesthesia, andthenumberofwomen Figure 4.3 • • • • •

Symmetricandcompletebilaterallossoflighttouchfromtheﬁ upper tomidthoracicspinallevel. peritonealcavity,whichissuppliedbysplanchnicnervesfroman midline incision)butalsorelevantvisceralstructuresandthe to sixththoracic(T of temperaturesensationfromT Partialblockabovetheselevelsiscommon. (Figure some patientsﬁ greater andsomeanesthesiologistsuselossofpin-prickbecause Theinter-patientvariabilityinassessmentoflighttouchappears with slightlylowercephaladdistributionsofblock. Ifneuraxialopioidisincluded,pain-freeconditionsmaybepresent ture andlighttouchistypical. Atwo-dermatomedifferentialbetweencompletelossoftempera-

Percentage experiencing pain 4.3 ) 10 20 30 40 50 60 The numberofparturientsattainingaparticular levelofanalgesia 0 >T ndlighttouchdiscriminationdifﬁ 2 5 T –T 2 6 )totheﬁ fth sacral(S T 3 Anesthetic level

T 4

3 –T T 4 5 toS RussellIF,Levelsof

T 5 6 5 isusuallyadequate. )dermatomeorloss cult. T

Monitoring Undergeneralanesthesia required. factory andoxygenationadequate,givesupplementaloxygenif Reassurethepatientthatventilationatrestislikelytoremainsatis- median nerve(C Checkfornormalgripstrength,whichindicatesafunctioning cervical nerverootdermatomes,butrarelycauseclinicalconcern. Sensorychangesmayreachupperthoracicandoccasionallylower Capnography. once apneaisinduced. the lungandmaximizesperiodbeforehypoxemiacommences with 100 (C should beelevatedto90 End-tidaloxygen. • • intubation. •

Fallingorlowend-tidalcarbondioxide mayindicatean infl Inspiratorydipsindicatespontaneous ventilatoryeffortsandmay assessing ventilationwitharterialblood gasanalysis. morbid obesity,heavysmoking,other lungdisease)consider whom thearterial-alveolardifferencemaybeincreased(e.g., TargetanET-carbondioxideof30–32mmHg.Inpatientsin cardiac output. 3 –C uence useofneuromuscularblockingdrugs. 5 )andafunctioningdiaphragm. % oxygen.Thisconfi rms satisfactorydenitrogenation of Anormaltraceafterintubationconfi 5

–C 8 Priortoinduction,end-tidal(ET)-oxygen ,T

, clinicalobservationofrespiratoryrateand % 1 )andthusalsointactphrenicinnervation , anumberofroutinemonitoringtech- ormore,ifpossible,by

“preoxygenation”

rms tracheal rms

inadequate inadequate cient

97 Obstetric Anesthesia 98 Anesthesia for Cesarean Delivery Inspeciﬁ Other Parameters • • are common(25 AnECGshouldbeusedroutinelyduringgeneralanesthesia.Changes Electrocardiography (ECG) • • employed, buthavelimitationssuchas: Automateddevices(noninvasiveoscillotonometry)areusually • minute untilstable. and aftergeneralanesthesiainduction,itshouldbemeasuredeach and becontinuedfrequentlyduringthecase.Immediatelypost-spinal Bloodpressure(BP)monitoringshouldcommencebeforeanesthesia Cardiovascular Monitoring • • • • •

Doppler esophagealcardiacoutput monitors) maybemorereliable Pulsepressureandstrokevolume variation cially thosehavinginotropeinfusions. urement isusuallyreservedforselected criticallyillpatients,espe- Centralvenouspressure Failuretoreadduemovementorshaking racy inthepresenceofhypertensivediseaseorsevere Under-readingofdiastolicpressureinparticular,andreducedaccu- should besoughtandapostoperativetroponinassayconsidered. Ifchestpainisexperienced,ST-segmentchanges( obese patient). risk ofbarotrauma,althoughthismaybediffi cult inthemorbidly Airwaypressure presence ofsignifi Spirometryand/orarterialbloodgasanalysis oxygenation. guides toadequatefl noninvasive monitoringisunreliable(e.g.,morbidobesity). hemorrhage, majorcardiacandrespiratorydisease)orwhen sary inpatientsathighrisk(e.g.,severepreeclampsia,intrapartum ContinuousBPmeasurementviaanarterialcannulamaybeneces- gery andafterthefetusisdelivered. BPshouldbemeasuredatleasteveryfi ve minutesthroughoutsur- Pulseoximetry. csituations,othermonitoringmaybevaluable. % –60

cantrespiratorydisease. Oxygensaturation shouldbekeptbelow40cmwater(duetothe uid administrationorﬂ % ), althoughrarelyclinicallysigniﬁ orpulmonarywedgepressuremeas-

> 95 uid responsiveness.

% conﬁ rms adequate measurement(e.g., isusefulinthe >

cant. 1–2mmHg) hypotension.

• heart rateshouldbechecked: in severeprematurityinfants(<26–28weeks),butthereafter,thefetal Cardiotocographicfetalheartratemonitoringisdifﬁ cult tointerpret Fetal Monitoring • • • pregnant women. means ofreducingtheriskawarenessinhigh-riskgroupssuchas index (BIS)monitorhasbeenvalidatedinalargerandomizedtrialas general anesthesiaforcesareandelivery.Forexample,thebispectral Depthofanesthesia(hypnosis)monitorsarepotentiallyusefulduring Brain Monitoring • • • change inanestheticplan). tion (Chapter14)andexpeditious delivery(whichmayinvolvea Chapter 12)requireurgentattention, includingintrauterineresuscita- Somenonreassuringpatterns(e.g., severefetalbradycardia, •

as thoseoccurringatthetimeofcesareandelivery. not suffi ciently reliabletofollowacutephysiologicalchangessuch blood pressurechanges,butcurrentlymostmonitoringsystemsare with specifi c indications.Cardiacoutputchangesareasrelevant measurement ofstrokevolume)isusuallyreservedforpatients such asarterialpulsewaveformanalysisortransesophagealDoppler Cardiacoutputmonitoring drowsiness. overdosingthatleadstomyometrialrelaxationandneonatal ing canguidedepthofanesthesiaassessmentandhelpavoid IncombinationwithET-anestheticdrugmonitoring,BISmonitor- anesthesia. BISisquickandeasytoapplyimmediatelypriorinductionof quate depthofanesthesia. associated withaverylowriskofrecalland40–55targetforade- BISmonitoringdisplaysanindexfrom0to100,with60orless and responsetofl systolic anddiastoliccardiacfunction,pulmonaryarterypressure, guide therapyincriticallyillpatientsrelationtoventricularfi Transthoracicortransesophagealechocardiography Whileregionalblockisdeveloping Nearthetimeofinductiongeneralanesthesia Regularlyorcontinuouslyinthepresence offetalcompromise.

uid challenges.

(includingnoninvasivemethods

lling, may

99 Obstetric Anesthesia 100 Anesthesia for Cesarean Delivery • • tive cesareansectionifanepiduralcatheterhasnotbeenplaced. used anesthetictechniqueforbothelective(scheduled)andnonelec- Inmostdevelopedcountries,spinalanesthesiaisthecommonly Advantages andDisadvantages(Table 4.12 ) Incidence ofhighblockrequiringintubationapproximately1in2,000–5,000 • Finite durationofsurgicalanesthesia(∼90–150minutes) anesthetic, withlittleabilitytoinﬂ uence loworhighblock Single-shot techniquerequireschoiceofaﬁ xed doseofsubarachnoidlocal point orsimilarneedles(∼0.5 Low incidenceofpost-duralpunctureheadachewith26–27gaugepencil including intrathecalmorphine Effective postoperativeanalgesiaachievablewith“single-shot”injection No riskoflocalanesthetictoxicity Low incidenceofintraoperativepain( higher incidenceofhypotension(∼60 Reduction incardiacoutputgreaterthanwithepiduralanesthesiaand Disadvantages Low incidenceofparesthesiaduringinsertion( Low failurerate(0.5 • • • Rapid onsetofdensesensory andmotorblock anesthesia Establishes denovoregionalanesthesiamorerapidlythanepidural Advantages Spinal Anesthesia Table 4.12

Spinal Anesthesia

is minimizedbyuseofnon-cuttingbevelneedles(seeChapter13). tension iswellmanagedandpost-duralpunctureheadache(PDPH) Maternalsatisfactionwithspinalanesthesiaishigh,providinghypo- thoracic spinewhensupine,alsocontributeinlaterpregnancy. sac, andahighercephaladlocationofthelowestpoint neural sensitivity.Areductioninthesizeoflumbarintrathecal from earlyinpregnancy,suggestingahormone-inducedchange Doserequirementsinpregnantpatientsfallbyapproximately30 when surgicaltimeislikelytobeprolonged making asingle-shotapproach unsuitableforcomplexordifﬁ good surgicalconditions valuable forCategory1and2non-electivecesareandeliveries reassuring forthepatient Advantages andDisadvantagesof % –4 % ) % –1 % ) % –80 ∼ 5 % ) % , especiallyﬁ rst 4–8minutes) ∼ 10 % ) cult cases cult

• • Inthelateralpatientposition,onsetofsensoryblocktoT • • lateral decubitusorsittingposition.Theposition: Theblockmaybeplacedwiththewomanpositionedineither Patient Positioning Techniques andEquipment block failuremayoccur. arachnoid ropivacaine),soifsurgeryisdelayedorundulyprolonged, noid bupivacaine,dependentondose)or45–90minutes(withsub- sensory blockregressionbeginsafter60–180minutes(withsubarach- feasible forallbutthemostemergentofcesareandeliveries.However, Therapidonsetofblock,within5–15minutes,makesspinalanesthesia vertebral interspace.L • • • Inmostpatientsthespinalcordterminates attheL Safe InsertionTechnique pelvic tiltpositionwhilesurgicalanesthesiaestablishes. incidence ofhypotension. most superﬁ to L (but nottoT

Afterthesubarachnoidinjectionofdrugs,applyaleftlateralor is hypovolemicorhassyncope. Shouldbeavoidediftheumbilicalcordispresenting,woman Improvesventilation supracristal lineacrossthetopof iliaccrests(“Tuffi er’s line”) fl tion ofthemidlineandincreasesrateeffl Makesinsertioneasierinobesewomen,becauseithelpsvisualiza- cephalad spreadoflocalanesthetic. sory blockmonitoredfrequentlywhenattemptingtoimprove Tippingthebedhead-downshouldbedonecautiouslyandsen- tal butslopesslightlyheaddown. Inthelateraldecubitusposition,vertebralcanalisnothorizon- was usedtorescuefailedepiduralanesthesia. thetic tomid-thoracicdermatomes,especiallyifspinalanesthesia or elevatingthebedhead)torestrictcephaladspreadoflocalanes- curve (e.g.,byplacingpillowsundertheshoulders,neckandhead, Oncethewomanislyingdown,accentuateherupperthoracic Usesurfacelandmarkstohelpidentify theinterspace.The uid (CSF)fromasmallgaugespinalneedle. 3 ).Tominimizetheriskofspinalcord injury,selectalowlumbar cialinterspace. 3 –T 5 )ismorerapidandtheremaybeaslightlylower

–L 4

isfrequentlyused,beingthelargest and

uxofcerebrospinal 1 level(rangeT

imaginary 10 12

101 Obstetric Anesthesia 102 Anesthesia for Cesarean Delivery AsuggestedapproachtoneedleinsertionisshowninTable general, thesesmallgaugeneedlesareeasytouseinthepregnant needle, Figure needle (e.g.,24–27gaugepencil-pointWhitacreorSprottestylespinal Everyattemptshouldbemadetouseonlyanon-cutting-edgespinal Spinal Needles loss-of-resistance, theninsertthespinalneedle. If experiencingdiffi culty, trytoidentifytheepiduralspacefi rst using withdrawal (weakevidenceforreduced post-dural punctureheadacherate) If usingaQuinckecuttingedgespinalneedle,replacethestyletprior to Aspirate CSFeasily,theninjectspinaldrugs drug atconnectionwheninjecting)butwithout movingtheneedletip attach drugsyringecarefullywithslighttwisting motion(toavoidlossof Withdraw thestylet,confi rm freeeffl ux ofcerebrospinalfl uid (CSF)and • transient. If paresthesiaoccurs(approximately10 • Feel for“duralpop”asneedlepenetratesthedura-arachnoidaftertenting • • Use apencil-pointspinalneedle midline) prevent lateraldefl ection ofafi ne gauge spinalneedleawayfromthe Insert anintroducerneedle1–2cmintotheinterspinousligament(to e.g., 0.5 anesthetic; Infi ltrate intradermal,subcutaneous Table 4.13

and isdifﬁ • • • crosses theL leading toinjury. injected becauseoftheriskintraneuralinjectionanddisruption, and theneedleshouldbewithdrawn.Drugorsolutionmustnot If theparesthesiaisnottransient,contactwithneuraltissueimplied Incidence approximately70–80 Sprotte style24–26gauge Whitacre style26–27gauge

anatomy. ing vertebralinterspaces,andassistsinvisualizingspinalcanal Theuseofultrasoundimagingimprovestheaccuracyidentify- needle placement. Ahigherlevelthanappreciatedisoftenmistakenlyselectedfor in 25 Anesthesiologistsonlycorrectlyidentifythevertebralinterspace % –1 % –35 % lidocainewithepinephrine1:200,000–400,000 culttovisualizeinobesepatients. Suggested ApproachtoSpinalNeedleInsertion 4.4 4 % spinousprocessinmostpatients,butshows ofcases. ) toreducetherateofPDPH(seeChapter13).In

% with26–27gaugespinalneedles ± ligamentoustissuewithlocal % ofcases)thisshouldbevery

variability variability 4.13 . Anaesthesia andAnalgesia,p.248.2000Wiley-Blackwell. Regional Anaesthetictechniques.In:PrinciplesandPracticeofObstetric needles ofequivalentsize.Modiﬁ ed fromHoldcroftAandThomasTA. incidence ofpost-duralpunctureheadachethansharp-bevel(Quincke) (c) Whitacre,(d)Atraucanneedle.Theseneedlesresultinalower Figure 4.4 tration above21 Duringregionalanesthesia,theadministrationofoxygeninaconcen- Oxygen Therapy of PDPH(1in100–200). space inmostpatients(the“duralpop”),andhaveanacceptablerate population, providetactileindicationofentryintothesubarachnoid • • healthy fetus. 35 tinely inhealthywomenhavingelectivecesareandelivery;because

% using ananestheticcircuitandtight-ﬁ Aninspiredconcentrationof100 and oxygenfreeradicalsthatareinjurious tolipidcellmembranes. than 10minutesbecauseofanassociated increaseinlipid ent thisconcentrationofoxygenshould probablybelimitedtoless venous oxygencontent.Inthepreterm ornonlaboringparturi- ing 60 Fornonelectivecesareanduetofetalcompromiseconsiderprovid- –40 ( a )( % % inspiredoxygendoesnotincreasefetaloxygenationofa –100 Spinal needletipdesignfor(a)GertieMarx,(b)Sprotte,

% % inspired oxygen to modestly increase fetal umbilical inspiredoxygentomodestlyincreasefetalumbilical viaanair-entrainingfacemaskisnotjustiﬁ

b )( % ttingfacemask. canbeachieved,ifneeded, c )(

peroxidation peroxidation d ed rou- ed )

103 Obstetric Anesthesia 104 Anesthesia for Cesarean Delivery • • anesthesia areallpartlydose-related(Figure pain, thedegreeofmotorblock,anddurationeffectivesurgical range ofdoseslocalanesthetic,buttheincidenceintraoperative Anadequatesensoryblockdistributioncanbeachievedwithawide Drug Distribution • • except inexceptionalcases(e.g.,achondoplasticdwarfi lumbar interspaceordirectionofneedlebevelisnotrecommended vertebral columnlengthoronadministrationfactorssuchasthe dose administeredbasedonpatientfactorssuchasweight,heightor in spreadoflocalanestheticisalsosignifi cant, suchthatalteringthe • • Inchoosingdrugsanddrugdosesforspinalanesthesia,aimsare: Subarachnoid DrugSelection 1995;20(2):91. delivery: Acomparisonoftwodoses hyperbaric bupivacaine. with permissionfromDeSimone,C.,etal . Spinalanesthesiaforcesarean blocked forasignifi cantly longertimewiththehigher dose. hyperbaric bupivacaine,12mgor15mg, showingmorespinalsegments Reprinted Figure 4.5

Motorblockoftheshortestpossiblepostoperativeduration. surgery. Anadequateblockdurationtomeettheanticipatedof Postoperativeanalgesia. Minimizationoftheincidenceintraoperativepain. clinicallyrelevant“highblock.” Amidtoupperthoracicsensoryblock,butalowincidenceof Level of sensory blockade Alowincidenceofhypotension,nauseaandvomiting,shivering. L C T T T T T 11 T 9 7 5 3 1 7 0 Onset anddurationofsensoryblockafter subarachnoid 20 15 mg 12 mg 40

080 60

Time ( min ) 4.5 100 ). Individualvariability 120

sm). Reg. Anesth.

140

Suitableintrathecallocalanestheticsare: Local Anesthetics Choice ofDrug • • • being opioids.Opioids: Anumberofanalgesicadjunctsaresafetoadd,themostvaluable Adjuncts make hypotensionorhighblockmorelikely. tion ofblock,withalowerincidenceintraoperativepain Higherdosesoflocalanestheticgiveabetterqualityandlongerdura- • • • • • • •

Examplesare: Hyperbaricbupivacaine(indextrose8 • • • • Ropivacaine • TetracaineorLidocaine Lowertheeffectivedoseoflocalanesthetic. • • • • Reduceintraoperativepain(number-needed-to-treat[NNT]of4). Reduceintraoperativenausea. Morphine(50–150 Diamorphine(300–400 Sufentanil(2.5–5 Fentanyl(6.25–15

Thisisreadilyavailableandwidelyused. Injectatleast10mgifusedalone(range10–15mg). Injectatleast8mg(range8–12.5mg)ifopioidisadded. Hyperbaricsolutionsarefavoredoverplain0.5 combination havealsobeenusedsafely). are sittingandcausefewerhighblocks(bothformulationsin tion ofmotorblock,spreadmoreconsistentlyinpatientswho (slightly hypobaricinCSF)becausetheyresultshorterdura- Hasfewadvantagesoverbupivacaine. recommended. Thesearelesssatisfactory,haveotherproblemsandnot rapidly). tively canbeaproblem,althoughnormalfunctionreturnsmore Produceslessintensemotorblock(movementintraopera- approximately 45–60minutes,whichmayprovetobeaproblem). Hasshorterdurationthanbupivacaine(regressionbeginsafter combinedwithopioid). Requireslargerdoses(15–25mg,dependingonwhether

mcg) mcg) mcg)

mcg)

% –8.25

% ) %

bupivacaine

but also

105 Obstetric Anesthesia 106 Anesthesia for Cesarean Delivery • repeat cesareanorwhenhysterectomy isplanned). and/or postoperativeanalgesiaare desired(forexampleamultiple spinal-epidural anesthesiaispreferablewhenprolonged cesarean delivery.Spinalanesthesiahasadvantagesandcombined able, epiduralanesthesiaisnowrarelyusedforelective(scheduled) Even inresource-richcountrieswheretheequipmentisreadilyavail- AcomparisonofepiduralandspinalanesthesiaisshowninTable Advantages andDisadvantages Other Adjuvants respect toseriousmorbidityisexcellent(seealsoChapter5). in timing(6–18hours)aftermorphine,butitssafetyrecordwith (1 in250–500formilddepression),beinggreatestandmostdelayed clinically relevantopioid-inducedrespiratorydepressionisverylow so supplementaryanalgesiamustusuallybeprovided).Theriskof postoperative analgesia(duration4–24hours,median12 phine) orhydromorphone,morphineproducesclinicallyuseful metabolized inneuraltissuetomorphineand6-monoacetylmor- limits itseffectivenessduringsurgery.Likediamorphine(whichis Intrathecalmorphineanalgesiaisofslowonset(30–60minutes),which anesthesia forcesareandeliveryis: Anexampleofaneffectiveandsaferegimenfor“single-shot”spinal • • • • • •

Epidural Anesthesia Epiduralanesthesiashouldbeconsidered when: hypertension; see also Chapter10). (e.g., certainstenoticvalvulardiseases, cardiacfailure,pulmonary prevent hemodynamicchangesassociated withsympatheticblock Aslowlytitratedtechnique(over45–90 minutes)isappropriateto Epinephrine(adrenaline)200mcgdoesnotenhancetheefﬁ efﬁ Ketamine,midazolamandmagnesiumenhancelocalanesthetic intra- andpostoperativesedation. moderatepostoperativeanalgesiceffect(upto6hours),butcauses Clonidine60–150mcgprolongsthedurationofblockandhasa local anestheticwithopioid. Morphine100mcg Fentanyl15mcg Hyperbaricbupivacaine12.5mg cacybutareexperimentalandshouldnotbeusedroutinely.

cacy of cacy 4.14 .

• for laboranalgesia. delivery whenanepiduralcatheterhasalreadybeenplaced,usually Theprincipalindicationforepiduralanesthesiaisnonelective • • • Headache onlyifinadvertent duralpuncture(incidence0.5 Risk oflocalanesthetictoxicity Risk ofshiveringpossiblygreater hypotension Cardiac outputbettermaintained andlowerincidenceseverityof Other EffectsandComplications • Less effectiveblock Higher failurerate(3 Slower onset10–30minutes Onset andEffi subarachnoid effectsafterdrugtransferintocerebrospinalfl Primarily conductionblock of spinalnerverootsandganglia,aswell Mechanisms Spinal Anesthesia Table 4.14 • and volume,butlessinfl uenced bypatientposition Distribution affectedbymultiple factorsincludinglevelofinjection,dose, consistent thanintrathecaldistribution Anatomical distributionthrough epiduralandparavertebraltissuesless

best avoided (e.g., raised intracranial pressure; see also Chapter 10). best avoided(e.g.,raisedintracranialpressure;seealsoChapter10). Suddenchangesinsubarachnoidspacepressureorduralpunctureare or apatientwithdifﬁ general anesthesiaisamajorissue(e.g.,themorbidlyobesewoman risk (e.g.,womenwithfetalcompromiseduringlabor)orwhere when anemergency(Category1)cesareandeliveryisasigniﬁ anesthesia mayfailanddelaysurgery.Thisisparticularlyimportant factorily already;otherwise,attemptingconversiontoepidural Ideallytheepiduralcathetershouldhavebeenfunctioningsatis- Theincidenceofintraoperativepain ishigher(5 potentially faster). the mosturgentCategory1cases, for whichgeneralanesthesiais all categoriesofnonelectivecesarean deliverywiththeexceptionof can beestablishedwithin10–15minutes (makingitsuitablefor Iftheepiduralcatheterisfunctioning well,epiduralanesthesia under spinalanesthesia, butchangingtoaspinal technique is incidence ofintraoperativepain5 incidence ofconversiontogeneralanesthesia1 Epidural Anesthesia:Differencesfrom cacy

% –10

cultairway). % ) % –20

% % –3 % (versus<1 % –4 uid %

% ) –20 cesarean % % ) )than cant

107 Obstetric Anesthesia 108 Anesthesia for Cesarean Delivery • compromising successfulbilateralblock. position throughout.Thisminimizes aortocavalcompressionwithout anesthesia forsurgicaldelivery,keep thewomaninleftlateral when converting(“toppingup”)labor epiduralanalgesiato Thespreadofepiduralsolutionisminimallyinﬂ uenced bygravity,so Management ofEpidural Anesthesia • • • midline. reduced. Withthepatientsitting,itmaybeeasiertoidentify compression isminimizedandtheriskofepiduralveinpuncture Chapter 3).Withthepatientlyinginlateralposition,aortocaval Therearemanyapproachestoepiduralcatheterinsertion(see Techniques andEquipment

of- guided paramedianepiduralinsertionusingaspring-loadedloss- calculatetheskintoepiduralspacedepth.Real-timeultrasound- the midline,identifyspecificinterspacesandscolioisis, imaging Indifficultcasesandobesewomen,theuseof described. placement between eachinjectionbyrepeatedcatheter aspiration 2–5 minutesapartdependingonurgency). Testforintravenous Useanincrementaldosingapproach toextendtheblock(5–10ml, insertion to<5cm. space andtoinsertasecondepiduralcatheter,limitingcatheter priate tomoveseveralinterspacescephaladalowthoracicinter- Rarely,ifalowbilateralblockwillnotextendcephalad,itisappro- catheter duringreinsertion. technique andtoavoidthepotentialriskofdamagingoriginal necessarytoremovetheoriginalcatheter,bothensurean Iftheepiduralcatheterneedstobereplaced,itwillusually injected epiduralsolution. ecal CSFcompartmentasaresultofcompressionbyrecently predictable block,duetothereducedvolumeoflumbarintrath- usually unnecessary.Italsoresultsinagreaterriskofhighandless half ofthelumbarinterspace. Itisusuallyeasieriftheepiduralneedleﬁrst insertedinthelower resistance syringe(Episure assessmentisincreasinginpopularity,servingtolocate

TM ,IndigoOrb,U.S.A)hasbeen

ultrasound aseptic • • Otherepidurallocalanestheticsofsloweronsetare: • • • advantages. Thepreferreddrugsfor“topping-up”are: cesarean delivery.Mixtureshavebeenused,butdonotofferanyreal dural analgesiaorinstitutingablocktoestablishsurgicalanesthesiafor Anumberoflocalanestheticsaresuitableforeitherextendingepi- Local Anesthetic Epidural DrugSelection • • • • • • Epidural AnalgesiatoAnesthesia Table 4.15

• • 0.5 0.5 plus sodiumbicarbonate8.4 2 • 3 newly inserted(seeChapter3). Consideratest-doseforintrathecalplacementifthecatheteris aseptic conditions)viatheconnectoronly. through aliquidcontainingﬁ lter andconnector,or(understrict lidocaine, oruse3 (adrenaline) 1:200,000plussodiumbicarbonate 8.4 Position thepatientonleftsidethroughout Administer 5–10ml2 presence ofcerebrospinalﬂConsider anintrathecaltest-dose(seeChapter3) uid (subarachnoidplacement) intravascular placement Check thelocationofepiduralcatheterbyaspirationtoexclude Check thelocationofepiduralcatheterbyaspirationtoexclude Check theepiduralcathetersitetoexcludedislodgement • • •

% %

utes) andcardiotoxicitypotentialisless. Onsetissimilarorslightlyfasterthanbupivacaine(10–30min- and decreasestheincidenceofintraoperativepain. approximately 6.5resultsinamorerapidonset(7–10minutes) AddingbicarbonatetoalkalinizethepHofsolution some countries. Onsetisveryrapid(5–15minutes)butthisdrugnotavailablein % % 2-chloroprocaine. lidocaine(lignocaine)withepinephrine(adrenaline)1:200,000 repeatagain2–5minutelyuntilblockadequate (usually10–20mltotal) use thelargerdoseand shorterintervalforCategory1or2 non-elective cesareandelivery consider addingfentanyl 50mcgand/orclonidine75ifnorecent epidural opioid,orbilateral symmetricblocknotpresent levobupivacaineor0.75 bupivacaine. Suggested ApproachwhenConverting % 2-chloroprocaine

% lidocaine(lignocaine)withepinephrine

% % 0.1ml/ml ropivacaine

% 0.1mlperof

109 Obstetric Anesthesia 110 Anesthesia for Cesarean Delivery and timecostsare incurred. compared withsingle-shot spinalanesthesiaandadditional equipment elective cesareandeliverythereisno evidenceforoutcomebeneﬁ ThedisadvantagesofCSEAarerelatively minor,althoughfor • • • • opioid (seeTable it isstronglyrecommendediftherehasbeennopreviousexposureto but canincreasetheincidenceofpruritusandsedation.Nevertheless back-up andforpostoperativeanalgesiaisrecommendedwhen: anesthetic techniquewithplacementofanepiduralcatheteras number ofhigh-riskpatients.Thecombinationaconventionalspinal techniques (Table Thisdualtechniquedeliverstheadvantagesofbothspinalandepidural Advantages andDisadvantages not ofbeneﬁ concentrations andpermitsafeadministrationoflargerdoses,butis 2.5–5 mcg/ml)tolidocaineisrecommendedreducepeakplasma Theadditionofepinephrine(concentration1in200,000–400,000or Adjuncts • • • •

Combined Spinal-EpiduralAnesthesia(CSEA) Additionofalipophilicopioiddecreasesintraoperativesurgicalpain, block. anesthesia, andconsenthasbeen obtained torepeataregional “Toppingup”anepiduralcatheter has failedtoproduceepidural tolerant patient). abdominal surgeryinadditiontocesareandelivery,oranopioid- Postoperativeanalgesiaislikelytobechallenging(e.g.,major additional surgery. pathologies, orthelikelihoodofobstetrichemorrhageandcomplex conditions(e.g.,morbidobesity),thepresenceofintra-abdominal Prolongedsurgeryislikelybecauseofknowndifﬁ cult surgical Ariskexiststhatsurgerymaybedelayed. Clonidine(dose75–300mcg)isan Diamorphine3mg Sufentanil15–20mcg Fentanyl50 used intheUnitedStates. 4–6 hours,butcausessigniﬁ longs thedurationofblockandprovidespostoperativeanalgesiafor twithotherlocalanesthetics. mcg 4.15

4.16

). Choicesinclude:

),makingitveryusefullogisticallyandina

cantdose-dependentsedation.Itisnot α 2

-adrenergicagonistthatpro-

routine routine

ts Therearetwoalternativeinsertiontechniques: Insertion Techniques andEquipment • • single interspaceapproach.Thisequipment: there arealsoanumberofpurpose-designed “kits”availablefora AlthoughCSEAcanbeperformedusing separateneedlecomponents, Kits • • • • Good hemodynamicstability Regional anesthesiaofprolonged duration High qualityspinalblockofrapid onset or less) • • May requireconversionto Marginally slowerinsertion time anesthesia alone) Possibly higherincidenceofparesthesia duringinsertion(versusspinal Disadvantages Lowest failureandconversion togeneralanesthesiarate(both Advantages Spinal-Epidural Anesthesia Table 4.16 Possibly lowerrateofpost-dural punctureheadache High qualitypostoperativeepidural analgesia

Asinglevertebralinterspace,needle-through-needletechnique. • • lumbar epiduralinsertion,thenlowspinalanesthesia. Separatevertebralinterspacetechnique,withlowthoracicorupper a separatehollow passageorepiduralneedleback-eye). Mayincorporate a meansofguidingthespinalneedle (through of theepiduralneedle( Ensuresanadequateprotrusionofthe spinalneedlethroughthetip epidural augmentationoflowspinalanesthesia(T normal salineorlocalanesthetic)useasequentialtechniquewith aid cephaladdistributionusingepiduralvolumeextension(5–10ml low dosesofintrathecalbupivacaine(5–10mg)withlipophilicopioid spinal anesthesiaalone(iftheepiduralcathetercannotbeinserted) epidural anesthesiaalone(ifthesubarachnoidspacecannot be located)

obese womanorwhenhemodynamicstabilityisvital. ing theblockandhasapotentialsafetyadvantageinmorbidly Thisallowsbettertitrationandlowerdrugdoseswhenestablish- perform andispreferredbymostpatients(Figure Thisisbyfarthemostpopularapproachbecauseitquickerto Advantages andDisadvantagesofCombined > 11mm).

12 –S 5 ) 4.6 ). ∼ 1

111 Obstetric Anesthesia 112 Anesthesia for Cesarean Delivery anesthesiologists. sitting ratherthanlateralpatientpositionispreferredbymany women inwhomthedistancetoepiduralspaceisincreased, • • • • Elsevier. Birnbach DJ,GattSP,DattaS., from RawalN.etal.Thecombinedspinalepiduraltechnique,p.166.In: space needle-through-needleapproach. Reprinted withpermission Figure 4.6 arachnoid space(Figure midline, thespinalneedlemaynotenterorremainwithinsub- Iftheentryofepiduralneedleintospaceisnotin

TherearethreemethodsofestablishingCSEA. epidural localanesthetic orsaline5–10ml followed immediately (atmostwithin5–10minutes)by injectionof intrathecal drug(bupivacaine3.5–8 mg withfentanylorsufentanil) CSEAby“epiduralvolumeextension” (EVE)usingalowdoseof • • or withoutopioid) Conventionalspinalanesthesia(usingbupivacaine10–12.5mgwith 3.5–8 mgwithfentanylorsufentanil) SequentialCSEA,usingalowdose of intrathecaldrug(bupivacaine and possiblefailuretoinjectsomeorallthespinaldrugsolution. penetrating theduraandarachnoid,reducingneedlemovement Maysecurethespinalneedlesothatitstipremainsimmobileafter

(to T Thislimitsthespinalblock(e.g.,T ment theblockifnecessaryandforpostoperativeanalgesia. Inthiscaseuseoftheepiduralcatheterisreservedtosupple- 3 –T Spinal needle Combined spinal-epiduralinsertionusingthesingleintervertebral Subarachnoid space 5 )usingepidurallocalanesthetic. Epidural needle Epidural space Dura mater

4.7 Textbook ofObstetricAnesthesia. 2000, ).Forthisreason,especiallyinobese

10 –S 5 )whichislaterextended

2000, Elsevier. p. 176.In:BirnbachDJ,GattSP,DattaS permission fromRawalN.,etal.Thecombinedspinalepiduraltechnique, mechanisms mayapplyforfailureofspinalanesthesia. Reprinted with spinal-epidural anesthesia.(a)–(c)resultintechnicalfailure.Similar Figure 4.7 • useful arewhen: Situationswhenthesequentialor EVE CSEAmethodsareclinically Choice ofMethod

• • • bance isparticularly important(e.g.,maternalcardiac disease) Alowincidenceof maternalhypotensionandhemodynamic distur-

of inadequatecephaladspreadsubarachnoid drug. Ifthewomanissittingthismethod associatedwithahigherrisk be rapid(maximum60–90min). establishing blocktocompletionofsurgerycanbeguaranteed Thismethodissuitableforroutineuseonlywhenthetimefrom cephalad direction. Theepiduralinjectionextendsspreadoftheintrathecaldrugina Position anddirectionofthespinalneedleduringcombined

(d) (b) (a) (c)

., TextbookofObstetricAnesthesia.

113 Obstetric Anesthesia 114 Anesthesia for Cesarean Delivery Theadvantagesofcontinuousspinalanesthesia(CSA)are: Advantages, Disadvantages andApplications needle haspuncturedtheduraandarachnoidmater(a“wettap”). reinsertion ofthecatheterintoepiduralspacewhen The latterapproachispopularintertiaryunitsasanalternativeto some countries)andstandardepidural“macrocatheters”areused. tries. Currently,bothpurpose-designedmicrocatheters(availablein injuries resultedintheirwithdrawalfromthemarketsomecoun- small gaugeintrathecalmicrocatheterswereintroduced,butneural select circumstances.Interestinitreemergedthelate1980swhen Thistechnique,ﬁ rst usedinobstetricsthe1940s,isonly • • most commonlyalipophilicopioid. priate forsequentialapproaches,itisessentialtoincludeadjuncts, apply (seeabove).Becauselowdosesofbupivacainearemostappro- Theusualspinalandepiduralanestheticdrugsconcentrations Drug SelectionforCSEA thetic injectionafter45–60minisadvisableifsurgeryongoing. menced andcompletedrapidly,additionalepidurallocalanes- with ahigherriskofintraoperativepainifthecesareanisnotcom- more costly.SequentialCSEAandespeciallyEVEmaybeassociated ThemaindisadvantagesofconventionalCSEAarethatitisslowerand • • •

Continuous SpinalAnesthesia Controlofcephaladsensoryblockheightislikelytobemoredifﬁ mobilization(forgreaterpatientsatisfaction)aredesired. Ashorterdurationofmotorblockandearlierpostoperative sia, orinapatientwhohaspreviouslyexperiencedhighblock) or titrationofspreadisimportant(e.g.,afterfailedepiduralanesthe- impossible intubation). high block,orfromgeneralanesthesia (e.g.,severeasthmaor Theabilitytotitratedruginwomen athighriskformorbidityfrom morbidly obesewoman). achieve epiduralorspinalanesthesia havepreviouslyfailed(e.g.,ina Asafe,reliableanestheticcanbe performed whenattemptsto previous vertebralcanalsurgery). anesthesia hasasubstantialriskoffailure(e.g.,severescoliosisor altered neuraxialanatomy,inwhomepiduralorsingle-shotspinal Successfulblockcanbeestablishedinpatientswithabnormalor

cult cult

• • • • • • • • • • proceduralist’sexperience.Successfulandsafeinsertiondependson: Technicalissueswithplacementarecommon,irrespectiveofthe Insertion Technique Therearetwomaintypesofcatheterandkits: Equipment Equipment andTechnique • •

Thedisadvantagesinclude: Accurateneedleplacement needle placedintheepiduralspace. after placement.ThecatheterisintroducedwithaCrawfordstyle mounted overaninternalneedleorstylet,whichcanbewithdrawn Catheter-over-needlekitsavailablewith22or24gaugecatheters also beused. eters, 24gauge,whichpassthrougha20gaugeTuohyneedle,can noid space(designateda“macrocatheter”).Pediatricepiduralcath- needle (unintentionallyordeliberately)placedintothesubarach- Anepiduralcatheter(20or22gauge)insertedthroughan possibly necessitatingsurgicalremoval. Theriskofmicrocatheterbreakageduringinsertionorwithdrawal, morbidly obese. AhighincidenceofPDPH,thoughtheisloweramong block. injection ofepiduraldrugdosesresultinginhighor“totalspinal” Thepossibilityofcathetermisuse,inparticular,unintentional with frequentusethefailureratefalls). high overallfailurerate(asas20 Difﬁ culty withmicrospinal catheterplacement,contributingtoa 0.25–0.5 ml) Titrationofbolusdoses(e.g.,bupivacaine 1.25–2.5mginvolumesof likely withslowinjection) Rapidinjectionofdrugs(localanesthetic maldistributionismore tion cannotbepredicted) Insertionofonly3–4cmcatheter (thedirectionandﬁnal tiploca- has beenplacedintrathecallyforlaboranalgesia. Effectiveanesthesiaforoperativedeliveryafteranepiduralcatheter congenital heartdisease). pulmonary hypertension,aorticstenosis,cardiomyopathy,adult induced cardiovascularchangespoorly(e.g.,certaincardiac Stablehemodynamicsinthoselikelytotoleratesympathetic-

% insomereports,though

diseases, diseases,

115 Obstetric Anesthesia 116 Anesthesia for Cesarean Delivery including subanestheticdosesofketamine,maybeadded. to resultinplasmaconcentrationsreachingthetoxicrange.Sedation, bupivacaine (upto150mg)orropivacaine(300areveryunlikely total dosemustbeconsidered.Maximumrecommendeddosesof required, solutionsoflowtomediumconcentrationareused,and ilioinguinalnerveblocks).Aslargevolumesoflocalanestheticare or fi eld blockofthelowerabdomen(bilateraliliohypogastricand out instillationoflocalanestheticintotheperitonealcavityandwound, approximately 0.5 are infrequent.Inabilitytoobtainasatisfactoryspinalblock(incidence Technicalfailures(failedorabandonedinsertion,inadequateblock) Failed SpinalAnesthesia Management ofFailedBlock beforeSurgery anesthesia. suitable technique,buthasnotyetbeenevaluatedasacomponentof anesthetic infiltration oftheabdominalwall(Figure experienceinperformingcesareandeliveryunderprogressivelocal Indevelopingcountriesinparticular,someobstetriciansgain Local Infiltration orFieldBlock shot spinalanesthesiaareoftenagoodidea. tion oflocalanestheticintheCSF.Opioidadjunctsasusedforsingle- Hyperbaric solutionscanbeusedbutmaycontributetomaldistribu- Plain0.5 Drug Selection CSEA) maybeduetoseveralfactors: • •

Dealing withFailed RegionalAnesthesia

Thetransversusabdominisplane(TAP)blockalsoappearstobea • • CSF volume, subarachnoid and extradural cysts, arachnoid adhesions CSF volume,subarachnoid andextraduralcysts,arachnoid adhesions Maldistributionoflocalanestheticdue toanatomicalfactors(high side thedura). errors, lossfromthesyringe-needle connectionordepositionout- Deliveryofaninadequatedoselocal anesthetic(doseselection

used) andfrequentblockassessment. syringes, ﬁlling ofthedeadspacewithincatheter(andﬁ Forsafety,payattentiontodetailwithrespectuseofsmall with bupivacainemaybe5–17.5mg). Doserequirementsvarywidely(rangeforsurgicalanesthesia % bupivacaineisusuallytitratedtothedesiredleveloreffect.

% –4 % forspinalanesthesiaand0.5

4.8 ), withorwith-

% –2 lter, if % for • • • be animportantfactorinobtainingagoodblock. for unilateralorasymmetricspreadhead-downposture)canalso ful. Manipulationofpatientpositionpost-injection(e.g.,changingsides Agoodassistantwhohelpspositionthepatientoptimallyisveryhelp- • • 1975;45(2):165. Advantages oflocalanesthesiaforcesareansection. Reprinted withpermissionfrom RanneyB.andStanageWF. Figure 4.8

Strategiesto“rescue”abilateralbutlowspinalblockinclude: will besuffi after whichoftenonlyasmallvolume oflocalanesthetic(3–5ml) Insertionofanupperlumbarorlow thoracicepiduralcatheter, block). distribution shouldbecheckedvery frequentlytoavoidahigh (although cautionisrequiredwith these maneuvers,andsensory Repositioningthepatienthead-downwithherhipsfullyfl exed Dosingtheepidural catheterifaCSEAwasperformed. Otherrarecauses. the wronganatomiccompartmentorspace Mistakinginfi ltrated localanestheticforCSF,leadingtoinjectionin positioning, orlowinjectionlevel and trabecula,previoussurgeryorseverescoliosis),poorpatient Method oflocalfi eld blockofthelowerabdominalwall. cienttoestablishsurgicalanesthesia. IA

IB IC IE 2 4 3 1 ID 12 11 10 9

8 7 6 5

Obstet Gynecol .

117 Obstetric Anesthesia 118 Anesthesia for Cesarean Delivery • • Iftimeallowsa“top-up,”upto85 • • 5 Thisismorecommonthanfailedspinalanesthesia(incidence Failed EpiduralAnesthesia quality orheightoftheblockinclude: develop satisfactoryepiduralanesthesia.Strategiestoimprovethe and anxiouspatient,withtheirsupport person. anesthesiologist mustbeprepared to dealwithpaininanunsedated used), especiallywhensurgerytakesmorethan45–60minutes.The • • can reach20 lower withspinalcomparedepiduralanesthesia,buteither pinprick orcoldatmid-thoracicdermatomes.Theincidenceofpainis presence ofapparentlyadequatesensoryanesthesiatolighttouch, peritoneum,isnotuncommonduringcesareandelivery,eveninthe larly frompelvicorganssuchastheovary,fallopiantubes,or Despitegoodsomatic(abdominalwall)block,visceralpain,particu- Management ofIntraoperative Pain surgical anesthetic. intraoperatively, despitehavingestablishedanapparentlysatisfactory regional analgesiaandanesthesiamayfailorprovetobeunsatisfactory An essentialpartoftheconsentprocessistowarnwomenthat beneﬁ anesthesia, mustbebasedonpersonalexperience,individualrisk- a repeatregionalanesthetictechnique,ortochangegeneral Thedecisiontoabandonuseoftheepiduralcatheterandperform • •

% –15

Assessmentofthepatientisimperative. Unsatisfactoryanalgesiapreviously,duringlabor Alargenumberofsupplementarybolusdosesduringlabor Failuretoaddopioidthelocalanesthetic Morbidobesity. Re-dosewithahighconcentrationoflocalanesthetic. vided atleast4cmofcatheterremainsintheepiduralspace). Withdrawthecatheterslightly(about1cm)beforere-dosing(pro- and documented. will involvesensation,andtheblock distribution mustbere-checked Thepatientshouldalreadyhavebeen awarethattheexperience clonidine 75–150 Addadjunctssuchaslipophilicopioid(e.g.,fentanyl50mcg)and/or t assessment,theurgencyofdeliveryandwoman’swishes. % ) andispredictedbyfactorssuchas: % –50

mcg. (typically5 % –20 %

% ofthesecaseswillultimately ifneuraxialopioidhasbeen

• • • • • necessary. Thereareanumberofanalgesic options,whichcanbeusedif

• • and thelocationofpainshouldbenoted. Theseverityofpain(e.g.,onaverbalnumerical0–10ratingscore) Thetimingofpaininrelationtosurgeryisimportant. • • Psychologicalsupportandreassurancecanbecrucial. • • • • drug ifthepatientisobviouslyfearful.Anxiolysiswith50 Considerasmalldoseofananalgesicdrugandalsoanxiolytic • midazolam 1–2mg,canbehelpful. nitrous oxideinoxygenviatheanestheticcircuit,orintravenous 0.02 mcg/kg/min). StartwithIVopioid(e.g.,fentanyl25–100 mcgorremifentanil0.01– •

nerve (C the skindistributionofcervicalnerverootsphrenic Upto5 intraoperative pain. Surgicalexteriorizationoftheuterusincreaseslikelihood is notuncommonandcannormallybemanagedsatisfactorily. Painarisingduringpelvicorganinspectionandperitonealclosure sia willberequired. Painduringinitialincisionishighlyindicativethatgeneralanesthe- shoulder. times counter-irritation,withvigorousrubbingofthepainful Shoulder tippaincanbereducedbyhead-uptabletiltandsome- subdiaphagmatic peritoneumbybloodandamnioticfluid. manipulation brieﬂy inordertogaincontrol. at thetimeofdelivery,consideraskingthemtostopsurgical Informtheobstetricianofsituationandplan.Unless infant contactandinteraction. Usedistractiontechniques,especiallybyencouragingmaternal– conversion togeneralanesthesia. rapport, andifpainissevere,immediatelyraisethepossibilityof Ascertainherfeelingsabouttheproposedtreatment,maintain know howyouintendtotreatit. pain isoftenshort-livedandresolvesfully,letthepatient Reassurethewomanthatpainwillbedealtwith,mild Documenttheeventsandmanagement. Follow up with the patient, and counsel the woman postoperatively. Followupwiththepatient,andcounsel thewomanpostoperatively. % 3 ofwomenexperienceupperchestorshoulderpainin –C 5 ).Thisisthoughttoresultfromirritationofthe

% –70

119 Obstetric Anesthesia 120 Anesthesia for Cesarean Delivery • • • it should be used within 4 hours because it supports bacterial growth. it shouldbeusedwithin4hoursbecausesupportsbacterialgrowth. sodium thiopentalandsuccinylcholine)athand.Ifpropofolisprepared, Some liketokeepdrugsforinductionandintubationofthepatient(e.g., This includesinductionofgeneralanesthesiaduringtheoperation. anesthesia thatrequireintervention(seethefollowingandChapter13). Theanesthesiologistmustbepreparedforcomplicationsofregional due toComplications Management ofFailedRegionalAnesthesia • • • • and potentiallylife-threateningcardiovascularchanges. Regionalanesthesiaforcesareandeliveryisassociatedwithsigniﬁ Maternal Hypotension • •

Regional Anesthesia Management of EarlyComplicationsof ble psychomimeticeffects. administrationbecauseofpotentialoversedationandtheundesira- Specific consentfromthepatientshouldbeobtainedbefore that generalanesthesiaisinducedandairwayreﬂ exes arelost. required untilsedated).Caremustbetakennottogivesomuch Asalastresort,considerIVketamine(e.g.,5mgrepeatedas abdominal woundpainduringclosure). abdominal orpelvicpain)beneaththerectussheath(forsomatic ropivacaine) eitherintotheperitoneum(foradnexialorgeneralized Cavalcompressionmayreducevenous return. venous return. Venodilationmay,insomecircumstances, alsocausereductionof block anddecreasedperipheralvascularresistance. Modestbloodpressurereductionisanticipatedduetosympathetic Asktheobstetriciantoinjectlocalanesthetic(e.g.,20–30ml0.5 effect. ing thattheseandlocalanestheticwilltake5–15minutesto Giveepiduraladjuncts(fentanylorsufentanil,clonidine),recogniz- or atatimeofpossibleblockregression). Injectepidurallocalanesthetic(especiallyifneartheendofsurgery Areductioninheartrateviavarious mechanismsmayoccur. ing tounderperfusion ofmaternalvitalorgansandthe placenta. preload, strokevolume,andheartrate (thuscardiacoutput),lead- Acombinationofeffectscanreduce bloodpressure,leftventricular

cant

• mised (nonreassuringfetalheartrate patternsappear). potential aspirationorcardiacarrest) orifthefetusappearscompro- becomes symptomatic(nausea,vomiting, syncope,collapseand Treatmentoffallingbloodpressure iswarrantedifthewoman • • • under regionalblock,dependingonthedefi Hypotension occursin80 from baselineof10 hypotension, buttypicallyuseafallinsystolicarterialbloodpressure fetal compromiseisundetermined.Differentstudiesvariablydefi ne and durationofreduceduteroplacentalfl ow thatleadstosignifi degrees ofhypotensiondiffersbetweenindividuals,andthedegree during anesthesiaforcesareandelivery.Theclinicalimpactofsimilar Attentiontomaternalbloodpressureandheartrateisfundamental

in cardiacoutputduringpregnancy. fl as analysisofarterialpulsewaveformsandnoninvasiveDoppler inadequate uteroplacentalbloodfl ow. Newtechnologies,such tility indicesandneonatalarterialacademia,bothofwhichrefl in cardiacoutputcorrelateswithincreasedumbilicalarterypulsa- as bloodpressureiswellrecognized,becauseasignifi cental unit.Theimportanceofmaintainingcardiacoutputaswell infer thestateoforganperfusion,includingthatuteropla- sure andheartratematernalsymptomshavebeenusedto under typicalclinicalconditions,changesinmaternalbloodpres- pressure. Giventheinabilitytoreadilymeasurecardiacoutput Organperfusiondependsonadequatecardiacoutputandblood values. blood pressureasclosepossible topre-anestheticbaseline Neonatalacid-basestatusisbestmaintained bykeepingmaternal (Figure typically occurwithseverehypotensionorfallincardiacoutput hypotension, whilematernalsyncopeorafallinfetaloxygenation Maternalnauseaalmostalwaysreflectsmoderatetosevere active labororwhohaveseverepreeclampsia. Bloodpressurechangesappearlesssevereinwomenwhoare signifi anesthesia, butbedsidemethodstopredictwomenathigherriskof Bloodpressurefallswithin5–10minutesofinductionspinal ow assessments,arepotentialmeansofestimatingacutechanges canthypotensioncurrentlydonotshowclinicalutility. 4.9 ). % –30 % –90 % ,oranabsolutevalueof80–100mmHg. % ofwomenhavingcesareandelivery

nition.

cant decrease

ect cant

121 Obstetric Anesthesia 122 Anesthesia for Cesarean Delivery • • • • • Preventativemeasuresthatarehelpfulinclude: rapidly redistributestotheextravascularfl tion inducesatrialnatriuretichormone-relatedvasodilation,andfl preventing ortreatingmaternalhypotension.Crystalloidadministra- Intravenouscrystalloidadministrationisofnoorlimitedeffi cacy in Prevention ofMaternal Hypotension (1968). ephedrine duringspinalhypotension,p.917,CopyrightElsevier Vasopressors inobstetrics.I.Correctionoffetalacidosiswith AmericanJournalofObstetricsandGynecology,Vol.102 administration tothemother.Thisarticlewaspublishedin spinal anesthesia-inducedhypotension,hypoxia,oxygenandephedrine Figure 4.9

Lowerlimbcompressionstockingscombinedwithlegelevation. 0.25–0.5 mg,ephedrine 5–10mg). Vasopressorboluses(e.g.,phenylephrine 50–100mcg,metaraminol nylephrine 25–50mcg/min,metaraminol 250mcg/min). Titratedinfusionofavasopressordrug (e.g.,startingwithIVphe- starting withlowdosesofspinallocal anesthetic(4–8mgwithopioid). Slowestablishmentofepiduralanesthesia, oruseofsequentialCSEA, related allergicreactions,however. colloid 500–1,000ml.Thisisassociatedwithalowriskofcolloid- Preloadingorcoloading(concurrentwiththeonsetofblock) PaO2 100 120 20 40 60 80 0 23 minutes Control period Changes inarterialoxygentensionthefetusafter Spinal Oxygen to mother 105 Maternal hypotension 15 Time inminutes

20 uid compartment. Ephedrine to 25 mother

, ShniderSM,etal. 035 30 Maternal artery Fetal artery

40 uid

use fl 30 years,basedonanimalresearchofeffectsuteroplacentalblood namic properties(Table ease ofuse,directandindirectfetaleffects,otherpharmacody- Thechoiceofvasopressorisinfl hypertension and better controlfromhigherdoses.Thisalsoproducesmoreiatrogenic Theefficacy ofvasopressortherapyisdose-dependent,withgenerally Vasopressor Therapy Phenylephrine hasbeenbetterevaluatedthanother acidoticneonate,itarguablymaybenefi clinical signifi cance. Whileitisalmostcertainlydetrimentaltothe dependent fashion.Themagnitudeofeffectissmallandunknown direct metaboliceffectonthefetus,whichreducesfetalpHinadose- use ofephedrineisnowcontroversial-ithasbeenshowntohavea reduce cardiacoutput(duetoarefl ex fallinheartrate).Routine • • nifi Thispotentiallylethal complicationofepiduraltechniques wasasig- Background Systemic LocalAnestheticToxicity tocin administered,vasopressorsare seldomrequired. Onceafullautonomicandsensory block hasbeenachievedandoxy- agonists, andcomparedwithephedrine: • drug injection,ortreatmentwith100–150mcgboluses: or 100mcg/ml)runat25–75mcg/minfromthetimeofsubarachnoid Aprophylacticinfusionofphenylephrine(e.g.,10mgin100mlsaline • • • ow. Althoughstillwidelyused,manyanesthesiologistsnowroutinely

Ephedrinewasconsideredthevasopressorofchoiceforover cant cause ofmaternaldeath20yearsago, but isnowaveryrare prevent maternalhypotensionandnauseain90 A combinationofstrategies,including Prophylacticvasopressorinfusionismoreeffectivethantreatment. treating with glycopyrrolate (0.2–0.4 mg) or atropine (0.2–0.6 mg). treating withglycopyrrolate(0.2–0.4 mg)oratropine(0.2–0.6mg). 10 Minimizesmaternalsymptomsrelatedtohypotension(incidence Is associated with better maternal and neonatal acid-base outcomes. Isassociatedwithbettermaternalandneonatalacid-baseoutcomes. infusion. Ismoreeffectiveinpreventingmaternalsymptomswhentitratedby Mayreducematernalcardiacoutputduetoreﬂ stopping theinfusionchangingtoa < 50bpm).Bradycardiacanbecorrectedbydecreasingthedoserate, α %

1 versus -adrenergicagonistssuchasphenylephrine(Figure > 50 α % 1

-adrenergicagonistssuchasphenylephrinemay withoutvasopressor). 4.17 ). uenced byfactorssuchasavailability, β tthehealthyneonate. 1

-agonist such as ephedrine, or -agonistsuchasephedrine,or

α 1

-adrenergicagonists,will ex bradycardia (avoid ex bradycardia(avoid % ofwomen.

1 -adrenergic

4.10

123 Obstetric Anesthesia 124 Anesthesia for Cesarean Delivery is exceptionallyrare. rise inlocalanestheticbloodconcentrations leadingtoclinicaltoxicity when carefulattentionispaidtomaximum recommendeddoses,a epidural analgesiaduringlaborand“topping up”forcesareandelivery, induced changesinthemyocardium. Yet,despitethefrequencyof binding, reducedclearanceoflocal anesthetics,andprogesterone- from bupivacaineandropivacainebecause ofreducedplasmaprotein to thisimprovementinsafetyareshownTable event (estimatedincidence1in10,000).Possiblefactorscontributing • • • • Ephedrine Cesarean Delivery Blood PressureControlatRegionalAnesthesiafor Table 4.17 • • Phenylephrine • • • • • Metaraminol • • • •

Thepregnantwomanappearsmoresusceptibletosystemictoxicity • • Rapid onsetandeasilytitrated No effectonfetalacid-basestatus Typical doses0.2–0.5mg(bolus)or0.25–0.5mg/min (infusion) authorities nowdisagree,partlyduetolimitedefﬁ Considered thevasopressorofchoiceformanyyearsbut Rarely inducesventriculartachyarrhythmias • • more potent Potent direct The mostthoroughlyevaluatedalternativetoephedrineand 80times deﬁ Results inasmallreductionumbilicalarterypHandincreasebase Onset slightlydelayed(1–2minutes) • Typical intravenousdoses5–15mg(bolus)or1–5mg/min(infusion) • Rapid onsetandshortduration(5–10minpost-bolus)facilitates Potent directandindirect (infusion) No effectonfetalacid-basestatus titration Typical intravenousdoses100–150mcg(bolus)or25–75mcg/min Direct andpredominantlyindirect

increases peripheralvascularresistance cardiac outputstableorfalls increases heartandcardiacoutputwithmildperipheral marked peripheralvasoconstrictionwithreﬂ ex reductionin vasoconstriction tachyphylaxis maybeaproblem heart rate cardiac outputincreasesslightlyinitiallybutmayfallwithbradycardia cit

Features ofThreeVasopressorDrugsfor α 1-adrenergic agonist

α 1-adrenergic agonistwithsome β -plus weak α 1-adrenergic agonist cacy 4.18 .

β -activity during pregnancy(incidence5 serious toxicity.Epiduralveincannulationoccursmorefrequently Intravenouslocalanestheticinjectionisthemostlikelycauseof Intravenous Injection 1996;76(1):63. arterial pressureduringspinalanaesthesiaforcaesareansection. Randomized trialofbolusphenylephrineorephedrineformaintenance bolus (_)groups. Reprinted with permissionfromThomasDGetal. induction ofspinalanesthesiaintheephedrinebolus(_)andphenylephrine heart rate(HR)andcardiacoutput(CO)frombaselinevaluesafter Figure 4.10 reduced by: cularly, anteriorepiduralspace.Intravenous catheterplacementis azygous venoussystemandprominent veinsinthelateraland,parti- • • •

Useofaﬂexible, soft-tipepiduralcatheter.

Epiduralinsertionwiththewomanin thelateralposition. CO (% change) HR (% change) SAP (% change) Epiduralsaline(5–10 mlormore)injectedpriortocatheterization. –20 –10 –20 –10 10 20 30 10 10 20 0 0 0 21 134567891 11 31 15 14 13 12 11 10 9 8 7 6 5 4 15 14 3 13 21 12 11 10 9 8 7 6 5 4 3 21

Mean percentagechangesinsystolicarterialpressure(SAP), 101112131415 9 8 7 6 5 4 3 5% Studentizedrange:E 5% Studentizedrange:E 5% Studentizedrange:E Time from induction(min) Time % –10 % )asaresultofthedilated =15.8, P =11.6, P =14.9, P

=17.8 =11.3 =17.6 Br JAnaesth.

125 Obstetric Anesthesia 126 Anesthesia for Cesarean Delivery • • • sary toreliablydetectthechanges. so continuousmonitoringofheartrateandbloodpressureareneces- rent painfuluterinecontraction.Theresponseistransient,however, • bpm (after30–90seconds)intheabsenceof increase systolicbloodpressureby15mmHgandheartrate10 Intravenousbutnotepiduralepinephrine(adrenaline)15mcgwill Test-Dosing safety ofepidurallocalanestheticinjection: azepines). Anumberofstrategiesshouldbeappliedtoincreasethe response maybemodiﬁ ed somewhatbyotherdrugs(e.g.,benzodi- the rateofrisearterialconcentrationinvitalorgans.Theindividual’s concentration andtoxicitydependonthedrug,doseinjected, Afteraccidentalintravenousinjectionoflocalanesthetic,theblood Deaths fromLocalAnestheticToxicity Table 4.18 • • • • • • • •

tion andallowdetection ofsubjectivesymptomsbefore seizuresor 30–50 secondsbetweendoses(to reduce peakplasmaconcentra- Incrementalinjectionoflocalanesthetic, in5mlaliquots,waiting serious complications. 30 mg,orfentanyl100mcg,mayproduce clinicalsymptomsbutnot Lidocaineorchloroprocaine100mg, bupivacaine25mg,ropivacaine women withhypertension,cardiacdisease, orarrhythmias. when false-positiveresponsesoccur,andshouldbeavoidedin Epinephrinetest-doseshavelimitations,especiallyduringlabor lar placementofmulti-holedepiduralcatheters. and cathetersystemarehighlysensitivefordetectionofintravascu- Alwaysaspiratethecatheterlookingforblood.Aﬂ Publicity andeducation levo-bupivacaine) Management oftoxicitywithintravenousIntralipid“lipidrescue” toxicity Newer drugswithhighertherapeuticindices(e.g.,ropivacaineand (catheter aspiration,test-dosing,useofmulti-holedcatheters) Incremental epiduraldosing,observingforsignsandsymptomsof and delivery Better preventionanddetectionofintravascularcatheterplacement The reductioninlocalanestheticdosesforepiduralanalgesialabor injection thanlumbarepidural) The increaseduseofspinalanesthesiaforelectivecesareandelivery The declineinuseofcaudalblocks(muchhigherriskintravenous Factors PossiblyContributingtotheDeclinein

β -blockade oraconcur-

uid-fi lled fi lled lter or epiduralanesthesia isrecommended.Thisincludes womenwith logical consequences,atitratedtechnique suchassequentialCSEA and ventilation. oxygen mustbegivenandimmediate preparationmadeforintubation required. intercostalmusclescanbeexpectedandevengreatervigilanceis lower, amorecompletemotorblockofabdominalandthoracic though motorweaknessisusuallyatleasttwodermatomallevels • • Themanagementofsystemictoxicity(Table no morethan1in10patientsexperiencetypicalsymptoms: arrhythmic properties.Afteraccidentalintravenousinjection,probably amide localanesthetics,cardiacarrestisunlikelybecauseithasanti- where sensoryblocktoiceandpinprickextendswellaboveT monitored andreassuredwhileawaitingblockregression.Incases peak expiratoryfl ow andvitalcapacity.The parturientshouldbe surgical anesthesiahasanimpactonrespiratoryfunction,reducing Regionalblocktoalevelthatmeetstheclinicalrequirementsfor High BlockandRespiratory Depression be evident to seizures,myocardialdepressionandperipheralvasodilationmay Whenlidocaineisaccidentlyinjectedintravascularly,inaddition Systemic Toxicity • • • •

Inwomenforwhomhighblockhas particularlyundesirablephysio- Ifhypoventilationleadstoachange inmentalstateorhypoxemia, tion andcardiacarrest). sudden onsetre-entrantventriculararrhythmias,ﬁ Cardiotoxicity(myocardialdepression,bradycardia,hypotension, twitching, seizures)thendepression. visual disturbance,alteredmentation,restlessness,slurredspeech, Centralnervoussystemexcitation(tinnitus,circumoraltingling, develop mayindicateintravascularinjection. cardiac arrest)isrecommended.Failureofanepiduralblockto Airwaymanagement,avoidinghypoxiaandhypercarbia. Intravenouslipidinfusion.Thisimprovesthesuccessofresus Circulatorysupport. Suppressionofseizures. ment inmyocardialmitochondrialfunction(seeChapter3). appears relatedtobindingoflocalanestheticinplasmaandimprove- in animalmodelsandalso,itappears,humans.Themechanism — but, incontrasttobupivacaineandotherlong-acting

4.19

) isbasedon:

citation

2 brilla- ,even

127 Obstetric Anesthesia 128 Anesthesia for Cesarean Delivery Theexactmechanismofhighregionalblockisoftenunclear. Causes ofHighBlock ally alsocardiovascularsupport. intubation (preferablywithcricoidpressure)andventilation,usu- tion orapnea,lossofconsciousness.Suchaneventwillmandate a highblockleadstoimpairedphonationorswallowing,hypoventila- had ahighblockinthepast.Inapproximately13,000–5,000women, correct dosemaybedifﬁcult (e.g.,achondroplasia);orthosewhohave severe respiratoryorcardiacdisease;thoseforwhomjudgingthe • • IV=intravenous Use AdvancedLifeSupport algorithmsforcardiacarrestduringpregnancy • Give lipidinfusion • • • • Circulation • Seizures: Avoidpatientinjury • • • Airway andBreathing Get help Table4.19

withdrawal of20–30 mloflocalanestheticcontaminated CSFand eter thoughttobeentirelylocatedin theepiduralspace).Immediate example subarachnoidinjectionofepidural solutionthroughacath- Drugsmaybeunintentionallyinjected intotheincorrectspace(for cranial nervesandautonomic (e.g.,Horner’ssyndrome). occur (epiduralorsubarachnoid), involving cervicalnerveroots, Exaggeratedspreadwithintheplanned areaofdistributionmay • intervals) andinfuse0.25ml/kg/min 20 • • • • Treat arrhythmias • • • Treat hypotensionandbradycardiaaggressively Avoid aortocavalcompression Check heartrate,bloodpressureandapplyECGmonitoring Give ananticonvulsantasrequired(usuallyself-terminating) Watch forpost-ictalairwayobstruction Avoid hyperventilationaswellhypoventilation Maintain aclearairway,giveoxygenandventilate

% Intralipid1.5ml/kgbolus(repeat uptotwiceat3–5minute IV amiodarone300mgandavoidphenytoin,calciumchannelblockers IV phenylephrine100–200mcgthen50–100mcg/min IV norepinephrine0.05–0.5mcg/kg/min IV epinephrine10–100mcgboluses IV atropine0.6–1.2mg IV midazolam2–5mg IV diazepam5–10mg IV thiopental50–100mgorpropofol25–50

Management PlanforLocalAnestheticToxicity

• • anesthetic include: Theclinicalcharacteristicsofextensive subarachnoidspreadoflocal Total SpinalBlock spinal nerveroots,asisseenwithepiduralspread.(Figure medium acrossthespinalcanal,butnoextensionoutlininglateral on thelateralview,withsmoothcentraldistributionofcontrast typical appearanceofsubduralcontrastonX-rayis“railroadtracks” ing maybeworthwhiletoenablecounselingofthepatient).The eter shouldberemoved(althoughconﬁ rmation byradiologicalimag- Thediagnosisofsubduralblockisclinical,sooncesuspectedthecath- • • • • • • undetermined, butitisnotrare. the arachnoidmaterremainsintact.Theincidenceofsubduralblockis may alsooccupyortraversethistissueplane.NoCSFisseenbecause can becomesubduralorintradural.Amulti-holedepiduralcatheter Duringanapparentlyuneventfulepiduralneedleinsertion,thebevel Subdural Block

Respiratoryfailuremayoccur,butisuncommon. paralysis andseverehypotensionarerare). anteriornerveroots,andthusmotorautonomicnerves(motor Onsetisusuallymorethan20minutes,withrelativesparingof with achangeinthepatient’sposture). time within30minutesofspinalinjection, sometimesinassociation Risingsensoryandmotorblockleading todyspneaorapnea(atany high spinalblock. allowing thedrugtoentersubarachnoidspaceandresultina Intheory,largeﬂ uid volumesmayrupturethearachnoidmater, Approximately5 ric spreadisseen,evenaftersmallvolumesofinjectedsolution. Presentationisvaried,butusuallyextensivecephaladandasymmet- mater, leadingtohighcephaladandintracranialextension. genic dissectionofacellularlayerbetweentheduraandarachnoid Subduralorintraduralblockmayoccur,withdrugspreadbyiatro- by ananesthesiologist,andtheeffectsmonitored). ture (thus,allbolusdosesmustbegivencautiously,preferablyonly noid afterreplacementofanepiduralcatheterfollowingduralpunc- Epiduraldrugmaytransferthroughabreachintheduraandarach- beneﬁ replacement withsalinehasbeensuggested,butisofunproven t.

ofcasesresultinarestrictedlowblock.

4.11 ).

129 Obstetric Anesthesia 130 Anesthesia for Cesarean Delivery Epidurograms . 1998,TaylorandFrancis. permission fromCollierCB,Epiduralblocksinvestigated.In: contrast fromthemid-lumbartomid-thoracicregion. Reprinted with catheter. Arrowsindicate“railroadtrack”bilateraldistributionofsubdural epidurogram afterinjectionofradiographiccontrastthroughtheepidural Figure 4.11 • normal epiduraldrug responses.Somecaseseriesnote thathighspinal epidural catheter,althoughrarelyspinal blockoccursafterpreviously Themostcommoncauseisundetected intrathecalplacementofan •

Confusion,restlessness,severedrowsiness orunconsciousness. Moderatetoseverehypotension(and possiblecardiacarrest). Typical appearanceofsubduralspreadonanteroposterior An Atlasof

• • sensitive. segments. accentuate thethoraciccurveandlimitspreadtomid-thoracic important, withelevationoftheshouldersandupperthoracicspineto cessful. Attentiontopatientpositioningimmediatelyafterinjectionis after recent“toppingup”ofanepiduralcatheterhadprovedunsuc- block ismorelikelywhenspinalanesthesiarepeated,orinitiated Themanagementofveryhighblockissupportive(Table Management • appears exceptionallyrare. opioidsgivenpriortocesareandeliveryhasnotbeenquantiﬁ Theincidenceofsevererespiratorydepressionduetoneuraxial Opioid-Induced Respiratory Depression although substandardcarestillleadstomaternaldeaths. sciousness andadequateventilation.Afullrecoveryisexpected, and sedation,untilblockregressionissufﬁ ventilation,alongwithnaloxone,oxygen,cardiovascularsupport and monitor.Inmostcases,treatmentwillrequireintubation patients remainconsciousandclinicallystableenoughtoobserve • • •

Nomethodofdetectioncatheterlocationiscompletely “safe” doseoflocalanesthetic,suchas3ml1.5 Atest-doselookingforrapidonsetofsacralblock(byinjectinga looking forCSF. Beforeeachinjection,anepiduralcathetershouldbeaspirated, 0.5 indicative. the aspiratedsolutiontoprecipitateinsodiumpentothalarealso is highlysuggestiveforCSF,andthewarmthofCSForfailure tissue ﬂ uid) areunreliable.However,glucosecontentofﬂ uid BedsidetestsforCSF(asopposedtosaline,epiduralsolutions,or in particularafterinitialinsertion. ventilation orventilatory responsestocarbondioxide. supports anoptimumdoseof100–150 mcg)donotaffectminute Intrathecalmorphineiswidelyused, butdoses<250mcg(evidence to causehypoventilationbutworrisome casereportsareveryrare. Epiduralfentanyl100mcgorsufentanil 10–50mcghavethepotential or withoutrespiratorydepression,within 5–30minutesofinjection. cause sensorychangesinacervicalor cranialnervedistribution,with Rarely,intrathecallipophilicopioidssuchasfentanylorsufentanil % ropivacaineor2mlof0.5

% bupivacaine)shouldbe

cientforthereturnofcon- %

lidocaineor

4.20 considered, ed, but ed, ). Some

131 Obstetric Anesthesia 132 Anesthesia for Cesarean Delivery • • • tory depressionoccursinapproximately1500cases. Nevertheless,afterneuraxialmorphine,clinicallydetectablerespira- may beasaferor more sensibleoption( Tables a numberofcircumstancesandpatients forwhomgeneralanesthesia regional anesthesiaafteradequatediscussion. Neverthelessthereare delivery andevenwomenwhoinitially requestitusuallyconsentto Generalanesthesiaisinfrequentlythe preferredoptionforcesarean Indications IV=intravenous Make adiagnosisandcounsel thepatientlater required ifwellmanaged) Monitor thefetusifundelivered (urgentcesareandeliveryisnotlikelytobe • • • Monitoring andcirculatorysupport 2–4 hours) Extubate onceventilationadequate andpatientisconscious(usuallywithin pressure andventilateusingcontinuedintravenoussedation Intubate (withorwithoutsedation andparalysisasrequired)usingcricoid • • • Get help Table 4.20

General Anesthesia

Depressionisusuallymild,andnaloxoneinfrequentlyrequired. Task ForceonNeuraxialOpioids(seealsoChapter5). and depth,basedonpracticeguidelinessuchasthoseoftheASA least observationalmonitoring,suchassedation,respiratoryrate Administrationofepiduralorintrathecalmorphinemandatesat Presentationistypicallydelayed3–12hours,andthuspostoperative. • • • • • Avoid aortocavalcompressionifundelivered arterial bloodpressure) Correct hypotensionandbradycardia Monitor maternalhemodynamics(includingnoninvasiveorcontinuous Determine ifintubationandventilationisrequired(unconscious,apneic) Give naloxoneifopioidmaybecontributingtorespiratorydepression Airway, oxygenationandventilation:givehighinspiredoxygen

IV phenylephrine100–200mcgthen50–100mcg/min IV norepinephrine0.05–0.5mcg/kg/min IV vasopressin20unitsthen0.2–0.4units/min IV atropine0.6–1.2mg IV crystalloidinfusion Management PlanforHighBlock 4.4 and

4.21 ).

Prerequisites are informedconsent,fullpreparation andplanning convert togeneralanesthesiainthe eventofmassivehemorrhage. beginning witharegionaltechnique but maintainingalowthresholdto reduce bloodloss,andinmanycases clinicalexperiencesupports morbidly adherentplacenta)iscontroversial. Regionalanesthesiamay erative andpostpartumhemorrhage (e.g.,anteriorplacentaprevia, • • • • • • • • • • Table 4.21

Theuseofgeneralanesthesiaforwomen atriskofmajorintraop- Severe respiratoryimpairmentwhensupine uncorrected pulmonaryedema) Respiratory failurerequiringventilation(e.g.,severe pneumoniaor • • • • • • • • • Potential contraindicationtoregionalanesthesia Emergency (category1)cesareandeliverybecausethereisthethreatof successful delivery underregionalanesthesia Anatomical abnormalitieswhereregionaltechniquesareunlikelytobe Previous traumaticexperiencewithregionalanesthesiaorcesarean immediate fetaldeath Maternal refusalofregionalanesthesia • • • Uncooperative patient suspected neurologicalcomplication Mental statedisturbance Recent eclampticseizurewithsignsofpossiblefurtherseizuresora

infection concerns(systemicsepsis,lumbarskininfection,acuteviral disease) neuraxial canalhematomaconcerns(severethrombocytopenia, or acquiredbleedingdisorders) circulatory collapseconcerns(e.g.,hemodynamicallyunstabledueto normalized ratio e.g., plateletcount<50x109/dl;coagulopathy,international hypovolemia, severesepsis) concern reconsequencesofduralpunctureinthepresenceraised cardiac diseaseswhereexcessive reductioninafterloador intracranial pressure(e.g.,cerebraltumor) pulmonary hypertension) raised intracranialpressureorcentralnervoussystempathology of venousreturnmaybedisastrous(e.g.,severeaorticstenosisor (e.g., largeintracranialtumor) where changeincerebrospinalﬂ psychiatric illness drug-induced state severe needlephobia severe scoliosis extensive lumbarsurgery certain spinalmusculardisorders Indications forGeneralAnesthesia > 1.5;therapeuticanticoagulation; certainhereditary

uid pressuremaybedetrimental

133 Obstetric Anesthesia 134 Anesthesia for Cesarean Delivery • ness andreturnofprotectiveairwayreﬂexes attheendofsurgery. The endotrachealtuberemainsinplaceuntilthereturnofconscious- induction andintubationisrecommendedforpulmonaryprotection. tracheal tube,sountilwehavemoresafetydata,rapidsequence not offerthesameprotectionagainstaspirationasacorrectlysited for generalanesthesiacesareandelivery.Supraglotticairwaysdo it willreduceregurgitationintothehypopharynxandisrecommended incidenceofaspiration,andcausesproblemswhenappliedincorrectly, • • cricoidpressure(Figure Chapter 2),areatriskforregurgitationandaspiration.Although Pregnantwomen,beingconsideredtohavea“fullstomach”(see Principles ofInductionandMaintenance • • techniques arereservedforspecialcircumstances. allow lowerconcentrationsofinhalationalanesthetic.Alternative delivery; postdelivery,intravenousopioidisusedforanalgesiaandto Maintenance ofanesthesiaiswithinhalationalpriorto followedbytrachealintubationwhilemaintainingcricoidpressure. for cesareandeliveryisanintravenousrapidsequenceinduction, Therecommendedapproachfornearlyallcasesofgeneralanesthesia Technique andDrugs familiarity withsuchanapproach. to managehemorrhage,andamaternitysettingwithresources opioid isalsousuallyomitted. opioids arenotusuallyused,tominimize fetalexposure.Intravenous

Priortooratinduction,anxiolytic drugssuchasmidazolamand activation)tolaryngoscopy andintubation.Thisresponse causes nervous system,adrenalcatecholamine andneuroendocrine in selectedpatientstoobtundthe “stress response”(sympathetic remains controversialpractice. risk factorsforaspirationandhavingelectivecesareandelivery.This airway) hasbeenusedinfastedwomenoflowbodyweight,withno Airwaycontrolwithasupraglotticairway(i.e.,laryngealmask thermia isarisk. Totalintravenousanesthesiacanbeusedwhenmalignanthyper- patients withacompromisedorexpecteddiffi Awakeintubationfollowedbyintravenousinductionmaybeusedin in apredicteddiffi Aninhalationalinductionwithsevofl urane mayrarelybeindicated Administrationofopioid(orother drugs, Table

cultairwayorseverelyneedle-phobicpatient. 4.12

)hasnotbeenproventoreducethe

cultairway.

4.22 ) iswarranted

• • gastric contentintothepharynx. Figure 4.12 intubation responses(Table options, whichmaybeusedincombination,aresuitabletoobtund occasionally neonatalrespiratorydepression.Anumberofother intubation response,butmaycausepost-intubationhypotensionand Intravenousremifentanilisthemosteffectiveopioidtoobtund • and equipmentisuseful.Thisshould include: previously. Priortogeneralanesthesia, achecklistofrequirements Detailsofpatientassessmentand preparation havebeendescribed Patient Preparationand Positioning only afewminutes’exposurebeforebirth. sufﬁ cient tocausesigniﬁ cant neonataldrowsiness,providedthereis titrated, canbemonitoredanddonotachievefetalconcentrations • •

Inhalational(volatile)anestheticdrugscanbeused.Theyareeasily maternal opioidshavebeengiven. Informthestaffmemberresponsibleforneonatalresuscitationif disease. poorly controlledhypertension,ischemicheartandseverecardiac Opioidsareconsideredforwomenwithseverepreeclampsia, vascular eventinhypertensivewomen. hypertension, tachycardiaandincreasestheriskofacerebro- Readyaccesstoa“difﬁ induction) Aspirationprophylaxis(withatleast anoralantacidshortlybefore Free-ﬂ owing intravenousaccess Application ofcricoidpressuretopreventregurgitation cultairway”cartandequipment 4.22 ).

135 Obstetric Anesthesia 136 Anesthesia for Cesarean Delivery • • • • • • secured. gowned andgloved,readytostartassoontheairwayis to be,preppedanddraped.Thesurgicalteamshouldlikewisebe table (notinaninductionroom)andwiththepatientalready,orready tion usuallytakesplaceafterpositioningthepatientonoperating Tominimizethedurationoffetalexposuretomaternaldrugs,induc- • • Local anesthetics • • Vasodilators maternal sideeffectsofsevereburning,ﬂ ushing andheadache) Magnesium 30–60mg/kg(after intravenousanestheticinduction,toavoid • • Beta-blockers • • • Opioids and TachycardiainResponsetoIntubation Table 4.22

Fullpreparationfortrachealintubation Attentiontopatientpositioning(pelvictiltandairway) Thoroughpreoxygenation(denitrogenation) port or pillow, to prevent the head falling to the left after induction. port orpillow,to prevent theheadfallingtoleftafter induction. Considerplacingabolstertotheleft sideofthehead,usingasup- less riskwithregurgitation). results inmorerapidandeffective denitrogenationandarguably genation, especiallyifsheisobese, beforelayingherdown(this Considerplacingthewomanhead up30degreesduringpreoxy- and aligningtheviewtolarynx(Figure creating spaceattheanteriorneckforeasieraccesstomouth improved byelevatingthethoraxandthenheadonpillows, Accesstotheairway,especiallyinmorbidlyobesewoman,is table tiltmaymakethewomanfeelinsecureaboutfalling.) left) bymeansofapelvicorlumbarwedgetabletilt.(15degrees Patientpositioningmustincludelateralpelvictilt(preferablytothe lidocaine (lignocaine)1mg/kgslowly hydralazine 10–15mg nitroglycerin (glyceryltrinitrate)250–500mcg labetolol 25–50mg esmolol 0.5–1mg/kg respiratory depression) post-intubation hypotensionandoccasionallytransientneonatal remifentanil 1mcg/kg(slowbolusover60seconds,withriskof alfentanil 7.5–10mcg/kg(bolus) fentanyl 5–10mcg/kg(bolus) Intravenous DrugsthatReduceHypertension

4.13 ).

• • • nonpregnant individuals. stores (i.e.,areducedfunctionalresidualcapacity)comparedwith Pregnantwomenhavehigheroxygenconsumptionandlower Preoxygenation anesthesia. Noteelevationoftheuppertorsoandheadneck. the neckandmouthviewatdirectlaryngoscopyinductionof Figure 4.13 • oxygenated priortogeneralanesthesia. Thus,itismandatorythatallwomen havingcesareandeliveryarepre- •

adequate denitrogenation isincreased. Ifthepatienttalksandmaskis removedbriefl y, thetimeto fi tight-fi Ahealthypregnantwomangiven100 can beattemptedifpreoxygenationisnotperformed. woman attheonsetofapnea,leadingtocyanosisbeforeintubation Maternaloxygentensionfallsattwicetherateofnonpregnant 100%oxygen(FiO such thatoxygensaturationis minutes achievesanarterialoxygentensionof350–550mmHg, small airwayclosureinthesupineposition). respiratory disease(leadingtohigheroxygenconsumptionand/or is reducedbyfactorssuchasobesity,labor,sepsis,smokingand Thissafeperiodinwhichtocontroltheairwayandstartventilation after apnea. rmingnolargeleak). tting facemaskat10L/min(anormal capnographytracecon- Positioning oftheobeseparturienttoimproveaccess

2 1.0)shouldbedeliveredthrougha circuitand

> 90 % forapproximately3–5

% inspiredoxygenfortwo

minutes

137 Obstetric Anesthesia 138 Anesthesia for Cesarean Delivery although theseappearlesscommon thaninnonpregnantpatients. psychomimetic effects,inparticular hallucinationsandnightmares, It israrelyusedindevelopedcountries becauseofitspostoperative for inductionandtheninfused for maintenanceandanalgesia. Ketamine induction) comparedwithpentothal. induction andarguablyagreaterchanceof“light”anesthesiapost- response curve(thusrequiringsometitrationduringrapidsequence effectively (duetoperipheralvasodilation),andshowsaﬂ Propofol • • • cause tissuenecrosisifextravascularspreadoccurs. and effectiveuse.Itmustbemixedwithdiluent,highalkalinitycan Sodiumthiopental Intravenous AnestheticDrugs • • • • •

refl Withsuccinylcholine,itmayincreasemassetertone,andairway with propofol. and lessmood-enhancementduringtherecoveryphase,compared Pentothalisabarbituratethatcausesmoremyocardialdepression saturation afterinduction. nasopharyngeal insuffl ation ofoxygenat5L/minwillhelpmaintain Forobeseparturientshavingnonelectivecesareandelivery, 6–10 repeatedvitalcapacitybreathsissuffi ventilationbutinemergencycaseswheretimeisatapremium, > End-tidaloxygenconcentrationsshouldbemonitored,aimingfor woman. mechanics andspeedtheprocess,especiallyinmorbidlyobese The25–30degreesemi-erectpositionmayimproverespiratory neonatal sedationthananinhalationalanesthetic. Ifcontinuedasamaintenanceinfusion,propofolresultsinmore hyperthermia risk(totalintravenousanesthesia). asthma (lessactiveairwayrefl exes versuspentothal)ormalignant while othersreserveitforspecific indications.Theseincludesevere Someanesthesiologistsprefertousepropofolbecauseof because theavailabilityofpentothalisdiminishinginsomeplaces. endorsed foruseinpregnancy,itisnowwidelyused,especially Propofolhasgoodrecoverycharacteristics,andalthoughnot 90 exes showmoreactivitythanafterpropofol. % priortoinduction(thisusuallyrequires3minutesattidal (2–2.5mg/kg)isaphenolthatcontrolshypertensionmore (1.5mg/kginitially)iswidelyusedin developingcountries

(thiopentoneorPentothal)hasalonghistoryofsafe

cient).

atter dose- atter familiarity, familiarity,

• • • • • Atypicalinductionsequenceafterpreoxygenationis: Muscle Relaxants Rapid SequenceInduction,CricoidPressureand hypovolemic patient. may causenausea.Itprovidesgoodhemodynamicstabilityinthe in obstetrics.Itcausesmyoclonicmovementandpainoninjection;it Etomidate • • •

Itisassociatedwithgoodneonataloutcomes. hypertensive patients). Ketamineincreasesmaternalbloodpressure(soisbestavoidedin Intravenoussodiumpentothal4–5mg/kgorpropofol2–2.5mg/kg. reduced dose)withpropofolorpentothal. lemic (e.g.,fromprepartumhemorrhage),andmaybecombined(in Itprovidesmorestablehemodynamicsinpatientswhoarehypovo- isolation ofthelungshasbeenconfi pressure shouldnotbereleaseduntiltrachealtubeplacementand remanipulation orremoval,toallowintubation.Ideally,cricoid the thyroidcartilage,itmaydistortlaryngealviewandrequire from theanesthesiologist.Ifappliedtooforcefullyorhighnear (2–3 kgor20–30NewtonsofforcetowardC cervical vertebrae.Atrainedassistantappliessuffi cient pressure occluding thehypopharynxagainstparavertebraltissuesand gastric contentreachingthelaryngealinletandbronchialtreeby lost (Figure Applicationofcricoidpressurebyanassistantasconsciousnessis ventilation). on clinicalneed,suchasabdominal musclelaxityandtoleranceof a nondepolarizingneuromuscularblocking drugmaybegiven(based plasma pseudocholinesteraseconcentrations duringpregnancy), after succinylcholine,thelongerduration resultingfromlower Whenneuromuscularfunctionreturns(typically5–15minutes capnography. tube location(intrachea,abovecarina)confi rmed clinicallyandby not seen)laryngoscopyandintubationareperformed,correct Afterfasciculationshaveceased(orafter45secondsiftheyare mum of150mg). Intravenoussuccinylcholine(succinylcholine)1.5mg/kg(toamaxi- (0.3mg/kg)hasnotbeenadequatelyevaluated 4.12 ). Cricoidpressurephysicallypreventsregurgitated

rmed.

6 )underinstruction

139 Obstetric Anesthesia 140 Anesthesia for Cesarean Delivery response topentothalandsevofl reduces theresponsetonociceptivesurgicalstimuliandincreases stimuli), isreducedbyapproximately25 thetic drugpotencyforinhibitionofspinalcordresponsestonoxious Theminimumalveolarconcentration,orMAC(whichrefl Inhalational Anesthetics (ET-3 1.5 MAC. increases at tocolytic effectof0.5MACvolatile anesthetic.Bloodlossonly tion. Themyometriumwillmaintain normalcontractilitydespitethe ET-sevofl ET-anesthetic concentrationequivalentto0.75–1MAC(e.g., can’t ventilate”scenario. often excessiveandconsidereddangerousina“can’tintubate, paralysis (30–60minutesbeforereversalcouldbeattempted)was dose of0.6–1.0mg/kg,butuntilrecentlytheresultingduration It providessuitableintubatingconditionsin60–90secondsaftera a goodsideeffectprofi le (otherthanrareallergicreactions). good intubatingconditionswithin45–60seconds. follow repeatadministration.Ithasthefastestonset,creating frequent thaninthenonpregnantpopulation.Bradycardiamay the riskofaseriousreactionis1in4,000.Myalgiahowever,less in malignanthyperthermiaandsomeothermusclediseases, may influence futurepractice. reverse anintubatingdosewithin3minutes,andthisnewdrug Succinylcholine Isofurane(ET-0.6 Tominimizeperiodsof“light”anesthesia,aimtoreachan • • •

Rocuronium Residualparalysisshouldalwaysbereversed. (e.g., ulnarnerveandadductorpollicisresponse). Neuromuscularblockshouldbemonitoredbynervestimulation (sometimes onlytheinitialdoseofsuccinylcholineisrequired). 0.15 mg/kgoratracurium0.1mg/kg)becausesurgerymaybefast Smalldosesofshort-actingdrugsarepreferable(e.g.,mivacurium % ) areallsuitableinhalationalanesthetics, withslightlydiffering urane 1.5 urane > 1MAC,andtheuterusrespondsto oxytocinatupto hasitsproponentsforintubationbecauseof % % hassomedisadvantages )asrapidlypossibleafterintravenousinduc- –0.8 % ),sevoﬂ urane (ET-1.5 Sugammadex

urane. % duringpregnancy.Labor — (16mg/kg)willfully it iscontraindicated

% )anddesﬂ urane

ects anes- ects

• • • signifi interval isespeciallyimportant,becauseplacentalbloodfl status andclinicalconditionatbirth.Theuterineincisiontodelivery be moreimportantthandrugeffectsininfl ( hypotension,hypoxemia,hypocarbia(<25mmHg)orhypercarbia Theimpactofmaternalphysiologicalderangements,suchas induction todeliveryinterval. such thatneonatalsedationisminimalatbirthirrespectiveofthe system drugexposureislimitedbydilutionandhepaticmetabolism, tends tominimizefetalexposure.Inaddition,centralnervous falling concentrationgradientacrosstheplacentatofetus,which nous anestheticconcentrationafterbolusinjectionproducesarapidly Despiterapidplacentaltransfer,thedeclineinmaternalintrave- Neonatal Considerations The DeliveryPhase,includingFetaland of administration. analgesic requirements,andhasnodisadvantagesaftershortperiods Nitrous oxideisausefuladjunct,reducinginhalationalanestheticand pletion ofsurgery,rapidarousalforawakeextubationisachieved. intravenous anestheticeffectsiteconcentrationfallsrapidly.Atcom- rapid onsetandoffset.Post-inductionthisallowsup-titrationasthe pharmacologic properties.Thelattertwoarepopularbecauseoftheir • (Figure with highermaternalinspired oxygenandoxygenation Althoughfetaloxygentensioninthe umbilicalveinandarteryincrease • • >

Physiologicalaimsduringanesthesiaareto: 34mmHg)onplacentalbloodﬂ ow andgasexchangearelikelyto ics areevenslowertoequilibrate. venous concentrationslagwellbehind.Otherinhalationalanesthet- ibrates inmaternalbloodwithin20–30minutes,butumbilical preferably occurwith15minutesofinduction.Nitrousoxideequil- Tominimizefetalexposuretoinhaledanesthetics,deliveryshould neonate, butthisisseldomsevere. Opioidsproducedose-dependentrespiratorydepressioninthe ionized, soshowminimalplacentaltransfer. Polardrugssuchastheneuromuscularblockingarehighly Ventilatetonormocarbia(30–32mmHg or4–4.3kPa). Maintainbloodpressureatpre-anesthetic levels. Keepoxygenationsaturationsatisfactory ( cantlyduringthisperiod. 4.14 ), thisconfersnoapparentbeneﬁ t tothehealthyneonate

uencingneonatalacid-base >

95 % ).

owdeclines

141 Obstetric Anesthesia 142 Anesthesia for Cesarean Delivery delivery. of 30 cord bloodoxygencontentafteradministrationofmaternalinspired general anesthesiaforcesareandelivery.Umbilicalvenous(a)andarterial(b) Figure 4.14 2009;103:559 Figure1. during generalanaesthesiaforCaesarean section. Randomized double-blindcomparisonof differentinspiredoxygenfractions with group100. Reprinted withpermissionfromNganKeeWD,etal . (b) (a)

% , 50 Oxygen content (ml dl–1) Oxygen content (ml dl–1) 10 12 10 12 14 16 18 20 14 16 18 20 ∗ ∗ 0 2 4 6 8 0 2 4 6 8 % or100 P<0.01comparedwithgroup100. Effect ofmaternaloxygenationonneonatalduring % frominductionofgeneralanesthesia atcesarean ru 0Group50 Group 30 Group 30 *** ** ru 0Group100 Group 50 ** ∗ ∗ ∗ Br JAnaesthesia . P<0.001compared Group 100 bolus (1–5iu)andbyinfusion(5–30iu/h). reduce postpartumbleedingandincreaseuterinetone,usuallybyIV when 100 at birth.Thehypoxemicfetusmayachievehigheroxygentensions inspired oxygenisofoutcomebeneﬁ free radicalformationincreases,soitisunclearwhetherhighmaternal • • • • • • aiming forend-tidalvaluesof0.1MACasquicklypossible. As surgeryends,inhalationalanestheticsarereducedandceased, tube tosuctionthestomachshouldbeconsideredduringanesthesia. patient withautonomicneuropathy),passingalargeboreorogastric Ifawomanhaseatenrecentlyorgastricstasis(e.g.,diabetic The ExtubationPhase transversus abdominisplaneblocks(Chapter5)canbeused. Alternate oradjunctivemethodsofpostoperativeanalgesia,including morphine 0.1–0.15mg/kgisgiventoprovideanalgesiaatarousal. Postdelivery,anintravenousopioidsuchasfentanyl3–5mcg/kgor

Intravenoussyntheticoxytocinisgivenimmediatelyafterdeliveryto Sideeffectssuchaspalpations,nausea,headacheandﬂ tion. tachycardia, andincreasedcardiacoutputafterrapidadministra- Oxytocincausesvasodilation(mildbloodpressurereduction), of 2iuappearsaseffective5atscheduledcesareandelivery. increasing thisto3iuafteroxytocinexposureduringlabor).Adose 95 dose of5iuiscommonlyusedbutatelectivecesareandeliverythe Theoptimaluterotonicdoseisuncertain.“ProductInformation” and briefdurationofclinicaleffect(5–15minutes). Oxytocinhasarapidonset(within1–2minutes)butshorthalf-life position (topreventaspirationafter regurgitation). Extubationissafestifconductedwith thewomaninleftlateral nium, inthefuturepossiblysugammadex) shouldbegiven. 10 mcg/kgoratropine20(or afterrocuroniumorvecuro- < 0.9)thenneostigmine20–50mcg/kg andeitherglycopyrrolate Ifneuromuscularfunctionrequiresreversal(train-of-fourratio ischemic heartdisease,uncompensatedhypovolemia). or evencardiacarrest(e.g.,severevalvularsubvalvularstenosis; increase incardiacworkmightprecipitatefailure,ischemia Bolus administrationshouldbeomittedforwomeninwhomthe % effectivedoseis<1iu(withdown-regulationofreceptors % inspiredmaternaloxygenissupplied,buttoxic t.

ushing occur.

143 Obstetric Anesthesia 144 Anesthesia for Cesarean Delivery • • • • • of thegastro-esophagealsphincter. effect oftheexpandingabdominalcontentsonangleandfunction symptoms areverycommoninlatepregnancy,exacerbatedbythe the loweresophagealsphincterbeginsinﬁrst trimester,andreﬂ that predisposetoregurgitation(Chapter2).Hormonalrelaxationof more commoninpregnancyasaresultofthegastrointestinalchanges Aspirationpneumonitisisararecomplicationthatthoughttobe Characteristics Aspiration • (Table Anumberofmeasurestopreventaspirationareappropriate Prevention ofAspiration •

General Anesthesia Management ofComplications has beenattributedto: elective cesareandelivery.Thislowincidenceofclinicalaspiration is verylow(estimate1in600–2,000)buttwiceaslikelyatnon- • Therateofsigniﬁ delivery is1in100–200. Therateofregurgitationduringgeneralanesthesiaforcesarean sive careunit,oraftercollapseseizure). erative period(e.g.,insedatedorunconsciouswomentheinten- Manycasesofaspirationnowoccuroutsidetheimmediateperiop- Supplementaloxygenshouldbegivenpost-extubation. quately, hasfunctioningairwayreﬂ Extubationshouldbedelayeduntilthepatientisbreathingade- • Fasting • < 5 Improvedcriticalcarehasledtoafallingmortalityrate(estimated •

thepredominantuseofregionalanesthesia theuseofrapidsequenceinductionforgeneralanesthesia precedence overfasting status. Labor isunpredictable,however,and theneedtodelivertakes Labor Anesthesia GuidelinessuchasASA’s pharmacologicalaspirationprophylaxis % ). 4.10 describeacceptedpracticefororal intakeinparturients. andFigure4.15): andACOG’s cantaspirationassociatedwithgeneralanesthesia

Committee OpiniononOralIntakeduring Practice GuidelinesforObstetric

exes, andrespondstocommand.

• or lost,airwayprotectionbyintubationiswarranted.Despitealackof Wheneverconsciousnessorairwayreflexes aresignifi Management ofAspiration Davies JM. stomach: factorsofimportance totheanaesthetist,vol.37,1990, p.902, permission fromSpringerScience: and laryngealrefl exes topreventaspirationintothetrachea. regurgitation intothepharynx;andmaintenance ofactiveupperairway With kind esophageal sphincterpressureandrefl ux. (4)Cricoidpressuretoprevent of suddenincreasesinintragastricpressure. (3)Preventionoffallinlower stomach andreductionofgastricfl uid volumeandacidity.(2)Prevention associated withobstetricanesthesia.(1) Emptying ofsolidsfromthe Figure 4.15 •

anesthesia byeffectiveapplicationofcricoidpressure. Preventionofregurgitationintothehypopharynxoninduction likely tocauselunginjury) • Reductionofgastricacidity(gastriccontentpH

entering labormayretainsolidsformanyhours). labor andopioidanalgesiamarkedlyimpairemptying(women Pregnancypersedoesnotaltergastricemptying,butpainduring Measures directedatpreventingaspirationpneumonitis

4 Canadian JournalofAnesthesia , The 1 3 2 > cantly impaired

3ismuchless

145 Obstetric Anesthesia 146 Anesthesia for Cesarean Delivery and difﬁ and chest,mucosaledemaoftheupper airwayandoccasionallylarynx, higher becauseofanatomicalchanges (fatdepositionintheface,neck pregnant woman. anestheticprioritieswheneverprofessional contactismadewitha Nevertheless, airwayassessmentandmanagementplanningare anesthesia forcesareandeliverycanbeexceptionallysafe. the latterisfalling,andepidemiologicaldatashowsthatgeneral maternal death.Thereissomeevidencethattheincidenceof of “closedclaims”andaretheleadingcauseanesthesia-related complications ofairwaymanagementcomprisealargeproportion Despitetheinfrequentuseofgeneralanesthesiaforcesareansection, Failed Intubation • • • • • natal unit,ortheintensivecareunit. ent oneachfacility’sresources;thismaybethelaborward,post- Thebestenvironmentforcontinuingrespiratorycarewillbedepend- ventilation. under bronchoscopicvision,shouldbeperformedpriortocontrolled of boththeupperairwayandtracheobronchialtree,preferably should beassessedforsoiling.Ifpossibleandappropriate,suctioning are important. regurgitation risk,sosafepatientpositioningandtimingofextubation the lungsareisolated.Bothinductionandextubationtimesof evidence foroutcomebeneﬁ t, cricoidpressureshouldbeuseduntil

Duringpregnancy,theincidence of diffi cult intubationismuch Ifregurgitationiswitnessedandaspirationsuspected,theairway infection. Antibioticsaregivenbasedonmicrobiologicalevidenceof inspired oxygen,andrespiratorycareareneeded. required and,ifso,whatventilatorysupportstrategies,increased Adecisionshouldbemadeastowhethercontrolledventilationis done (thoughsignsmaynotappearforseveralhours). X-ray lookingforevidenceofinfi ltrates orconsolidationshouldbe of oxygenation(pulseoximetry,arterialbloodgasanalysis).Achest Respiratoryfunctionshouldbecloselymonitored,withassessment observation forpostoperativedyspnea,cough,andfever. Patientassessmentincludesphysicalexaminationofthechestand purposes). Thegastricfl cultyinoptimizingthepositionof patient). uid pHshouldbecheckediffeasible(forprognostic

• • • • • to intubate. be assessedaslikelytodiffi cult, and1in20–50willprovediffi training and“failedintubationdrills.” may beinsuffi cient. Thishasincreasedtheimportanceofsimulation decreased useofgeneralanesthesiainmostdevelopedcountries) been raisedthattrainingandexperience(whichhasfallenwiththe Dealingsafelywiththeairwayisofprimaryimportance.Concernhas • local anesthesia. some obstetricianshavetheexpertise toperformthesurgeryunder bation mayberequiredifregional anesthesia iscontraindicated,and remains essentialincaseofhighorfailed block.Awakefi anesthesia isthebestoption,butpreparedness forgeneralanesthesia during laborisawisestrategy.When diffi culty ispredicted,regional are ofknownorpredicteddiffi culty. Earlyepiduralcatheterization and planning.Obstetriciansmustbeencouragedtoreferwomenwho Managementofthediffi cult airwaystartswithassessment(Table Assessment andPlanning

Caseseriesandcohortstudiessuggestthat1in15–20womenwill diffi (obesity maybeindependentlyassociatedwithagreaterriskof reserve, aswellconcurrentmedicalconditionsandobesity by theparturient’shigheroxygenconsumptionandlower Maternaloutcomesassociatedwithdiffi cult intubationareaffected (bronchospasm, laryngospasm)in1100,generalanesthetics. Severehypoxemiaoccursin150,andotherairwaycomplications delivery. ment andoccursin1100–200generalanestheticsforcesarean Regurgitationmaybeassociatedwithdiffi cult airwaymanage- 10,000. general anesthesiaforcesareandeliveryisestimatedas1in5,000– Theincidenceof“can’tintubate,can’tventilate”situationsduring familiarity oftheattendinganesthesiologists. goscopy), theincidencevaryingaccordingtoexperienceand sia is1in250–3000(mostcasesbeingagrade3viewatdirectlaryn- Theincidenceofabandoned(“failed”)intubationatgeneralanesthe- anesthesiologists. more frequentlyinurgentcasesconductedbylessexperienced deliverywhentimepressureisgreat,andfailedintubationoccurs Generalanesthesiaisoftenrequiredfornonelectivecesarean cultairwaymanagement).

beroptic intu-

cult 4.9 )

147 Obstetric Anesthesia 148 Anesthesia for Cesarean Delivery • • • • anesthesiologist intheoperatingarea.Thismightinclude: Anarrayofspecialdevicesandequipmentmustbeavailabletothe Specifi • • must focuson: Whendifficult intubationoccursafterinductionofanesthesia,theplan • Dealing withaDiffi • of theairwaywithlidocainegelsandspray. pre-procedural aspirationprophylaxisandoptimizetopicalanesthesia require expertiseandmaybetime-consuming.Whenpossible,give Avarietyofawakeintubationtechniqueshavebeendescribed,butall • is outlinedinTable representing adequatemaskventilationversusinadequateventilation, an immediatethreattothelifeoffetus,basedontwopathways, example ofaverysimplifi are complicatedbytheconsiderationspertainingtofetus.An patients, butarenotspecific toobstetricpatientsandsituations,which Anumberofpracticeguidelines(e.g.,theASA)existfor • •

Anintubating(Fastrach tubes, tubeexchangecatheters Stylettes,bougies,small(e.g.,6.0mm)internaldiametertracheal Aﬁ Airway ScopeAWS-S100,theGlidescope Short-handle,Bullardorvideolaryngoscopes(e.g.,thePentax the laryngoscopicview;soadjustit early(e.g.,byrequestingless other supraglotticairwaydevicesoraCombitube Preventionofairwaytrauma. neous ventilationresumes). Oxygenation(oxygendesaturationwillalwaysoccurbeforesponta- Usetheoralrouteifpossibletoavoidnasaltraumaandepistaxis. minimal placentaltransfer). of secretionswithananticholinergic(glycopyrrolate,whichhas Considermildsedation(e.g.,remifentanilormidazolam)anddrying Cricothyrotomydevicesandpercutaneoustracheostomysets Incorrectlyappliedcricoidpressure (Figure displacement asaresultoflefttable tilt. the chest(Figure obese women,includingelevationof theheadandshouldersabove Attentiontooptimalpatientpositioning isparamount,especiallyin beropticlaryngoscope c Equipment c

cult Intubation cult

4.23 . 4.13 edapproachforasituationinwhichthereis ).Also,headsupportishelpfulto prevent ® )laryngealmask,ProSeal

® ,theAirTraq 4.12 ® ®

laryngealmask, )canworsen nonobstetric

® )

• • • • • Continue surgery(onlyifairwaycontrolledandoxygenationsatisfactory) or intubation) Wake thepatient(changeto combinedspinalepiduralanesthesiaorawake Decide whetherto: • • • • Declare failedintubationand callforhelp • • • • • conditions anesthesiologist shouldmakeasecondattempttointubateunderoptimal Provided patientisstillwell oxygenated,themostexperienced Grade 3or4laryngoscopicviewoninduction Management Algorithm Table 4.23 • • • preferred cricothroidotomytechnique If unabletooxygenate/ventilate(“can’tintubate,can’tventilate”)use

and releaseitcompletelyifnecessary pressure, pushingtotherightorhigheronthyroidcartilage) Callforhelpassoonpossible! ventilation andoxygenation. Repeatdosesofsuccinylcholineshould notusuallybegiven oxygenation issatisfactoryandairway traumacanbeavoided. Asecond,optimalattemptatintubation canbemade,provided airway isthesafestoption. maintaining spontaneousventilation aftercontrolofadifﬁ cult • Insert andventilateusingLMA,ProsealIntubatingi-gel • rapid onset/offsetinhaledanestheticin100 Allow spontaneousventilationtoresumeandmaintainanesthesiawith Ventilate viafacemask Oxygenate Do notgivemoreneuromuscularblockingdrug Maintain cricoidpressureandleftpelvictilt Intubate withabougieandsmallertrachealtube Change laryngoscope Apply thyroidcartilagepressure Adjust cricoidpressure Adjust headorneckposition Melker size5.0Seldingerairwaytechnique Scalpel, ﬁ nger andbougie/trachealtubetechnique Percutaneous needle/cannulatechniquewithjetventilation

maintain cricoidpressureunlessimpedingplacementofairwaydevice or ventilation use twohandstoopentheairway,maximizejawthrustandseal, insert anoralairwayandgetasecondpersonto“bag” Simpliﬁed UnanticipatedFailedIntubation

— % oxygen the ﬁ rst priorityiseffective

—

149 Obstetric Anesthesia 150 Anesthesia for Cesarean Delivery • • • antecedentsare: Althoughawarenesscanoccurdespitethebestofcare,main Contributors toAwareness • delivery. Ifawarenessoccurs,itislikelytocausepatientdissatisfaction. discussed whenobtainingconsentforgeneralanesthesiacesarean all incidenceinanesthesiaof1500–1,000).Itshouldbespeciﬁ cally cesarean deliveryrepresentahigh-riskpopulation(Table nancy andconcernaboutfetaldrugexposure,pregnantwomenhaving pain lessfrequent.Asaresultofthephysiologicalchangespreg- sensations (e.g.,intubation),withvisualandemotionalmemories commonly describedeventsaresounds,conversationandtactile Awarenessreferstoexplicitrecallofintraoperativeevents.Themost Awareness method mostfamiliartotheanesthesiologistshouldbeattempted. sure stillapplied,canbeconsidered. using faceorlaryngealmaskventilation,preferablywithcricoidpres- diate dangertothelifeoffetus,thencontinuingoperation the safestapproach;ifoxygenationcanbeachievedbutthereisimme- Ifoxygenationcanbeachieved,thenallowingthewomantowakeis •

Awarenessisreportedatarateof1in150–400(higherthantheover- Ifcricothrotomyisrequiredbecauseofseverehypoxemia,the This“post-traumaticstressdisorder”mayleadtolitigation. symptomssuchasanxiety,phobia,sleepandmooddisturbance. Somewomenhavelong-termpsychologicaldisturbance,with vaporizer). priate dosingorfailureofdrugdelivery (e.g.,anemptyorturnedoff Failuretoprovideadequateanesthetic agent,throughinappro- succinylcholine forfentanyl). (e.g., asyringeswapofcephalosporin antibioticforpentothalorof Humanerror,includinginadvertent failuretoadministeranesthetic • • • easier toinsertandallowoxygenation. Asupraglotticairwaydevice,suchasthelaryngealmask,mayprove avoided. Nasal instrumentationandrepeatedimpactsonthelarynxarebest

Thei-gelairwayhasalsobeenused. and isdesignedtoallowintermittentpositivepressureventilation. or preferablyﬁ Anintubating(Fastrach TheProSeal

® laryngealmaskaddsprotectionagainstaspiration

beroptic-guidedintubation. ® )laryngealmaskallowssubsequentblind

4.24 ).

• • • • • • • general anesthesiaforcesareandeliverythesestrategiesinclude: tenance, ormeansofdetectinganinadequatedepthanesthesia.For transition fromintravenousinductiontoinhalationalanestheticmain- duced withaviewtoreducingawareness.Theseaddresshasteningthe Anumberofpracticechangesandnewtechnologieshavebeenintro- Prevention ofAwareness • • • Limitation ofvolatileanesthetic deliverybasedon: anesthetics Higher rateofairwaydifﬁ culty andthusdelayeddeliveryofinhalational Avoidance ofintravenousopioids untilafterdelivery current bodyweight?) Uncertainty aboutintravenous drugdosing(basedonpre-pregnancyor • High cardiacoutputduringpregnancy General AnesthesiaforCesareanDelivery Table 4.24

Useofrapiduptakevolatileanesthetics(e.g.,sevoﬂ • index [BIS]). Depthofanesthesia(brainfunction) monitoring(e.g.,bispectral induction). end-tidal concentrationtoatleast 0.75MACafterintravenous (“overpressure” withhighinitialconcentrations,torapidlyincrease Rapiduptitrationofvolatileanestheticusingagentmonitoring Moreliberaluseofopioidspriortodelivery. anesthesia) ordrug-related(e.g.,chronicbenzodiazepineuse). (e.g., pasthistoryofawarenessduringapparentlyuneventful Increasedpatientrequirementsforanesthesia,whichmaybegenetic compromise orinpatientswithpoorcardiacreserve). Constraineddrugadministration(e.g.,duringseverehemodynamic thetic duringmultipleattemptstoestablishaclearairway). Inadequatevigilance(e.g.,failuretogivemoreintravenousanes- antepartum hemorrhageorhemodynamiccompromise) concern aboutneonataleffects concern aboutmaternalhypotension(especiallyinpresenceof concern aboututerinemyometrialrelaxationandbleeding uptake ofvolatileanestheticdrugs rapidredistributionofintravenousanestheticfromeffectsitesandslower tothal 4–5mg/kg more consistentlyachievesanadequate depth induction, althoughanargumentcan bemadethatsodiumpen- Pentothal(2–2.5mg/kg)isbeingmore widelyusedforintravenous Reasons forHigherRiskofAwarenessduring

urane,

desﬂ

urane). urane).

151 Obstetric Anesthesia 152 Anesthesia for Cesarean Delivery • • • supine position,whenlargevenoussinusesarefrequentlyopen. compared withtheheartandpertainsatcesareandeliveryin 2.5–5 cmwater).Thisisthecasewhensurgicalsiteelevated the siteofsurgeryisnearorbelowatmosphericpressure(gradients Airmayenterthevenouscirculationwheneverpressureat Mechanisms andBackground Venous AirEmbolism patient andtoorganizeongoingreview. chology servicesshouldalsobeusedtosupportandcounselthe has clearlyoccurred,frankdiscussioniswarrantedandclinicalpsy- (Table exactly whathasbeenrecalled,usingastructuredseriesofquestions Apatientreportingawarenessneedsconsultationtoascertain Management ofthePatientReportingAwareness whether awarenesswasunlikely,possible orprobable. If anyevidenceofawarenessisencountered,obtainanarrativeand decide • • • • Ask: Awareness Table 4.25

based onDopplerchanges(detectionof0.1mlbubbles). 90 Theincidenceofsubclinicalairmicroemboliisapproximately exteriorized (placingitwellabovethelevelofheart). Theriskofairentrainmentmaybeincreasediftheuterusis and closure. Smallairembolioccurmostcommonlybetweenuterineincision • Did youhave anydreamsduringyouranesthetic? Can yourecallanything between? What wasthe ﬁ rst thingyouremembered whenyouwokeup? What isthelastthingyourememberbeforegoingtosleep?

% oxide. end-tidal sevoﬂ urane concentrationof1.5 consciousness isverylow(i.e.,<55–60)requires,forexample,an ToachieveBISvalueswithintherangeatwhichchanceof is high. can reducetheriskofawarenessbutnumber-needed-to-treat of anesthesia.End-tidalanestheticmonitoringandBIS –95 4.25 % ). Ifthestoryisconvincing,orlackofadequateanesthesia

basedonchangesinend-tidalnitrogenand40 Patient QuestionnairetoEvaluatePossible

% in50 %

nitrous %

–70 % • • • • • • detection ofitspathophysiologicconsequences. Thedetectionofvenousairembolismisbasedonmonitoringand Diagnosis • be absent,minororsevere(includingcardiacarrest). Dependingonthesizeofairembolus,cardiovascularchangesmay • bidities. Thecardiovascularresponsetoembolizedairincludes: obstruction tothepulmonarycirculation,andpatient’scomor- atrium andventricle(whichmaybeupto20minutes),thedegreeof of entrainment,theamounttimeairistrappedwithinright Thephysiologicconsequencesdependonthevolumeofairandspeed • • • through acentralvenouscathetershould beattemptedin • • • causing clinicalcompromiseisshown inTable Thesuggestedplanofmanagement ofalargevenousairembolus Management

ventilation-perfusionmismatchandhypoxemia coronaryarteryischemia. Oxygendesaturationwillfollowaclinicallysignifi embolus thatmandatesimmediateaction. Arapidfallinend-tidalcarbondioxideisanearlyfeatureofalarge very sensitivebutnotlikelytobeofclinicalrelevance. AsmallriseinET-nitrogenconcentrationduringgasmonitoringis diography mayrevealairbubbles,butarenotindicatedroutinely. Centralvenouspressureortransthoracic/transesophagealechocar- of microemboli. ing turbulentflow. Itisnotclinicallyusefulgiventhehighfrequency Dopplerultrasoundisverysensitivebutnotspecifi c, oftendetect- increasedpulmonaryandrightheartpressures reducedorarrestedcardiacoutput ally rare. volume Alargeairemboluscausinganlockintherightheart(estimated of air. A“mill-wheel”murmurprobablyonlydevelopswithalargevolume Seizuresmayresultfromcerebralhypoxia. during regionalanesthesia. Chestpain,dyspneaandlossofconsciousnessaremanifestations through apatentforamenovale,resulting incerebralairemboli. Focalneurologicaldefi cits can resultfromparadoxicalembolism

100ml),leadingtocardiovascularcollapse,isexception-

4.26

cantembolus. . Aspirationofair compromised compromised

153 Obstetric Anesthesia 154 Anesthesia for Cesarean Delivery

Further Reading suggested. circulation andtoaidaspirationfromtherightheart,havealsobeen or slighthead-uptopreventmovementofgasintothepulmonary position tolowertheuterusbelowlevelofheart,andsupine minimize pulmonaryinﬂ ow obstruction,butreverseTrendelenburg controversial. Thelateralhead-downpositionhasbeensuggestedto tion. Thebestpositioninwhichtoplacethepatientisunknownand patients, asthemostrapidmeansofpotentiallyrestoringcircula- • Rapidly insertacentralvenous catheter • • • • Supportive cardiorespiratory therapy • • • Stop airentrainment Table 4.26 6. 5. 4. 3. 2. 1.

Administer vasoactivedrugs(metaraminol,phenylephrine, Attempt aspirationofairfromtherightatriumandventricle right heartintothepulmonarycirculation particular externalcardiacmassage,todispersetheairlockfrom the rightventricle If circulationisinadequateorabsent,commenceadvancedlifesupport,in position tofl oat theairbubble awayfromthepulmonaryinfl ow tractin norepinephrine) tosupportthebloodpressure If circulationispresent,considerplacingthepatientinleftlateral Give 100 vessels Consider placingthepatientslightlyheadup Ask theobstetriciantofl ood thewoundwithsalineandcloseanyopen Advise theobstetricianofsuspecteddiagnosis Database ofSystematicReviews hypotension duringspinalanaesthesiafor caesareansection . Cyna AM IntJObstetAnesth , . 2001 Andrew ; anaesthesia forelectivecaesareansection isawasteoftimeandmoney 10 M . : , 30 - 35 Emmett . RS , 10.1002/14651858.CD002251.pub2 . Thompson KD 1145 , - 1163 . Paech MJ. Morgan P. The useofcombinedspinalepidural acid-base status:ameta-analysis . Spinal anaesthesiainobstetrics . Reynolds F , 2006 ; 61 Seed : 786 PT. - Levy 791 . DM. Anaesthesia forCaesareansectionandneonatal 109 : 1370 Emergency Caesareansection:bestpractice - . criteria defi1373 ne the“optimal”technique?(editorial) . Benhamou D , Wong C. Neuraxial anesthesiaforcesareandelivery:what % oxygen,ceasenitrousoxide andventilateifrequired Management ofLargeVenousAirEmbolism 2006 , Anaesthesia . 2005 ; 60 : 636 - 653 . et al. Techniques for preventing Issue 4 . Art. No.:CD002251.DOI: Can JAnaesth . 1995 ; 42 : Anesth Analg . 2009 ; Anaesthesia . Cochrane 11. 10. 9. 8. 7.

Anesth . 2006 ; 15 : 227 - 232 . technique forcaesareansectionandshouldbemodiﬁ Levy DM , 17 : 292 Meek - 297 T . . Traditional rapidsequenceinductionisanoutmoded Group. Difﬁ NJ McDonnell , MJ anaesthesia forcaesareansection . prospective studyofawarenessandrecallassociatedwithgeneral MJ Paech , 2005 ; 14 KL : obstetrics revisited:prescriptionforacure.(editorial) 2 Scott - , 4 . OM Clavisi Lipman , etal. S and delivery , the ANZCATrialsGroup. . A Carvalho spinal anesthesiawiththecatheter-over-needletechniqueforcesarean B , Brock-Utne J. Alonso E , The demise ofgeneralanesthesiain Gilsanz F , Gredilla E , etal. Observational studyofcontinuous with generalanaesthesiaforcaesareansection observational studyofairwaymanagementandcomplicationsassociated Int JObstetAnesth . 2009 ; 18 : 137 - 141 . cult andfailedintubationinobstetricanaesthesia:an Paech , OM Clavisi , etal. and the ANZCATrials Int JObstetAnesth . 2008 ; 17 : 298 - 303 . . Int JObstetAnesth . 2008 ; ed Int JObstetAnesth . . Int JObstet

155 Obstetric Anesthesia Chapter 5 Post-Cesarean Analgesia

Craig M. Palmer , MD

Introduction 156 Informing the Patient 157 Epidural Opioids 157 Intrathecal Opioids 170 Continuous Intrathecal Analgesia 175 Non-Neuraxial Nerve Block 176 Patient-Controlled Analgesia (PCA) 177

156 Nonsteroidal Agents (NSAIDs) 179

Introduction

In 1979, Wang and colleagues reported that epidural morphine provided effective, long-lasting analgesia in patients suffering cancer pain. This report sparked a surge of innovation in our approach not only to post-cesarean analgesia, but also to most acute postsurgical pain control. The ensuing three decades have brought an enormous number of reports describing novel analgesic approaches following cesarean delivery, which continue to this day. Cesarean delivery is the most frequently performed inpatient operation in the United States, and probably throughout the world. Given our understanding of postoperative pain management in this population, planning an anesthetic for cesarean delivery should also include planning for adequate postoperative analgesia. For many years, intramuscular narcotics were the mainstay of analgesia after cesarean delivery; in some settings, they may still be used. Recent decades, however, have seen a major shift in methods of postoperative analgesia in obstetric patients, due to our improved understanding of CNS pharmacology, and improvements in technology. • • which provides18to24hoursofgood toexcellentanalgesia. • • • not beappropriateforallwomen. erative paincontrolonalltheircesareanpatients,thatmethodmay undertaken. Whilemostpracticestendtouseasingleformofpostop- for postoperativepainmanagementbeforetheircesareandeliveryis options withthepatient,parturientsshouldbeinformedabout Justaseveryelectiveanestheticshouldbeginwithadiscussionof indicate improved analgesia with total diluent volumes of 10 to 12 ml. indicate improvedanalgesiawithtotaldiluentvolumesof10to12ml. morphine isadministeredataconcentrationof0.5mg/ml.Somereports minimum volumeof5to6mlshouldbeused;mostcommonly,epidural not furtherimproveanalgesia,butdoestendtoincreasesideeffects.A 4 mg(Figures5.1and5.2).Increasingthedosebeyondthisleveldoes morphine increases,analgesiaimproves,untilthedosereachesabout follows aconsistentdose-responserelationship.Asthedoseofepidural sia aftercesareansection. Morphine iscurrentlythemostwidelyusedepiduralopioidforanalge- effective forpost-cesareananalgesiaindosesrangingfrom2to10mg. thereafter, anumberofstudiesreportedepiduralmorphinetobe epidural morphinewaseffectiveforreliefofcancerpain.Shortly Asnotedabove,in1979,theﬁrst reportswerepublishedshowingthat Epidural Morphine

Epidural Opioids Informing thePatient Theoptimaldoseofepiduralmorphine isapproximately4mg, Analgesiafollowingepiduralmorphineforpost-cesareanpainrelief ing theﬁ morphine, anincreaseddosewillusually notproveeffective(assum- Ifapatientdoesnothavegoodresponse tothisdoseofepidural most part,parturientsrespondremarkably consistently. Aswithanymedication,thereisinterindividual variation,butforthe availability ofsupplementalanalgesiaifnecessary. Patientsshouldbeinformedofthepossibilitysideeffects,and advantages thatpatientsshouldbeinformedabout. Eachoptiondiscussedbelowmayhavedifferingadvantagesanddis- a numberofoptionsattheirdisposal. Itisimportantforanesthesiologiststobefamiliarwithandmaintain rstdosereached the epiduralspace).

157 Obstetric Anesthesia 158 Post-Cesarean Analgesia morphine: adoseresponsestudy. Palmer CM,NogamiWM,VanMarenG,AlvesD.Post-cesareanepidural after increasingdosesofepiduralmorphine. Reprinted withpermissionfrom Figure 5.1 morphine: adoseresponse study. Palmer CM,NogamiWM,VanMarenG, AlvesD.Post-cesareanepidural until thedosereachesapproximately4mg. Reprinted withpermissionfrom self-administered PCAmorphineusefor supplementalanalgesiadecreases epidural morphine.Asdoseofmorphine increasesfrom0to5mg, Figure 5.2 10 20 30 40 50 60 70 80 0 0 Cumulative useofsupplementalIV-PCAmorphineanalgesia Cumulative 24-hourPCAmorphineuse with increasingdoseof PCA morphine use (mg) 10 20 30 40 50 60 70 80 90 0 42 5.0 mg 3.75 mg 2.5 mg 1.25 mg 0.0 mg 0.00 Epidural morphinedose(mg) 812 Time post-injection(h) Time 1.25 Anesth Analg . 2000;90(4):887–891. Anesth Analg . 2000;90(4):887–891. 2.50 3.75 2016 5.00 4 • • • will acknowledgeituponquestioning(Figure5.3). 100 morphine administration.Insomeseries,theincidenceapproaches Pruritusisthemostconsistentlyreportedsideeffectafterepidural Pruritus side effects. Whileaneffectiveanalgesic,epiduralmorphinecanhavesignifi cant Side EffectsofEpiduralMorphine the doseisreducedbelow3mg. A higherfailurerate(i.e.,diminishedanalgesia)becomesapparentif patients willrequiresupplementationwithothersystemicanalgesics. Evenatadoseof4to5mg,dueinterindividualdifferences,some • different fromeachother. UnpublisheddatafromPalmerCM. than thefourepiduralmorphinegroups, whichwerenotsignifi epidural morphine.Thecontrolgroup,Group 0,wassignifi Figure 5.3

Itoccursmostoftenonthefaceortrunk,butmaybegeneralized. Pruritusafterepiduralmorphineisnotsigniﬁ Pruritusassociatedwithepiduralmorphineisusuallymild. below). more efﬁ cacious toinstitute systemicanalgesia,suchasIV-PCA(see Forfailuresofanalgesiafollowingepiduralmorphine,itisusually % . Whilenoteveryparturientwillvolunteerthesymptom,most 0.0 2.5 5.0 7.5 Cumulative 24-hourpruritusscoresafter varyingdosesof

0.00 * E p idural mor 1.25

2.50 p hine dose 3.75 ( cantlydose-related. m g)

cantly lower cantly 5.00 cantly

159 Obstetric Anesthesia 160 Post-Cesarean Analgesia morphine. Nauseaandvomitingarelessfrequentthanpruritusafterepidural Nausea andVomiting • • as “late”;i.e.,occurring3–10hours after administration. Respiratorydepressionafterepidural morphineistypicallydescribed Characteristics 10 (0.4 epidural morphinereported4patientswitha respiratory rateofbelow or less)intheobstetricpopulationisatmost0.2 cant respiratorydepressionafterepiduralmorphine(atdosesof5mg 0.25 delivery foundarespiratoryratebelow10inonly12patients,or review of4880parturientsreceivingepiduralmorphineaftercesarean The riskatclinicallyuseddosesisquitelow,however.Aretrospective piratory depressionwasrecognizedasapotentiallyserious Shortlyaftertheintroductionofepiduralmorphinetoclinicaluse,res- Respiratory Depression time thanmorelipophilicopioids(i.e.,fentanylorsufentanil). (unbound) inthecerebrospinalﬂ uid (CSF)forasigniﬁ cantly longer of thebrain.Morphine,whichishighlyhydrophilic,remainsfree chemoreceptor triggerzonelocatedinthebaseoffourthventricle Epiduralmorphinecancausenauseaandvomitingbystimulatingthe Possible Mechanism secondary tothesurgeryitself(see“IntrathecalMorphine”below). administration maynotbedifferentthanplacebo,andactually series haveindicatedthatnauseaandvomitingafterepiduralmorphine

understanding ofthephenomenonawaitsfurtherinvestigation. other excitatoryneuronalpathwaysandprotectivereﬂexes. Afull opioid receptorsinpruritusmaybeprimarilybyfacilitationof plex thanasimpleμ-receptorrelatedphenomenon.Theroleof is unknown.Theavailableevidenceindicatesittobemorecom- Theexactmechanismbywhichepiduralmorphinecausespruritus Thereportedincidencerangesfrom11 is readilyreversed bynaloxone. Ventilatorysupportmaybenecessary ifdiagnosisisdelayed,butit to respiratoryacidosis. Itismanifestedasagradualdecline in respiratoryrate,whichleads % .Aprospectivestudyof1000parturientswhoreceived5mg % ).Suchreportsindicatethattheincidenceofclinicallysigniﬁ

% toabout30 % –0.3 %

. complication. complication. %

.Some

- tion in cervical CSF peaks 3–4 hours after injection (Figure 5.4). tion incervicalCSFpeaks3–4hoursafterinjection(Figure5.4). can causedirectcentraldepressionofrespiration.Morphineconcentra- dural morphineisduetoslowcephaladmigrationwithintheCSFwhich Thecharacteristic“delayedonset”ofrespiratorydepressionafterepi- • • depression afterepiduralmorphineinclude: Concurrentconditionsthatmayincreasetheriskofrespiratory • • • • depressant medicationsareadministeredconcurrently,suchas: (especially over5mg).Riskalsoincreasessignifi cantly whenother Theriskofrespiratorydepressionlikelyincreaseswithincreasingdose for anyotherpurpose withoutpermission. Association fortheStudyofPain(IASP). Thefi gure maynotbereproduced This fi gure hasbeenreproducedwithpermission oftheInternational epidural administrationinpatientswithcancer pain. Cousins MJ.Cephaladmigrationofmorphine inCSFfollowinglumbar morphine. Reprintedwithpermissionfrom GourlayGK,CherryDA, time inpatientsafterlumbarepiduraladministration of10mgepidural Figure 5.4

sleepapnea. obesity magnesium. sleepaids anxiolytics additionalopioids Cervical cerebrospinalﬂ uid (CSF)morphineconcentrationsvs. Cervical CSF morphine concentration (ng/ml) 100 200 300 400 500 600 700 800

Time ( min )

Pain. 1985;23:317–326. 360300240180120600

161 Obstetric Anesthesia 162 Post-Cesarean Analgesia may beaconsequenceofthesurgicalprocedureitself, opioid antagonists.Asnotedabove,nauseaandvomitinginthissetting Treatmentoptionsfornauseaandvomitingincludeantiemetics Nausea andVomiting it becomesbothersometothepatient,optionsinclude: Mostcasesofpruritusaremildanddonotrequiretreatment.When Pruritus they donotrequiretreatment. Sideeffectsofepiduralmorphinearegenerallymild.Inmostcases Treatment ofSideEffects(Table 5.1 rapid systemicuptakeorintravascularinjectionofthedrug. ) epiduralmorphine,isalsopossible.Thiseventprobablyarisesfrom morphine, andconventionalantiemeticsareabetterﬁ • • • • depression Respiratory vomiting Nausea and Pruritus Side effect Table 5.1

“Early”respiratorydepression,withinminutesafterinjectionof erally eithertoocostly,orhavesigniﬁ ron, havebeenreportedeffectiveintreatingpruritus,butaregen- Othertreatments,includingpropofol,droperidol,andondanset- start at0.4–0.6mg/handtitrateasneeded). (0.04–0.2 mgintravenously,followedbyacontinuousinfusion Inrarecases,naloxonemaybenecessarytorelieveseverepruritus effectively reversed,butanalgesiaisnotaffected. pruritus withoutsigniﬁ cant sideeffects.Atthis dose, pruritusis Nalbuphine(5mgintravenously)isaneffectivetreatmentfor relief asitsantihistaminergiceffect. ated withdiphenhydraminemaybeasinstrumentalinproviding Diphenhydramine,12.5–25mgintravenously.Thesedationassoci- Side EffectsofEpiduralMorphine <0.25 10–30 Up to100 Incidence % % % Assisted ventilation if necessary Naloxone 0.2–0.4mgIV nalbuphine 5–10mgIV or ondansetron 4mgIV or Droperidol 0.625mgIV naloxone 0.04–0.2mgIV or diphenhydramine 12.5–25mgIV or Nalbuphine 5mgIV Treatment

cantsideeffectsthemselves.

rstoption. not

theepidural parturients healthy Very rarein morphine epidural related to Usually not necessary rarely Naloxone Usually mild Comments

—

• • • • intravenous naloxone. Earlyorlate,thetreatmentofchoiceforrespiratorydepressionis Respiratory Depression has beenlargelydisappointing. Preemptivetherapytopreventthesideeffectsofepiduralmorphine Preemptive Therapy • • up to4hours(Figure Epiduralfentanyl,50–100mcg,rapidly providesprofoundanalgesiafor Fentanyl Other EpiduralOpioids • • • •

relieve nauseaandvomitingthatistrulyopioid-related. Intravenousnalbuphine,5–10mg,orverylow-dosenaloxone,can an effectivetreatment. Intravenousondansetron,4mg,orasimilarantiemetic,isgenerally Whileanumberoftreatmentscanpreventsideeffects,they if thepatientisobtundedwhilewaitingfornaloxonetohaveeffect. Instituteartiﬁ cial ormechanicalsupportofventilationimmediately ment todeepbreathing)canbeeffective. milder formsoftreatment(supplementalnasaloxygen,encourage- are effectiveinidentifyingtheseinfrequentpatientsearly,when rate andincreasedlevelsofsedation(seebelow).Suchprotocols erative orders)areintendedtodetectthisdeclineinrespiratory rate, andincreasingsomnolence.Monitoringprotocols(inpostop- abrupt onset.Itisheraldedbyagradualdecreaseinrespiratory Respiratorydepressionafterepiduralmorphinedoesnothavean though inashorter timeframe. Epiduralfentanyl can causeallthesamesideeffects as morphine, improve orprolongpainrelief. Increasingthedoseofepiduralfentanyl beyond100mcgdoesnot dry mouth. delivery, butmustbeappliedseveralhoursinadvance,andcauses of nauseaandvomitingduringtheﬁ rst 24hoursaftercesarean Prophylactictransdermalscopolaminedecreasestheincidence somnolence. Epiduralbutorphanolmodestlydecreasessideeffects,butcauses but bothdecreaseanalgesiainadose-dependentfashion. Intravenousnaloxoneandoralnaltrexonecanpreventsideeffects, also eitherdecreaseanalgesiaorcausesideeffectsoftheirown.

5.5 ).

generally generally

163 Obstetric Anesthesia 164 Post-Cesarean Analgesia • management. Ostheimer GW.Epiduralfentanylforpost-cesareandeliverypain (standard error). Reprinted withpermissionfromNaultyJS,DattaS, after dosesofepiduralfentanylrangingfrom0to100mcg.Dataaremean Figure 5.5 • • • Others morphine isitsrapidonset. Likefentanyl,themajoradvantageofepiduralsufentanilover Sufentanil

for cesareandelivery(Figure Whileusefulasanintraoperativeadjunctduringepiduralanesthesia profound respiratorydepression. When givenintravenouslyatthese doses,sufentanilcanproduce Littledataisavailabletoevaluatetheriskofrespiratorydepression. provide analgesiaforupto4hours. equianalgesicdosesofepiduralmorphine.Larger(upto50ug) Theincidenceofsideeffectsiscomparableto,orhigherthan, utility asapostoperativeanalgesic. dose increasesup toabout25mg,butfurtherincreasing thedose analgesia fromepiduralmeperidine (pethidine)increaseasthe Meperidine(pethidine). Duration ofcompleteanalgesia(visualanalogpainscore0)

Anesthesiology. 1985;63(6):694–698. Duration of complete analgesia (min) 150 200 100 250 300 350 50 0 0 Epidural fentanyldose(μg) 12.5

Thespeedofonsetandduration of 5.6 ), fentanyl’sshortdurationlimitsits 25

* 50 * 75 * 100 delivery painmanagement. Naulty JS,DattaS,OstheimerGW.Epiduralfentanylforpost-cesarean 50 mcg,nopatientcomplainedofpain.Reprintedwithpermissionfrom under epiduralanesthesiavs.doseoffentanyl.Atdosesabove Figure 5.6 • • • • Mixed Agonist/AntagonistOpioids

provides noadditionalbeneﬁt (Table 12 hrs.Thesideeffectproﬁ morphine, butthedurationofactionisconsiderablyshorter,about A doseof1.0mgprovidesanalgesiacomparableto5epidural Hydromorphone its shortduration. hrs, andwhilesideeffectsareinfrequent,clinicalutilityislimitedby from 5to15hrsafter2.5mg. but reportsofthedurationanalgesia areinconsistent,ranging Diamorphine(heroin) the durationofanalgesiaafter4to5mgisonly6hrs. Methadone epiduralmorphine. Thelowincidenceofpruritusafter epidural Butorphanol

Percent of patients Percentage ofpatientsfeelingpainduringcesareandelivery 100 25 50 75 0 hasamorerapidonsetthanepiduralmorphine,but hasafasteronsetbutshorter durationthan 0

isasemisyntheticderivativeofmorphine. Anesthesiology. 1985;63(6):694–698. 12.5 Epidural fentanyldose(μg) hasbeenusedasanepiduralanalgesic, leissimilartomorphine. 25

5.2 ) . 50 0 Painrelieflastsabout2.5 75 00

100

165 Obstetric Anesthesia 166 Post-Cesarean Analgesia • • • effect of extending the duration of a single injection of morphine. effect ofextendingthedurationasingleinjectionmorphine. degrade overtime,slowlyreleasingtheenclosedmorphine.Thishas a suspensionintotheepiduralspace.Inspace,liposomes free morphineencapsulatedinmicroscopicliposomes,whichisinjectedas tion ofmorphineforepiduraluse.Theformulationconsistspreservative- In2004,theU.S.FoodandDrugAdministrationapprovedanewformula- Extended-Release EpiduralMorphine • • Diamorphine Methadone Morphine Opioid Table 5.2 Fentanyl Meperidine Sufentanil Hydromorphone

side effectissomnolence,seeninupto50 to 30mg,fromaboutonehourthreehours.Itsonlysigniﬁ duration ofanalgesiaincreasesasthedoseisincreasedfrom10mg Nalbuphine incidence ofsomnolencearesigniﬁ butorphanol isitsmajoradvantage,buttheshortdurationandhigh Therecommendeddoseforpost-cesarean analgesiais10mg. to thoseofstandardepiduralmorphine. Sideeffectsofextendedreleaseepidural morphinearecomparable with adurationofapproximately48hours. analgesia ofthesamequalityasstandardepiduralmorphine,but Theslowreleaseofmorphineintotheepiduralspaceresults however, soitsusecannotberecommended. The safetyofneuraxialnalbuphinehasnotbeencarefullyevaluated, would bethatofan intrathecalmorphineoverdose. releasing thecontainedmorphinemore rapidly.Theclinicaleffect the extendedreleaseformulation degrademuchmorerapidly, Ifunintentionallyinjectedintheintrathecal space,theliposomesof Summary ofEpiduralOpioidOptions isanothermixedopioidagonist/antagonist.The Dose .– g 5–6 2.5–5 mg 4–5 mg 3.5–4 mg 0mg U o4 Useful asanintraoperative Up to4 50 mcg 5m 25 mg 02 c 10–20 mcg . g Approx. 12 1.0 mg (hours) duration Reported 5–15 18–24 2–3 prx Also usefulintraoperatively Approx. 3 cantshortcomings

Comments the USA Heroin—not availablein “Gold standard”

analgesic Local anestheticeffects %

ofpatientsafter30mg.

cant • Epinephrine,anaturallyoccurringcatecholaminewithboth Epinephrine Non-Opioid EpiduralAnalgesics pathways ofthespinalcord. activation of or spinalinjection,itproducessigniﬁ cant analgesia,mostlikelyfrom istration, ithassigniﬁ cant antihypertensive actions. After Clonidineisan Clonidine • • • systemic uptake. goals aretodecreasetheincidenceofsideeffectsand analgesics. Theprimarygoalistoprolonganalgesia,andsecondary β

-adrenergic agonistactions,hasbeenusedwithavarietyofepidural • • dine resultsinsigniﬁ cant sedationanddecreasedbloodpressure. Involunteers,thebolusadministration of700mcgepiduralcloni- administered. phrine mayreducetheinfusionrateandtotalamountofopioid Ifusedasacomponentofcontinuousepiduralinfusion,epine- expense ofanincreasedincidenceorseveritysideeffects. shorter-acting opioids.Thisprolongationoftencomesatthe Inparturients,epinephrinemayprolongtheanalgesiceffectsof analgesia (Figure phrine resultsinnotonlyprolongedanesthesia,butalsoenhanced intrinsic analgesicproperties.Administeredwithlidocaine,epine- Alpha-2agonismislikelyresponsibleformostofepinephrine’s

may benecessary. Temporary respiratorysupport,i.e.,mechanicalventilation, likely benecessarytocountertheeffectsofoverdose. closely monitoredinanICUsetting.Analoxoneinfusionwill Anypatientsufferingsuchanunintentionalinjectionshouldbe critical effectslikepruritusandnausea. as respiratorydepressionandunconsciousness,wellless These couldincludepotentiallylife-threateningsideeffectssuch massive overdose,andsigniﬁ cant sideeffectswouldresult. either standardorextendedreleasemorphinewouldresultina Theunintentionalintrathecalinjectionofanepiduraldose α α -adrenergicreceptorswithindescending inhibitory

-adrenergictype-2receptoragonist. After oraladmin- 5.7 ).

epidural α

-and

167 Obstetric Anesthesia 168 Post-Cesarean Analgesia RegAnesthPainMed. 1999;24(6)541–546. increases intensityofsensoryblockduringepiduralanesthesiawithlidocaine. Reprinted withpermissionfromSakuraS,etal.Theadditionofepinephrine lidocaine 1 analgesic/anesthetic properties.(GroupP,plainlidocaine1 not merelyprolonged,itwasenhanced,illustratingepinephrine’sintrinsic added toepidurallidocaine1 Figure 5.7 • • • • • delivery. Thereareavarietyofwaystoprovide epiduralanalgesiaafter Summary ofEpidural Analgesics

mended forroutineuseinparturients. Duetobloodpressureandsedativeeffects,clonidineisnotrecom- gesia itisbestadministeredviacontinuousinfusion. Duetoarelativelyshortdurationofaction,forpostoperativeanal- cost ofgreatersedationandlowerbloodpressure. anesthetic infusionsimprovespostoperativeanalgesia,butatthe Innonobstetricpopulations,theadditionofclonidinetolocal tion. estly augmentintrathecalmorphineanalgesiaaftercesareansec- At adoseof150mcg,epiduralclonidinehasbeenshowntomod- epidural postoperative analgesia.Immediatelyafterdelivery, lasting epiduralopioidavailable,and isthemainstayofsingle-shot Despitetheoccurrenceofsideeffects, morphineisstillthelongest- intraoperative comfortandprovides earlypostoperativeanalgesia. Fentanyl,50–100mcg,mixedwith the localanesthetic,enhances

% withepinephrine1:200,000). Percent of maximum possible effect Epinephrine augmentationofepidurallidocaineanesthesia.When –10 10 20 30 40 50 0 02 Time afterepidurallidocaine(min) Time % , sensoryblockofanelectricalstimuluswas 04

06 Group E Group P % ; GroupE,

administer administer 0 cesarean

• • • • useful (Table occurrence ofsideeffects,standardpostoperativeordersarevery Becauseofthetheoreticalriskrespiratorydepressionand Postoperative MonitoringandSurveillance

ble on-lineat Depression AssociatedwithNeuraxial OpioidAdministration, for thePrevention,Detection,and ManagementofRespiratory update recommendationsforpatientcare.The Society ofAnesthesiologistsconvenedaTaskForcein2007to administration isararebutpreventableevent,theAmerican Recognizingthatrespiratorydepressionafterneuraxialopioid patients whoreceiveneuraxialopioids. TheAnesthesiaPatient management recommendations. analgesics intheearlypostoperativeperiod,optionsinclude: Fortheparturientwhorequiressigniﬁ cant amountsofadditional and mayrequireadditionalanalgesics. adequate formostpatients,somewomenwillfalloutsidethenorms studies havevalidatedeachofthesemedicationsandtechniquesas Eachparturientmustbetreatedasanindividual.Whilemultiple epiduralcatheterforpostoperativeanalgesia. intraoperative analgesia;morphineisthenadministeredviathe administered withtheinductiondoseoflocalanesthetictoenhance part ofthesameanestheticformaximumopioideffect.Fentanylis Bothepiduralfentanylandmorphineareoftenusedas 30 minutesormorearenecessaryformaximumeffect. 3.5 to4mg,inavolumeof810ml.Becauseslowonset, • • extremely uncommon. sedatives ornarcotics,respiratorydepressionofthisdegreeis naloxone andnotifytheanesthesiologist.Inabsenceofother eight breathsperminute,thenurseshouldimmediatelyinject 24 hoursafterepiduralmorphine.Ifrespiratoryratefallsbelow Nursesshouldcheckandrecordrespiratoryrateshourlyfor18to •

Somegroupshaveadvocatedmore intensivemonitoringofall Asneeded(PRN)intravenousanalgesics Oralanalgesics PCA(intravenous) 5.3 ). www.asahq.org

, outlinespeciﬁ c precautionsand

Practice Guidelines

availa-

169 Obstetric Anesthesia 170 Post-Cesarean Analgesia analgesia. sia hasincreased,so hastheuseofintrathecalopioidsfor postoperative ably performedunderspinalanesthesia. Astheuseofspinalanesthe- the UnitedStatesatleast,majority ofcesareandeliveriesareprob- sia forcesareandeliveryoverthelast severaldecadesmeansthatin Thoughharddataarenotavailable, theresurgenceofspinalanesthe- Morphine Table 5.3 10. Intrathecal Opioids population thaninthepostsurgicalatlarge. risk ofseriousrespiratorycomplicationsislowerintheobstetric care unitsetting,andmostobstetricanesthesiologistsfeelthatthe current technologythisisrarelypracticaloutsidetheintensive postoperative period.Whilethisisacommendablegoal,with others haverecommendedcontinuouspulseoximetryinthe tion inallpatientsreceivingepiduralandPCAopioids,while monitoring ofbothrespiration(i.e.,capnography)andoxygena- Safety Foundation(APSF)in2007recommendedcontinuous 9. 8. 7. 6. 5. 4. 3. 2. 1. This protocolcovers24haftereachdoseofneuraxialnarcotic. anesthesiologist oncall. For pain,pruritus,ornausea/vomitingunresponsivetoabove,page vomiting: Nalbuphine, 5mgIVq4hPRNitching. For nausea/ For pruritus: analgesia: Supplemental give naloxone,0.2mgIVslowlyover2min;notifyanesthesiologist. Measure andrecordrespiratoryrateq1h;for<8/min, Main IVaccessorheparin-lockatalltimes. One ampulenaloxoneatbedsidealltimes. anesthesiologist. No sedativesornarcoticsadministeredexceptbyorderof ______(date). Epidural/intrathecal ______,___mg,administeredat____hourson Postoperative NeuraxialOpioidOrders vomiting. Ondansetron 4mgIVq6hPRNnauseaand Ibuprofen 400mgPOq6hPRN or Ketorolac 15mgIVq6hPRN or Morphine 2mgIVq1–2hPRN

• • • Side EffectsofIntrathecalMorphine analgesia. Dose-response relationshipofintrathecalmorphineforpost-cesarean mean (standarderror).ReprintedwithpermissionfromPalmerCM, morphine from0to0.5mginparturientsaftercesareandelivery.Dataare Figure 5.8

supraspinal receptorsynergycanbe foundinanimalmodels. phine likelyactsatsupraspinalreceptors.Supportforthisspinal- occupies spinalreceptors,andparenteralsystemic(PCA)mor- level, butalsoelsewherewithintheCNS;intrathecalmorphine requires occupationofopioidreceptorsnotonlyatthespinal the doseofintrathecalmorphinesuggeststhatoptimalanalgesia phine atafairlyconstantratedespiteﬁve- to tenfoldincreasein phine increasesﬁ analgesia isnotenhancedevenwhenthedoseofintrathecalmor- when self-administeredPCAmorphineisusedtoquantifyanalgesia, relief aftercesareansectionwithsurprisinglysmalldoses.Instudies, In parturients,intrathecalmorphineproducesexcellentpain Morphineisthemainstayofintrathecalpost-cesareananalgesics. Pruritusoccursin 40 seen aftertheadministrationofepidural morphine. Sideeffectsafterintrathecalmorphine arecomparabletothose dependent (Figure The factthatpatientscontinuetoself-medicatewithPCAmor- Anesthesiology . 1999;90(2):437–444.

Mean 24-hourPCAmorphineuseafterdosesofintrathecal Mean PCA morphine use (mg, 24 hour total) 10 20 30 40 50 60 70 80 0 . . . . . 0.5 0.4 0.3 0.2 0.1 0.0 ve-fold,from0.1to0.5mg(Figure 5.9 ). % Intrathecal mor –80 % ofpatientsandis somewhatdose- p hine dose ( m g)

5.8 ). et al.

171 Obstetric Anesthesia 172 Post-Cesarean Analgesia post-cesarean analgesia.Anesthesiology.1999;90(2):437–444. Palmer CM,etal.Dose-responserelationshipofintrathecalmorphinefor intrathecal morphinefrom0to0.5mg. Reprinted withpermissionfrom Figure 5.9 • • • effects. vide over18–20hoursofgoodanalgesia whileavoidingexcessiveside cesarean analgesialiesbetween0.1 mg and0.2mg,whichshouldpro- the optimaldoseofintrathecalmorphineforclinicalusepost- Basedontheverysteepdoseresponsecurveofintrathecalmorphine, Dosing •

Vomitingoccursrarelyafterlowdoses(0.1mg)ofmorphine. • Clinicallysigniﬁ and a standardized dose of intrathecal morphine may not completely and astandardized doseofintrathecalmorphinemaynot completely Alsosimilartoepiduralmorphine,interindividual variationdoesoccur, very useful,andpostoperativemonitoring isessential. Aswithepiduralmorphine,standardized postoperativeordersare •

to carbondioxidechallengeisnotdepressed. Atclinicallyrelevantdoses(<0.25mg),therespiratoryresponse decreased SaO tory ratelessthan10/minute,andonly1requirednaloxonefor morphine aftercesareandelivery,only6hadarecordedrespira- Inareviewofover1900patientsreceiving0.15mgintrathecal Mean 24-hourpruritusscoresinparturientsafterdosesof 24-hour pruritus score 0 1 2 3 4 5 6 cantrespiratorydepressionisrare,butcanoccur...... 0.5 0.4 0.3 0.2 0.1 0.0 2 . Intrathecal morphinedose(mg)

• • • bupivacaine forcesarean delivery. from HuntCO,etal.Perioperativeanalgesiawithsubarachnoid fentanyl 0 to50mcginparturientsaftercesarean delivery. Reprinted withpermission Figure 5.10 cal beneﬁ Fentanylisoftenusedforanalgesiaatcesareandelivery;maximalclini- Fentanyl Other IntrathecalOpioids •

morphine’s longdurationforoptimaleffect. bined inasingleanesthetic,capitalizingonfentanyl’srapidonsetand Aswithepiduraltechniques,fentanylandmorphineareoftencom- limits thevalueofintrathecalfentanylasapostoperativeanalgesic. Therelativelyshortdurationofeffectiveanalgesiaevenathighdoses but thedurationofeffectiveanalgesiaisshorter. Inconjunctionwithlidocaineanesthesia,fentanylhassimilareffects cotic usageisnotaffected. morphine and PCA supplementation. morphine andPCAsupplementation. insure optimalanalgesiamaybethroughacombinationofintrathecal eliminate theneedforsupplementalanalgesics.Thebestwayto 6.25 mcgoffentanyl(Figure increases from71.8minuteswithoutfentanylto192with Thedurationofeffectiveanalgesiafromintrathecalbupivacaine

Duration of effective analgesia (minutes) toccursatverylowdoses. Duration ofeffectiveanalgesiaafterfentanyl dosesrangingfrom 100 150 200 250 300 50 0 0 2.5 Intrathecal fentanyldose(μg)

5 Anesthesiology. 1989;71(4):535–540. 5.10 6.25 ),but24-hoursupplementalnar-

12.5 25

37.5 50

173 Obstetric Anesthesia 174 Post-Cesarean Analgesia morphine (thereis noevidencetosuggestanyincreased beneﬁ Forsingle-shotspinalanesthesiafor cesarean delivery,0.1to0.2mgof Summary after cesareandelivery. operative analgesiaordecreasethe needforsupplementalanalgesics intrathecal morphine0.2mgdoesnot increasethedurationofpost- morphine postoperativeanalgesia.Theadditionofepinephrineto prolong thedurationofanesthesia,itdoesnotaugmentintrathecal Whileepinephrinecanbeaddedtointrathecallocalanesthetics Non-Opioid IntrathecalAnalgesics • • • • Others • tions includemethadoneandoxymorphone. Otherintrathecalopioidsthathavebeenusedinnonpregnantpopula- Fentanyl Morphine Opioid Post-Cesarean Analgesia Table 5.4 Oxymorphone Methadone Buprenorphine Sufentanil

nausea andvomitingintraoperatively. pruritus, nausea,andvomiting. when administeredintrathecally,withpredictablesideeffectsof Oxymorphone consistentqualitythanmorphine,evenatdosesashigh20mg. Methadone its onlyadvantagewouldseemtobealowerincidenceofpruritus. after bupivacainespinalanesthesia,perhapsaslong6to7hours; Buprenorphine sufentanilasapostoperativeanalgesic. fentanyl. Likefentanyl,ashortdurationlimitstheusefulnessof Sufentanil requires treatment;fentanylcanactually Pruritusoccursfrequentlywithintrathecalfentanylbutrarely Summary ofIntrathecalOpioidOptionsfor upto10mcg,hasverysimilaranalgesicproperties producesanalgesiaofshorterdurationandless providesapproximately16hoursofanalgesia 0.045mg,alsoprolongsthepain-freeinterval →

Dose .–. g 18–24 hours 10–20 mc 0.1–0.2 mg pt 0mg 3–4 hours Up to10mcg Doses anddurationsnotwellcharacterized Limited experience.

decrease

Reported Duration 3–4 hours theincidenceof t to a to t

• with pulseoximetry. setting (suchasanintensivecareor step-downunit)withcontinuous tanil however,patientsshouldbe monitoredinahigherintensity agents. Whenusingcontinuousinfusions containingfentanylorsufen- onset andrelativelyshortduration ofaction,arethebest-suited Generallyspeaking,thehighlylipid-solubleopioids,withtheirfast • • bupivacaine, remainsthebestchoiceofpostoperativeanalgesic. dose above0.2mg)and10–15mcgoffentanylwitheitherlidocaineor Advantages have anintrathecalcatheterinplace. Continuousintrathecalanalgesiacanbeusedinthosepatientswho • Disadvantages • • • • • •

Continuous IntrathecalAnalgesia for mostparturients aftercesareandelivery. Sufentanil,5mcg/h(andoftenless), will provideadequateanalgesia catheters. Thereisahigherincidenceofheadachewithlargerdiameter Medicationscanbereadilytitratedtopatientcomfort. Additionalbolusescanbegivenforbreakthroughpain. Relativelyfewcatheteroptionsareavailableinmostlocales. anesthesia. Ifnecessary,thecathetercanbeusedtorapidlyinducesurgical ing ofpatientsisessential. Aswithepiduralmorphineanalgesia,closepostoperativemonitor- (i.e., 1.0ml)syringetominimizetheriskofaccidentaloverdose. technique, itisprudenttomeasurethesedrugswithatuberculin Becauseoftheverysmallvolumesopioidsusedwiththis postoperative analgesia. Fentanylenhancesintraoperativecomfortandprovidessomeearly can beequallyeffective. analgesics withinhoursaftertheirsurgery,oralpainmedications IV-PCA morphine,butasmanyparturientsareabletotolerateoral cant discomfort,supplementalanalgesiaisappropriate.Thismaybe tive analgesiaformostparturients,butifapatientishavingsigniﬁ Morphineprovides18to24hoursofgoodexcellentpostopera-

175 Obstetric Anesthesia 176 Post-Cesarean Analgesia • • • • • Ilioinguinal NerveBlock cesarean analgesia. Peripheralnerveblockhasbeenusedwithmixedsuccessforpost-

bupivacaine Fentanyl/ a Sufentanil Medication Post-cesarean Analgesia Table 5.5ContinuousIntrathecalInfusionTherapy for approximations. bags areslightlyoverﬁ lled, thereforethesenumbersareveryclose 5 ml0.5

Non-Neuraxial NerveBlock To mixinfusion:Beginwith50 mlnormalsaline;withdraw15ml;add eral anesthesiaorwhohavecontraindications toneuraxial Ilioinguinalnerveblockmaybeuseful inpatientswhorequiredgen- plemental postoperativemorphinerequirements weredecreased. conjunction withoralibuprofenon aﬁ xed dosageschedule,sup- allowing forcontinuousinfusionoflocal anesthetics.Whenusedin muscles anteriorly(theplanewhere theilioinguinalnerveslie), plane betweenthetransversusabdominusandinternaloblique Usingultrasoundguidance,cathetersmaybeintroducedintothe patients notreceivingtheblock. 0.15 mg,postoperativeanalgesicrequirementsdidnotdifferfrom Whenilioinguinalblockiscombinedwithintrathecalmorphine, sic requirementscomparedtothosereceivingnoblock. vacaine hasbeenshowntomodestlyreducepostoperativeanalge- infusion (Table5.5). may beassociatedwithgreatermotorblockthanthesufentanil nyl 15mcg/hwithbupivacaine1.5mg/h).Thislattercombination Acombinationofbupivacaineandfentanylcanalsobeused(fenta- incision, bilateralilioinguinalnerveblockwith10ml0.5 InpatientswhoundergocesareandeliverywithaPfannenstielskin % bupivacaineand5mlfentanyl. Note:Mostcommercialinfusion 2.5 mg with bupivacaine Fentanyl 25mcg c –. c/ Mix as1mcg/ml 5–7.5 mcg/h 5 mcg nta ou Initial Bolus

1.5 mg/h Bupivacaine Fentanyl15mcg/h Infusion

Run at3ml/h bupivacaine 0.5mg/ml. fentanyl 5mcgand Mix infusion infusion Comments

a analgesics. analgesics. with % bupi-

• • • • • • analgesia. (IV-PCA) andepidural(PCEA)PCAhavebeenusedforpost-cesarean lar insomepracticesforpost-cesareananalgesia.Bothintravenous Patient-controlledanalgesia(PCA)iseffectiveandhasbecomepopu- Intravenous PCA and blocksensoryinnervationoftheanteriorabdominalwall. posteriorly, inthetriangleofPetitviaalossresistancetechnique, muscles. Itispossibletointroducelocalanestheticsintothisplane wall runsbetweenthetransversusabdominusandinternaloblique Asnotedabove,sensoryinnervationtotheanteriorabdominal Transversus AbdominusPlaneBlock

Patient-Controlled Analgesia(PCA) patients receivingtheblock(withropivacaine0.75 below), supplementalmorphineusewassignifi cantly lowerin oral acetaminophen,rectaldiclofenac,andIV-PCAmorphine(see Usedaspartofamultimodalanalgesicregimenthatincluded tive analgesiatoindividualrequirements. post-cesarean analgesia,andaneffective waytotitratepostopera- techniques (i.e.,single-shotintrathecal orepiduralmorphine)for PCAisanexcellentchoicetouse in combinationwithneuraxial infusion isused. offset bythefactthatincidenceofnauseaishigherwhenabasal may decreasepainscoreswithmovement. Useofabasalinfusiondoesnotchange24-houropioidusage,but equipotent dosesareused. consistentdifferenceinpatientsatisfactionorsideeffects,when ThechoiceofopioidforusewithIV-PCAdoesnotmakeany than intramuscularinjections. BothIV-PCAandneuraxialmorphinearemarkedlymoreeffective self-administered PCAprovidesparturients. was equallyhigh,probablybecauseofthefeelingcontrolthat morphine inoneseries,overallpatientsatisfactionwithIV-PCA sia wasratedsuperior(bypatients)toanalgesiaprovidedbyIV-PCA Whilesingleinjectionepiduralorintrathecalmorphineanalge- benefi side) thanthosewhoreceivedshaminjections.Themajorityofthe twasinthefi rst12hoursaftersurgery.

Thisminoradvantageis

% 1.5mg/kgeach

177 Obstetric Anesthesia 178 Post-Cesarean Analgesia • (Figure and sedationscoresarepredictablyhigherintheIV-PCAgroup mately 50 WhenmeperidineisusedforPCEA,parturientsuseapproxi- • • than atruespinalmechanism. the analgesiceffectsaremediatedprimarilybysystemicuptakerather total dosesofopioidusedbyparturientsraisethequestionwhether with fentanylorsufentanilprovidescomparableanalgesia,butthehigh Comparedtosinglebolusepiduralmorphine,useofopioid-onlyPCEA • • • tages inthepost-cesareanpatient: Patient-controlledepiduralanalgesia(PCEA)hasanumberofadvan- Patient-Controlled EpiduralAnalgesia(PCEA) analgesia aftercesareansection. with permissionfromPaechMJetal.Meperidineforpatient-controlled PCA. Painscoreswereconsistentlylower inthePCEAgroup. Reprinted received PCEAandthedashedlinerepresents theperiodtheyreceived after cesareandelivery.Thesolidlinerepresents theperiodparturients analgesia (intravenousPCA)andpatient-controlled epiduralanalgesia(PCEA) Figure 5.11

VAS pain score (0–100) Backgroundinfusions Backgroundinfusionsgenerallyincreasetotaldrugdelivery. not signiﬁ AswithintravenousPCA,abasal(or“background”)infusiondoes Itgivestheparturientadegreeofcontroloverheranalgesia. erative period. Itmaydecreasetheneedforphysicianinterventionsinpostop- (epinephrine) inmultiplecombinations. Itallowstheuseoflocalanesthetics,opioids,andotheradjuncts 10 20 30 40 0 0 5.11 ). % cantlyimprovethequalityofpainreliefwithPCEA. lessopioidviathePCEAroutethanIV-PCAroute, A comparisonofpainscoresbetweenpatient-controlled 4

do increasesedation. 8 Anesthesiology. 1994;80:1268–1276.

Time (h) 12

62 24 20 16

down ofsynapticallyreleasedAch)havealsobeenusedwithPCEA. adrenergic receptors)andneostigmine(whichpreventsthebreak- Clonidineandepinephrine(whichbothpresumablyactivate Other AdjunctsforPCEA • • analgesia. remains a useful technique for selected patients and populations. remains ausefultechniqueforselectedpatientsandpopulations. spinal anesthetictechnique,withoutanepiduralcatheterinserted.PCEA many practicescesareandeliveryislikelytoperformedwithasingle-shot a functioningepiduralcatheterinthe postoperative period.Further,in phine isamatterofdispute.Adisadvantagethenecessitytomaintain Whether itoffersdistinctadvantagesoverepiduralorintrathecalmor- PCEAcanbeaneffectivetechniqueforpost-cesareananalgesia. • • • to neuraxial morphine, NSAIDs have shown inconsistent results. to neuraxialmorphine,NSAIDshave showninconsistentresults. complete analgesiaformostpatientsafter acesareandelivery.Asadjuncts TheNSAIDsarenotpotentenough inandofthemselvestoprovide • • •

Nonsteroidal Agents(NSAIDs) LocalanestheticsarefrequentlyaddedtoPCEAforpost-cesarean PCEA solutionprovides. Itisunclearwhatbenefi t, ifany,includingdilutebupivacaineina PCEA fentanylwithoutaddedbupivacaine. ambulation, butepiduralfentanylconsumptioniscomparableto Aconcentrationofbupivacaine0.01 or buprenorphine. to interferewithambulationwhenusedincombinationfentanyl Theconcentrationoflocalanestheticmustbelowtoavoidsignifi use withPCEA. Neitherclonidineorneostigminecanberecommendedforroutine and vomiting. Neostigmine,evenatverylowdoses,signifi cantly increasesnausea rate. Clonidinecausessignifi cant decreasesinbloodpressureandheart Aconcentrationofbupivacaineaslow0.03 within hoursofsurgery. cant sensoryormotorblockade,asmanypatientsareambulatory dine signifi WhencombinedwithsufentanilPCEA,bothepinephrineandcloni- cantlyreduceepiduralopioiduse.

% doesnotinterferewith

% hasbeenreported

α -2

179 Obstetric Anesthesia 180 Post-Cesarean Analgesia • • • or asanalternativetooralopioid ifaparturientisintolerant. as a“rescue”analgesicincombination withotheranalgesicmodalities, post-cesarean populationhasbeen very limited,butithasbeenused pinephrine neuronalreuptake.Reporteduseasanoralanalgesicinthe has alowafﬁnity formuopioidreceptor.Itinhibitsserotonin andnore- Tramadolisasynthetic4-phenyl-piperidineanalogueofcodeine,which Other OralAgents alternative therapywillbenecessary. helpful, NSAIDswillbeineffectiveadjunctsformanypatients,and dosing. Theanesthesiologistmustremainawarethatwhilepotentially be administeredonascheduledbasisratherthanPRN(“asneeded”) intrathecal orepiduralopioidsareminimal.Whenused,theyshould Ingeneral,thedrawbackstouseofanNSAIDinconjunctionwith of valueinthispopulation. tion fortheiruse.Nevertheless,nonsteroidalagents(NSAIDs)maybe opioid use,atthispointitisdifﬁ cult tomakeablanketrecommenda- • • lar, orrectalroutes. Various NSAIDsmaybeadministeredviatheintravenous,intramuscu- AnumberofNSAIDshavebeenusedinthepost-cesareanperiod. • •

WhileinsomesituationsNSAIDscandecreasepostoperative A25mgdosecanbeadministeredevery 4to6hours. administration followingcesareandelivery. Propoacetamoliswidelyusedinsomepartsoftheworldviarectal seizure threshold. orders orseverepreeclampsia,as it hasbeenshowntodecrease Tramadolshouldprobablybeavoided inpatientswithseizuredis- about 40 or ketoprofendecreasepostoperativeanalgesicrequirementsby Whenadministeredviacontinuousintravenousinfusion,diclofenac cesarean deliverywithmixedresults. Ketorolac hasalsobeenadministeredIVonascheduledbasisafter but ketorolacissomewhatinconsistentandofshortduration. Ketorolac30mgIMisroughlycomparabletomeperidine75IM, parenteral analgesics. of ﬂ uids, andcantakeanoralNSAIDasadjuncttoneuraxialor after delivery,manyparturientsareabletotoleratesmallamounts Whileunrestrictedoralintakemaynotresumeforupto24hours parenteral alternativetooralmedicationsmaybenecessary. some periodoftimefollowingdelivery;duringthisperiod,a ManypatientswhohavehadacesareandeliveryremainNPOfor % whencomparedtoplacebo.

12. 11. 10. Further Reading 7. 4. 3. 2. 6. 5. 9. 8. 1.

in combinationwithbupivacaineandfentanyl infusion: arandomized,double-blind,dose-ﬁ epidural fentanylto0.5 Paech MJ , Pavy TJG , Orlikowski CEP , et al . Postoperative epidural Helbo-Hansen HS Pain , . 1985 Bang ; CSF followinglumbarepiduraladministrationinpatientswithcancerpain 23 U . : , 317 - 326 Lindholm . P Gourlay , etal. GK Anesthesiology. , Maternal effectsofadding 1988 Cherry ; cesarean section:Acomparisonwithepiduralandintramuscularnarcotics 68 DA . : , 444 - 448 Cousins . MJ Eisenach JC . , Cephalad migrationofmorphinein Grice SC , Dewan , DM . Patient-controlled analgesiafollowing Anesth. 1993 ; 2 : 21 - 26 . after cesareansection . Paech MJ caesarean delivery , . Moore JS , McDonnell NJ Evans , SF Keating . ML Meperidine forpatient-controlledanalgesia , Muchatuta NA , morphine inman . Wang JK , Nauss LA , Thomas JE . Pain reliefbyintrathecallyapplied morphine: adoseresponsestudy . Palmer CM Anesthesiology. , 1999 Nogami ; relationship ofintrathecalmorphineforpost-cesareananalgesia 90 . : 437 - 444 . Palmer CM , Emerson S , Voulgaropoulos D , etal. Dose-response 1323 - 1328 . 389 - 394 . lidocaine spinalanesthesiaforcesareandelivery . Palmer CM AnesthAnalg. , 2001 Voulgaropoulos ; 92 D : , Palmer 244 - CM 245 Alves . D . Continuous intrathecalsufentanilforpostoperativeanalgesia . . Subarachnoid fentanylaugments postcesarean analgesia . Cohen SE , Desai JB , Ratner EF , et al . Ketorolac andspinalmorphinefor Anesthesiology . 1979 ; 50 : 149 - 155 . Anaesth IntensiveCare 2009 ; 37 : 539 - 551 . WM % bupivacaineforcaesareansection . Anesthesiology . 1994 ; 80 : 1268 - 1276 . Int JObstetAnesth. 1996 ; 5 : 14 - 18 . , Van Maren G , etal. Post-cesarean epidural Anesth Analg. 2000 ; 90 : 887 - 891 . etal. Analgesia after nding trialofclonidine . Anesth Analg. 1997 ; 84 : Reg Anesth . 1995 ; 20(5) : Int JObstet

181 Obstetric Anesthesia Chapter 6 Anesthesia for Surgery During and After Pregnancy

Michael J. Paech , FANZCA Robert D’Angelo , MD Laura S. Dean, MD

Anesthesia for Reproductive Technologies 182

182 Anesthesia in Early Pregnancy 184 Anesthesia in Later Pregnancy 188 Pharmacological Considerations During Pregnancy 189 Radiological Exposure 191 Anesthesia for Fetal Surgery 192 Anesthesia for Postpartum Sterilization 195

Anesthesia for Reproductive Technologies

Assisted reproductive technologies (ARTs) involve a sequence of hormonal stimulation of the ovaries followed by egg retrieval and subsequent embryo transfer. Depending on the timing of intervention, these procedures may involve transcervical, transabdominal or laparoscopic approaches, each of which has a number of anesthetic options. Assisted reproductive technology results in a higher incidence of multiple gestation and ectopic pregnancies, both of which are associated with higher maternal morbidity and mortality than singleton pregnancy. Additionally, as ART success rates increase among women of advancing maternal age, preexisting comorbidities become more apparent. Pregnancy resulting from ART has a greater chance of preterm delivery and birth of babies that are small for gestational age. • • speciﬁ avoid unnecessary,costly,andemotionallystressfuldelays.Some for patientstofollowfastingguidelinespriorsurgeryinorder ductive technologiesrelyontimingforsuccess,soitveryimportant Allpatientsshouldhaveapreoperativeassessment.Assistedrepro- Anesthetic Implications centration, oligura,andthromboembolicevents. therapy. Thesyndromepresentsasascites,pleuraleffusion,hemocon- stimulatinghormone(FSH)andhumanmenopausalgonadotropin Ovarianhyperstimulationsyndromecanoccurasaresultoffollicle • • • • •

NumerousARTprocedurescanbeperformedandareoutlined: Hormonalstimulationandoocyteretrieval In-vitrofertilization unless immediatetransferisplanned. oocytes areretrievedbyultrasound-guidedvaginalaspiration, cycle, allowingforsubsequentretrievalofmultipleoocytes.Most therapies encouragetheproductionofmultipleovarianfolliclesper tube vialaparoscopy. inseminated. Fertilizedeggsaretransferredtothedistalfallopian Zygoteintrafallopiantransfer(ZIFT). after whichfertilizationoccursinvivo. directly intothedistalfallopiantubeviaalaparosopicapproach, and inspected.Ifmature,theyaretheninjectedwithdonorsperm Gameteintrafallopiantransfer(GIFT). via atranscervicalapproach. transferred intothefallopiantubesoruterinecavity,usually Embryotransfer inseminated. mizes theconcentrationofanesthetic infollicles. sia maybenecessary.Spinalanesthesia isalsoappropriateandmini- time ofactualretrieval,soprogression todeepsedationoranesthe- intravenous sedation,butmovement needstobeavoidedatthe Transvaginaloocyteretrievalismost commonlyperformedunder regardless ofanestheticchoice. nance ofhemodynamicstabilityremainstheprimaryconcern choice ofanestheticdrugsandtechniquesisunclear,butmainte- ence withoocytefertilizationorembryoimplantation.Theoptimal UniquetoanesthesiaforARTistheaddedgoaloflimitinginterfer- cconsiderationsshouldbeconsidered. . Oocytesthatwerefertilizedsuccessfullyare . Followingretrieval,oocytesareincubatedand

Oocytesareretrievedand

Oocytesareretrieved

. Hormonal

183 Obstetric Anesthesia 184 Anesthesia for Surgery • • remember that: during initialembryodevelopmentand organogenesis(days14to56), ered bynon-anesthesiologists. or withoutregionalanesthesia(e.g.,paracervicalblock),isoftendeliv- countries, butgeneralanesthesiaisusedinfrequently;sedation,with Termination ofpregnancyisalsoacommonprocedureinsome common operationforwhichgeneralanesthesiaisusuallyprovided. require evacuationofretainedproductsconception,thisisavery (incidence 15 conception maybenecessary. With embryoorfetaldemise,evacuationofretainedproducts operations fortraumaticorotherinjury,andoncologicaloperations). tis orovariancystaccidents,neurosurgeryforcerebrovascularevents, (e.g., laparosocopyorlaparotomyforacuteappendicitischolecysti- tent cervix,andanarrayofnonobstetricoperationsprocedures requiring anesthesiaincludeinsertionofcervicalsutureforincompe- during pregnancy.Intheearlytomidsecondtrimester,procedures • 1 •

Anesthesia inEarlyPregnancy % Whenevercontinuedfetalviabilityisdesired,andparticularly Earlypregnancyloss(mainlypriorto13weeksgestation)iscommon vasoconstriction. maternal bloodpressureandcardiac outputandavoidingperipheral Adequateuteroplacentalperfusion must beassuredbymaintaining the fetus(e.g.,vasoactivedrugsmay affectplacentalbloodﬂ Drugsmayhavebothdirect(pharmacologic) andindirecteffectson Laparoscopicproceduresareusedforembryotransfer. oocyte retrievalaresuitable. analgesia, althoughthesameanestheticoptionsasthoseusedfor Transcervicalembryotransfercanoftenbeachievedwithout • • • • –2

Trendelenburgpositioningmayreducechestwallcompliance. oxide orvolatileinhalationalanesthetics. nous inductionagents,musclerelaxation,andeithernitrous Generalanesthesiaismostcommonlyperformedusingintrave- pain. Peritonealanddiaphragmaticirritationmaycausepostoperative a rarecomplicationiscarbondioxideembolization. Pneumoperitoneumisusuallyachievedwithcarbondioxide,and % ofwomenwillexperienceaconditionrequiringsurgery % –20 % ofallpregnancies).Althoughnotwomen

ow).

• always thesafetyofmother. Theprimaryconcernduringnonobstetricsurgerypregnancyis humans whenusingstandardconcentrationsatanygestationalage.” anesthetic agentshavebeenshowntoanyteratogeniceffectsin American SocietyofAnesthesiologistsnotes:“Nocurrentlyused American CollegeofObstetriciansandGynecologiststhe A jointstatementon and sothatinformedconsentcanbeobtainedfromthepatient. analgesic drugsonpregnancy,sothatsounddecisionscanbemade anesthesiologist mustunderstandpotentialeffectsofanestheticand of anestheticorsedativedrugsassumesparticularimportance.The genital tract(e.g.,cervicalsuture),abdomen,orpelvis. current disease,withfetallossmorelikelyafteroperationsonthe Other factorsthatarelikelymoreimportantmaternalillnessand surgery but nancy, andprematureorlowbirthweightdelivery,areincreasedby Epidemiologicalstudiessuggestthattheriskoflossaviablepreg- Anesthetic PrinciplesandManagement • • • • •

Duringearlypregnancy,theteratogenicandcarcinogenicpotential the inhalationalanestheticagentsarepopularandappearsafe. Midazolam,opioids(e.g.,IVfentanylorremifentanil),propofoland surgical andmedical emergencies). viability (althoughinevitably,urgent surgerywillbemandatedby Essentialbutnonurgentsurgeryshould bedeferreduntilafterfetal systems,especiallythecentralnervous system.) have potentialnonteratogeniceffects ondevelopingfetalorgan after pregnancy.(Thoughneverdemonstrated inhumans,drugs Wheneverpossible,electivesurgery shouldbepostponeduntil cal stress,andsometimeslifelongimpactonthechild’shealth. potentially involvescostlyhealthcare,severeparentalpsychologi- ity andmortalityimplications(seeChapter11);pretermdelivery weeks thereafter,whenprematuredeliveryhassubstantialmorbid- both uptothetimeofviability(23–24weeksgestation)andin Theeffectofanesthesiaonthefetusremainsaprimeconsideration, pregnancy). the pelvisatapproximately20weeksgestation(orearlierifmultiple Aortocavalcompressionisapossibilityaftertheuterusrisesoutof ably doesnotdiffergreatlyfromnonpregnantpatients. tional age;priorto16weeksgestation,theriskofaspirationprob- Aspirationprophylaxisshouldbeconsideredbasedonthegesta- not inﬂ uenced byanesthesiaoranesthetictechnique. Non-obstetric surgeryduringpregnancy

bythe

185 Obstetric Anesthesia 186 Anesthesia for Surgery listed inTable does notusuallybecomeclinicallyrelevantfor3–4weeks. patterns requiresspecialexpertise. anesthetic drugsandhypothermia,sointerpretationoffetalheartrate Lossofbeat-to-beatvariabilityandfetalbradycardiaareeffects • • • • the followingapply: assess fetalwell-beingandtheabsenceofcontractions. monitoring canbeperformedbeforeandaftertheprocedureto sought butsimultaneouselectronicfetalheartrateandcontraction considered viableandthesituationallows,expertadviceshouldbe fetal heartratepriortoandaftersurgeryissufﬁ cient. Ifthefetusis to viability,at22–24weeksestimatedgestationalage,ascertainingthe Provide effectivepostoperativeanalgesia risks andfetaldrugexposure) If suitable,useregionalanesthesiawheneverpossible(tominimizematernal Consider themeritofcontinuousintraoperativefetalmonitoring Maintain normalpregnantphysiology Avoid drugsthatstimulateuterinecontractility Avoid drugswithpotentialforfetalharm the exposureoffetustoradiationduringimaging During assessment,beawareofthechangesresultingfrompregnancyand (22–24 weeks) If possible,defernon-electivesurgeryuntilafterfetalviability Postpone electivesurgeryuntilafterpregnancy Communicate withthesurgeonregardingurgencyofsurgery Term Pregnancy Table 6.1

Althoughnotevidence-based,thecoreprinciplesofanesthesiaare Afterfetaldeathinutero,acoagulopathymaydevelopovertimebut Intraoperativeelectronicfetalmonitoringmaybeappropriatewhen Fetalmonitoringshouldbeconsideredonacase-by-casebasis.Prior delivery. Thewomanhasgiveninformedconsenttoemergencycesarean to interveneduringthesurgicalprocedureforfetalindications. Aproviderwithobstetricalsurgeryprivilegesisavailableandwilling monitoring. Itisphysicallypossibletoperformintraoperativeelectronicfetal Thefetusisviable. Key PrinciplesofAnesthesiafromEarlyto 6.1 andamanagementplanoutlinedinFigure

6.1 .

• and tactful. after sedationorspinalanesthesia. from hospitalcanusuallybeachieved asquicklyormorethan women, sogeneralanesthesiaisnormally preferred.Rapiddischarge Thisisanoccasionofconsiderableemotionaldisturbanceformany of Conception Anesthesia forRemoval ofRetainedProducts Figure 6.1 Delay untilpostpartum lciesreyEssentialsurgery Elective surgery

Whenprovidinganesthesiaforthis procedure,becompassionate Avoid nonsteroidalanti-inflammatorydrugsafter27weeksgestation Provide optimalregionalorgeneralanesthesiawithsafedrugs Consider fetalmonitoringifgestation24ormoreweeks Consult aperinatologistifgestation22ormoreweeks may causepreoperative pelvicpain,nausea,andfever. Beawarethatdrugsusedforcervical ripening(e.g.,prostaglandinE2) viability. until afterfetal defer surgery to thewoman, If minimalrisk

Management planforapregnantwomanrequiringsurgery. first trimester Pregnant womanrequiringsurgery proceed withsurgery If risktothemothersignificant, second/third trimester Emergency surgery

187 Obstetric Anesthesia 188 Anesthesia for Surgery • • • • • • • • • advantagesof: is discussedindetailChapter12.Regionalanesthesiahasthe choosing betweengeneralandregionalanesthesia.Fetalmonitoring to continue,theprinciplesconsideredinChapter4applywhen Inprovidinganesthesiaforwomeninwhomthepregnancyisexpected • Ifspinalanesthesiaischosen: •

Anesthesia inLaterPregnancy Hypotensionshouldbemanagedaggressively. ache, andprovidedwithadviceonhow toseekfollow-up. Patientsshouldbeinformedaboutpost-discharge post-spinalhead- tries becauseoftransientlumbarpain andneurotoxicityissues). tive recovery(hyperbariclidocaineis nolongerusedinmanycoun- compared withspinalbupivacaine,thus promotingrapidpostopera- mcg) toachievealessintensemotor blockofshorterduration Plainropivacaineisanoption(atleast15mg,withfentanyl10–20 visceral pain)andprovidegoodanalgesia. NSAIDs postoperatively,decrease“cramping”discomfort(uterine IV ketorolacorparecoxibintraoperatively,oneofthemanyoral tive pain.Nonsteroidalanti-inﬂ ammatory drugs(NSAIDs)suchas the procedureisnotusuallyassociatedwithprolongedpostopera- Opioidanalgesicrequirementsarevariablebutoftenminimal,as airway (LMA)deviceisappropriate. age andpatientsymptoms,althoughinmostcasesasupraglottic Decisionsaboutaspirationriskmustbemadebasedongestational of highsympatheticactivityandcardiacoutput. duration ofeffectshorterbecauserapidredistributionasaresult IVanestheticrequirementsatinductionmaybeincreasedandtheir anxiolysis. Mostwomenwillbenefitfrompreoperativeorpreinduction Avoidingissuesrelatedtocertainanestheticandanalgesicdrugs. Avoidingtherisksassociatedwithdifﬁ 30 Localanestheticdoserequirementsarereduced(byapproximately Spontaneousventilationisusuallysuitable. •

% the midsecondtrimester. patients withsymptomaticreﬂ ux, andismostoftenusedafter Rapidsequenceinductionandtrachealintubationisreservedfor ) fromtheﬁ

rsttrimester.

cultairwaymanagement.

• • • • similar tononpregnancy: hypotension needmanagement.Thetypicalphysiologicchangesare physiological derangementssuchashypoxemia,hypercarbia,and are generallyverygood,andbetterthanafterlaparotomy,although neum hasbeenperformedsafelyinmanypregnantwomen.Outcomes Complexlaparoscopicsurgerywithcarbondioxidepneumoperito- Anesthesia forLaparoscopicSurgery drugs areshowninTable Considerationsrelevanttocommonanestheticandanalgesic • • • controversial. making thisareaofpracticeandpain managementchallengingand sic drugshavenotbeenadequately evaluatedduringpregnancy, be teratogenicinhumans,butanumberofanestheticandanalge- • possible. maternal oxygenationandbloodpressure. cases ofseverefetalbradycardiaarereportedinthepresencegood rises isusuallywelltoleratedbythefetus.Nevertheless,occasional Thedecreaseinplacentalbloodﬂ ow asintra-abdominalpressure •

Pregnancy Pharmacological ConsiderationsDuring Ingeneral: Ingeneral,surgeryshouldbedeferreduntilthesecondtrimesterif Provide prophylaxis against postoperative venous thromboembolism. Provideprophylaxisagainstpostoperativevenousthromboembolism. decrease uteroplacental ﬂ ow. Thismyometrialeffectdiminishesin Ketamineincreasesuterinetone, which isundesirableandmay Anincreaseincardiacoutputpostinduction. neum thatmayrequireincreasedminuteventilationtonormalize. Anincreaseinend-tidal(ET)-carbondioxidewithpneumoperito- ing thepneumoperitoneum. resistance andmeanarterialbloodpressureatthetimeofestablish- Afallincardiacoutputsecondarytoincreasedsystemicvascular Asfaraspossible,shieldthefetusfromradiation. adequateventilationandalveolarrecruitmentstrategies. normocarbia (approximately30–32mmHg)ifpossible,using Uselowpressurepneumoperitoneumandmaintainmaternal Single doses of a benzodiazepine appear safe throughout pregnancy. Singledosesofabenzodiazepineappear safethroughoutpregnancy. Keepmaternaloxygenationnormalorhigh.

6.2

.Noanestheticdrughasprovento

189 Obstetric Anesthesia 190 Anesthesia for Surgery • • • • • • • •

appears safe. ated withfetalloss,butexposurewithinscavengedenvironments exposure tonitrousoxideduringearlypregnancyappearassoci- fetus, asplacentaltransferisrapid.Highlevelsofoccupational actions raiseconcernsaboutapotentialeffectonthedeveloping no evidenceofteratogenicityorfetotoxicityinhumans,these deoxyribonucleic acid(DNA)formationandcelldivision.Despite and reducedthymidinesynthesis;thishaspotentialeffectson administration, resultinginraisedhomocysteineconcentrations Nitrousoxideinhibitsmethioninesynthaseafteracouplehoursof Amongcommonanalgesicdrugs: 27 weeksestimated gestationalage. especially after32weeksgestation. Theyareideallyavoidedafter hypertension duetoprematureclosure oftheductusarteriosis, rocolitis, neonatalintracranialhemorrhage, andpulmonary tion, andinlatepregnancywithfetal renaltoxicity,necrotizingente- NSAIDsinearlypregnancyareassociated withspontaneousabor- effects butnoevidenceofteratogenesis, soappearssafe. considered safe.Likeopioids,tramadolhasreversibleadverse Acetaminophen(paracetamol),opioids,andlocalanestheticsare nitroglycerin (glyceryltrinitrate[GTN])appearssafe. SodiumPentothal(sodiumthiopentalorthiopentone)issafe. used duringpregnancy,’’whichcreatesoff-labeluseissues. In somecountriesitwasreleasedwiththecaveat“Shouldnotbe transfer, withoutapparentaffectonfertilizationorpregnancyrate. used duringreproductivetechnologytechniquesinvolvingembryo has notbeenreportedtocauseproblems.Italsowidely Propofolhasbeenextensivelyusedinearlyandlaterpregnancy anesthesia forcesareandelivery. later pregnancywhenketamineiseffectiveandsafeforgeneral Neuromuscularblockingdrugsdonotcrosstheplacentainsigniﬁ Thesafetyofnitrousoxideisunclear,butitcaneasilybeomitted. and causenoknowndirectfetalhazards. Theinhalationalanestheticsaretocolytic(usuallyausefuleffect) Theacuteadministrationofvasoactivedrugssuchas cant amounts.

-blockers and

• potential hazardsof: Radiationexposureduringearlypregnancyisaconcernduetothe based onpotentialfetalhazards. mal maternalevaluationandsafecare,soitshouldnotbewithheld Nevertheless,radiologyisadiagnosticmodalitythatcriticaltoopti- • • • • • • • • • • Nitrous oxide • • Midazolam, diazepam,temazepamandotherbenzodiazepines Nonsteroidal anti-inﬂ Concern DuringPregnancy Table 6.2

Radiological Exposure

Ingeneraltheriskofhazarddependson: during breastfeeding. Parecoxib andcelecoxibappearsafeforshort-termadministration ommendations, althoughnospecifi c concernshavebeenreported. noids (e.g.,gabapentin,pregabalin)areinsufficient toallowfi Dataoncyclooxygenase2-specific inhibitors(coxibs)andgabapenti- embryodamageandfailuretoimplant organogenesis exposure. death,growthrestriction,andpostnatalneoplasiaafterpost- weeks) after exposureduringorganogenesis(secondtoeighthgestational deathorcongenitalmalformations(especiallybrain,eyeandskeletal) thefetalestimatedgestationalage and othersmaybe“allornothing,”especiallyinthefi theradiationdose(butthereareonlyriskthresholdsforsomehazards theradiationdoserate. • • • • best avoidedinthefi rst trimesterduetoassociationwithpregnancyloss gestation becauseofpotentialfetaleffects: in populationstudies best avoidedafter27weeksgestationandcontraindicated 32weeks easily avoided probably safewithshort durationuse(<2hours) appear safe with short-termuse(i.e.,perioperative)orsingledose chronic useinthefi rst trimesterassociated with cleftpalate

necrotizing enterocolitis renal damage premature closureoftheductusarteriosis intracranial hemorrhage Anesthetic andAnalgesicDrugsofPotential ammatory drugs ammatory

rst trimester) rst trimester) rm rec-

191 Obstetric Anesthesia 192 Anesthesia for Surgery than 150–200mGy(15,000–20,000mrad)exposurethereisa5 by 30per1000foreach10mGy(1000mrad)ofexposure.Atgreater abnormality increasesfromabaselinenonexposurerate(60per1000) 99 alent toamilliSievert[mSv]or100millirads[mrad])thenthereis of mentalretardationand3 radiation dosesofvariousproceduresareshowninTable aimed morethan10cmfromthefetusarenotdangerous,and patient canserveasaguidetototalexposure.Ingeneral,X-raybeams required overtimeathermoluminescentdosimeterattachedtothe the fetuswithaleadapron.Whenmanymaternalexposuresare different equipment,techniques,maternalsizeandwithshieldingof and isbeginningtoaddresssomeofthesedifﬁ monetary constraints.Thisdisciplineofmedicinecontinuestoevolve delivery. However,fetalsurgeryhasmanysocial,ethical,legaland anomalies thatmaybeamenabletosurgicalinterventionprior Advancesindiagnostictechniqueshaveimproveddetectionoffetal performed as: • • • Mrad =millirads. mGy=milliGray CT abdomen CT chest CT head Intravenous pyelogram Pelvic X-ray Chest X-ray Head &cervicalspine Imaging Fetus Table 6.3

Anesthesia forFetalSurgery Ifthefetusisexposedtolessthan50–100mGy(amilliGrayequiv- Theradiationexposureofthefetus(doseabsorbed)varieswith Dependingonthefetalultrasounddiagnosis,interventionsmaybe % minimallyinvasiveendoscopicapproaches openintrauterineapproaches exuterointrapartumtherapy(EXIT) chanceitwillnotdevelopchildhoodcancer.Theriskofany Estimated RadiationExposuretotheShielded

% riskofneonatalorchildhoodcancer.

3000/25 1000 50 500 350/20 2/< 0.01 0.02 Exposure (mrad/mGy)

cultissues. 6.3 . % risk

• • • • this patientpopulation Anesthetic goalsfornonobstetricsurgeryduringpregnancyapplyto dures typicallyrequiregeneralanesthesiawithuterinerelaxation. with localorneuraxialanesthesia,whereasopenintrauterineproce- Mostminimallyinvasiveendoscopicprocedurescanbeperformed Anesthetic Implications loss. but tightclosureoftheuterustopreventsubsequentamnioticfl complete uterinerelaxationtoassurecontinuedplacentalcirculation, Surgicalconcernsuniquetothissubspecialtyincludethenecessityfor • • • • • • Theprinciplesare: Anesthesia forEndoscopic FetalSurgery utero fetalanalgesiaandanesthesia. Additional fetalconsiderationsareintraoperativemonitoringandin teratogenic drugs,andpreventiondetectionofpretermlabor. • extensive ultrasound-guided endoscopicprocedures. Neuraxial(spinalorepidural)anesthesia appearsbenefi • • include: have signifi cant morbidityandarecorrectable

Indicationsforsurgicalinterventionincludethoseanomaliesthat congenitalpleuraleffusions congenitalheartdefects syndrome) complicationsofmonochorionictwins(twin-twintransfusion myelomeningocele fetalcardiacarrhythmias fetalchylothorax of neuromuscularblockingandanalgesic drugsifwarranted. Administerdirectumbilicalvenous or fetalintramuscularinjection percutaneous minimallyinvasiveprocedures. nal andfetalsedation(e.g.,IVremifentanil infusion,midazolam),for Localanesthesiashouldbeusedontheabdominalwall,withmater- and ensureleftuterinedisplacementifappropriate. Thepatientshouldbefasted;administeranonparticulateantacid, sacrococcygealteratoma congenitaldiaphragmatichernia congenitalcysticadenomatoidmalformation obstructiveuropathies

—

speciﬁ cally maternalsafety,avoidanceof

in utero.Examples

cial formore

uid

193 Obstetric Anesthesia 194 Anesthesia for Surgery • Theprinciplesare: Anesthesia forOpenFetalSurgery • • • • • • • • Theprinciplesare: Procedures Anesthesia forExUteroIntrapartum(EXIT) • • • (a rangeofsurgicalprocedures)iscommenced. of thefetusaredelivered;intubationisaccomplishedandfetalsurgery Thefetusisgivenintramuscularanalgesiaandtheheadshoulders • • •

Consideraneuraxialprocedureforpostoperativeanalgesia. and ensureleftuterinedisplacementifappropriate. Thepatientshouldbefasted;administeranonparticulateantacid, Arapidsequenceinductionisindicatedforgeneralanesthesia. ean deliverymaybenecessaryintheeventofuterinerupture. for 2–3dayspostoperatively.Itshouldbenotedthaturgentcesar- Closemonitoringoffetalheartrateanduterineactivityisnecessary be continuedpostoperatively,watchingforpulmonaryedema. are oftennecessarytoachievefulluterinerelaxationandmay Additionaltocolytics(IVnitroglycerinormagnesiumsulfate) surgeons forintramuscularadministrationwithinthesterileﬁ eld. Medicationsforfetalanesthesiaandimmobilityaregiventothe rhage. Hysterotomyisperformedwithstaplestoavoiduterinehemor- relaxation. Formaintenance,inhalationalanestheticsprovideusefuluterine Consideraneuraxialprocedureforpostoperativeanalgesia. and ensureleftuterinedisplacementifappropriate. Thepatientshouldbefasted;administeranonparticulateantacid, Arapidsequenceinductionisindicatedwithgeneralanesthesia. uterine relaxation. anesthesia, usinghighdosesofIVnitroglycerin (100–500mcg)for Anoptionforlessextensivefetal surgeryisneuraxialmaternal relaxation isimmediatelyreversedto avoiduterineatony. Whentheumbilicalcordisclamped followingfetalsurgery,uterine hemorrhage. Hysterotomyisperformedwithstaplestoavoiduterine vides uterinerelaxation. Formaintenance,high-concentrationinhalationalanestheticpro-

increase maternalcomplications. tubal ligationduringtheﬁ rst eighthoursafterdeliverydoes Practice GuidelinesforObstetricAnesthesiasuggestthatpostpartum controversial. TheAmericanSocietyofAnesthesiologists(ASA) of thiselectivesurgeryandthechoiceanesthesiaaresomewhat diate hoursfollowingvaginaldelivery.Themostappropriatetiming Postpartumtuballigation(PPTL)isacommonprocedureintheimme- • • before anesthesiaandsurgery. delivery, socarefulassessmentofhemodynamicstatusisrequired patient mayhavelostasigniﬁ cant volumeofbloodduringlaborand Thepostpartumperiodisatimeofalteredmaternalphysiology. Anesthetic Implications the newborntobecompleted. woman moretimetoconsiderherdecisionandfortheassessmentof However,delayingtheprocedure6weeksafterdeliverygives • • • • ligation: Toreduceriskofgastricaspiration,forimmediatepostpartumtubal • • •

Anesthesia forPostpartumSterilization

Theadvantagesofimmediatepostpartumsterilizationare: Theriskofaspirationmustbeconsidered. avoidanceofinconvenientfurtherhospitalizations enhancedsurgicalexposureoftheenlargeduterinefundus lowercost tion. poorpatientcompliancemaypreventreturnfordelayedsteriliza- more followingdelivery. but theincidenceofreﬂ ux normalizesapproximately24hoursor Loweresophagealsphinctertoneisdecreasedduringpregnancy, have delayedgastricemptyingduringtheearlypostpartumperiod. pregnant controls,butthosereceivingopioidsforlaboranalgesiamay patients atanytimeintervalafterdeliverywhencomparedtonon- ThereisnodifferenceingastricvolumeorpHpostpartum Thepatientshouldbefastedfor6hours priortosurgery. Administeranonparticulateantacid within30minutesofsurgery. women withsymptomaticreﬂ Considerusingmetoclopramideor anH2-receptorantagonistin

ux.

not

195 Obstetric Anesthesia 196 Anesthesia for Surgery predictable sensorylevels. Advantagesofspinaltechniquesincludeareliable,denseblockand • • • • Foranepiduraltechnique: • • ligation. Eitherepiduralorspinaltechniquesaresuitableforpostpartumtubal Neuraxial Anesthesia catheter, underlyingmedicalconcerns,andanestheticrisksfactors. into accountthepatient’spreferences,presenceofanepidural the choiceofanesthesiaisdeterminedonanindividualbasisandtakes In practice,thetimingofprocedureinrelationtodeliveryand countries, butintheUnitedStates,neuraxialanesthesiaispreferred. eral anesthesia.Localanesthesiafortuballigationisusedinsome tubal ligation(PPTL)islikelytoreduceriskwhencomparedwithgen- TheASAguidelinesstatethatneuraxialanesthesiaforpostpartum Anesthetic Techniques • • • • •

Administersedativesforpatientcomfortasrequired. SpinalblockforPPTLiseffi Smallvolumesoflocalanestheticeliminate toxicityconcerns. 2 of epiduralfailure). analgesia wasinadequateortheprocedure isdelayed(ahigherrisk Ahighqualityblockcanbeachieved, especiallywhenlaborepidural local anestheticinincrementaldoses(i.e.,3 time consumingdosing. volumes oflocalanesthetic,increasingthepotentialfortoxicityand ure ratewithincreasingtimefromdelivery,andtheneedforlarge Thedisadvantagesofepiduralanesthesiaincludeanincreasedfail- functioning epiduralcatheterisalreadypresent. Theprimaryadvantageofanepiduraltechniqueexistswhena ExtendthesensoryblocktodermatomesT arachnoid andintravenoustestdoses. Reconfi rm correctlocationof thelaborepiduralcatheterbysub- planned, becauseofdelayedgastricemptying. ConsideravoidingIVopioidsifimmediatepostpartumtubalis Confi partum procedures. Neuraxialanesthesiaisusuallypreferredforallimmediatepost- % lidocainewithepinephrine[adrenaline]). rmIVaccess.

cient,simple,andhasaquickonset.

4 –T

2-chloroprocaineor

6 withshortacting

• Thedisadvantagesofspinalanesthesiaarerelativelyminor :

• Foraspinaltechnique: • ity ofdifﬁ general anesthesiaforPPTLincludetheriskofaspirationandpossibil- epidural catheterinplace.Theprimaryissuesassociatedwithuseof an additionalregionalprocedureinwomenwhonolongerhave Generalanesthesiaofferstheadvantageofefﬁ ciency andavoids General Anesthesia • • • • • • Further Reading 7. 5. 4. 3. 2. 1. 6.

Asuggestedtechniqueincludes: alowriskofpost-duralpunctureheadache theincreasedriskposedbyanadditionalprocedure. Chooseasmallgauge(<24gauge)pencilpointspinalneedle. Conﬁ 10–20 mcg). Administerintrathecalbupivacaine7.5–10mg(withfentanyl StandardASAmonitoring. Rapidsequenceinductionwithtrachealintubation. prolonged durationinpostpartumpatients. lar blockingdrugsshouldbeusedonlyasnecessary,bothhavea Lowdosesofbothdepolarizingandnondepolarizingneuromuscu- women withoratriskofpostpartumhemorrhage. decrease uterinebloodlossinthepostpartumperiod,especiallyfor Inhalationalanestheticconcentrationshouldbeminimizedto

A mechanisticandtoxicologicreview . Sanders RD , Weimann J , Maze M . Biologic effectsofnitrousoxide: undergoing abdominalsurgery . Shaver SM Perinatol. , 1999 Shaver ; 23 DC : Gaiser 507 - . RR 514 Perioperative assessmentoftheobstetricpatient CurrOpinAnaesthesiol. , . 2008 Kurth ; 21 CD : De Buck 293 - . F 297 Anesthetic considerationsforfetalsurgery Anesthesiol Clin. , . . 2007 Deprest Winter ; J 45 , Tsen : 99 LC - Van deVelde 113 2009 . M ; . 105 Anesthesia forassistedreproductivetechnologies : . . reproductive technologies.VitoratosN 201 Anesthesia forfetalsurgery . - . 205 . Vlahos NF , Giannakikou I , Vlachos A . Analgesia andanesthesiaforassisted nonobstetric surgery . Mhuireachtaigh RN , O’Gorman DA . Anesthesia inpregnantpatientsfor rmIVaccess. cultairwaymanagement.

J ClinAnesth . 2006 ; 18 : 60 - 66 .

J PerianesthNurs. 2005 ; 20 : 160 - 166 .

Anesthesiology. 2008 ; 109 : 707 - 722 . Int JGynaecolObstet.

Int

Semin

197 Obstetric Anesthesia 198 Anesthesia for Surgery

10. 8. 9.

Anesthesia . American SocietyofAnesthesiologistsTaskForceonObstetric Practice GuidelinesforObstetricAnesthesia . An updatedReportbythe Wong CA , Loffredi M , Ganchiff period . Gin T , Cho AMW, Lew JKL, etal . Gastric emptyinginthepostpartum term pregnancy . Anaesth IntensiveCare. 1991 ; 19 : 521 - 524 . Anesthesiology. 2007 ; 106 : 843 - 863 . Anesthesiology . 2002 ; 96 : 1395 - 1400 . JW , et al . Gastric emptyingofwaterin teria defining bothpreeclampsiaandsevere(Table Obstetricians andGynecologists(ACOG) hasestablishedspecifi hypertension, proteinuriaandedema,theAmericanCollegeof the puerperium.Althoughclassictriadofpreeclampsiaincludes induced hypertension(PIH)andchronicthatpersistsinto “Hypertensive disordersofpregnancy”includesbothpregnancy- increase inbothmaternalandfetalmorbiditymortality. Hypertension duringpregnancyisaconditionthatleadstomarked an elevatedbloodpressureisalwaysconsideredabnormal. Bloodpressuredecreasessomewhatduringanormalpregnancy,and care providercan have animpactbyincreasingthesafety of preeclampsia. Withanunderstanding ofthiscondition,theanesthesia Eclampsia istheconditiondefi ned byaseizureascomplication of preeclampsia canbehighlyvariable fromoneindividualtoanother. Introduction Despitethese“classic”defi nitions, theclinicalpresentation of Summary Anesthetic Options Anesthetic Management Obstetric Management Complications Pathophysiology Introduction Robert D’Angelo , MD Kenneth E . Preeclampsia Nelson , MD Hypertension and PregnancyInduced Chapter 7

212

199

202

200

207

203 206 anesthesia. c cri- c 7.1 ).

199 200 Pregnancy Induced Hypertension • • include: pathophysiologic changesofpreeclampsia. unknown ifthisimbalancecausesPIHor,rather,isaneffectofother abnormally low,animbalancethatfavorsvasoconstriction.Itremains thromboxane levelsincreasemarkedlywhileprostacyclinare but thebalancefavorsprostacyclinandthusvasodilation.InPIH, pregnancy, boththromboxaneandprostacyclinlevelsincrease, Theexactcauseofpreeclampsiaremainsunknown.Innormal Table The anestheticimplicationsofpreeclampsiaaresummarizedbrieﬂ • liver, andkidneys. Thecombinationofaconstricted vasculature and organ systemincludingbutnotlimited tothebrain,lungs,heart, Preeclampsiaisamultisystemdisorder thatcanaffecteverymajor •

• ∗ Severe Preeclampsia Table 7.1 • preeclampsia andeclampsia.

Pathophysiology Source:theACOGPractice Bulletin#33.Diagnosisandmanagementof

Additionalindicatorsimplicatedashavingaroleinpreeclampsia lackofnormalincreasesrenin,angiotensin II,andaldosterone reducednitricoxide elevatedendothelin increasedcapillarypermeability. • • • • • •

Severe Preeclampsia: • • •

Mild Preeclampsia: • •

Cerebral: Headache,scotomata,alteredlevelofconsciousness Pulmonary: Pulmonaryedema,cyanosis Hepatic: Increasedliverfunctiontests Epigastric orrightupperquadrantpain Renal: Oliguria,elevatedcreatinine Hematologic: Thrombocytopenia HELLP Syndrome: 1–2 Hypertension: SBP 3–4 Evidence of End-OrganInvolvement Proteinuria: Hypertension: SBP Proteinuria: 24hrcollection 7.2 . + proteinwithurinedipstick + proteinwithurinedipstick Criteria fortheDiagnosisofMildand ≥ 5gin24hourcollection

H emolysis, E levated L iver Enzymes, L ow P latelets

≥ 160mmHgorDBP ≥ 140orDBP ∗

Obstet Gynecol. 2002;99:159–167. ≥ 300mgproteinor

≥ 90mmHgor

≥ 110mmHg y in progressive increase typicallystartsinthesecondtothird trimester. Althoughelevatedbloodpressure isthehallmarkofdisease,a Cardiovascular distress syndrome. tered magnesiumsulfate,canincrease theriskofacuterespiratory boluses inpatientswithseverepreeclampsia, especiallythoseadminis- oncotic pressureandincreasedvascularpermeability.Largeﬂ uid pulmonary edema.Thiscanbeattributedtoareductioninplasma Approximately3 Pulmonary compartments. as watermovesfromtheintravascularspaceintootherbody “leaky capillarymembranes”leadstointravascularhypovolemia, • • • Table 7.2 • •

• Airway: •

• Magnesium:

Blood PressureControl: • • • Eclampsia: • • • • • • • Thrombocytopenia: • • •

but expectincreasedsensitivity Use Exaggerated edema Anticipate difﬁ No reductionof 75,000/mm Consider smallertrachealtube(6.0–6.5mm) Avoid nasalintubation Be awareofpotentialseizureregardlessseveritypreeclampsia Magnesium forprophylaxisandtreatment Benzodiazepines orbarbituratesforseizuresunresponsiveto magnesium Especially importantwithGAtoblunttheexaggeratedresponse laryngoscopy Baseline control with: • • Titrate toDBP90–100mmHg Especially importanttoassesswhenusingregionalanesthesia reduce theriskofepiduralhematoma Acute controlwithnitroglycerine,magnesium,opioids Recent PlateletCount Start withthresholdof100,000/mm –usually within6hoursofregionalblock

Hydralazine 5mgIVq20min upto20mg Labetalol 5mgIV,doubledose q10minupto300mgtotaldose nondepolarizing relaxants sparingly andtitratetoeffect

Anesthetic ImplicationsofPreeclampsia

3 ifcontraindicationstoGA) % cult intubation cult

ofpatientswithseverepreeclampsiawilldevelop succinylcholine doseforrapid sequenceinduction,

3 (considermodifyingaslow

201 Obstetric Anesthesia 202 Pregnancy Induced Hypertension • • ity ofdisease,ascapillarypermeabilitytheglomerulusincreases. vent complications.Thedegreeofproteinuriaincreaseswiththesever- failure israre,urineoutputshouldbemonitoredcloselytohelppre- Proteinuriaisamarkerforrenaldysfunction.Althoughchronic Renal • related totheseverityofdisease. severe preeclampsia.Thedegreeofthrombocytopeniaisgenerally tional totheseverity ofdisease.Itischaracterized byprogressive Themorbidityandmortalitythatoccurs withpreeclampsiaispropor- Severe Preeclampsia • • Thrombocytopenia(i.e.,plateletcountbelow150,000/mm Coagulation patient. Bloodvolume,CVP,andPCWPcanvarymarkedlyfrompatientto below 100,000/mm up to30 • •

Complications

Preeclampticparturientsmayexhibit: Aplateletconsumptioncascadeensues. platelets. Thiscausesthromboxaneandserotonintobereleasedbyactivated unknown, damagetotheendotheliumhasbeenimplicated. Althoughthemechanismofthrombocytopeniainpreeclampsiais pulmonary edemaandintracranialhemorrhage. blood pressurecontrolisrequiredtopreventcomplicationssuchas Anexaggeratedhypertensiveresponsetolaryngoscopy.Close necessary, vasopressorsshouldbeadministeredcautiously. Anexaggeratedresponsetoexogenouscatecholamines.When Glomerulopathy is correlated with the severity of the preeclampsia. Glomerulopathyiscorrelatedwiththeseverityofpreeclampsia. Oliguriamayoccurwithseverepreeclampsia. • •

toring, or other monitors to assess preload and cardiac function. toring, orothermonitorstoassesspreloadandcardiacfunction. vascular volumemaynecessitatepulmonaryarterialpressuremoni- Urineoutputlessthan0.5ml/kg/hdespiteapparentlyadequateintra- can developpulmonaryedema. preload andavoidingoverloadmustbemaintained,orthepatient Carefulbalanceinhydrationbetweenmaintainingadequaterenal % ofpatientswithpreeclampsia,yettheplateletcountfalls 3 inlessthan10

ofpatientspresentingwith

3 )occursin

• the syndromeareoutlinedinTable of hypertensionandproteinuria.Signssymptomsassociatedwith severe preeclampsia,thesyndromehasbeendescribedinabsence p rates aremoreoftenusedoutsidetheUnitedStates).Ifpreeclampsia prophylaxis intheUnitedStates,whilebenzodiazepinesandbarbitu- pertensives andseizureprophylaxis(magnesiumisusedfor With moreseverecases,inpatientcontrolisrequired,usingIVantihy- the outpatientsetting,withgoalofvaginaldeliverynearertoterm. Conservativemanagementinvolvescontrollinghypertensionin • • evidence ofprogressiveseveritydisease. be closelymonitoredanddeliveryisusuallyindicatedwhenthere the individualclinicalsituation,andcanchangeabruptly. Obstetricmanagementofpatientswithpreeclampsiawilldependon HELLPisanacronymfor HELLP Syndrome (Table and becomesseverewhenadditionalobjectivecriteriaaremet includes objectivemeasuresofhypertensionandproteinuria increases neonatalandmaternalmorbiditymortality.Preeclampsia deterioration ofmaternalandfetalwell-being,significantly • • • • HELLP Syndrome Table 7.3 •

Obstetric Management latelet count.Althoughusuallyconsideredtobeatype,orsubset,of

Factorsusedtodetermineobstetricmanagementinclude: severityofthehypertension presenceofcomplicationssuchasthrombocytopeniaandoliguria fetalcondition. • • Thrombocytopenia Nausea and vomiting Epigastric orrightupper quadrantpain Malaise • Regional anesthesiamay becontraindicated

Platelet count canfallprecipitously Maternal morbidityincreases signiﬁ cantly astheplateletcountfalls below 50,000/mm Develop plan forgeneralanesthesia 7.1 ). Signs andSymptomsAssociatedwith

h emolysis,

7.3 e levated .PatientswithHELLPshould

l iver enzymes,and

l ow

203 Obstetric Anesthesia 204 Pregnancy Induced Hypertension • it isnoteffectiveasanantihypertensive. ated witheclampsia.Althoughittransientlydecreasesbloodpressure, progressing disease,orastreatmenttoreducethemorbidityassoci- is usedprophylacticallyinpatientswithseverepreeclampsiaorrapidly Magnesiumsulfateraisestheseizurethreshold.InUnitedStates,it Magnesium Pharmacologic Agents well-being ofboththemotherandfetus. management, cesareandeliverymaybethebestoptiontoensure cannot becontrolled,oriffetaldistressoccursinspiteofmedical • • • • • • • • Alpha methyldopa(Aldomet) agents. Commonagentsutilizedinclude: lampsia, andmaybeaccomplishedwithanyofseveralpharmacologic Bloodpressurecontrolisamajorgoalofthemanagementpreec- Antihypertensives nesium sulfateduringsurgery. cial careshouldbetakentoavoidaccidentalrapidinfusionofthemag- (Table siologist, especiallywhenmanagingageneralanesthetic Magnesiumadministrationhassigniﬁcant implicationsfortheanesthe- Hydralazine •

Therecommendeddosingscheduleformagnesiumsulfateis: Magnesiumhasanarrowtherapeuticindex. mended forrecurrentseizures. Anadditional2–4gmadministeredover10minutesisrecom- 1–2 gm/hinfusion. 4–6gmloadingdoseadministeredover20minutesfollowedbya Bloodlevelsshouldbemonitored. tendon reﬂexes mustalsobemonitored. Clinicalsignsoftoxicitysuchassedationandlosspatellardeep by inhibitionofdopamineformation Indirectlyinhibitsdopaminergicand adrenergicneurotransmission Administeredorally therapy First-lineagentusedtotreatmildpreeclampsiaduringoutpatient Administeredintravenouslyduringhospitalization Directactingarterialandarteriolar vasodilator 7.4 ). Musclerelaxationmustbecarefullymonitored,andspe-

• Labetalol • • • • mmHg butthefetalstatusmustbemonitored. The goalisgenerallytoachieveadiastolicbloodpressureof90–100 hypotension andsubsequentreductionofuteroplacentalbloodﬂ Allintravenousantihypertensivesmustbecarefullytitratedtoavoid tomy withinductionofregionalanesthesia, resultinginhypotension. population includethepossibility ofanexaggeratedsympathec- Theanestheticimplicationsofantihypertensive agentsinthis • • • • • • Table 7.4

Maycausereﬂ 45 minutesforfulleffect OnsetafterIVadministrationtakesseveralminutes,andupto Administeredintravenouslyduringhospitalization Usuallythefetustoleratesreductioninmaternalblood of 5–8hours,eliminatedviahepaticmetabolism OnsetafterIVadministrationtakesseveralminutes,hasahalf-life 7:1 intravenously) Nonselectivebetaandalphablocker(beta:alphaeffect3:1orally, the fetus. accompanying bloodpressurereduction maynotbetoleratedby but inasmallnumberofcases,the reductioninuterineperfusion lead tolife-threateningcardiovascularcollapse Inadvertent rapidinfusionofmagnesiumduringcesareandeliverycan • • • • Mild sedation relaxants viabothpre-andpostsynapticmechanisms delivery Potentiates effectsofbothdepolarizingandnondepolarizingmuscle Possibly smallincreaseinintraoperativebloodlossduringcesarean Mild reductioninbloodpressure •

Hold theinfusionduringcesareandeliveryifbeingadministered stimulator reduced, ifusedatall,andtheeffectmonitoredusinganerve prophylactically topreventeclampsia Continue theinfusiononaseparateIVpolewithtubing eclampsia during cesareandeliveryifbeingadministeredastreatmentfor intubation scenario The doseofnondepolarizingmusclerelaxantsshouldbesigniﬁ Time torecoveryfromsuccinylcholineisprolonged,although sequence induction Long durationofsuccinylcholinepotentiallycomplicatesdifﬁ reduction ofsuccinlycholinedoseisnotrecommendedduringrapid

Anesthetic ImplicationsofMagnesiumSulfate ex tachycardia

cult pressure, cantly ow.

205 Obstetric Anesthesia 206 Pregnancy Induced Hypertension • • • more diffi cult. Thistechnicaldiffi culty isfurthercomplicated bya airway mucosafriabilitycombineto makeendotrachealintubation patient. Weightgain,breastengorgement, upperairwayedema,and Generalanesthesiacarriesincreased riskspecifi c tothepregnant Airway thrombocytopenia areoutlinedinTable for theanestheticmanagementof thepreeclampticpatientwith promptly, couldleadtopermanentneurologicinjury.Recommendations expanding epiduralhematoma,whichifnotrecognizedandtreated cated bythrombocytopenia,uncontrolledbleedingcouldresultinan does notpresentaproblem.Inthepatientwithpreeclampsiacompli- sible topreventduringepiduralorspinalplacement,butnormally contraindicated cannotbedefined. Traumatoepiduralveinsisimpos- cytopenia. Theplateletcountatwhichneuraxialanesthesiabecomes Asnotedabove,30 Coagulation caring fortheseparturients: severe preeclampsia,importantfactorsshouldbekeptinmindwhen Althoughtheplasmavolumecanvarysignifi cantly inpatientswith Volume Status General Considerations • in SVR. and volatileinhalationalagentsmaycauseanexaggeratedreduction Similarly, duringgeneralanesthesia,intravenousinductionagents

Anesthetic Management used withcaution,duetoriskofanexaggeratedresponse. Vasopressorssuchasphenylephrineorephedrineshouldbeinitially sulfate. in patientsadministeredhighdosesoflabetalolandmagnesium overload causingpulmonaryedema.Thisriskmaybeexaggerated Crystalloidsshouldbeusedwithcautionduetotheriskofvolume even duringhigh,densespinalanesthesia. nonexistent. Asubsetofpatientswillremainseverelyhypertensive Hypotensionfromregionalanesthesiarangesprofoundto antihypertensive medicationspriortoorduringinduction. must alwaysbeconsidered,andusuallyrequiresadditional Theriskofahypertensiveresponsetolaryngoscopyandintubation

% ofpatientswithpreeclampsiadevelopthrombo-

7.5 .

• • pain inthepreeclampticbecauseit: Epiduralanalgesiaisconsideredideal forthemanagementoflabor Regional Analgesia Labor andVaginalDelivery an attempttoreduceoverallrisk(Table presenting withseverepreeclampsiashouldalwaysbeconsideredin Anaggressiveapproachtoprovidingregionalanesthesiainpatients management ofthedifﬁcult airwaymustbemade(Table must bemadeforadifﬁ cult intubation. Inallcases,preparationsfor general anestheticmaybeunavoidable.Inthesecases,fullpreparation regional anesthesia,orwhenanesthesiaiscontraindicated,a feasible. However,whenafetalemergencyarises,leavinglittletimefor sia, makingregionalanesthesiaanespeciallyattractivealternativewhen nancies. Allofthesefactorscanbefurtherexaggeratedbypreeclamp- decreased FRCandincreasedoxygenconsumptionpresentinallpreg- • • • • Patient withThrombocytopenia Table 7.5 •

Anesthetic Options

reducescatecholaminelevels reduceshyperventilation • Platelet levelatwhichriskofepiduralhematomaincreasesisunknown • • Few expertswouldrecommendaregionalanesthetic,underalmostany circumstance, inapatientwithplateletcount<50,000/mm Epidural hematomaisrarebutpotentiallyneurologicallydevastating • • Platelet countshouldbeobtainedbeforeperformingaregionalblock The roleofthromboelastographyremainsunknownbutmaybeanother factor toconsiderwhentheplateletcountfallsbetween50–75,000/mm

In absenceofotherconfoundingfactors,riskisnegligiblewitha platelet countover100,000/mm Risk isprobablyhigherwithepiduraltechniquesthansingle-shot spinal techniques After consideringbeneﬁ ts ofregionalanesthesiaintheindividual patient weight,usingathresholdof75,000/mm patient andotherfactors,suchasairwayclassiﬁ In patientswiththrombocytopenia,aplateletcountshouldbe precipitous declinecanbeassociatedwithseveredisease In patientswithanormalplateletcount,thelikelihoodof obtained within6hoursoftheregionalprocedure,becausea count <100,000/mm Anesthetic ManagementofthePreeclamptic 3 within24hoursisnegligible

7.7 ). 3 isreasonable cation and cation 7.6 3

207 Obstetric Anesthesia 208 Pregnancy Induced Hypertension • patient requestslaboranalgesia. secured andadditionallocalanestheticsareadministeredwhenthe inserted andtested.Ifbilateralanalgesiaisobserved,thecatheter severe thrombocytopenia. epidural catheterthanattemptingtheprocedureinapatientwith oping anepiduralhematomaisprobablylesswithindwelling sary. Further,ifseverethrombocytopeniadevelops,theriskofdevel- for generalanesthesiashouldurgentcesareansectionbecomeneces- recommended toreduceriskandincreasesafetybyreducingtheneed “Early”epiduralplacementinthepatientwithseverepreeclampsiais • Management Cart • • • • • • Severe Preeclampsia Table 7.7 ∗ Table 7.6 • • • • • • • • airway. an updatedreportbytheASAtaskforceonmanagementofdifﬁ

Source:thePracticeguidelines formanagementofthedifﬁ

After obtaininginformedconsent,theepiduralcathetershouldbe allowsflexibility forvaryinglaboranalgesianeeds allowstheabilitytodoseforanesthesiawhenC/Sisrequired. Endotracheal tubeguides(assortedintubatingorlightedstylettes, Exhaled CO tracheal Combitubeorahollowjetventilationstylet Cricothyrotomy kitwithorwithoutjetventilation Emergency noninvasiveairwayventilationdevicessuchasanesophageal- Retrograde intubationequipment manipulation forceps) Flexible fi beroptic intubationequipment Emergency tracheostomykit Diffi cult AirwayAlgorithmreadilypostedoncartandinoperating rooms Assorted laryngoscopesandblades Generalanesthesia onlywhenregionalanesthesiaiscontraindicated regional anesthesia without anexistingepiduralcatheterand withoutcontraindicationsto Spinalanesthesia forcesareansectionwhenthepatientpresents (technique isdescribedindetailChapter 9) Earlyepiduralcatheterplacement andtestingwheneverpossible Intubating LMAorProseal Assorted laryngealmaskairwaysorsupraglotticairwaydevices(e.g., Assorted endotrachealtubesandstylettes •

Emphasis onbloodpressure reductionandbluntingthehypertensive response tolaryngoscopy Anesthesiology. 2003;98:1269–1277. Reducing AnestheticRisksinPatientswith Suggested EquipmentforDifﬁ 2 detector ∗

® LMA)

cult Airway

cult airway: cult cult preeclampsia. Further,aspinalneedle istheoreticallysaferthanan when comparingspinalandepidural anesthesiainpatientswithsevere hypotension andamountsofvasopressor requireddoesnotdiffer hypovolemia secondarytocausessuch ashemorrhage.Thedegreeof with severepreeclampsiathanmight beobservedinpatientswith in bloodpressureobservedduringsympathectomy islessinapatient sia isnotentirelysympatheticallymediated. Forthisreason,thedrop tension andresultingindirecthypovolemiaassociatedwithpreeclamp- sympathectomy anduncontrollablehypotension;however,thehyper- With severehypovolemia,spinalanesthesiapotentiallycausesarapid ean section(C/S)inthepatientwithseverepreeclampsia(Figure Recentdatahaveconﬁ rmed thesafetyofspinalanesthesiaforcesar- Spinal andCombinedEpidural clinical trials. been calledintoquestioninrecentyearsanumberofrandomized Manyofthesetraditional,non-evidenced-basedassumptionshave • • • • seen aspreferableforthefollowingreasons: tigated inrandomizedcontrolledtrials,epiduralanesthesiahasbeen Though mostoftheseassumptionshaveneverbeenrigorouslyinves- for patientswithseverepreeclampsiarequiringcesareansection. Traditionalteachinghasencouragedepiduraloverspinalanesthesia Epidural Anesthesia Cesarean Section in Chapter3. receiving magnesiumsulfate.Alternativelaboranalgesicsarediscussed However, sideeffectsfromanalgesicsmaybemorelikelyinpatients lampsia, systemicanalgesiamightbecometheonlysafeoption. Whenregionalanesthesiaiscontraindicatedinthepatientwithpreec- Systemic Analgesia • •

Thetechniqueimprovedbloodpressurecontrol. drops inmaternalbloodpressureanduterineperfusionpressure. incremental dosing,wasthoughtnecessarytoavoidprecipitous Thegradual-onsetsympathectomy,whichcanbeachievedthrough depletion. Thesepatientscanpresentwithextremeintravascularvolume Vasopressorrequirementswerelower. Intravenousﬂuid volumerequirementswerelower. Thetechniqueiseasiertoadaptforlongersurgicalduration.

7.1 ).

209 Obstetric Anesthesia 210 Pregnancy Induced Hypertension • • vant whengeneralanesthesiacannot beavoided(Table ment oftheupperairway.Thefollowing recommendationsarerele- management becauseofincreasedextravascular ﬂuid causingengorge- Preeclampsia increasesthedifﬁ culties encounteredduringairway preeclampsia onlywhenregionalanesthesiaiscontraindicated. Generalanesthesiashouldbeconsideredforpatientswithsevere General • than aspinalanestheticwhenprolongedsurgicaltimeisanticipateddueto: generally thesameaswouldbeusedinanonpreeclampticpatient. likely tocauseepiduralveintrauma. epidural needleinapatientwith“borderline”coagulopathyasitisless 1999; 90:1276-1282. Figure basedoninternaldataandadaptedfromHoodDD.Anesthesiology is thelowestbloodpressurerecordedfromdeliverytoendofsurgery. blood pressurerecordedbetweeninductionanddelivery“PostDelivery” pressure recorded20minbeforeinduction,“RAtoDelivery”isthelowest in mmHganddonotdifferbetweengroups.“PriortoRA”istheblood The dataarepresentedasthelowestmeanarterialbloodpressurerecorded presenting forcesareansectionandadministeredregionalanesthesia(RA). Figure 7.1 • • •

A combined spinal epidural (CSE) anesthetic may be more appropriate Acombinedspinalepidural(CSE)anestheticmaybemoreappropriate Dosesofmedicationsforspinalanesthesiainthepreeclampticare Twoanesthesiaprovidersshouldbe presentifatallpossible. a greatersafetymargin overﬁ whenever possible,asﬁ ve minutesoftidalvolumebreathingoffers Thoroughlypreoxygenate/denitrogenate withatightmaskseal Priorpelvicorabdominalsurgery MultiplepriorC/S Multiplegestation Morbidobesity

Lowest mean BP ± SD 100 110 120 130 140 60 70 80 90 The illustrationrepresents206patientswithseverepreeclampsia

ro oR At eieyPost delivery RAtodelivery Prior toRA

vevitalcapacitybreaths alone.

Epidural (n Spinal (n =137) =69) 7.8 ):

• • • • • Recommended Technique Table 7.8 •

• • • • tion in addition to standard rapid sequence induction agents include: tion inadditiontostandardrapidsequenceinductionagentsinclude: Pharmacologicagentswhichmaybeusedpriortoairwaymanipula- doses ofinductionagent(i.e.,sodiumpentothalupto7mg/kg). orrhage. Considerationshouldbegiventouseofhigherthannormal potential complicationssuchaspulmonaryedemaandintracranialhem- Preventhypertensionduringlaryngoscopyandintubationtoreduce • Maintenance: • • • Airway: • • • •

• Preparation: • • • • • • Induction:

to inductionandtitrated toeffect Sodiumnitroprusside:infusioninitiated at0.5mcg/kg/minprior during inductionasneeded Nitroglycerine:50–100mcgboluses immediatelypriortoand Hydralazine:atleast20minpriortoinduction Labetalol:atleast10minpriortoinduction Esmolol:upto2mg/kgbolusimmediately priortoinduction 50/50 O • • • • Awake intubation • Prepare fordifﬁ 0.5 MACvolatileagentpriortodelivery Nondepolarizing musclerelaxanttitratedtoeffect(reduceddosein patients administeredmagnesiumsulfate) Opioids andotheragentsasneededafterdelivery Consider additionalantihypertensivesforextubation (e.g.,esmolol, GTN) Antihypertensive pretreatmentpriortoanesthesiaachieveDBP 90–100 mmHgiftimeallows Standard monitors Left uterinedisplacement Limit intravenousﬂ • Preoxygenate for5min(4–6vitalcapacitybreathsinemergency) 6.5 or7.0mmtrachealtube Rapid sequenceinduction

When difﬁ cult intubationisanticipated Minimum 4mg/kgthiopental(upto7ifnecessaryforBP control) 1–1.5 mg/kgsuccinylcholine Consider fentanyl100–150mgandlidocaine100IV Nitroglycerine(GTN)200mcg(100bolusduringinductionand 100 mcgbolusduringlaryngoscopy) Cricoid pressureuntilbreathsoundsidentiﬁ ed andpositiveETCO General AnesthesiaforCesareanSection: 2

2 O priortodelivery cult intubation cult uid administration uid

211 Obstetric Anesthesia 212 Pregnancy Induced Hypertension Further Reading • • complications. Anestheticriskscanbereducedby: ment, andareatincreasedriskforsigniﬁ cant obstetricandanesthetic Patientswithseverepreeclampsiausuallyhavemultisysteminvolve- • • •

•

1. 6. 7. 5. 2. 4. 3. 9. 8.

Summary assessingplateletcountwhenappropriate earlyepiduralcatheterplacementwheneverpossible controllingbloodpressure,especiallyduringgeneralanesthesia traindicated reservinggeneralanesthesiaforwhenregionaliscon- preexistingcatheterisnotpresent utilizingspinalanesthesiaforurgentcesareansectionwhen • preparingfordifﬁ • •

Practice Bulletin#33 . Diagnosis andmanagementofpreeclampsiaeclampsia . ACOG comparison oftwotechniques . Norris MC Cardiovasc Ther , . 2009 Dewan ; the managementofhypertensivedisorderspregnancy 7 DM . : 1581 - . 1594. Preoxygenation forcesareansection:a Polley LS Huda SS , 28 : 172 - anticoagulated patient:defi197 ning therisks . . report bytheASAtaskforceonmanagementofdiffi Practice guidelinesformanagementofthediffi cult airway:anupdated Horlocker TT , 1999 ; 90 Wedel : in severelypreeclampticpatients:aretrospectivesurvey 1276 DJ . - , 1282. Benzon H Hood , DD Anesthesiology , . 2003 Curry ; 98 R : 1269 - . 1277 Spinal versusepiduralanesthesiaforcesareansection . eds. Sibai BM . Hypertension (Chapter28) . In Gabbe SG , Niebyl JR , Simpson JL , Gynecol Sibai BM Practice . Diagnosis, prevention,andmanagementofeclampsia . Tsen LC , Livingstone 2002 : 945 - 1004 . Fentanyl:100–150mcgbolusimmediatelypriortoinduction Remifentanil:1mcg/kgbolusimmediatelypriortoinduction Lidocaine:100mgduringinduction Obstetrics: Normaland ProblemPregnancies ,

. 2005 ; 105 : 402 - 410. 4 th . Chapter 45:HypertensiveDisorders . In Wong CA Freeman DJ , Nelson SM . Short andlongtermstrategiesfor

Ed . Philadelphia, PA : Mosby Elsevier . 2009 : 975 - 1008 cultairwaymanagement. ,eds. Obstet Gynecol . 2002 ; 99 : 159 - 167 . Chestnut’sObstetricAnesthesiaPrinciplesand Anesthesiology . 1985 ; 62 : 827 - 829.

et al

Reg AnesthPainMed . 2003 ; . Regional anesthesiainthe

4 th Chestnut DH ,

. Churchill cult airway cult Anesthesiology . Expert Rev

. Obstet Polley LS .

, • • Thehumanuterusisanextremelyplastic organ. uteroplacental unitanditsphysiologic adaptiontothebirthprocess. it effectivelyrequireanunderstandingofthenormalanatomy maternal mortality. have conﬁrmed thathemorrhageremainsoneoftheleadingcauses ensure thehealthandwell-beingofmotherinfant.Severalseries into anemergentsituationrequiringprompt,aggressivetreatmentto pregnancy, laborordelivery,quicklyturninganuneventfulpregnancy Hemorrhagiccomplicationscanariseatalmostanypointduring

Introduction Uteroplacental AnatomyandNormalDelivery Understandingthecausesofmaternalhemorrhageandtreating Atterm,theuterus weighswelloverakilogram. Anonpregnant,parousuterusweighs onlyabout70g. Risks ofTransfusion Transfusion inObstetrics Fetal Hemorrhage Hysterectomy Anesthetic Management:Peripartum ofObstetricHemorrhage Non-Operative InterventionsforManagement Postpartum Hemorrhage Intrapartum Hemorrhage Prepartum Hemorrhage Assessment oftheBleedingParturient Uteroplacental AnatomyandNormalDelivery Introduction Craig M. ObstetricHemorrhage Palmer , MD Chapter 8 213 232 233 234 216 226 234 224 232 215

213

213 214 Obstetric Hemorrhage • • • • boundary betweenthemotherandfetus. Thedeciduaisaspecializedformofendometrium,whichformsthe than endothelium,andreturnstothematernalcirculation(Figure8.1). intervillous spacelinedbyplacentaltrophoblasticsyncytiumrather blood actuallyleavesthematernalcirculation,circulatesthrough Thematernalbloodsupplytotheplacentaisunique,inthat • • • • blood ﬂ ow totheuterusmaybewellover15percentofcardiacoutput. ing increaseinbloodﬂ ow totheuterusandplacenta.Atterm,maternal Alongwiththisincreaseinsizeandweight,thereisacorrespond-

blood loss: empty uterinecavity.Twomechanisms normallypreventongoing halt bloodloss,theywouldcontinue tospurtbloodintothenow supplied theplacentaaretorn:in absenceofamechanismto Withseparation,themyriadsmall endometrialarteriesthat gives risetonewendometrium. behind intheuterusbasalzone ofthedeciduathatultimately Atdelivery,theplacentaseparatesfromplacentalbed,leaving the capillaries,andbloodreturnstofetusviaumbilicalvein. within thechorionicvilli.Oxygenandnutrientexchangeoccursin by thepairedumbilicalarteries,whichbranchintocapillaries Onthefetalside,deoxygenatedbloodisdeliveredtoplacenta placentatotheendometrialveins. maternal circulationthroughopeningsinthebasalplateof exchange occurs,andmaternalbloodisdrainedbackintothe villi, whichcontainthefetalcapillaries.Oxygenandnutrient maternal bloodintotheintervillousspacetobathechorionic Maternalarterialpressureprovidesthedrivingforcethatcirculates actual bloodsupplytotheplacenta. Intheplacentalbed,smallendometrial(orspiral)arteriescarry from theovarianarteries. Avariableportionofthebloodsupplytoplacentamaycome tion ofthebodyuterusandplacentalbed. Theascendingbranchoftheuterinearterysuppliesmajorpor- arteries. which ariseasabranchoftheanteriortrunkinternaliliac Theprimarymaternalbloodsupplyisfromtheuterinearteries, •

volume. tion duetothedevelopingfetus,placenta,andamnioticﬂ uid both steroidhormonesproducedduringpregnancy,anddisten- Theincreaseinsizeofthemyometriumoccursresponseto

contraction. Obstetrichemorrhagemostoftenresultsfromimpaired • et al. Reprinted withpermissionfrom CunninghamFG,MacdonaldPC,GantNF, and returnstothematernalcirculationthroughendometrialveins. enters viatheendometrialarteries,circulatesthroughintervillousspace before returningtothefetalcirculationviaumbilicalvein.Maternalblood through capillariesinthevilliwhereoxygenandnutrientexchangeoccurs, placenta. Deoxygenatedbloodfromthefetusentersplacentaandfl Figure 8.1 bleeding anddegreeofhypovolemia. cause, symptomsofhemorrhage generally refl ect theamountof blood lossisthecrucialfi rst stepinmanagement.Regardlessofthe parturient, recognizingthatthepatientmayhavesufferedsignifi cant Whilethereareanumberofwell-describedcausesbleedinginthe thevilloustree 1. Fetalcirculationin

Assessment of theBleedingParturient Main stemvillus examination ofthepatientandassessment ofvitalsigns. Recognition anddiagnosisoftheproblem willbeginwithphysical Inmanycases,theremaybelittle external evidenceofbleeding. • • (oxygenated blood) Umbilical vein

disruptedvessels. contractionofthemyometriumphysicallycompresses constrict; theelasticityofarteriolesallowsthemtoretractand Williams Obstetrics,19 th ed, pp.165–207.1993,McGraw-Hill. Schematic cross-sectionoftheanatomyanormalhuman circulation Fetal Anchoring villus

inintervillousspace 2. Maternalcirculation (deoxygenated blood) Umbilical arteries

Amniochorionic membrane Placental septum pathways 3. Maternalblood Endometrial artery Deoxygenated blood Oxygenated blood Endometrial vein myometrial

Amnion chorion Smooth Decidua basalis Myometrium parientalis Decidua ows

215 Obstetric Anesthesia 216 Obstetric Hemorrhage complete. normally implantedplacenta;inrareinstancestheseparationmaybe Placentalabruptionreferstotheprematurepartialseparationofa • • • • Deﬁ Placental Abruption have beenassociatedwithahigherincidenceofabruption(Table8.1). Whilethereisnosinglecauseforabruption,anumberofconditions Risk Factors Increased age Increased parity Uterine leiomyoma Cocaine abuse Cigarette smoking External trauma Premature ruptureofmembranes Chronic hypertension Pregnancy-induced hypertension(PIH) Placental Abruption Table 8.1

Prepartum Hemorrhage Thismayoccureitherprepartumorintrapartum. prepartum, intrapartum,orpostpartum. of obstetrichemorrhagecanbegenerallyclassiﬁ ed asoccurring Whilethereissomeoverlapbetweencategories,thecauses normal. hemorrhage shouldbeexcludedasacauseevenifbloodpressureis be apparent.Thoughthereareanumberofcausestachycardia, to bemaintained,thoughtachycardiavaryingdegreesmay with bloodlossofoneliterormore,systemicpressuretends Mostparturientsareyoungandinrelativelygoodhealth.Even 1 in77and86deliveries. for diagnosis,buttheincidencehasbeenestimatedtobebetween Thereportedfrequencyofabruptiondependsonthecriteriaused nition

Factors AssociatedwithIncreasedRiskof

• • • and infrequently,fetaldemise(Table8.2). fetal heartrateabnormalities,pretermlabororuterinehypertonus, associated withuterinetendernessorbackpain.Othersignsinclude Themostcommonsymptomofabruptionisvaginalbleeding,usually Symptoms andPresentation • • surfaceareamayresultinasphyxia. blood lossusuallyresults.Forthefetus,decreaseinplacental effective myometrialcontractioncannotoccur,andongoingmaternal by myometrialcontraction.Theuterusdoesnotempty;therefore, as discussedabove;inabruption,placentalseparationisnotfollowed associated withdeliveryisusuallylimitedbymyometrialcontraction, Abruptionhasbothmaternalandfetalimplications.Uterinebleeding Implications fetal distress,maternalhypotension orcoagulopathy. Upto90 Clinical Course study. and LavinJP.Selectivemanagementofabruptioplacentae:Aprospective Reprinted withpermissionfromHurdWW,MiodovnikM,HertzbergV, Fetal demise 34 Preterm labor 66 Increased uterinetone/contractions Fetal distress Uterine tendernessorbackpain Vaginal bleeding Sign/symptom Table 8.2

Severeneurologicdamagemayoccureveninsurvivingneonates. 750 deliveries,andaccountsforabout15 Abruptionissevereenoughtobefatalthefetusinabout1 blood canbesequestered behindtheplacentaina “concealed” Whilesomevaginalbleedingisusually apparent,upto3000mlof (Table 8.3). usually markedlyunderestimatesthe actualmaternalbloodloss Itisimportanttonotethattheamount ofvisiblevaginalbloodloss Whenabruptionoccurs,perinatalmortalityisapproximately10 stillbirths. Obstet Gynecol. 1983;61(4):467–473. % ofabruptionswillbeeithermildor moderate,without Signs andSymptomsofPlacentalAbruption

17 22 60 78 Frequency (percentofcases)

% ofthirdtrimester

% .

217 Obstetric Anesthesia 218 Obstetric Hemorrhage Inseverecases,maternalcoagulopathycanoccur. 1993, McGraw-Hill. Macdonald PC,GantNF,etal. of externalbloodloss. Reprinted withpermissionfromCunninghamFG, to 3litersofbloodmaybelostinaconcealedhemorrhagewithoutevidence External (vaginal)bleedingisusuallyapparentinbothconditions,althoughup Figure 8.2 • • have beenproposed: Twopossiblemechanismsforthedevelopmentofthiscoagulopathy • • • • check: Ifabruptionissuspected,bloodshould bedrawnimmediatelyto Anesthetic Management(Figure8.3)

of abruption(Figure placenta remainscircumferentiallyadherentaroundacentralarea hemorrhage withoutexternalbleeding.Thismayoccurwhenthe plateletcount; activationofcirculatingplasminogen,or apparent. appear inthematernalcirculation,andclinicaloozingmaybecome and decreasedlevelsofFactorsVVIII;ﬁ brin-split products Thisismanifestedasthrombocytopenia,hypofibrinogenemia, coagulation (DIC)duringpregnancy. Abruptionisthemostcommoncauseofdisseminatedintravascular extrinsic clottingpathway. alternatively,placentalthromboplastinmaytriggeractivationofthe hemoglobinandhematocrit; hemorrhage hemorrhage Concealed abruption Placental External Hemorrhage fromplacentalabruptionandplacentaprevia.

8.2 ). Williams Obstetrics,19 th ed , pp.165–207.

placenta previa

Partial necessary, with general anesthesia usually indicated for these reasons. necessary, withgeneral anesthesiausuallyindicatedfor thesereasons. a nonreassuringfetalheartrate),emergent cesareandeliverymaybe Withasevereabruption(i.e.,withongoing bloodloss,coagulopathy,or • and theplateletcountisstableroughly75,000orhigher. assuming thereisnoevidenceofuncorrectedmaternalhypovolemia • • • • • Subsequentmanagementdependsontheseverityofsituation. • • abruption. Figure 8.3

Regionalanesthesiacanalsobesafelyemployedinthesepatients, Labormaybeinducedwithcontinuousfetalmonitoringassuming: rate abnormalities. if thereisongoinghemorrhage,or therearesignificant fetalheart Regionalanesthesiashouldbeavoided ifthemotherishypovolemic, noevidenceofcoagulopathy; thepresenceofareassuringfetalheartrate. noevidenceofmaternalhypovolemia; noongoingbloodloss; Bloodshouldalsobesentfortypeandcrossmatch. fi fi brin-splitproducts. brinogen; Management oftheparturientwithsuspectedplacental

anesthesia O.K. Mild abruption allow tolabor Observe or Regional

• Fibrinsplitproducts • Fibrinogen • PT/PTT Coagulation studies: hemoglobin/hematocrit Type andcrossmatch Abruption suspected Start large-boreIV Send bloodfor:

Ongoing hemorrhage cesarean delivery Non reassuring

FHR trace Emergent - or

219 Obstetric Anesthesia 220 Obstetric Hemorrhage Lippincott, Williams & Wilkins. maternal resuscitation.In:NorrisMC, Reprinted withpermissionfromFerouzF.Peripartumhemorrhageand bleeding Massive bleeding Severe bleeding Moderate Mild bleeding blood loss Amount of in theParturient Table 8.3 very low.SeealsoChapter3. dural hematomaandadditionalmorbidity;inmostcasesthisriskis some parturients.Theriskisthatoftheoreticallycausinganepi- spinal anestheticforcesareandelivery,canbeconsiderable regional anesthetic,eitheranepiduralcatheterforlaborora such patientsissimplyarisk-beneﬁ t analysis.Thebeneﬁ ts ofa regional anesthetic.Thedecisiontoemployanesthesiain times lower,iftherearestrongmaternalindicationsforusinga low as70,000whenperforminganeuraxialanesthetic,andsome- Mostobstetricanesthesiologistswillacceptaplateletcountas Clinical SignsandSymptomsofBloodLoss 2400 ml) volume (over 40 (up to2400ml) blood volume 30 (up to1600ml) blood volume 20 1000 ml) volume (upto 15 % ofblood % –35 % –25 % ofblood % of % of

Oliguria oranuria Marked tachycardia Peripheral pulsesabsent Systolic bloodpressure<80mmHg Mental statuschanges/disorientation Profound shock Oliguria Tachypnea (respirations Hypotension Cold, clammy,pallidskin Marked tachycardia(heartrate120–160) Urine output<1ml/kg/h Positive tilttest Positive capillaryblanchingtest Moderate tachypnea Decreased pulsepressure Tachycardia (heartrate110–130) Normal urineoutput Negative tilttest Normal bloodpressureand respiration Mild tachycardia Clinical ﬁ Obstetric Anesthesia,2nded . 1998, nding

> 30/min) the hypovolemicparturientpresentsadditionalconsiderations. Inadditiontoroutineprecautionsforcesareandelivery(Chapter4), General AnesthesiaintheHypovolemicParturient(Table8.4) • • induction agent. of choice. supports bloodpressurethroughsympatheticstimulation,istheagent signiﬁ cantly decreasematernalbloodpressure. • • • Maintenance (post-delivery) • • • Maintenance (pre-delivery) • • Anesthetic agents • • • Routine precautions Adequate IVaccess Parturient Table 8.4 • Monitoring •

Because be inplace. at leastone(ideallytwo)large-boreIV(16gaugeorlarger)should severely volumedepleted.Adequateintravenousaccessisessential; Ifaparturientistachycardic,hypotensive,oroliguric,shelikely blood volumewithoutanychangeinvitalsigns(Table8.3). A healthytermparturientcanlose10to15percentofcirculating the ﬁrst anestheticconsiderationshouldbematernalvolumestatus. Oncethedecisiontoproceedcesareandeliveryhasbeenmade, Invasive? Considerarterial line Inhalational agent:isoﬂ Continue relaxation(followtrain-of-four) oxygenation) Inhalational agents:0.5MACorlessifmaternalbloodpressure tolerates Nitrous oxide(upto 70 Nitrous oxide(withongoingfetalstress,100 Relaxation: succinylcholinerelaxantofchoice Induction: ketamine,1–1.5mg/kg Assistance available Denitrogenation Aspiration prophylaxis—oralsodiumcitrate Opioid—fentanyl Routine: ECG,BP,PO, ET-CO

sodium pentothal General AnesthesiaintheHypovolemic

Propofol urane 0.2 urane % ) iftolerated isamyocardialdepressant,whichcanalso isavasodilator,itnotanappropriate 2 andFoley % orsevoﬂ urane 0.5 urane % O 2 indicatedforfetal % foramnesia Ketamine

, which

221 Obstetric Anesthesia 222 Obstetric Hemorrhage SaO Afterdelivery,upto70 term isabout1in200–250deliveries. partial, ormarginal(Figure8.4).The incidenceofplacentapreviaat over orclosetothecervicalos. It canbeclassifi ed ascomplete, Placentapreviareferstoanabnormal implantationoftheplacenta, • • • • • Defi Placenta Previa venting adequateuterinecontractionandinhibitinghemostasis. infi Evenfollowingdelivery,bepreparedformassivebloodloss.Blood which cancontributetobloodloss. all theinhaledanestheticagentscausedose-relateduterinerelaxation, anesthetic allowsuseofminimalconcentrationsinhaledanesthetic;

emergent situation. judgment maybetheonlytoolavailableinarapidlychanging, ideally basedonlaboratoryevidenceofderangements,butclinical trates, andevencryoprecipitate.Useofthesebloodproductsis not onlyPRBCsbutalsofresh-frozenplasma,plateletconcen- may requireaggressivetreatmentofthecoagulopathy,utilizing normal withinseveralhours,butgettingcontrolofthebleeding Oncehemorrhageiscontrolled,coagulationshouldreturnto ltrating themyometriummayresultina“Couvelaire”uterus,pre- maximizeoxygendeliverytothefetus. be necessarytostophemorrhage. Inraresituations,internaliliacarteryligationorhysterectomymay for adequateuterinecontraction(seebelow). Inadditiontooxytocin,otheruterotonicagentsmaybenecessary toring andrepeatedblooddrawsforlabwork. placement ofanarteriallineforcontinuousbloodpressuremoni- Intheunstableparturient,seriousconsiderationshouldbegivento gas analysis). hematocrit, coagulationstatus,andacid-basebalance(arterialblood blood pressure,additional“stat”labsshouldbesenttocheck Ifaggressiveﬂ decreased placentalperfusion,deliveryof100 despite clearevidenceofbeneﬁ t, inthesettingofpotentially Afterinductionbutbeforedelivery,supportofthefetusiscritical; nition 2 remainsadequate,andconversiontoa“nitrous/narcotic”

uid resuscitationfailstorestoreadequatematernal

% nitrousoxidemaybeusedifthematernal

% oxygenwill

• • Figure 8.4 ultrasonography. diagnosis canbemadeorconﬁ rmed readilywithtransabdominal the areaofdisruptionissmall,butit maybesuddenandsevere.The proven otherwise.Bleedingdueto previa maystopspontaneouslyif in thethirdtrimestershouldbeconsidered placentapreviauntil bleeding inthethirdtrimester;for thisreason,allvaginalbleeding Theundiagnosedplacentapreviausually presentsaspainlessvaginal Signs andSymptoms section. area, respectively,oncediagnosed,deliverywillalwaysbeviacesarean the fetuscantoleratebloodlossorofplacentalsurface normal placentalimplantationoccurs.Becauseneitherthemothernor implanted hasfewercontractileelementsthanthecorpus,where delivery. Further,theloweruterinesegmentwhereplacentais the uteruscancontracteffectively,i.e.,onceisemptyafter hemorrhage willensue.Aswithabruption,bleedingcontinueuntil of placentaprevia,theoveroswilldetachandmaternal Withtheonsetoflaborcervicalosbeginstodilate;in Implications

cesarean delivery (see Chapter 11), or a history of prior previa. cesarean delivery(seeChapter11),orahistoryofpriorprevia. Previaismorecommoninthemultipara,particularlythosewithprior implantation siteawayfromthecervicalos. the thirdtrimester,asenlargementofgraviduteruscarries centage ofpreviainearlygestation,butmosttheseresolveby Routineprenatalultrasonographygenerallyidentiﬁ es ahigherper- Total Classiﬁ cation ofplacentaprevia. Partial

Mar g inal presence

223 Obstetric Anesthesia 224 Obstetric Hemorrhage • agement is“expectant” Whendiagnosedpriortoabout32weeksgestation,obstetricman- elective cesareandeliveryundertakenoncematurityisconﬁ gestation, fetalmaturityisassessed(usuallybyamniocentesis),and won’t startbleeding). partum, butismost commonlyanintrapartumevent, asuterine Uterinerupturemayoccurprepartum, intrapartum,orevenpost- • tion andclinicalpresentation. Managementofthediagnosedpreviadependsonstagegesta- Anesthetic Management Deﬁ Uterine Rupture

Intrapartum Hemorrhage nated theneedfordoubleset-up. raphy, anditsexcellentaccuracyindiagnosis,haveallbutelimi- delivery. Today,thewidespreaduseandavailabilityofultrasonog- prepped anddrapedinpreparationforanimmediatecesarean speculum examintheoperatingroom,butwithherabdomen set-up” — even torrentialhemorrhage,theexamwasperformedasa“double vaginal speculumexam.Becausethisexamcanprovokebrisk, previa wasmadebydirectexaminationofthecervicaloswitha Inthenot-so-distantpast,deﬁ nitive diagnosisofplacenta Due to the increased risk of bleeding near term, after about 32 weeks Duetotheincreasedriskofbleedingnearterm,afterabout32weeks use ofregionalanesthesia. maternal hypovolemiaisastrongrelativecontraindicationtothe maternal volumestatus(heartrate,bloodpressure,urineoutput); anesthesia canbeemployedfollowingcarefulassessmentof Iftheinitialbleedingepisodehasstoppedspontaneously,regional placenta aredelivered. and stabilizethemother usually necessary,asitisthemostrapidwaytodeliverinfant indicated. Withrapidormassivebloodloss,generalanesthesiais Inthefaceofongoingbleeding,expeditiouscesareandeliveryis nition

the parturientwasplacedinlithotomypositionfor —

primarily, bedrestandhope(thatthepatient —

blood losswillcontinueuntilinfantand

rmed. rmed.

• • • • ity isusuallylow(about0.1 contractions increaseinforce.Whiletheassociatedmaternalmortal- infant andexplore theabdomentocontrolhemorrhage. sion orshock,generalanesthesiais indicatedtorapidlydeliverthe and/or hypotension(Table8.6).Ina parturientwithobvioushypoten- abdominal pain,shoulderthedisappearance offetalhearttones, Symptomsofruptureincludevaginal bleeding,severeuterineor Signs andSymptoms previous uterinescar,fromapriorC-section. Byfar,themostcommoncauseofuterineruptureisseparationa Risk Factors(Table8.5) Chapter 11. considerations forvaginalbirthaftercesareandelivery”(VBAC)in strophic forboththemotherandinfant.Seealso“Anesthetic • • • • Internal trauma: Uterine distention(macrosomia,hydramnios) Fetal malpresentation Grand multiparity Excessive oxytocinstimulation External trauma Previous uterinescar(priorcesareansection:“VBAC”) Table 8.5

rupture istraumatic. Maternalmortalityishigheriftherenoprioruterinescar,orthe neonatal mortalityisincreasedbyafactorof10. patients thanthosewithoutauterinescar,andifruptureoccurs, Theriskofuterineruptureis3to15timesgreaterforVBAC through uterinemuscle. tissue; thislowerincisionhealsmuchmoresolidlythanan the low-transversesegmentincisionisprimarythroughconnective Theclassicalincisionextendswellintothemyometrium,whereas dehisce duringlaborthanalow-transversesegmentscar. Ascarfromaclassical(vertical)uterineincisionismorelikelyto Manual exploration Internal version Curettage Forceps, vacuumuse

Causes ofUterineRupture

% intheUnitedStates),itcanbecata-

225 Obstetric Anesthesia 226 Obstetric Hemorrhage to bleed.Retainedplacentaoccursinabout1 able tofullycontract,andarteriesofthedeciduabasaliswillcontinue Iftheuterusdoesnotemptycompletelyafterdelivery,itwillbe • hours. loss usuallyoccursimmediatelyafterdelivery,orwithinonetotwo delivery isconsideredpostpartumhemorrhage,trulysigniﬁ Whiletechnically,anyvaginaloruterinebleedingwithin6weeksafter Deﬁ Retained Placenta • relax theuterus: two factors:uterinerelaxationandanalgesia. Anestheticmanagementofretainedplacentamusttakeintoaccount Anesthetic Management ally requiresmanualexplorationoftheuterus. • Abdominal tenderness Atypical abdominalpain(not associatedwithuterinecontractions) Hypotension Abnormal laborpatternoruterine hypertonus Vaginal bleeding Fetal heartrateabnormalities/fetalstress Uterine Rupture Table 8.6

Postpartum Hemorrhage Inordertomanuallyexploretheuterus,itisusuallynecessary blood lossinobstetrics. Postpartumhemorrhageisthemostcommoncauseofserious been usedforthis Traditionally,theinhalationalagents(halothane,isoﬂ urane) have nitroglycerinwillproduce uterinerelaxationwithin30–45 seconds sia (Table8.7).Bolusintravenousadministration of100–200mcg ine relaxation,whichdoesnotrequire inductionofgeneralanesthe- Nitroglycerinhasbeenshowntobe an effectivealternativeforuter- volume status,etc. associated concernsofaspirationrisk, airwaymanagement,maternal tions meansinducingageneralanesthetic, however,withallthe they areveryeffectiveuterinerelaxants.Useattheseconcentra- nition

Signs andSymptomsofIntrapartum

— at inhaledconcentrationswellover1MAC,

ofdeliveries,andusu- cant blood Anesthetic Management the riskofuterineatony. Anumberoffactors,listedinTable8.8,havebeenshowntoincrease Risk Factors blood in5minutes. gravid uterus,acompletelyatonicuteruscaneasilylose2litersof With 15 ies, andisthemostcommoncauseofseriousbloodlossinobstetrics. Uterineatonyoccursinvaryingdegreefollowing2 • • Deﬁ Uterine Atony dural andpotentiallyvasodilatingthepatient. tion mustbepaidtomaternalvolumestatusbeforedosingtheepi- from labor,thiscanbeusedforanalgesia but again,carefulconsidera- may needtobetaken.Ifaparturienthasanepiduralcatheterinplace Nitroglycerindoesnotprovideanalgesia,however,soothermeasures • • • • • • • • Side effects:hypotension Action Administration: bolusdosing Prepare appropriatedilution Trinitrate) forUterineRelaxation Table 8.7

Initialmanagementofuterineatony ismedical. should beashort-livedsideeffect. temic vasodilation,maternalhypotensioncanbesigniﬁ that lastsonly60–90secondsduetoitsshorthalf-life.Duesys- • Fluidresuscitation R Onset 30–45seconds Begin with100mcgbolus NTG suppliedas50mg/10mlvial(5mg/ml) Duration 60–90seconds relaxation) Increase byincrementsof100mcguntildesiredeffect(i.e.,uterine Result: 100mcg/ml Add to500mlnormalsaline nition x is often underestimated. Volume resuscitation can be lifesaving. is oftenunderestimated. Volumeresuscitationcanbelifesaving. Thisshouldalwaysbetheinitialintervention, asmaternalbloodloss withphenylephrinebolusIVasnecessary %

ormoreofmaternalcardiacoutputattermgoingtothe Clinical UseofNitroglycerin(Glyceryl

% to5 cant,butthis % ofdeliver-

227 Obstetric Anesthesia 228 Obstetric Hemorrhage • and prostaglandins(Table8.9). onics arecurrentlyavailableforclinicaluse:oxytocin,ergotalkaloids, process ofpostdeliveryhemostasistooccur.Threeclassesuterot- which increaseuterinecontractilityandtoneallowthenormal Theinitialmanagementofuterineatonyiswithuterotonicagents, Use ofUterotonics • • • • • Medications Infection Retained placenta Uterine distention Dysfunctional labor High parity Table 8.8 • • • • • • •

• not offeranybeneﬁ infused asrapidlypossible;increasingthedosebeyondthisdoes Oxytocin below). Thesestepsmayallowavoidanceofoperativeintervention(see Useofuterotonics • Methylergonovine Externaluterinemassage Oxygensupplementation(highﬂows viafacemask) uterine tone. and isparticularlyeffectiveforproducing asustainedincreasein alkaloid, isasecond-lineagentforthe treatmentofuterineatony, Prolonged oxytocinuseduringlabor Chorioamnionitis Multiple gestation Inhalational anesthetics Tocolytic agents Macrosomia Polyhydramnios

which speciﬁ Oxytocinisanaturallyoccurringneurohypophysealhormonefor using twointravenouslines. rapid oxytocininfusionarenecessary concurrently,consider tension ifadministeredrapidly;both rapidvolumeinfusionand Systemically,oxytocinisavasodilator,andmayaggravatehypo- Conditions AssociatedwithUterineAtony isusuallytheinitialtherapy

creceptorsexistinthemyometrium.

t. (Methergine

® ),acommerciallyavailableergot — up tofortyIU/lmaybe

Misoprostolisalsoaprostaglandinanalog (PGE • used totreatuterineatonyinthedeveloping world. this reason,whilenotusuallyaseffective asoxytocin,itissometimes carboprost, itisthermostableanddoes notrequirerefrigeration.For

the burningsensationsufferersfeltintheirextremities. breaks of“ergotism”werenamed“St.Anthony’sFire”because vasoconstriction andevengangrene.DuringtheMiddleAges,out- particularly rye.Ingestionofcontaminatedgraincancauseintense 400 years;theyarederivedfromafungusthatgrowsupongrain, Theergotalkaloidshavebeenusedinobstetricsforover • • • • • • • is astableanalogofthenaturallyoccurringprostaglandin,Pg-F Carboprost

tive contraindicationtoitsuse. due to Systemically,methylergonovinecancausehypertension,likely other therapyshouldbeinstituted. 0.4 mg;iftwodosesdonotrestoreappropriateuterinetone, Methylergonovineisadministeredintramuscularlyatadoseof given viacontinuousinfusion,asdoesoxytocin. Becauseithasarelativelylonghalf-life,doesnotneedtobe the patient’sasthma. increase uterinetoneshouldbeweighed againsttheseverityof be usedwithcautioninasthmatics; theurgencyofneedto Duetoitspropensitycausebronchospasm,carboprostshould have thesameeffectasintravenousadministration. used withcaution,asrapiduptakebyuterinevenoussinusescan nary hypertension.Intramyometrialadministrationshouldalsobe associatedwithseverebronchospasm,andsystemicpulmo- and bronchoconstrictor.Intravenousadministrationcanbe Carboprostisapotentsystemicandpulmonaryvasoconstrictor, intravenously. signiﬁ Carboprostisanextremelyeffectiveuterotonic,butithas to 1.0mg. intramyometrially. Totaldoseshouldprobablynotexceed0.75 Itisgivenata0.25mgdoseIM,orcanbeinjecteddirectly cant systemicsideeffects;itshouldneverbeadministered α -adrenergic stimulation;systemichypertensionisarela-

tromethamineisathirduterotonicoption.Carboprost

1 ).Unlikeoxytocinand

2 α .

229 Obstetric Anesthesia 230 Obstetric Hemorrhage

Table 8.9 Uterotonic Agents Medication Class Administration Dosing Side effects Comments Oxytocin Neurohypophyseal Infusion Up to 40 IU/l Hypotension with Initial therapy hormone rapid infusion Methylergonovine Ergot alkaloid Intramuscular 0.4 mg IM; repeat once Hypertension Sustained increase in uterine tone Carboprost Prostaglandin Intramuscular 0.25 mg IM repeat up to Systemic and Never administer Intramyometrial 1.0 mg total Pulmonary intravenously hypertension, bronchospasm action becomesnecessary. or less,butitisnotusuallydiagnoseduntilafterdelivery,whenprompt Theoverallincidenceofplacentaaccretaisabout1in2500deliveries Risk Factors results. separation oftheplacentaisnotpossible,andcontinuingbloodloss disrupts themyometriumandcanresultinseverebleeding;complete Withanyofthevariations,separationplacentaafterdelivery • • • • the placenta implants directly onto (placenta accreta) the myometrium. the placentaimplantsdirectlyonto(placentaaccreta)myometrium. and cleavageplanebetweentheplacentauterus;initsabsence, the deciduabasalislayer.Theformsnormalinterface refers toabnormaldevelopmentandimplantationoftheplacentawithout Placentaaccreta(andvariantsplacentaincretaandpercreta) Deﬁ Placenta Accreta accrete, pp.210–214, Copyright(1997),withpermissionfrom Elsevier. Issue no.1,MillerDA,etal.Clinicalriskfactorsforplacentaprevia-placenta Reprinted fromthe 2 ormore 1 0 Number ofpriorC/S Cesarean Delivery Table 8.10

structures. the myometrium,andmayimplantonotherintra-abdominal Placentapercretaoccurswhentheplacentaactuallyinvadesthrough (Table 8.10). prior C-sections,theincidencehasbeenreportedtobeover33 risk alsoincreases.Inpatientswithaplacentapreviaand2ormore prior C-section:asthenumberofC-sectionsincreases, increases evenfurtherinthosewithbothplacentapreviaanda dence ofplacentaaccreta:patientswithknownprevia.Risk Onepatientpopulationisknowntohaveapredictablyhigherinci- 22,150. previous cesareandelivery),theriskofplacentaaccretaisonly1in Intheabsenceofplacentaprevia,andwithoutauterinescar(i.e.,no Placentaincretareferstoaplacentathatinvadesintothe nition

Risk ofPlacentaAccretaandPrevious American JournalofObstetricsandGynecology , Vol.177

33.7 14.7 3.4 Risk ofplacenta accreta( % ) myometrium, myometrium, %

231 Obstetric Anesthesia 232 Obstetric Hemorrhage • • loss maybeeffective. Insomesituations,non-operativeinterventionstodecreaseblood is substantial,and themajorvesselsarelocateddeep inthepelvis; ectomy. Asnotedabove,maternal blood ﬂ ow totheuterusatterm options. Moreoften,surgicalintervention isnecessary,usuallyhyster- lems suchasplacentaaccretamay becontrolledwithnoninvasive Oninfrequentoccasions,signiﬁ cant hemorrhage secondarytoprob- •

of ObstetricHemorrhage Non-Operative InterventionsforManagement Hysterectomy Anesthetic Management: Peripartum • Advancedmaternalage, helpful inmanagementofobstetrichemorrhagetwo Radiologicinterventions. • reported upto80 intrauterine balloonwith400mlsalinefor24hourshasbeen used forcontrolofbleedingesophagealvarices.Inﬂ ation ofthe ing secondarytouterineatony.Suchcathetersaremorecommonly Blakemore tubehasbeenreportedforthecontrolofuterinebleed- Intrauterinetamponade centa accretainthepresenceofplacentaprevia.

confi Placementofpreoperativeiliacballooncatheters. for treatmentofacute,severehemorrhage. reported effective.Itshouldbenotedthatthisisrarelyanoption selective catheterembolizationoftheoffendingvesselshasbeen ous bleedingmayoccur.Insuchsituations,radiologicallyguided management followingdelivery(vaginalorcesarean),lessvigor- Postpartum embolization surgeon toperformtheindicatedprocedure. can beinflated, haltingbloodfl ow totheuterus,whichallows blood loss.Immediatelyafterdeliveryoftheinfant,balloons erally beforesurgeryhasbeenreportedhelpfulincontrolling placement ofballooncathetersintheinternaliliacarteriesbilat- ean delivery,suchasaconfi rmed diagnosisofplacentaaccreta, rmed tobeatsignifi cant riskofhemorrhage %

effectiveforcontrolofbleeding. > 35years,furtherincreasesriskforpla- . Infrequently,despiteoptimalmedical . IntrauterineplacementofaSengstaken- Interventionalradiologistshaveproven

Whenapatientis prior

situations: tocesar- • blood lossisfetal, notmaternal.Vasapreviaispresent whenplacental Vasapreviadiffersfromtheproblems discussedpreviously,inthatthe and platelettransfusionareoftennecessary. coagulation status:withsubstantialbloodloss,fresh-frozenplasma degree ofbloodlosswillalsodictatetheneedtosupportmaternal transfusion withpackedredbloodcellsisusuallynecessary.The circulating bloodvolume.Dependingonthedegreeofloss, Theprimarygoalduringaperipartumhysterectomyistomaintain • major ongoingbloodloss. considered), theanesthesiologistshouldanticipateadifﬁcult casewith and israrelyaccomplishedwithoutsubstantialbloodloss. control ofthesevesselsisthemajorobstaclefacingobstetrician, Deﬁ Vasa Previa • • •

Fetal Hemorrhage Oncethedecisiontoperformahysterectomyismade(oreven determinations ofhemoglobin,hematocrit,andcoagulationprofi arterial linealsoprovidesaconvenientmethodtodrawbloodforserial blood pressureswingscanberapid,unpredictable,andextreme;the Withregardtomonitoring,anarterialcannulaisextremelyuseful,as diffi become hypovolemic,vasoconstricted,andcold,itbecomesvery major bloodlosshasoccurred,becauseoncethepatient access forfluid resuscitation.Itisimportanttotrydothisbefore Thefi rst priorityshouldbetoestablishlarge-boreintravenous cases isalmostessential. Asecondpairofhands(i.e.,someonetoassistyou)helpinthese resuscitate heratthesametime. it isdiffi cult to attendtothepatientandaggressivelyvolume- occur usuallymakeforaveryuncomfortable,nauseouspatient,and strongly considered.Thewideswingsinbloodpressurethatoften sion toageneralanestheticandintubationofthepatientshouldbe anesthetic, ifthematernalairwaycanbereadilysecured,conver- Evenifthedeliveryhasbeenperformedwithanadequateregional O-negative bloodshouldberequested. crossmatched bloodisnotavailable,“emergencyrelease”type crossmatched bloodshouldbebroughttotheoperatingroom;if Anticipatingthelikelihoodofneedfortransfusion,typeand nition culttoplaceperipheralIVlines.

le. le.

233 Obstetric Anesthesia 234 Obstetric Hemorrhage promptly, fetalexsanguinationanddeathoftenresult. made immediatelyandsurgicaldeliveryoftheinfantaccomplished overlying bloodvessels,withrapidhemorrhage.Ifthediagnosisisnot Withtheonsetoflabor,cervicaldilationcausesdisruption Implications reimplantation. pregnancy wastheresultofinvitrofertilizationtechniquesand is about1in2500deliveries,butitmaybeashigh300ifthe Theincidenceofvasapreviainthegeneralobstetricpopulation Risk Factors resolution ofapartialplacentapreviaasgestationprogresses. velamentous insertionoftheumbilicalcord,orasaremnant other placentaltissue.Theconditionmaydevelopasaresultof fetal presentingpart.Theyareunsupportedbytheumbilicalcordor blood vesselsoverlietheinternalosofcervixinadvance human error,i.e., incompatible transfusionandcirculatory overload. noninfectious. Noninfectiousriskincludes thosemostoftendueto Therisksassociatedwithtransfusion canbeclassiﬁed asinfectiousand the beneﬁ transfusion therapymusttakeintoaccountnotonlytherisks,butalso employ it,duetotheperceivedrisks.Aconsidereddecision mon, butthereisoftenreluctanceonthepartofanesthesiologiststo Theneedfortransfusionintheobstetricpopulationisnotuncom- anesthetic technique. be accomplishedasrapidlysafelypossible,usuallywithageneral Oncethediagnosisisentertained,surgical(cesarean)deliveryshould Anesthetic Management bradycardia. is accompaniedbybleedingandfetalheartratedecelerations Vasapreviashouldbeconsideredanytimeruptureofmembranes Symptoms andPresentation •

Transfusion in Obstetrics Risks ofTransfusion Theperinatalmortalityofvasapreviaisashigh60 tsofthetherapy.

% .

• • has beenprovided. Complete(albeitslow)recovery hasbeen level of7.0g/dlorgreater,assuming appropriatevolumereplacement Inpractice,fewparturientswillrequire transfusionwithahemoglobin • • • • Theobviousbeneﬁ Beneﬁts ofTransfusion • also occur,butinfrequently. Infectiousrisks,i.e.,acquiringaviralinfectionfromtransfusion,can • •

restorationofcirculatingbloodvolume; increased tissuedeliveryofoxygen); increasedoxygen-carryingcapacity oftheblood(resultingin elevationofclottingfactors. cirrhosisorchronicactivehepatitis. patients infectedwilleventuallydevelopchronicdisease,either this diseaseisstillevolving,someexpertsbelievethatalmostall long enoughtobecomesymptomatic.Thoughourunderstandingof of theobstetricpopulationmeansthatonceinfected,mostwilllive apparent diseaseafterinfectionwithhepatitisC,buttheyoungage tially beinginfectious.Itcantakedecadestodevelopclinically LikeHIV,theriskofhepatitisCisabout1in2millionunitspoten- long-term sequelae,however. tially infectious.Onlyabout1in10patientsinfectedwilldevelop HepatitisBismorecommon,withabout1in200,000unitspoten- only about1unitin2millionarepotentiallyinfectious. transfusion isactuallyquitelow;withcurrentscreeningtechnology, FearofacquiringHIViscommon,buttheriskvia cause lessmorbidityandnolong-termsequelae. population thanmostpopulationsrequiringtransfusion,andshould Circulatoryoverloadshouldoccurlessfrequentlyintheobstetric mortality rateisprobablyintherangeof5 mechanismlikelyinvolvestransfusionofleukocyteantibodies.The to occuronceper5000plasma-containingcomponents.The transfusion. Whiletheincidenceisunknown,itoftencited lung injury)isprobablythemostcommoncauseofdeathfrom Acutelunginjury,alsoknownasTRALI(transfusionrelatedacute dures, toadministrationtherecipient. collection ofbloodfromthedonor,throughbankingproce- transfusion canoccuratanystepoftheprocess,from 19 peryearintheUnitedStates).Errorsresultinganincompatible units, butisfatalinonlyasmallnumberofcases(estimatedat AnABOincompatibletransfusionoccursabout1:12,000transfused tsoftransfusioninclude:

% –10 % .

235 Obstetric Anesthesia 236 Obstetric Hemorrhage a mechanismtomorerapidlyalert thebloodbanktoaproblem the helpofbloodbankingspecialists ineachinstitutioncanprovide Establishment ofanobstetricmassive transfusionprotocolwith for rapid,life-threateningbloodloss existsforeveryparturient. life-threatening situations.Obstetrics isnodifferent,asthepotential sive transfusionprotocols”hasbeen foundveryhelpfulinpotentially Inareasofclinicalpracticesuchastraumaanesthesia,theuse“mas- Obstetric MassiveTransfusion Protocol • • • circulating bloodvolumein3hours). setting ofmassivebloodloss( levels below3.0g/dl. reported inparturientswhorefusedtransfusiondespitehemoglobin

“average” parturientwithaBSAof1.7m 350 ml/min/m for almostallparturients)willincreaseoxygendeliverytoover Increasing cardiacoutputbyone-third,to8l/min,(withinreason output tocompensate,increasingoxygendelivery however: thenormalresponsetobloodlossisincreasecardiac will beonly277ml/min/m 6 l/min,andhemoglobinof6.0g/dl,calculatedoxygendelivery 300 to330ml/min/m Thecriticallevelofoxygendeliveryisprobablyintherange UseofbloodproductsotherthanPRBCsismostcommoninthe levels. Cryoprecipitateshouldbeusedtospeciﬁ cally raiseﬁ brinogen require replacementofcirculatingclottingfactorswithFFP. Acutely,massivebloodlossandrapidreplacementisalsolikelyto • • • bocytopenia. Themostcommon(earliest)derangementinthissettingisthrom-

donor units. Aunitofplasmapherizedplateletsisequivalentto5–8single raise theplateletcountby5,000–10,000/ Intheaverage(70–80kg)parturient,eachunitofplateletsshould platelet countover50,000/ Platelettransfusionshouldinfrequentlybenecessarywithastable 2 .

2 ofbodysurfacearea(BSA).Ina 2 .Suchasituationshouldbeunusual, > μ L. 150ml/min,orlossofover50

μ L. 2 ,cardiacoutputof proportionately. hypothetical

% of • • • ratios: not yetcontrolled,bloodproductsshouldbeadministeredinﬁ xed Onceacertainlevelofestimatedbloodlossisreached,ifbleeding • • • • anemia (hgb<11g/dl). and theirfetuses,assumingtheparturientdoesnothaveapreexisting Autologousdonationhasbeenfoundtobesafeforpregnantpatients Autologous Donation salvage. include autologousdonationofblood,andintraoperativeblood transfusion havebeenappliedtotheobstetricpopulation;these Inrecentyears,newstrategiestoreducetheneedforhomologous Blood StorageandSalvage event ofunexpectedbleeding,necessarystepswouldinclude: hemostasis. optimizing thepossibilityofcontrollinghemorrhageandmaintaining send totheoperatingroombloodproductsinpresetﬁ xed ratios, phone calls,anddelays.Suchprotocolswillalertthebloodbankto and obtainthenecessarybloodproductswithoutmultipleorders,

Theseprotocolsneednotbecomplicated.Asanexample,inthe parturient’smeasuredbloodlevelabove100mg/dl. Cryoprecipitateorfibrinogenconcentratetomaintainthe the parturient’sestimatedbloodvolume. Platelettransfusiononcebloodlosshasreachedroughly1.5times circulatinghemoglobinlevels. 1.5 timesthenormallevel,inadditiontomaintainingadequate a 1:1ratio.ThegoalshouldbetomaintainthePTwithin1 Packedredbloodcells(PRBCs)andfresh-frozenplasma(FFP)in infusion. restorationofcirculatingbloodvolume,initiallywithcrystalloid going scheduledcesareanhysterectomy. accreta, womenwithknownabnormal antibodies,orthoseunder- certain high-riskpatients,suchas those withplacentapreviaor Autologousdonationmayhavea placeinthemanagementof practical orcosteffectiveforroutine use. overall obstetricpopulationdoesnot makeautologousdonation candidates; thelowincidenceofneedfortransfusionin Thelimitationofautologousdonationisinidentifyingappropriate controlofthebleedingbyoperatingobstetricianorsurgeon;

237 Obstetric Anesthesia 238 Obstetric Hemorrhage • • response rateof80 hemorrhageinnorthernEurope,respondents toasurveyreported volumes. Inareviewofitsuse in treatingprimarypostpartum surgical approachesandrestoration ofclottingfactorsandblood controlling obstetrichemorrhagethat isunresponsivetoconventional some speciﬁ tion. RFVIIaisFDAapprovedonlyforthetreatmentofhemophiliaand factor IXtoIXa,andXXa,facilitatingcoagula- In thepresenceoftissuefactor,factorVIIafacilitatesconversion tein thatisstructurallysimilartohumanplasma-derivedFactorVIIa. RecombinantfactorVIIa(RFVIIa)isavitaminK-dependentglycopro- Recombinant Factor VIIa unfounded, usingpublishedredcellsalvageprotocols. cesarean deliverymightinduceamnioticﬂ uid embolismhaveproven obstetric population.Initialfearsthatautologoustransfusionduring Bloodsalvagehasrecentlybeenshowntobeaviableoptioninthe Blood Salvage Pre-op hematocrit<25 Placenta previa Abruption HELLP Syndrome delivery Diagnosis atcesarean Prospective useofCellSalvagemaybeHelpful Table 8.11

AnumberofrecentreportssuggestthatRFVIIamaybeeffectivein reported incidenceoftransfusionexceeds10 tion andtreatment protocolsforobstetrichemorrhage. RFVIIashouldonlybeusedinconjunction withstandardresuscita- an excellentoption.Table use. Inthosesettingswheremajorbloodlosscanbeanticipated,itis fusion atcesareandeliverydoesnotmakeitcosteffectiveforroutine Aswithautologousdonation,thelowincidenceofneedfortrans- cfactor-deﬁ ciencysyndromes. Clinical ScenarioswherePlanned, % toasingledoseofRFVIIa. %

15 36 14 15 Primary C/S transfusion: incidence of Reported 8.11 % % % %

listsseveralsituationswherethe %

of patients. ofpatients. 32 28 14 7 Repeat C/S transfusion: incidence of Reported % % % %

• • • • quences oftheiractions. which theywouldrefuse),andmake suretheyareawareoftheconse- determine exactlywhattherapies the individualwouldaccept(and of theparturient’sbeliefs.Rather, anesthesiologistshouldtryto planned surgery,itisimportanttonot makethediscussionachallenge WhencounselingtheJehovah’sWitness priortolabor,delivery,or passages suchasGenesis9:4andLeviticus17:10: in life-threateningsituations.Thisprohibitionisderivedfrom Bible, andincludeaprohibitionagainstreceivingbloodproducts,even Witnesses’ religiousbeliefsarebasedonaliteralinterpretationofthe alism ofmodernmedicine,asisthecasewithJehovah’sWitness. Onoccasion,religiousormoralbeliefsmaybeatoddswiththeration- Approach totheJehovah’sWitnessPatient • • RBCs =redbloodcells.FFP =freshfrozenplasma If stillbleeding • Exhaust allmedicaltreatment,thenusebloodcomponenttherapy Table 8.12

and willcuthimofffromamonghis people.” blood, IwillevensetMyfaceagainstthatsoulwhoeatethblood the strangerswhosojournamongyou,eatethanymannerof “AndwhatsoevermantherebeofthehouseIsrael,or ye noteat.” “Butﬂ esh withthelifethereof,whichisblood thereof,shall intensive careunitcosts. in otherbloodproducts,medications,andoperatingroom microgram),itscostshouldbeweighedagainstpotentialsavings WhileRFVIIaiscurrentlyveryexpensive(about$1USper bleeding (Table8.12). nously afterfailureofstandardbloodproducttherapytocontrol recommended aninitialdoseof90mcg/kgrapidlyinfusedintrave- AconsensusconferenceconvenedbythemanufacturerofRFVIIa Then considerrFVIIa90mcg/kgIVover3–5min If noresponse:Correcttemp,pH,s.Ca consider 2nddose 4u packedRBCs,FFP,Platelets Protocol foruseofRecombinantFactorVIIa

> hysterectomy

… repeat! + + , platelets,ﬁ

brinogen … then scriptural

239 Obstetric Anesthesia 240 Obstetric Hemorrhage

Further Reading moral beliefsoftheircareproviders. cases, careoftheJehovah’sWitnesscanalsoprovechallengingto used tostabilizeandimprovehematocritlevels.Unfortunately,indifﬁ forces theneedtodiscussoptionswithindividual. Individualacceptanceofvarioustherapiesvarieswidely,whichrein- • • include: • •

1. 5. 4. 3. 2. 9. 8. 7. 6.

Examplesofpracticeswhich Inthecasesofsevereanemia,syntheticerythropoietinhasbeen useofplasmaproductsotherthanPRBCs loop tothepatient’scirculation useofcell-salvageduringsurgery,withorwithoutacontinuous platelettransfusions. albumininfusion

Alﬁ Grobman Gynecol. 2008 ; causes, prevention,andrelationshiptocesareandelivery 199 . : 36.e1 . Clark SL , 1531 - 1536 Belfort . cell salvageinthecesareansectionpatient MA . , Dildy GA Waters , JH , 2008 ; 17 Biscotti : 37 C - , Allam 45 . J Potter registry 2000-2004 , . PS , Cox factor VIIinprimarypostpartumhemorrhage:theNorthernEuropean M , Yentis M . Cell salvageinobstetrics . and reportofthreecases . uterine relaxantforemergencyobstetric procedures.Reviewofliterature Riley , ET , 210 - 214 Flanagan . , placenta previa–placentaaccrete B . , Cohen , SE, Miller etal DA AmJObstetGyn. , 2006 Chollet . ; patients attemptingvaginalbirthaftercesareandeliverybepredicted? Intravenous nitroglycerin:apotent 195 JA : , Goodwin TM , et al Macones GA haemorrhage , . Alison GC , Karalapillai D Stamilo Obstet Gynecol. , DM , 2008 Popham ; associated withattemptedvaginalbirthaftercesareandelivery. 199 P : 30.e1 - . 30.e5 Recombinant factorVIIainmassivepostpartum . revic Z. Elbourne D. Pavord S , et al WA Int JObstetAnesth. 2007 ; 16 : 29 - 34 . , Lai Y , Landon MD ,

Obstet Gynecol . 2007 ; 110 : 1270 - 1278 .

1148 . Int JObstetAnesth . 1996 ; 5 : 264 - 268 . may et al . Maternal deathinthe21stcentury: et al . Amniotic ﬂ uid removalduring Am JObstetGynecol. 1997 ; 177 :

et al . Prediction ofuterinerupture

beacceptabletosomeWitnesses . Use ofrecombinantactivatedT et al . Clinical riskfactorsfor . Can uterinerupturein Anesthesiology . 2000 ; 92 :

Int JObstetAnesth. Am JObstet Am J cult cult 11. 10.

Welsh A Reviews. , 2009 McLintock ; obstetric disordersanditsacutehaematologicalmanagement 23 C . : , 167 - 176 Gatt . S Thachil , J , Toh CH , AustNZJObstetGynecol. 2008 ; recombinant activatedfactorVIIinmassiveobstetrichaemorrhage 48 . : 12 - 16 . et al . Disseminated intravascularcoagulationin et al . Guidelines fortheuseof Blood

241 Obstetric Anesthesia Chapter 9 Obesity

Robert D’Angelo , MD Medge D. Owen , MD

Introduction 242 Pathophysiology 243 Pregnancy and Obesity 245 Obstetric Complications 245 Fetal Complications 248 Anesthetic Considerations 248

242 Analgesia for Labor and Delivery 250 Anesthesia for Cesarean Delivery 256 Postpartum Care 262 Summary 263

Introduction

Obesity is a condition of excess body fat that is reaching epidemic proportions and becoming a worldwide public health problem. Obesity has joined underweight, malnutrition, and infectious diseases as major health problems threatening the developing world. • In 2006 the World Health Organization estimated that worldwide 1.7 billion people were overweight, 312 million were obese, and 155 million children were either overweight or obese. • In developed countries, including Europe and the United States, obesity affects more than 30 % of the population and is primarily associated with poverty. In contrast, in developing countries, affl u- ence carries a higher risk. Obesity results in an increased utilization of health care resources. In obstetric patients, obesity may be the most common high-risk problem seen by the anesthesiologist. • tion mustalsoincrease,butalargebodyhabitusmakesthisdiffi tion toweight.Tomeettheaddedenergydemands,minuteventila- consumption andcarbondioxideproductiontoincreaseinpropor- Increasedbodysizeincreasesenergyrequirements,causingoxygen Pulmonary gastrointestinalsystems(Table thetic implicationsoccurinthepulmonary,cardiovascular,and systems. Themostsignifi cant pathophysiologicchangeswithanes- cardiorespiratorysystem,andaffectsthebody’smostvitalorgan changes ofpregnancy,creatingmoreworkforanalreadystressed bidity andmortality.Obesityexaggeratesthenormalphysiologic Obesityduringpregnancyincreasestheriskofmaternalandfetalmor- commonly,BMIisusedtodefi ne obesity(Table and thereisnoaccepteddefi nition ofobesityinpregnancy.Most Manycriteriahavebeenusedtodefi ne obesity,withoutagreement, defi defi nition is200 • • Signifi cant PulmonaryEffects ∗ Table 9.1 • • • • • •

Pathophysiology BMI =Bodymassindex

40kg/m IntheUnitedStates,approximately40 a bodymassindex(BMI) position. breathing moredifﬁ cult, especiallyinthesupineorTrendelenburg Abdominalmassfurtherrestrictsdiaphragmaticmovement,making even greaterenergyexpendituretoliftthechestduringinspiration. Increasedchestwallweightdecreaseslungcompliance,requiring nedbyaBMI Normal18.5–24.9 Overweight25.0–29.9 O eiyII 35.0–39.9 30.0–34.9 Morbid Obesity Obesity III Obesity II Obesity I 2 . Weight Classiﬁcation byBMI % > 40kg/m ofidealbodyweight.Morbidobesityisgenerally > 40 > 40

Weight (kg) Height (m) 2 . > 30kg/m

9.2 ). 2

. 2

and10 % ofobstetricpatientshave % ∗ haveBMIsthatexceed

9.1 )butasimpler cult.

243 Obstetric Anesthesia 244 Obesity • • • • • • • Morbidobesityincreasesdemandsonthecardiovascularsystem. Cardiovascular • • • Obesity Table 9.2 • •

the riskofdeathfrom cardiovasculardiseasehasbeen reported. Inobeseyoungadults25–34years of age,atwelvefoldincreasein artery disease,andcardiacarrhythmias. cardio Thereisaclearrelationshipbetween obesityanddeathdueto function. that canleadtoleftventricularhypertrophy andabnormaldiastolic Obesityisassociatedwithathreefoldincreaseinhypertension the increasedpulmonarybloodﬂ Pulmonaryhypertensionisrelativelycommon,andcandevelopfrom Airwayresistanceanddiffusioncapacityusuallyremainnormal. result. lung segments,ventilation/perfusionmismatchandhypoxemiacan Sincepulmonarybloodﬂow preferentiallyoccursinthedependent compliant,nondependentlungareas. in dependentpartsofthelung,shiftingventilationtomore Abdominalandchestwallweightalsopromoteairwayclosure airway closureduringtidalventilation. capacity (FRC)maybecomelessthanclosingcapacity,resultingin Lungvolumesandcapacitiesarereduced,functionalresidual • • • • • Gastrointestinal • • • • Cardiovascular • • Pulmonary Systemic •

Hiatal hernia Delayed gastricemptying Insulin resistance

↑ Chronic hypertension Cardiacoutput

↓ V/Q mismatch Chronic hypoxemia Pulmonary hypertension

↑ Energyrequirements ↑ O

↑ CO FRC vascular causes,includingischemic heartdisease,coronary 2 consumption 2 production Pathophysiologic ChangesAssociatedwith ow, chronichypoxemia,orboth.

obese patients.ThisincreasedventilationaccountsforsimilarPaCO • • • • • tidal volumeproducehigherPaO obese patients,butduringpregnancy,hormone-inducedincreasesin obese patient.Frequentshallowrespirationsaremoreefﬁ cient for Insomeinstances,pregnancymayofferadegreeofprotectiontothe • are increased.Evenwhenfasting: delayed gastricemptyingand,duringpregnancy,therisksofaspiration Obesepatientshaveanincreasedprevalenceofhiatalherniaand Gastrointestinal Obesity associates with an increased risk of antepartum complications. Obesityassociateswithanincreasedriskofantepartumcomplications. Antepartum with obesityandoccurthroughoutthepuerperium. complications. Numerousobstetricproblemshavebeenassociated Obesityincreasestheriskofanesthesia,obstetric,andfetal/neonatal not additive. FRC isdecreasedinbothpregnancyandobesity,theconditionsare values seeninbothobeseandnon-obesepregnantpatients.Although

Obstetric Complications Pregnancy andObesity Allobeseparturientsshouldbeconsideredtohaveafullstomach. pneumonitis. with agastricpHlessthan7.25,puttingthematriskofaspiration Mostobesepatientswillhaveagastricvolumemorethan25ml course oflaborand delivery. lead tofetalmacrosomia,aproblem thatcandramaticallyalterthe higher incidenceofgestationaldiabetes intheobeseparturientcan Obesitypriortopregnancy,weight gainduringpregnancy,andthe (Table ent ina“highrisk”categoryandcan complicate theobstetriccourse Independentofmedicalproblems,obesity aloneplacestheparturi- problems. mothers, whichmayaccountforsomeofthecoexistingmedical Obesemotherstendtobeolderandmoreparousthannon-obese A nonparticulate oral antacid prior to surgery should be considered. Anonparticulateoralantacidpriortosurgeryshouldbeconsidered. 9.3 ).

2 levelscomparedwithnonpregnant

245 Obstetric Anesthesia 246 Obesity labor frequentlyoccurs.Fetalmacrosomiamayleadtocomplicated ous onsetoflabor(Table non-obese controls,butareatgreaterriskforlateorfailedspontane- Obeseparturientsareatlowerriskforprematurelaborcomparedto Peripartum and intestinalobstructionduringpregnancy. that undergobariatricsurgeryareatincreasedriskofmalabsorption associated withobesitymaybereducedfollowingweightloss,women ric surgeryeachyearintheUnitedStates.Althoughobstetricrisks patients andmanypregnanciesareunplanned. changes necessaryforsustainedweightlossisdifﬁ cult forobese combination ofdietandexercisecanbeeffective,makingthelifestyle obese patientsloseweightbeforebecomingpregnant.Althougha • • • • • • • • Associated withObesity Table 9.4 Associated withObesity Table 9.3 • • • • • • • • •

Alternatively,nearly50,000premenopausalwomenundergobariat- Becauseobesityincreasesobstetricrisk,itisrecommendedthat • Obstructive sleepapnea Hyperlipidemia Preeclampsia Chronic hypertension Gestational hypertension Gestational diabetes Insulin resistancesyndrome • Intrauterine fetaldemise Early miscarriage ↑Operativetime ↑ Operativebloodloss ↑ Cesareandelivery ↑ Instrumentaldelivery ↑ Failedinductionoflabor ↓ Spontaneousonsetoflabor Congenital anomalies Recurrent miscarriage

Neural tubedefects Omphalocele Peripartum ObstetricComplications Antepartum ObstetricComplications 9.4 ).Forthisreason,medicalinductionof (CPD) andarrestoflabornecessitatingcesareansection. vaginal delivery,butmorelikelyresultsincephalopelvicdisproportion • • • • • • Obesityincreasestheriskofpostoperativecomplications(Table Postpartum • • • • • • • • • • • • • • Associated withObesity Table 9.5

Diabetesmellitusalsoincreasestheriskofwoundinfection. increased riskforpulmonarythromboembolism. pregnancy-related hypercoagulability,obesepatientsareatan Withtheobesity-relatedincreaseindeepveinthrombosisand pneumonia. days followingabdominalsurgery,andatelectesismayleadto Restorationofnormalpulmonaryfunctionmaytakeseveral ary todecreasedbloodﬂ trauma, andtheinabilityofadiposetissuetoresistinfectionsecond- tracted surgicaltime,excessoperativetractioncausingtissue Postsurgicalwoundinfectionisrelatedtolargerincisions,pro- Approximately60 increases. TheincidenceofcesareansectionincreasesfurtherasBMI anticipated. Prolongedsurgicaldurationandincreasedbloodlossshouldbe indications. require cesareansection;halfofthesewillbeforurgentor with aBMI Theincidenceofcesareansectionisincreasedtwofoldinpatients risk factorsforcesareansection. Inductionoflabor,fetalmacrosomia,andobesityareindependent ↑ Sudden death Costofmedicalcare Prolonged hospitalization Wound dehiscence Wound infection Urinary tract infection Pneumonia Pulmonary embolus Deep veinthrombosis Thrombophlebitis Hemorrhage Postpartum ObstetricComplications > 35kg/m % 2 ofpatientsweighingover300pounds(135kg) . ow.

emergent

9.5 ).

247 Obstetric Anesthesia 248 Obesity • • • • • • • the anesthesiologist. mizing medicalmanagementandshouldincludeearlyconsultationby or emergentcesareansection,ananestheticplanisessentialforopti- Since asmany30 Inobeseparturients,thelackofananestheticplancanbedisastrous. FetalcomplicationsassociatedwithobesityarelistedinTable Table 9.6 • • • • • • • • • •

Anesthetic Considerations Fetal Complications

decrease cardiacoutput. Neonatalhypoglycemiacanalternewbornthermoregulationand dystocia, andasphyxia. Macrosomiaispositivelycorrelatedwithbirthtrauma,shoulder graphic visualizationisimpairedwithmorbidobesity. Prenatalfetalanomaliesmaybeundiagnosedbecauseultrasono- neonatal intensivecareunit,anddeath. Newbornsareatincreasedriskforcomplications,admissiontothe cussed below. increase theriskofsuddendeath.Obstructivesleepapneaisdis- Theincreasedriskofobstructivesleepapneainobesepatientsmay cal problemsisparamount. Evaluationoftheairwayandathoroughreviewcoexistingmedi- patients. recommends antenatalanesthesiaconsultationformorbidlyobese TheAmericanCollegeofObstetriciansandGynecologists(ACOG) ↑ NICUadmission Neonatal hypoglycemia Birth trauma Birth asphyxia Shoulder dystocia Breech presentation Multiple gestation Macrosomia Intrauterine demise Congenital anomalies Fetal ComplicationsAssociatedwithObesity

ofmorbidlyobeseparturientsrequireanurgent

9.6 . • • • • Recommendations cially ifthetableisarticulated. (227 kg),whichmaybeinsufﬁ cient formorbidlyobesepatients,espe- size andweight.Manyolderoperatingtablesareonlyratedfor500lbs ating tablesmustbeavailabletoaccommodatetheobesepatient’s Appropriatelysizedhospitalbeds,stretchers,wheelchairs,andoper- Equipment Problemsincludemonitoringandoccasionaldifﬁ cult intravenousaccess: • • and reducethelikelihoodofcomplications. Properpositioningoftheobeseparturient canfacilitateoxygenation Positioning intheLaborUnit • •

cially ifsheisimmobilizedduetoregionalanesthesia. Extrapersonnelareessentialtosafelytransportthepatient,espe- operating table,ortwoside-by-sideroomtables. Inrarecasesitmaybenecessarytoeitherusethelaborbedasan abdomen mayshiftmarkedlywhenthepatientistiltedleftward. patient mustbewellsecuredtotheoperatingtablebecause Leftuterinedisplacementmaycreateanunstablesituation.The 800 lbs(364kg)articulatedisrecommended. Anoperatingtableratedfor1,200lbs(545kg)unarticulatedand fi advance, particularlyregionalanesthesiatechniquesandawake decreased. Itisimportanttodiscussanestheticinterventionsin mechanical airwayobstructionwhenthelevelofconsciousnessis Ahistoryofobstructivesleepapneamaysuggestthepotentialfor pregnancy. been significant weightgainsincethepreviousanesthetic,orduring Apreviousuneventfulanestheticmaybeirrelevantiftherehas volume. venous accessisgenerallynotdiffi cult, duetoanexpandedblood Despiteincreasedamountsofsubcutaneousfat,establishingintra- heart. placed ontheforearmifispositionedatlevelof upper arm.Asanalternative,astandardsizedcuffmayalsobe the bloodpressurecuffshouldcoveratleasthalflengthof ments whenplacedonalarge,funnelshapedarm.Thewidthof Astandardbloodpressurecuffwillgivefalselyhighmeasure- beropticintubation.

249 Obstetric Anesthesia 250 Obesity • • • • Benefi ts ofEpiduralAnalgesia labor painreliefisepiduralanalgesia. Inobeseparturients,themostappropriateanesthetictechniquefor Epidural Analgesia is preferredwheneverpossible. or surgicaldeliveryrequiringprofoundanesthesia,regionalanesthesia Since thepotentialishigherinobesepatientsforcomplicatedvaginal of complications,includingopioid-inducedrespiratorydepression. obese patients.Moreoften,theyareineffectiveandincreasetherisk and perineallocalinfiltration atdelivery,maybeappropriateforsome Parenteralanalgesicsduringlabor,supplementedwithpudendalblock • • • • an anesthesiologist uponadmission,informedconsent obtained,and Ideally,morbidlyobeseparturients should beidentifi ed andseenby •

Analgesia forLaborandDelivery placed inthesupineposition. arrest hasbeenreportedwhenmorbidlyobesepatientshave and elevatedpulmonaryocclusionpressurescanoccur,cardiac Airway obstructionandcirculatorychangessuchashypotension pression maybeexacerbatedbytheweightofalargepanniculus. Thesupinepositionshouldbeavoidedbecauseaortocavalcom- to themotherandfetus. Oxygenadministrationishelpfulandmayprovideamarginofsafety closure, thusreducinghypoxemia. Elevationoftheheadbedalsoreducesprematureairway allows greaterdiaphragmaticexcursionduringrespiration. cardiovascular stressbyreducingintra-abdominalpressure,and off theabdomenandimproveslungexpansion.Ithelpsminimize Thesemi-recumbentorlateralpositiondisplacesthepanniculus Decreasedoxygenconsumption cesarean sectionberequired. administration thatcanbeutilized forsurgicalanesthesiashould Mostimportantly,epiduralanalgesia allowsforcontrolleddrug sure andcardiacoutput Decreasedcatecholaminesecretion thatmayincreasebloodpres- Decreasedworkofbreathing Improvedoxygenation

Reasons forEarlyEpiduralCatheterPlacementinObeseParturients terms. when therisksandbeneﬁ ts arepresentedinclear,understandable gesia. Patientsinvariablyconsenttoearlyepiduralcatheterplacement labor, andthenreactivatedlaterwhenthepatientrequestslaboranal- ter placement.Thecathetercanbetestedifthepatientisnotinactive during thecurrenthospitalizationisrequiredforearlyepiduralcathe- active labor.Acommitmentfromtheobstetricteamfordelivery an epiduralcatheterinsertedandtestedevenbeforetheonsetof • • • • • an ObesePatient technique forepiduralcatheterplacementislistedinTable Important PointsWhenPlacinganEpiduralCatheterin although locatinganinterspaceisnotguaranteed.Arecommended Thesittingpositionusuallyprovideseasieridentiﬁ cation ofmidline, • • • • • • • • Placement intheMorbidlyObeseParturient Table 9.7

Itmaytakelongertopositionthepatientandplacecatheter. urgent cesareansectionberequired. ing thelikelihoodofasuccessfulregionalanestheticshouldan Mostimportantly,thistechniqueminimizesoverallriskbymaximiz- anatomical landmarks. Blockplacementcanbetechnicallychallengingduetoobscured and improvescooperation,thusincreasingthechanceforsuccess. Catheterplacementbeforeactivelaborminimizespatientmovement the midline,perpendiculartoskinatanimaginarypointanchored Whenlandmarkscannotbepalpatedinserttheepiduralneedlein • • • Maintenance oflabor analgesia: dilutelocalanestheticwithopioid (0.0625 For: Early epiduralcatheterplacement Test catheterwith10ml2 > Secure catheterwithpatientinlateralposition 6cmcatheterinsertionlength Low midlineapproach(Figure 9.1 ) Sitting position

patient requestsanalgesia Adequate analgesia: administeradditionallocalanestheticswhen additional lidocaine5ml Inadequate analgesia: withdrawcatheter2–3cmandadminister Persistent inadequateanalgesia: removeepiduralcatheterandreplace % –0.125 Recommended TechniqueforEpiduralCatheter % bupivacaine

% lidocaine(2 + fentanyl2mcg/ml)

+ 5 + 3ml) 9.7 .

251 Obstetric Anesthesia 252 Obesity • • • • drawn fromtheC the ﬁ rst skincreaseabovetheglutealfoldandvertically byanimaginaryline in themidlineperpendiculartoskin at apointanchoredhorizontallyby parturient. Withthepatientinsitting position,inserttheepiduralneedle Figure 9.1

be insertedatleast6cmwithintheepiduralspacetominimize Oncetheepiduralspaceisidentifi ed, theepiduralcathetershould able epiduralneedlesshouldbereadilyavailable. required. Forthisreason,astockof5–6inch(127–152mm)dispos- is almostalwayssuffi cient, alongerneedlemayoccasionallybe needle length.Althoughastandard3.5inch(89mm)epidural dural spaceismorelikelymisdirectionratherthaninadequate Eveninthemorbidlyobesepatient,inabilitytoidentifyepi- direction andbacktowardsthemidline. towards thediscomfortwilldirectneedletipinopposite any leftorrightsideddiscomfort.Directingtheepiduralneedlehub Incasesofdiffi cult placement,thepatient canassistbyreporting but familiaritywiththetechniqueisessentialforsuccess. Ultrasound guidancemayalsofacilitateepiduralcatheterplacement the chanceofidentifyinglateralepiduralspace(Figure failure ratebyexaggeratingminordirectionalerrorsandincreasing Theincreaseddepthtotheepiduralspacecontributesahigh gluteal fold(Figure cally byanimaginarylinedrawnfromtheC horizontally bythefirst skincreaseabovetheglutealfoldandverti- Approach toepiduralcatheterinsertion in themorbidlyobese Lowest skin gluteal fold crease above 7 spinousprocesstotheglutealfold. 9.1 ). Gluteal fold C7 spinousprocess

7 spinousprocesstothe insertion site Low midline

9.2 ). • • • with a9cmskin-to-epiduralspacedistance. an approximate1.5cmdeviationfrommidlineinthemorbidlyobesepatient space inthenormalpatientwitha4cmskin-to-epiduraldistance,versus into anapproximate0.7cmdeviationfrommidlinewhenenteringtheepidural increases failurerate.Asdrawn,a9 exaggerates minordirectionalerrorsduringepiduralneedleinsertionand Figure 9.2 Skin (a)

bilateral analgesia and thecatheterwasinsertedearly, noadditional lidocaine)tofullytestthecatheter. Ifthepatientdevelops Administerenoughlocalanesthetic (usually10mlof1 and thecathetermarkingatskin intheanesthesiarecord. Once secured,recordthelengthof catheterintheepiduralspace 4 cminamorbidlyobesepatientwhen assumingthelateralposition. ﬂ catheter, sincethesittingpositiondecreasesskin-to-ligamentum Movethepatienttolateralpositionbeforesecuringepidural but familiaritywiththetechniqueisessentialforsuccess. Ultrasoundguidancemayalsofacilitateepiduralcatheterplacement dural space. for increasedmovementoftissuesbetweentheskinandepi- risk ofsubsequentcatheterdislodgementbecausethepotential avum distance.Theepidural cathetercanmoveinwardsasmuch Normal patient Increased skin-to-epiduralspacedepthinobesepatients

0.7cm off midline 9° off midlineangle Spinous process flavum Ligamentum ° off-midlineangleattheskin translates Skin (b) Morbidly obesepatient 1.5cm off midline 9° off midlineangle Spinous process

flavum Ligamentum %

–2 %

253 Obstetric Anesthesia 254 Obesity can bequicklyaugmentedinthe eventofcesareansection,but infusion forlaboranalgesia.Aswith epiduralanalgesia,theblock Asubarachnoidcathetercanbedosed incrementallyorbycontinuous Continuous SpinalAnalgesia • • • recommended. TheuseofCSEanalgesiainobeseparturientsisnotroutinely Combined SpinalEpidural(CSE) • • • • • Initiating LaborAnalgesia

be required. risk ofepiduralcatheterfailureshouldemergencycesareansection Thebenefi t offasteronsetlaboranalgesiadoesnotoutweighthe guaranteed. dural needleposition),adequateepiduralanesthesiacannotbe (since obtainingcerebrospinalfl uid indicateslikelymidlineepi- gested thatasuccessfulCSEimprovessubsequentcatheterfunction patient populationremainsunknown.Althoughithasbeensug- TheincidenceofepiduralcatheterfailurewithCSEintheobese cesarean sectionberequired. dural catheterthatmaybecomeproblematicshouldanemergency TheCSEtechniquedelaysrecognitionofapoorlyfunctioningepi- Althoughinitialepiduralcatheterfailuremaybeover40 replaced untilawell-functioningepiduralcatheterisestablished. Forinadequateanalgesia,theepiduralcatheterismanipulatedor relief. local anestheticsareadministereduntilthepatientrequestspain remain similartothoseofnon-obeseparturients. engorged epiduralveins),analgesicrequirementsgenerally ity (duetoareductioninepiduralvolumebyfattyinfi ltration or Althoughlocalanestheticrequirementsmaybereducedwithobes- established, epiduralopioidscanbeadministered. Once thecatheterfunctionisprovenandabilateralblockasbeen pain reliefandmaytheoreticallymaskamalpositionedcatheter. Opioidadministrationbyanyrouteproducessomedegreeof establish catheterfunction. Localanestheticsaloneorwithminimalopioidshouldbeusedto trols canbeobtained. parturients, eventualsuccessratescomparabletonon-obesecon-

% inobese

• • concerns: mended forroutineusebecauseofthefollowingtheoretical unilateral blockadeislesslikely.However,thetechniquenotrecom- SpinalcathetermanagementisoutlinedinTable • • • • Recommendations forContinuousSpinalAnesthesia • • • • • • • Management intheMorbidlyObeseParturient Table 9.8

Inadvertentwettapwithanticipatedimminentdelivery ecal localanesthetics,makingassessmentdiffi Duringalongcourseoflabor,tachyphylaxismaydeveloptointrath- trolled settingofthelaborward. doses mayincreasetheriskofhighspinalblockadeinuncon- intended forepiduraladministrationmaybeinjected.Theselarger mistaken foranepiduralcatheteranddosesoflocalanesthetic involved inthecareoflaborpatient,aspinalcathetermaybe a safetyconcern.Asmultipleanesthesiaprovidersaretypically Mostimportantly,anindwellingspinalcatheteronthelaborunitis dislodge thespinalcatheter. With4cmorlessofsubarachnoidcatheter,patientmovementmay impingement. increases theriskofspinalcordpenetrationornerveroot Catheterlengthsinsertedmorethan4cmintothespinalspace Urgentsituationswhendiffi Inadvertentwettapduringdiffi • • Anesthesia for CesareanSection: • • Sitting position Labor Analgesia: Secure catheterwithpatientinlateralposition 4 cmcatheterinsertionlength Low midlineapproach(Figure 9.1 )

least 5minbeforeadministeringadditional dose) level achieved Additional boluses: 1.25–2.5mgplainbupivacaineuntildesiredsensory

Initiation: 5mg0.5 bupivacaine

fentanyl 15–25mcg) Intermittent dosing: routineCSEboluses(1.75–2.5mgbupivacaine Continuous Dosing: routineepiduralsolutions(0.0625 Technique forSpinalCatheterPlacementand + fentanyl2mcg/ml)@1–2ml/hour % plainbupivacaine culttrachealintubationisanticipated

cultepiduralcatheterplacement

+ fentanyl15–20mcg(waitat cult. 9.8 .

% –0.125

% +

255 Obstetric Anesthesia 256 Obesity • • • reasons. spinal blockfromexaggeratedspreadoflocalanestheticforseveral Obesepatientsmaybeatincreasedriskofdevelopingahigh lus maymakesurgicalexposuredifﬁ shift theabdomenandcreateanunstablesituation.Thelargepannicu- morbidly obesepatient,sinceleftuterinedisplacementmaymarkedly Asdiscussedpreviously,caremustbetakenwhenpositioningany Positioning intheOR be avoidedifatallpossible. or intherecoveryperiod.Forthisreason,generalanesthesiashould secondary toairwayproblemsencounteredduringgeneralanesthesia tality. Inobesepatientsmostanesthesia-relatedmaternaldeathsoccur Duringcesareandelivery,obesityincreasestheriskofmaternalmor- • • • Techniques toFacilitateSurgicalExposure

Anesthesia forCesareanDelivery Trendelenburg positionwhenthepatient issupine. Glutealadiposetissuemayplacethe vertebralcolumninarelative Cerebralspinalﬂuid volumemaybedecreased. pated blockplacement. Difﬁ longed surgeries. thetic administrationtomaintainadenseT techniques (epidural,CSE,orspinal)allowadditionallocalanes- uterine incisionisnecessary.Furthercatheterfacilitatedregional sia teamssinceasupraumbilicalverticalskinincisionandclassical This techniquerequirescoordinationoftheobstetricandanesthe- tioning duringsurgeryasdictatedbypatientsymptoms(Figure related symptoms,considerutilizingreverseTrendelenburgposi- Inmassivelyobesepatientswithsupineaortocavalcompression- of sterilerodsorhooksthroughthepanniculusbysurgeons. techniques mustbeplannedinadvanceandrequiretheplacement ceiling hooks,ortoanorthopedicliftdevice.Utilizationofthese Thepanniculuscaneitherbeliftedandtetheredtoreinforced cardiac functionresultinginhypoxiaandhypotension. the panniculusonchestmaycompromisebothpulmonaryand Montgomery straps;however,inrarecases,themassiveweightof Retractionofthepanniculuscephaladontochestusing culty inidentifyinginterspacesmayleadtoahigher thanantici-

cult.

4 sensoryduringpro-

9.3 ).

and obstetricteams. skin incision,aclassicaluterineandcoordinationbytheanesthesia compression. ReverseTrendelenburgpositioningwillnecessitateavertical against thechest,whichcouldfurtheraugmentsymptomsofaortocaval syndrome usingreverseTrendelenburgpositioningtoreducetheweightload Figure 9.3 • in anobeseparturientinclude: Recommendedtechniquesthatreducethelikelihoodofhighspinalblock • coming fromthelaborward. morbidly obesepatients,whetherpresenting forelectivesurgeryor Epiduralanesthesiaisanexcellent choiceforcesareandeliveryin Epidural Anesthesia gently securetheairway. can stilloccur,andtheanesthesiaprovidermustbepreparedtoemer- Despiteutilizationoftechniquestominimizerisks,highspinalblocks • •

Ifapreexistingepiduralcatheterisin place,epidurallocal Shoulderandneckrollsinadditiontotheelevatedheadrest. administering hyperbariclocalanesthetic. Slightelevationoftheheadtominimizecephaladspreadwhen may beadministeredinthelaborroom, obviatingfailureshouldthe tissue. spinal columninpatientswithsigniﬁcant amountsofglutealadipose UtilizationofreverseTrendelenburgpositioningto“level”the Positioning themorbidlyobesepatientwithsupinehypotensive

anesthetics

257 Obstetric Anesthesia 258 Obesity • • ments arereducedbyapproximately20 Althoughithasbeensuggestedthatepidurallocalanestheticsrequire- • • vidual patientshavevaryingrequirements. • analgesia. administer opioidandlocalanestheticsolutionsforpostoperative dynamic controlcomparedtospinalanesthesia,andthefl Otherbenefits ofepiduralanesthesiaincludepotentiallybetterhemo- • • regional techniquesinobesepatients,placementcanbediffi Spinalanesthesiaisanoptionforcesareansection,butaswithother Spinal Anesthesia

be madeforreplacingtheepiduralcatheterinoperatingroom. Shouldinadequatesurgicalanesthesiapersist,considerationshould tional localanesthetics. 3–4 cmremainswithintheepiduralspace,andthenadministeraddi- the operatingroomtable,withdrawepiduralcathetersothat dosing inthelaborroom,itmaybeprudenttomovepatient Ifanesthesiaappearstobeinadequateforasurgicalincisionwhile room. catheter becomedislodgedduringtransporttotheoperating but allowforsubsequentdosingifnecessary. one-shot spinal.Thesetechniquessimilarly providerapidanesthesia spinal orCSEanestheticmaybemore appropriatechoicesthana Whenprolongedsurgicaldurations areanticipated,acontinuous inadequate ventilationinobesepatients. mid-thoracic sensorylevelsrequiredforcesareansectionmaycause Becauseofexcessiveabdominalandchestwallmass,eventheusual discussed. spinal blocksecondarytoadiposetissuedistributionwaspreviously Iftheblockexceedsdesiredsensorylevel,aslighthead-ﬂ novo quickly extendedforsurgicalanesthesia,butestablishingablock Inanemergency,awell-functioninglaborepiduralcanusuallybe affecting thesurgery. of theoperatingtablelessenspatientcomplaintswithoutadversely is insertedaboveL placement, possiblyleadingtospinalcorddamageiftheneedle superior iliaccrests.Thismayresultininadvertentlyhighneedle Fattydepositsaboutthehipscanleadtofalseidentiﬁ cation ofthe may taketoolongandaspinaltechniquebepreferable. 2 spinousprocess.Theincreasedriskofhigh

inobeseparturients,indi-

exibility to exibility cult. exion

• • • • • • this situation,theriskofafailedintubation andpotentialcatastrophic gist mayfeelcompelledtoproceed withrapidsequenceinduction.In consumes time,andinthepresence offetaldistress,ananesthesiolo- traindicated, anawakeintubationis recommended. Topicalanesthesia Ifadifﬁ cult intubationisanticipated,andregionalanesthesia iscon- • decreased FRCandincreasedoxygenrequirements. desaturation mayoccurdespiteadequatepreoxygenation,duetothe Inobeseparturients,swiftintubationisimportantbecauserapid primary anesthesiaprovidercanfatiguequickly. induction, sincemaintainingtheairwaymaybecomplicatedand Wheneverpossible,twoanesthesiaprovidersshouldbepresentfor • begin withspecialemphasisonairwayevaluation. be usedonlyinpatientswithcontraindicationstoregionalanesthesia. Inobeseparturients,generalanesthesiaforcesareansectionshould General Anesthesia

Anydiscussionofgeneralanesthesiaintheobeseparturientmust Obesityimpairsidentifi cation ofthe cricoidring,makingitdiffi tion ofthestomachmayoccurandincreaseriskaspiration. abdominal pressurecanimpedeventilation.Inthisscenario,insuffl Ifmaskventilationbecomesnecessary,airwayobstructionandhigh hypertension andcardiacarrhythmias. Hypoxemiaandhypercarbiacanprecipitatesuddenpulmonary insertion withastandardlengthhandle. sion ofashort,thickneckandpendulousbreastsoftenhamper Ashort-handledlaryngoscopeisalsousefulbecauselimitedexten- available. and equipmentfortranstrachealventilationshouldbeimmediately gum elasticbougie,standardandintubatinglaryngealmaskairways, Assortedlaryngoscopeblades,avarietyofendotrachealtubes, propensity forrapiddesaturationcanbedisastrous. Intheobesepatient,complexityofintubationcoupledwith complicate intubationefforts. Alargetongueandairwaysofttissueengorgementcanfurther patients undergoingabdominalsurgery. in anemergency. to properlyapplycricoidpressureandperformcricothyrotomy Diffi having cesareansection,comparedto13 cult intubationhasbeenreportedin33

% % innonpregnantobese

ofobeseparturients

cult a-

259 Obstetric Anesthesia 260 Obesity • • • Abalancedanesthetictechniqueisusedoncetheairwaysecured. • • • • • Technique forInducingGeneralAnesthesia • • • • Positioningrecommendationsthatmayfacilitatetrachealintubation: mise bydelayingsurgerytosecuretheairway. maternal outcomemustbeweighedagainsttheriskoffetalcompro-

operative anestheticaffects. superior inobesepatients,neweragents maylessenresidualpost- rane. Whilenosingleanestheticregimen hasbeenshowntobe is shorterwiththenewerinhalational agentsdesflurane andsevofl Whileisofl urane haslimitedbiotransformation,timetoextubation have longereliminationtimesinthe obesepatient. making itmorepredictable.Incontrast,sufentanilandalfentanilmay Fentanyleliminationissimilarinobeseandnon-obesepatients, in airwayobstructionfollowingextubation. be carefullymonitoredtominimizetheriskresidualweaknessand Regardless oftheagentutilized,neuromuscularblockademust larizing relaxantsbecausemetabolismisnotorgandependent. Atracurium,mivacurium,androcuroniumarepreferrednondepo- tilted leftward,visualizationmaybeobscured. Beawarethatwhentheheadispositionedmidlineandbody be parallelwiththefloor (Figure between theexternalauditorymeatusandsternalnotchshould tion. Ideally,afterproperpositioning,animaginarylinedrawn Utilizeshoulderandneckrollsbeforeattemptingtrachealintuba- Preoxygenatewith100 60 minutesofsurgery. 30mlofanonparticulateantacidshouldbeadministeredwithin Rapidsequenceinductionwithcricoidpressure(Sellickmanuever). prior toinduction. least 3minutes,with4vitalcapacitybreathstakenimmediately Succinylcholine1–1.5mg/kgofactualbodyweightupto200mg. in caseoffailedintubation. recommended dose,becauselargerdosesmayprolongawakening Sodiumpentothal500mg.Thisislessthantheusual4mg/kg and makevocalcordvisualizationdiffi chest inrelationtotheskull,whichmaymisalignoroglotticaxis Adiposetissueontheupperback(“buffalohump”)canelevate Proper“sniffi ngposition”isvital(Figure

% oxygenusingatightﬁ tting maskforat

9.4 ). cult. 9.4 ).

the head (9.4c). the head(9.4c). parallel alignmentmaybeimpossibletoachieve usingonlyasinglepillowunder ﬂ between theexternalauditorymeatusand thesternalnotchisparallelto reverse Trendelenburgpositioning(9.4b), sothatanimaginarylinedrawn general anesthesia.Utilizationofshoulder andheadrollsalone(9.4a)orwith Figure9.4 (c) (b) (a) oor, facilitates visualization of the vocal cords and tracheal intubation. The oor,facilitatesvisualizationofthevocalcords andtrachealintubation.The

Proper positioning of the obese patient prior to induction of Proper positioningoftheobesepatientprior toinductionof

261 Obstetric Anesthesia 262 Obesity • • • • • function, andleadstoearlymobilization. Adequate paincontrolreducessideeffects,improvesrespiratory to encouragedeepbreathinganddecreasetheriskofatelectasis. morbidly obese.Followingvaginaldeliveryomituseifpossible. Opioidscandepressrespirationandshouldbeusedcarefullyinthe Postoperative Pain Control cardiopulmonary complicationsduringthepostoperativeperiod. for severaldays.Theobesepatientshouldbecloselymonitored of respiratoryinsufﬁciency, andsupplementaloxygenmayberequired Postoperatively,themorbidlyobesepatientremainsatincreasedrisk ideal bodyweightandadjustasnecessary. Intraoperatively,initiateventilationwithtidalvolumesof10–12ml/kg • extubation. analgesics, andneuromuscularblockingagentsmaypostponetracheal suctioned. Residualanestheticeffects,increasedsensitivitytoopioid Followingsurgeryandpriortoextubation,gastriccontentsshouldbe

Postpartum Care Inpatientsrequiringoperativedelivery,paincontrolisimportant side effects. to producesuperiorpainreliefwhile minimizingopioid-induced inﬂ remains unknown,acombinationof opioidandnonsteroidalanti- Althoughtheidealmethodofpain controlinobesepatients Duringpregnancy,itisimportanttomaintainPaCO dioxide. ventilation duetoalargealveolar-to-arterialdifferenceincarbon End-tidalcapnographymaybeapoorguidetotheadequacyof tive awareness. use ofnitrousoxideandpossiblyincreasingtheriskintraopera- High-inspiredoxygenfractionsmayberequired,thuslimitingthe ance canproducehighpeakinspiratorypressures. patients. Largetidalvolumescoupledwithlowchestwallcompli- PEEPisrarelyindicatedandcanworsenhypoxemiainobese low tomid30s,andarterialbloodgasanalysismayberequired. patients, sinceitcanleadtocardiovasculardecompensation. Airwayobstructionmustbeavoidedifatallpossibleinobese ammatory agent(NSAID)isrecommendedwheneverpossible,

2 levelsinthe

• • apnea (OSA). sion, especiallyinobesepatientswithundiagnosedobstructivesleep Opioidsadministeredbyanyroutecanresultinrespiratorydepres- Anesthetic risksmaybereduced by earlyaggressiveintervention. morbidityandmortality,poses signiﬁ cant anesthetic challenges. Obesityduringpregnancyincreases theriskofmaternalandfetal • • • • Apnea (OSA) Documented orSuspectedObstructiveSleep Table 9.9 •

Summary

consists ofintermittentrespiratoryorsedationchecks,both. are candidatesforstandardpostoperativemonitoring,whichusually ObesepatientsreceivingopiodswithoutOSA-relatedsymptoms by anyroute(Table patients withsuspectedordocumentedOSAthatreceiveopioids ent withOSA.Considercontinuouspulse oximetry inobese Obesepatientsshouldbecarefullyscreenedforsymptomsconsist- duce adequatepainrelief. patient-controlled analgesiaorneuraxialadministration,canpro- Intravenousmorphine,administeredbyeitherintermittentbolus, since absorptionmaybelessreliableinobesepatients. Subcutaneousandintramuscularinjectionroutesshouldbeavoided, • • • •

Preoperative • • • • • Postoperative • • Intraoperative

NSAIDs wheneverpossible Supplemental oxygenuntilbaselineoxygenationisadequate Continuous pulseoximetry Utilization ofCPAPwhenpossible Assess patientsforsymptomsofOSA Sleep studyifsuspectedOSAandtimeallows CPAP shouldbeconsidered Patient shouldbeconsideredathighriskofdifﬁ Regional anesthesiawheneverpossible Avoid opioidswheneverpossible Extubate awakeinalateralorsemi-uprightposition andafterfull recovery ofneuromuscularblockade Recommendations forPatientswith

9.9 ).

cult intubation cult

263 Obstetric Anesthesia 264 Obesity Further Reading regional anesthesiaiscontraindicated. General anesthesiashouldbeutilizedinobeseparturientsonlywhen regional anestheticshouldanemergentcesareansectionberequired. sible, isrecommendedtoincreasethelikelihoodofasuccessful Early epiduralcatheterinsertionandtesting,asearlyinlaborpos-

4. 3. 2. 1. 7. 6. 5. 8. 9.

cerebrospinal ﬂ Hogan QH , 778 - 784. Prost catheters associatedwithpatientmovement R . , Kulier A Hamilton , etal CL . Practice 4 , Magnetic resonanceimagingof th Ed Riley . Philadelphia, PA ET : , Mosby Elsevier Tsen 2009 Cohen LC : , 1079 SE D’Angelo - 1094 R Wong . . , Changes inthepositionofepidural 2007 CA ; 109 Dewan : , eds. 419 DD - Catalano 433. . PM Chapter 50:Obesity . In . Management ofobesityduringpregnancy Chestnut . DH , Polley LS , abdominal pressure . Gynecol. 2004 ; cesarean deliveryrate-apopulation-basedscreeningstudy 190 . Weiss JL cesarean morbidity , . Malone FD , Perlow JH Emig obese parturients , . D , Morgan MM Hood . DD Massive maternalobesityandperioperative , Dewan DM . Anesthetic andobstetricaloutcomeinmorbidly with ObstructiveSleepApnea . ASA Practice GuidelinesforthePerioperativeManagementofPatients trends.html. Surveillance System . Accessed at : http://www.cdc.gov/obesity/data/ US ObesityTrends 1984-2008 . From theCDC’sBehavioralRiskFactor uid volumeandtheinﬂ : 1091 - 1097. Anesthesiology. 1993 ; 79 : 1210 - 1218. Am JObstetGynecol. 1994 ; 170 : 560 - 565. Anesthesiology. 1996 ; 84 : 1341 - 1349. Chestnut’s ObstetricAnesthesiaPrinciplesand et al . Obesity, obstetriccomplicationsand Anesthesiology . 2006 ; 104 : 1081 - 1093 . uence ofbodyhabitusand

Anesthesiology. 1997 ; 86 : Obstet Gynecol. Am JObstet death inmostdevelopedcountries. on cardiacdisease,whichistheleading causeofindirectmaternal important conditionswillbediscussedbrieﬂ y. Anemphasisisplaced the scopeofthischapter,keyissuesrelevanttomostcommonor ery. Whilecomprehensiveinformationaboutmanydiseasesisbeyond have asigniﬁ cantimpactonthecourseofpregnancy,labor,anddeliv- Almostanydiseaseormaladymaycoexistwithpregnancy,andmany Introduction Management oftheAnticoagulatedPregnantWoman Management oftheDrug-DependentPregnantWoman Psychiatric Disease Hematologic Disease Autoimmune orConnectiveTissueDisease Muscle, NeuromuscularandMusculoskeletalDisease Hepatic Disease Renal Disease Neurosurgery andNeurologicalDisease Pulmonary Disease Diabetes Cardiac Disease Introduction Michael J. and OtherIssues Paech , FANZCA CoexistingDisease Chapter 10 282 265 293 266 295 307 284 303

287

302 298 310 308

265 266 Coexisting Disease and Other Issues Cardiacdiseaseispresentin1 • an increaseinbloodvolume,oxygen demand,andcardiacoutput. • • • death. reasons whycardiacdiseasehasbecomealeadingcauseofmaternal death (10 countries itisthemostcommoncauseofindirectmaternal tionately responsibleformaternalmortalityandindeveloped Association Classiﬁ cation, basedonexercisetolerance(Table symptomatically asgestationincreases.TheNewYorkHeart impact onwomenwithcardiacdisease,whoarelikelytodeteriorate Physiologicadaptationtopregnancy(Chapter2)oftenhasanadverse Relevant PhysiologicalChangesinPregnancy from variousconditionsvaries(Table congenital heartdisease,buttheriskofdeathorseriousmorbidity contribute toischemicdisease. recreational useofillicitdrugs(e.g.,cocaine,methamphetamine)also and hypertension,particularlyamongtheobesepopulation,increased pregnancy ratesamongolderwomen.Therisingprevalenceofdiabetes nologies andsocialchangehavebeen,inpart,responsibleforhigher The extensionofthereproductiveagebyassistedtech- bearing age,andtheincidenceincreaseswithadvancingmaternalage. Ischemicheartdiseaseisnowmoreprevalentamongwomenofchild- • ated withhighermaternalmortality. typically deterioratesatleastoneclass,andClassIIIIVareassoci-

Cardiac Disease Themainphysiologicchangescontributing toworseoutcomesare Mostcardiacdeathsindevelopedcountriesarenowduetoadult symptomatic deteriorationbylatein thesecondtrimester. prepartum increaseincardiacoutput frequentlyassociatedwith Increasedcardiacworkmaycause decompensation,withthe Mostdeathsoccurinwomenwithundiagnoseddisease. nomic conditions. Rheumaticheartdiseaseremainsprevalentunderpoorsocioeco- disease reachreproductiveage. Morewomenwithadultcongenitalheartdiseaseorrespiratory disease appearwillingtoaccepttheriskofbecomingpregnant. Aspregnancybecomessafer,morewomenwithseverecardiac % –25 % ofallmaternaldeaths).Thereareanumber

% –3

ofpregnancies.Itisdispropor- 10.1 ).

10.2

), 1994:253–256. of theHeartandGreatVessels.9thed. Boston,MA:Little,Brown&Co; York HeartAssociation.Nomenclatureand CriteriaforDiagnosisofDiseases Source: AmericanHeartAssociation,Inc. Symptoms ofcardiacinsuffi ciency oranginapossible, evenatrest. Class IV:inabilitytocarryonanyphysicalactivitywithoutdiscomfort. Less thanordinaryactivitycausesfatigue,palpitation,dyspnea,angina. Class III:markedlimitationofphysicalactivity,patientcomfortableatrest. Ordinary physicalactivityresultsinfatigue,palpitation,dyspneaorangina. Class II:slightlimitationofphysicalactivity,patientcomfortableatrest. limitation ofphysicalactivity. Class I:nounduesymptomsassociatedwithordinaryactivityand Classification ofCardiacDisease Table 10.2 Moderate risk(mortality1 High risk(mortality5 Type ofCardiacCondition Table 10.1 Low-risk (mortality0.1 NYHA classifi cation 3or4 Severe ventricularfailure Coarctation oftheaortawith valvularinvolvement Marfan’s syndromewithaortic valveorrootinvolvement Severe aorticstenosis Pulmonary hypertension Cardiac arrhythmia moderate /mildmitralorpulmonarystenosis Mitral valveprolapse;aortic, mitral orpulmonaryregurgitation; Uncomplicated left-to-rightshunts Repaired congenitalheartdisease Uncomplicated aorticcoarctation Myocardial ischemia Moderate /mildaorticstenosis Severe mitralorpulmonarystenosis Unrepaired cyanoticcongenital heartdisease Systemic rightventricle/switch procedure Prosthetic heartvalve Single ventricle New YorkHeartAssociation(NYHA) Risk ofDeathorSevereMorbidityBasedon % –30 % –1 % –5 % ) % ) % ) The CriteriaCommitteeoftheNew

267 Obstetric Anesthesia 268 Coexisting Disease and Other Issues are anumberofquestionsandissuestoconsider(Table • Important careconsiderationsareindicatedinTable assessment andplanningteamforwomenwithmoreseveredisease. Anesthesiologistsmustbepartoftheantenatalmultidisciplinary General Considerations Discuss contraception • • Postdelivery management postpartum procedures Careful regionalorgeneralanesthesiaforoperativedeliveryand • • • • • • Intrapartum management Preparation forbothelectiveandnon-electivetimingofdelivery • Stabilization ofthediseaseandoptimizationphysicalcondition Consideration ofthromboprophylaxis Correction ofanemiaandinfection Fetal surveillance the disease Regular reviewoftheimpact ofthephysiologicalchangespregnancyon • • • Investigation toclarifydiagnosis andseverityofthepathophysiology workers intensivists, neonatologists,psychologists,andcommunityhealthcare obstetricians andmidwives,obstetricphysicians,anesthesiologists Team managementofthose with signiﬁ cant diseasebycardiologists, Early antenatalassessmentto determinethebestlocationfordelivery Pre-conception counseling Disease Table 10.3

contracted uterus,andthereliefofaortocavalcompression. induced sympatheticstimulation,autotransfusionofbloodfromthe Maximumcardiacstressoccursearlypostdelivery,duetolabor- medical management, watchforcardiacfailure high-dependency orcoronary careunitobservation decision whetherpushingcanbeallowedforvaginaldelivery ﬂ uid anddrugtherapies epidural analgesia monitoring and injectedprostaglandins) antibiotic prophylaxisaccordingtoguidelines medical therapy(e.g.,oxygen,oxytocicsgivenslowly,avoidergometrine e.g., beta-blockers,pulmonaryvasodilators,digoxin other speciﬁ echocardiography electrocardiography Principles ofCareforPatientswithCardiac c investigations c

10.3 10.4 ). , andthere

severe mitralstenosis). and failureofmedicalmanagement(for example,mitralvalvotomyfor labor ordelivery(Chapter3). molecular-weight heparinshasimplicationsforregionalblockand Substitution withunfractionatedheparinorthelonger-actinglow- avoided inpregnancyduetoteratogenicityandotherfetaleffects. monary hypertension,orapreviousthromboembolicevent,isusually patients foratrialﬁ brillation, mechanicalprostheticheartvalves, pul- Anticoagulanttherapywithwarfarin,whileindicatedinnonpregnant • • • • • How shouldhemodynamic or otheremergenciesbemanaged? What monitoringshouldbe used? What arethespecialconsiderations fortheabove? What methodofanesthesia forcesareandeliveryshouldberecommended? What methodoflaboranalgesia isadvisable? Where isthebestlocation for postpartumcare? What istheplanfordelivery, managementofdeliveryandthepuerperium? Where istheparturientbest delivered? What antenataltreatmentmust beinstitutednow? What investigationshavebeen andneedtobeperformed? and fetalcondition? What wasthestatusbeforepregnancy andwhatisthecurrentmaternal Whataretheanatomicalchangesandpathophysiologyofthiscardiacdisease? Woman withCardiacDisease Table 10.4

Rarely,cardiacsurgeryisrequiredbecauseofseveredeterioration viable, orafterdelivery. second trimester,whenorganogenesis iscompleteandthefetus Whennecessary,surgeryisnormally performedduringthelate patients thannonpregnant. Cardiacsurgicalmorbidityandmortality arehigherinpregnant (Table ered tohaveapoorbeneﬁ Antibioticprophylaxisagainstbacterialendocarditisisnowconsid- the ﬁ and investigation.Lessseverecongenitallesionsmaypresentfor Flowmurmursarecommon,butatypicalfeaturesmandatereferral be dismissed,astheymaypathological. tolerance, andedemamaybenormalforpregnancy,theymustnot Whilesymptomsofbreathlessness,fatigue,decreasedexercise rsttimeinteenageoryoungadultpregnancy. 10.5 ). Anesthetic QuestionsRelatedtothePregnant

t-riskratiobutisoccasionallywarranted

269 Obstetric Anesthesia 270 Coexisting Disease and Other Issues Mortality islow(1 and isthemostcommonvalvular lesion(aorticstenosisisrare). Mitralstenosismaybeisolatedor partofmixedvalvulardisease, Mitral Stenosis Specific CardiacConditions detail andmaintenanceofhemodynamic stability. • and either regionalorgeneralanesthesiacanbeusedsafely( Tables Cesareandeliveryisusuallyperformedforobstetricindications,and ∗ Oral: Amoxycillin 2g Cefazolin orceftriaxone1g clindamycin600mg Regimen forpenicillinallergy Vancomycin ifenterococcus is aconcern Cefazolin orceftriaxone1g Ampicillin 2gor Suggested intravenousregimen30–60minbeforetheprocedure • • Complex cyanoticcongenital disease Previous bacterialendocarditis Prosthetic heartvalvesorrepair materials infection orforcertaindentalprocedures Conditions whereprophylaxisisrecommendedinthepresenceof valve prolapse Not requiredforvaginalor cesarean deliveryinmostcases,includingmitral who haspositivebloodcultures Consider thediagnosisofendocarditis inanywomanwithacardiacdefect chorioamnionitis) infection thatcouldcausesignifi cant orrecurrentbacteremia(e.g., Required onlyforhigh-riskwomen havingcertaindentalproceduresorwith intrapartum antibioticprophylaxis When planningcare,specifi c instructionsshouldberecordedregarding Table 10.5 endorsed bytheAmericanCollegeofObstetriciansandGynecologists2008.

BasedonrecommendationsoftheAmericanHeartAssociationand

normocarbia andpumpﬂ ﬂ (10 Duringcardiopulmonarybypass,highratesoffetalmortality ow, maintaininghematocrit repaired diseasewithresidualdefects unrepaired cyanoticdisease 10.7 % –30 )byanexperiencedanesthesiologist,payingattentionto % Antibiotic ProphylaxisagainstEndocarditis ) canbereducedby:normothermicperfusion,pulsatile % )unlessassociated withNYHAClassIIIorIV, ows > 28 > 2.5L/min/m % , perfusionpressure 2 .

> 70 mmHg, ∗

10.6

• • • epidural analgesia isindicatedtoreducestress-induced tachycardia. Althoughthecardiovascularstress of laborisusuallywelltolerated, • or atrialfibrillation. Severemitralstenosis(valvearea<1cm nary hypertension,leadingtorightventricularfailure(Figure likely tobeassociatedwithlargeleftatrialsizeandsecondarypulmo- • Provide goodpostoperativeanalgesia • • Establish theblockslowly • • • • Maintain hemodynamicstability For regionalanesthesiaforoperativedelivery • • • Careful fl uid andhemodynamicmonitoring opioid byinfusionorpatient-controlledplussmallvolumeboluses initially followedbymaintenancewithlow-doseplainlocalanestheticand Spinal orepiduralopioid(with orwithoutlocalanestheticasanadjunct) For laborandchildbirth,regionalanalgesiaisbenefi in CardiacDisease Table 10.6

Managementinvolvescontrolofarrhythmiasandheartrate. Other anti-arrhythmic drugs or cardioversion may also be indicated. Otheranti-arrhythmicdrugsorcardioversion mayalsobeindicated. indicated topreventthrombusformation inthedilatedleftatrium. Inthepresenceofatrialfi brillation, anticoagulationwithheparin is pressure. Digoxinor Rapidheartratesreducediastolicfilling timeandincreaseleftatrial Atrialfi vasodilation withepiduralanalgesia minimize tachycardiaduetopainandconsidermildperipheral semi-upright ifheartfailure) epidural orslowincrementalspinalanesthesia) control maternalposition(avoidaortocavalcompression,nurse avoid single-shotspinalanesthesia(usesequentialcombined-spinal especially withshunts,severestenosisandcardiomyopathies avoid bolusesofoxytocinandergometrine avoid suddenchangesinpulmonaryorsystemicvascularresistance, prophylactic andtherapeuticvasopressor continuous bloodpressuremonitoringinmoreseriouscases avoid bolusesofoxytocinandergometrine continuous bloodpressuremonitoringinmoreseriouscases avoid intravenouspreloadingorexcessiveadministration • •

disease orcardiomyopathy titrated ephedrinetoavoidbradycardia,especiallyregurgitantvalvular heart disease stenotic valvulardisease,hypertrophiccardiomyopathyorischemic titrated phenylephrineorsimilartoavoidtachycardia,especiallywith brillationreducespreloadfromlossofatrialcontraction. Principles ofRegionalAnalgesiaandAnesthesia β -blockers maybenecessary. cial

2 10.1 ). )ismost

271 Obstetric Anesthesia 272 Coexisting Disease and Other Issues ened leftventricle. coronary diastolicﬁ lling, andinadequateoxygensupplytothethick- dispose tomyocardialischemiaorheartfailuredueinadequate Thislesionisrarebutserious.Painandlabor-inducedtachycardiapre- pathectomy (Table Aortic Stenosis anesthesia canbeused,withcaretominimizetheimpactofsym- ﬂ especially ifpreeclampsiaisalsopresent.Forthisreasonintravenous Patients areathighriskofdevelopingpulmonaryedemadelivery, stenosis: centralhemodynamicobservations. permission fromClarkSLetal.Laboranddeliveryinthepresenceofmitral (D) 4–6hourspostpartum;(E)18–25postpartum. Reprinted with second stageoflabor,15–30minbeforedelivery;(C)5–15postpartum; (PCWP) ineightparturientswithmitralstenosis.(A)Firststageoflabor;(B) Figure 10.1 • • a resultofthemild afterloadreductionandincreased blood volume. as mitralandaorticincompetenceoften improveduringpregnancyas Incontrasttostenoticvalvulardisease, regurgitantcardiaclesionssuch Valvular Incompetence • 152(8):986. uid volumesshould beminimized.

Forcesareandelivery,eitherepiduralorcombinedspinal-epidural Bradycardiamayreducecardiacoutputandcauseheartfailure. Valvereplacementisassociatedwith highfetalloss. during thesecondtrimesterifmedical therapyhasfailed. Withseverestenoticlesions,balloonvalvuloplastyisanoption

PCWP (mmHg) 10 20 30 40 Intrapartum changesinpulmonarycapillarywedgepressure 0 5 1 6 7 4 8 3 A

10.6 ). 2 BC Time D Am JObstetGynecol. 1985;

• undesirable chronotropiceffects)arerecommended. phenylephrine) ratherthanephedrineforvasoconstriction(toavoid • • trolled fashion,avoidingvolumeoverload andbradycardia. regional blockischosenitshouldbe establishedslowlyandinacon- anesthesia (EA)mayleadtosudden cardiovascularcollapse,soif shot spinalanesthesia(SA)andrapidestablishmentofepidural in mitralstenosis,ormyocardialischemiaaorticstenosis.Bothsingle- increases inheartrateandafterloadmayprecipitatepulmonaryedema merits ofregionalversusgeneralanesthesiacanbedebated.Sudden Intheabsenceofhighlevelsevidenceregardingoutcome, Regional orGeneralAnesthesia inValvularDisease? • • • venous ﬂ uid, andvasoactivedrugadministrationwith Monitoringofﬂuid balancetomaintainnormovolemia,judiciousintra- anesthetic/opioid combinationsdeliveredslowlybyinfusion)isideal. analgesia duringlabor(usingopioidsorlowconcentrationlocal Inrheumaticvalvulardisease,goodpainreliefwithepiduralorspinal Labor andAnestheticManagementinValvularDisease • • • •

Asuggestedapproachis: Ergotuterotonicsandinjectedprostaglandinsarebestavoided. eral vasodilatationandtachycardia. Oxytocinshouldbedeliveredslowlybyinfusion,toavoidperiph- pulmonary edemainthepresenceofseveremitralstenosis. Furosemidemaybenecessarytoreducetheriskofpostpartum asequentiallowspinal-epiduralorslow EAapproach if required,isadvisableforNYHAClassIIIorIVpatients. remifentanil orfentanyl,pluscontrolofheartratewitha (IV) fentanylorpatient-controlledintravenousanalgesiawith (pethidine) isunsatisfactoryandmaycausetachycardia.Intravenous Ifepiduralanalgesiaiscontraindicated,parenteralmeperidine allows controlleddeliverywithoutrepeatedValsalvamaneuvers. eral vascularresistance,maintainsnormalmaternalheartrate,and Thisminimizestheconsequencesofasuddenreductioninperiph- optimizationofmaternal oxygenation Mitralvalveprolapseiscommon,andregurgitationusuallytrivial. plan foranticoagulationisimportant. Atrialﬁ brillation iscommonwithseveremitralregurgitation,anda serious reductionincardiacoutput. decrease leftventricularvolume,increaseregurgitation,andcausea Withsevereregurgitation,hypovolemiaortachycardiamay

α -agonists

β -blocker

(e.g., (e.g.,

its

273 Obstetric Anesthesia 274 Coexisting Disease and Other Issues • thy, responsestoanestheticagentsmustbeconsidered. Ifusinggeneralanesthesiaforsevereaorticstenosisorcardiomyopa- • • may causeanabruptfallincardiacoutput. are suitableandcanbemanagedmoreorlessroutinely.Bloodloss cal statusisstableduringpregnancy,regionalanalgesiaandanesthesia disease issatisfactorilycorrectedsurgicallyinearlychildhood.Ifphysi- opmental abnormalitieswithgoodprognosis,especiallyifcomplex Theacyanoticgroupincludesavarietyofcardiacstructuralanddevel- Acyanotic andCyanoticCongenitalHeartDisease • • • niﬁ atrial septaldefect,andventri cular septaldefects).Thesevary insig- left-to-right shunts(suchaspatentductusarteriosis,ostiumsecundum plexity. Somearecyanotic(e.g.,TetralogyofFallot)andothersinvolve dissection, andvalvulardisease. tal heartdiseaseexceedthosefromischemicdisease,aortic Indevelopedcountries,maternalcardiacdeathsfromadultcongeni- Severe CongenitalHeartDiseaseandPulmonaryHypertension • • •

Therearealargenumberofcongenitaldisordersvaryingcom- cardiacoutputmonitoringshouldbeconsidered. analysis directarterialbloodpressuremonitoringandregulargas management ofhyperviscosity. others requireaggressivecontrolofphysiologicalvariablesand Somedisordersmayrequireonlyantibioticprophylaxis,while canceandrequireindividualassessment. Volatileanestheticsreducesystemicvascularresistance. be avoided. Nitrousoxideincreasespulmonaryvascularresistanceandshould mized (haveinotropicdrugsavailable). magnesium, and/orvasodilators),andmyocardialdepressionmini- Theresponsetointubationshouldbeattenuated(withopioids, increased. Supraventriculararrhythmiasare poorly toleratedasshuntis defects ﬁ Thesecundumatrialseptaldefect isoneofthemostcommon to-left shunting. sis inpregnancy,despiteparoxysmal arrhythmiasandpossibleright- lesion maynotpresentuntillatechildhood, buthasagoodprogno- valve withatrializedproximalportionoftherightventricle.This Ebstein’sanomalyisthedownwarddisplacementoftriscuspid rstdiagnosedinpregnancy.

right bundlebranchblock,mayreﬂ ect this(Figure with orwithoutcardiacfailure.Electrocardiogram(ECG),suchas pressure greaterthan30/15mmHgandrightventricularhypertrophy, Thisdiseaseisofspecialconcern,anddeﬁ ned aspulmonaryartery Pulmonary Hypertension disease withoutEisenmenger’ssyndrome. poor prognosticindicatorsforthefetusinmaternalcyanoticheart • hydration. the respiratorydepressanteffectsofsystemicopioids,andinadequate resistance, sopotentialhazardsincludepainduringprolongedlabor, hypercarbia, andacidosisincreasepulmonaryarterypressure Pre-pregnancypolycythemiaoroxygensaturation<85 • axis, andevidenceof rightventricularpressureoverload(V1–2). hypertension, showingsinusrhythmwith rightatrialPwaves(V1),aninferior Figure 10.2 •

Pulmonaryhypertensionmaybe: • • tive age Primary — lesions. aortic coarctationareotherexamplesofacyanoticcongenital Correctedventricularseptaldefect,patentductusarteriosusand severe hypoxemiafromrespiratorydisease(e.g.,cysticﬁ syndrome; seeFigure Secondary —

Mortalityisveryhigh(30 tolerated ance (e.g.,hypovolemiaorhypoxemia)aregenerallyverypoorly Increasesinpulmonary,andreductionsystemic,vascularresist- 1V 3V 5V6 V5 V4 V3 V2 V1 IIIaRaLaVF aVL aVR III II I

Electrocardiograph ofaparturientwithpulmonary a raredisorderthatpresentsinwomenofreproduc- due toreversalofleft-to-rightshunts(Eisenmenger’s 10.3 ),prolongedseveremitralstenosis,or % –50

% ).

10.2 % ).Hypoxia, brosis) onairare

275 Obstetric Anesthesia 276 Coexisting Disease and Other Issues (Figure to balancingfactorsaffectingpulmonary andsystemicresistance sia andanesthesiarequireslowtitration andintensemonitoring from hemorrhage,infection,andthromboembolism. Regionalanalge- for cardiovascularstability,buthas disadvantagessuchasmorbidity • • • Generalanesthesiaforcesarean delivery (Table • if relevant,andthecurrentconditionofheart. thorough understandingoftheoriginaldisease,correctivesurgery Anestheticmanagement(whetherregionalorgeneral)requiresa Figure 10.3

controlled epiduralanalgesia. nance maybewithlocalanesthetic-opioidinfusionorpatient- stability canbeachievedusingepiduralorspinalopioids;mainte- Laborepiduralanalgesiaisusuallyrecommendedandhemodynamic cated (Table Prophylaxisagainstbacterialendocarditismayornotbeindi- The implications of anticoagulation must be considered (Chapter 13). Theimplicationsofanticoagulationmustbeconsidered(Chapter13). quent paradoxicalembolism. avoided, becauseofthepossibilityIVairinjectionwithsubse- placement ishazardousandairinintravenousinfusionlinesmustbe Inthepresenceofashunt,loss-of-resistancetoairforepidural 10.4 ). Other pulmonary vascular resistance(PVR) Increasing pulmonary Factors affectingcardiacshunt. Nitric oxide vasodilators Decreasin 10.5 ). Hypoxia Acidosis Oxygen g PRDecreasin PVR Right-to-left

shunt vascular resistance(SVR) Increasing systemic anesthesia Regional Hypovolemia Acidosis Infection Surgical stress Pain, anxiety Sympathomimetics g SVR

10.7 )mayallow

• • • • • • • Provide goodpostoperativeanalgesia • • Stabilize hemodynamicsatextubation Choose themostappropriate neuromuscularblockingdrug Maximize oxygenation cardiac andvasculareffects Choose themostappropriate inhalationalanestheticwiththeleastadverse resistance) Consider whethernitrousoxide issuitable(increasespulmonaryvascular • • • intubation Obtund thesympatho-adrenal “stressresponse”tolaryngoscopyand extubation. Be vigilantforhemodynamic changes, especiallyatintubationand hypertrophic cardiomyopathy,andpoorlycontrolledcardiacfailure. anesthesia ratherthanregionalforsevereaorticstenosis, Perform anindividualrisk-beneﬁ t assessment,butconsidergeneral Disease Table 10.7

echocardiography maybehelpfulinspecifi Thermodilutionpulmonaryarterycathetersandtransesophageal pulmonary pressures. for thedetectionofhypoxemiafromshuntreversalorincreased Arterialoxyhemoglobinsaturationisavaluablenoninvasivetool course. after anapparentlyuncomplicated intra-andearlypostpartum Intensivepostpartumcareiswarranted, asdeathmaystilloccur duced forpulmonaryvasodilationafter delivery. implications forcentralneuraxialblock. Bosentanmaybeintro- bearing inmindthatplateletdysfunction maybeinduced,with PGI2) orsildenafi l maybetestedtodeterminepatientresponse, solized andintravenousprostaglandins(epoprostenol,iloprostor Pulmonaryvasodilatorssuchasnitricoxide,100 block anti-infl ammatory drugsifnorenalimpairmentorcardiacfailure abdominal wallregionalanalgesiae.g.,transversusabdominisplane(TAP) adjuncts suchasacetaminophen(paracetamol)and/ornonsteroidal patient-controlled intravenousanalgesiawithmorphine fentanyl 2mcg/kg esmolol 0.5mg/kg vasodilators, e.g.,glyceryltrinitrate(nitroglycerin)250–500mcg 5–10 mcg/kg;alfentanil10–20mcg/kg magnesium 40–60mg/kgpost-induction appropriate dosesofopioideg.remifentanil1mcg/kgover60s;fentanyl Principles ofGeneralAnesthesiainCardiac

csituations.

% oxygen,aero-

277 Obstetric Anesthesia 278 Coexisting Disease and Other Issues smoking, hypertension,diabetes).Mortalityishigh(30 p. 38,Copyright(1996),withpermissionfromElsevier. pulmonary hypertension:reviewoftheliteratureandclinicalpresentation, Vol. 5 , KhanMJ,Anestheticconsiderationsforparturientswithprimary per minute. Reprinted fromthe pressure (mmHg);PAP,pulmonaryarterybpm,beats with primarypulmonaryhypertension.CI,cardiacindex(l/min);AP,arterial Figure 10.4 in women Mostcasesofacutemyocardialinfarctionoccurinthethirdtrimester Myocardial IschemiaandAcuteCoronaryDissection several daysisspeciﬁ are unchangedduringpregnancy,and soarisewithin4hours,lasting isoenzyme ofcreatininekinase(CK-MB), maternaltroponinIlevels make interpretationmoredifﬁ cult. However, unlikethemuscle-brain such assinustachycardia,leftaxis deviation andST-Tchangesmay under regionalanesthesiaforcesarean delivery,changesintheECG closer theinfarctoccurstotermgestation). Duringpregnancyand Heart rate (bpm)/PAP (mmHg) 100 110 120 140 130 20 30 60 80 40 50 70 90 10 0 AP CI > Hemodynamic changesduringcesareansectioninaparturient 35yearsofagewhohavetypicalriskfactors(obesity, 1/8108 1/8107 3/2109 1/0110/70 110/60 140/90 130/82 120/78 110/88 130/80 118/78 3.65 –15–30 1530456075900 cformyocardialinjury. Epidural block 5.0 International JournalofObstetricAnesthesia, Time ( min 5.6 Incision ) Delivery 4.0

End of surgery % ,risingthe Heart rat Heart PAP e • • arrhythmias (Figure Duringpregnancy,benignarrhythmiasarecommonandserious Arrhythmias • • • • • • • • • and delivery,supplementaloxygenisrecommended. tion duringpregnancy.Regionalanalgesiaisrecommendedforlabor Vaginaldeliveryappearssaferthancesareanaftermyocardialinfarc- •

Medicaltherapiesinclude: by ratecontrolwith digoxin,anduseanticoagulation if necessary. thyrotoxicosis andotherheartdisease mustbeexcluded.Manage Newonsetatrialfi brillation isworrying;mitralvalvulardisease, Nitrates, Aspirinand/orclopidogrelforunstableanginaoracuteinfarction Heparinanticoagulation (Table Forgeneralanesthesia,amodifiedtechniqueshouldbeused preferable toephedrine. α • • or continuousspinalanesthesia)issuitableforoperativedelivery. Regionalanesthesia(incrementalepidural,sequentialspinal-epidural be helpful. are prudentandesophageal/transthoracicechocardiographymay Monitoringoftemperature,oxygenation,bloodpressureandECG thetic, andintravenousclonidine30mcgtotreatshaking). intravenous fluids, surfacewarm,useneuraxialopioidwithlocalanes- Increasesinoxygendemandduetoshiveringshouldbeavoided(warm atrial fi risk ofmaternalhemorrhage Thrombolysis(retaplase,alteplase)isassociatedwithaveryhigh acute syndromes) Percutaneouscoronaryintervention(thepreferredmanagementof • tachycardia). ciated withfetaleffects(lidocainemay bepreferableforventricular Someanti-arrhythmicssuchasphenytoin andamiodaroneareasso-

1-agonistvasocontrictors(e.g.,phenylephrine,metaraminol)are rably influences theendocardialtoepicardialbloodfl Highthoracicepiduralanalgesiaforpostoperativefavo- sympathectomy. to thecardiovascularconsequencesofrapiduncompensated Spinalanesthesiaorrapidepiduralarenotideal,due clopidogrelprecludesregionaltechniquesforaweek brillationorfl 10.7 ). β

-blockers andcalcium-channelantagonists β -blockersarepreferredforacute rate controlof 10.5

utter. ) arerare.

ow ratio.

279 Obstetric Anesthesia 280 Coexisting Disease and Other Issues • • • arrhythmias duringpregnancy. Reprinted withpermissionfromRotmenschHH,etal.Managementofcardiac Figure 10.5 MostcasesareduetoMarfan’ssyndrome. Aortic Dissection

because fetalheartratechangesaretransientandbenign. (starting at50–100joulesunderappropriategeneralanesthesia) tricular arrhythmiacanbetreatedwithdirectcurrentcardioversion Hemodynamiccompromisefromthesuddenonsetofanysupraven- vers andadenosine. Treatparoxysmalsupraventriculartachycardiaswithvagalmaneu- aortic dissection,especially inlatepregnancy. lapse orregurgitation,aorticrootdilatation andregurgitation, (ﬁ brillin genemutations), andisassociatedwithmitralvalvepro- Thisdiseaseisanautosomaldominant diseaseofconnectivetissue continuationoftherapy forindication • Re-evaluateperiodically safetothefetus • Usedrugsknownas required • Usesmallestdose Treat underlyingdisease Organic heartdisease Drug therapyonlyif arrhythmias persist Absent Management ofcardiacarrhythmiasduringpregnancy.

Drugs. 1987;33:628. Cardiac arrhythmia Antiarrhythmic therapy onlyif arrythmias underlying persist cause Treat cigarettesmoking;drugabuse • arrhythmogenicdrugs;alchohol,caffeine; • electrolytedisturbance • pulmonarydiseaseandthyroid Rule outothercauses,including

Normal cardiovascularstatus

threatening tomother Drug therapyonlyif symptomatic or arrhythmias are Present or fetus

• in youngadulthood. involving amutationatthemyosinheavychaingene.Itusuallypresents subaortic stenosis)isautosomaldominantwithvariablepenetrance, Thisdisorder(commonlytermedHOCMoridiopathichypertrophic Hypertrophic ObstructiveCardiomyopathy • induced) butlow-output cardiacfailurewithout apparent cause Cardiomyopathyhasvariousetiologies (e.g.,viralmyocarditis,drug- Peripartum CardiomyopathyandHeart-Lung Transplantation ephedrine canbeavoided. successfully, anddirect-actingvasoconstrictors shouldbeusedsothat careful slowlytitratedepiduralandgeneral anesthesiahavebeenused risk-beneﬁ t assessmentisnecessaryforoperativedelivery.Both Direct arterialbloodpressuremonitoringishelpful.Anindividual ery isvaluabletoreducecatecholaminereleaseinresponsepain. Epiduralorcombinedspinal-epiduralanalgesiaduringlaboranddeliv- • • tachycardia). arrhythmias (especiallythelossofatrial“kick”withﬁ Managementisdirectedtowardavoidanceofhypovolemiaand • • warrant: diameter greaterthan4cmorprogressivedilatationduringpregnancy Inadditiontoprepregnancycounseling,patientswithanaortic • •

Epiduraltechniquesforlabororoperativedelivery. tive management. episodic ventriculartachycardia/fi brillation andrequireperiopera- Implantedautomateddefibrillators maypreventsudden deathfrom and ventricularvelocity). diastolic ventricularfi β edema. death mayoccurduetoventriculararrhythmiasandpulmonary HOCMusuallyhasagoodoutcomeinpregnancy,butsudden arterial pressure. ventricular volume,increasedejectionvelocity,orlow left ventricularoutflowobstructionthatisworsenedbylow metric hypertrophyoftheinterventricularseptumproduces HOCMsharessimilaritieswithaorticstenosis,inthatanasym- Aggressivecontrolofhypertension Frequent transthoracic echocardiography to estimate aortic root size Frequenttransthoracicechocardiographytoestimateaorticrootsize Treatmentwith -blockersareusefultoreducetachycardia(thusincreasingend- β -blockers

llingandreducingmyocardialoxygendemand

brillation or

281 Obstetric Anesthesia 282 Coexisting Disease and Other Issues avoided. maintained, andlocalanestheticcontainingepinephrine(adrenaline) sant effectsofanestheticagentspredominate.Preloadmustbe ated by and ephedrine.Theeffectsofdirect-actingdrugsmaybeexagger- vagal tone,andisunaffectedbyindirect-actingdrugslikeatropine macokinetic changes). cyclosporine, whichappearssafeduringpregnancy,duetothephar- therapy mayneedadjustment(forexample,anincreaseddoseof between graftrejectionandinfectionrisk,immunosuppressive and maternaloutcomeisgenerallygood.Abalancemustbestruck increase thelikelihoodofanestheticinvolvement,althoughobstetric tion, highratesofhypertension,preeclampsiaandprematurelabor dysfunction. Cardiac transplantationoffersanalternativeforthosewithpersistent induction ofgeneralanesthesia. boembolism, severehypotension,bradycardiaandcardiacarrestat of globalheartfailure.Otherdramaticsymptomsincludemuralthrom- (60 cies, oftenpresentingduringthethirdtrimesteror,mostcommonly (“peripartum cardiomyopathy”)occursin12,000–4,000pregnan- (incidence about 6 Diabetesisthemostcommonmetabolic disorderinpregnancy Theprognosisisvariable,andapproximately50 • • •

Diabetes Thedenervatedhearthashigherrestingrateduetolossof Intherarecaseofsuccessfulpregnancyaftercardiactransplanta- Theprincipaltreatmentisthatofcardiacfailureandanticoagulation. Inperipartumcardiomyopathy,womenpresentwiththerapidonset available. tropes available.Intensivecareorcoronarysupportmustbe Invasivemonitoringisindicated,withvasodilatorsandino- ate tohighdoseopioidmethods(Table recumbent positionmayrequiregeneralanesthesia,usingamoder- Severelydyspneicpatientswhocannottolerateasupineorsemi- delivery (avoidingsingle-shotspinalanesthesia)appearssafe. beneﬁ Mildreductionofafterloadusingappropriateregionalanalgesiais % ), postpartum. t duringlabor,andwell-managedregional block forcesarean β -adrenoreceptorupregulation,andthemyocardialdepres- % intheUnited States) andisincreasing 10.7 ). % recoverfully.

• • line proteinuria.Incontrast,fetalmorbidityisverycommon. preeclampsia alsomorecommon,especiallyamongthosewithbase- insulin. betes isoftenmanagedwithdietcontrol,butsomewomenrequire hormonal changes(gestationalorClassAdiabetes).Gestationaldia- dependent type1)orariseduringpregnancyduetophysiological in prevalence.Itmaybepresentpriortopregnancy(usuallyinsulin- • • • • • and acidemia. emia andhyperinsulinemia,whichcaninturnleadtofetalhypercarbia Elevated intrapartummaternalglucoselevelsresultinfetalhyperglyc- Duringlabor,continuousmaternalbloodglucosecontrolisimportant. cate anestheticmanagement. delivery; gestationaldiabeticsareoftenobese,whichcanalsocompli- careful evaluationoftheairway,duetoincreasedriskurgent Theusualpreoperativeevaluationofthediabeticshouldincludea Management lactogen. Among gestational diabeticswhohavebeen managedwith rapidly immediatelyafterdeliverydue tothefallinhumanplacental Inthediabeticparturient,insulinrequirements areincreasedbutfall

Ingeneral,maternalrisksarefew,althoughobesityiscommonand Therearehigherratesofcongenitalabnormality. Neonatalhypoglycemiaisverycommon. lung maturation)aremorecommon. Intrauterinegrowthretardationandpretermdelivery(anddelayed instability, anddelayedgastricemptying. because ofitsimplicationsforregionalanesthesia,hemodynamic Diabeticsshouldalsobeassessedforautonomicneuropathy and diabetesinchildhoodoradolescence. Consequences includeshoulderdystociaatdelivery,andobesity of hyperglycemia,hyperlipidemiaandelevatedaminoacids. Macrosomiaismorecommonwithpoormaternalcontrolbecause trose infusionshouldbestarted(Table Ininsulin-dependentdiabetics,anintravenousinsulindripanddex- 4 hoursduringlabor. InClassA1parturients,bloodglucoseshouldbecheckedevery2to toring isnecessary. After delivery,insulinrequirements fall quickly,socontinuedmoni- adjusted tomaintainmaternalglucose between90and110mg/dl. be checkedviaﬁ ngerstick hourly,andtherateofinfusions

10.8

). Bloodglucoseshould

283 Obstetric Anesthesia 284 Coexisting Disease and Other Issues sia/anesthesia duringlabor. requirements usuallyrapidlyreturntoprepregnancylevels. insulin, thisisusuallynolongerrequired.Intype1diabetics,insulin severity ofpulmonarydisease.Dyspnea isacommonsymptomduring omy duringpregnancy(Chapter3) canalterthepresentationand Thesignifi cant changes thatoccurinpulmonaryphysiologyandanat- • • • management easier. time isbest,asthisminimizesthefastingperiodandmakesinsulin only nonglucose-containingfluids should beused. Ifafl • • > 220 181–220 141–180 100–140 <100 (mg/100 ml) Glucose Labor Based onFingerStickGlucoseMeasurementsduring Table 10.8

Pulmonary Disease Diabetesintheparturientisarelativeindicationforregionalanalge- Forscheduled(elective)cesareandeliveries,anearlymorningstart of surgicalanesthesiaifnecessaryurgently. Afunctioningepiduralcatheterprovidesarouteforrapidinduction insulin requirements. lamines, whichcandecreaseuteroplacentalperfusionandincrease Epiduralanalgesiahasbeenshowntodecreasecirculatingcatecho- Eitherspinalorepiduralanesthesiaissuitable. arrival, andinsulindextroseinfusionsbegunifnecessary. Bloodglucoseshouldbecheckedpreoperativelyanduponpatient hypoglycemia. Afterdelivery,theinfantmustbeobservedandmonitoredfor uid loadisconsideredbeforeinstitutionofregionalanesthesia, Suggested InsulinandGlucoseInfusionRates

(units.hr) Insulin dose 2.5 2.0 1.5 1.0 0

125ml.hr Intravenous ﬂ Normal saline Normal saline Normal saline D5 LR D5 LR

uids

• complicating upto6 Asthmaisthemostcommonpulmonarydiseaseofreproductiveage, Asthma (Table ated withthepregnantcondition. increased mortalityfromadultrespiratorydistresssyndromeassoci- loss. TheH1N1infl uenza pandemicof2009illustratedthemarkedly virus) areseriousdiseasesthatleadtopretermdeliveryorpregnancy nosa andtuberculuspneumoniainthosewithhumanimmunodefi terial pneumonia(streptococcuspneumoniae,pseudomonasaerogi- pregnancy, bothviral(infl uenza, mycoplasmaand legionella)andbac- cardiac pathologies,soworseningsymptomsmustbeinvestigated. pregnancy, butoccasionallyisaresultofundetectedpulmonaryand Physiologic Neonatal Obstetric Table 10.9

Itisrecommendedthatsmokingbeavoidedduringpregnancy Inpartbecauseoftheimpairedcellularimmuneresponseduring ual case,butmayfollowarecurrentpattern. approximately equalproportions.Itisunpredictableintheindivid- Itremainsunchanged,improvesorworsensduringpregnancyin Increased carboxyhemoglobinconcentrationandloweroxygenafﬁ Small airwaynarrowingandclosure Hyperactive airways Increased mucusanddecreased mucusclearance Childhood cancers Learning disorders Sudden infantdeathsyndrome Sleep disturbance Impaired suckling Increased incidenceofplacentalabruption Intrauterine growthretardation/lowbirthweight Preterm delivery Early pregnancyloss Hepatic enzymeinduction Impaired immuneresponse 10.9 ). Adverse EffectsofSmokingDuringPregnancy % ofpregnanciesintheUnitedStates.

nity ciency

285 Obstetric Anesthesia 286 Coexisting Disease and Other Issues • • • • • • • have multipleetiologies(Table is usuallypreferabletoavoidairwaymanipulation. severe asthmatic,orduringanacuteexacerbation,regionalanesthesia disease, andundertreatmentisanissue.Ifanesthesiarequiredina Cesareandeliveryratesarehigherinwomenwithmoderatetosevere • • respiratory distresssyndrome1in3,000–6,000;mortality40 Theseconditionsareuncommontorareduringpregnancy(adult Distress Syndrome Pulmonary Edemaand /or AdultRespiratory may reducetheriskofchildhoodatopy. receptor antagonistsappearsafeduringpregnancy.Breast-feeding methylxanthines, chromoglycatesandpossiblyleukotriene- • piratory care,ﬂuid restrictionanddiuresis. during nonpregnancy,beingtreatmentofthedisorder,supportiveres- Inhaled

emia, treatwithshort-actinginhaled Inthepresenceofacuteintraoperativebronchospasmandhypox- Regularfetalmonitoringshouldbeimplemented. restricted ﬂuid managementvital. Thelowercolloidosmoticpressure ofpregnancymakescautious β Bronchodilatewithpreoperativeinhaledornebulized drugs. Avoidtriggerssuchasaspirinandnonsteroidalanti-inﬂ ammatory prostaglandin-F Avoiddrugsthatarebronchoconstrictors(e.g.,ergotuterotonics, and air-trapping. preterm delivery,orhaveacuteexacerbationsofbronchospasm nancy maydevelophypoxiathatcontributestofetalmorbidityor Severeasthmaticswithincreasedairwayhyperactivityduringpreg- hospitalization. Approximately10 Thepatientshouldbenursedupright withlefttiltifpossible. to nonpregnantpatients. Oxygenrequirementsareincreasedinpregnantpatientscompared indicated. thetic duringmaintenanceandinductionwithketaminemaybe general anesthesia,anincreasedconcentrationofvolatileanes- -sympathomimetics, inhaledsteroidsandotherdrugs. β 2

-agonists,inhaledandoralsteroids,anticholinergicdrugs, 2α

, morphine). % ofwomenwithseverediseasewillrequire

10.10

). Managementissimilartothat β

2 -sympathomimetics; ifusing

)and • essary for : Neuroanesthesiaisrarelyrequiredduringpregnancybutmaybenec- Neuroanesthesia Neurosurgery andNeurologicalDisease • • • • • applied. neuroanesthesia andobstetricanesthesiamustbereconciled Intheabsenceofevidence-basedguidance,principles Fluid administration Cardiac disease Preeclampsia Infection Aspiration ofgastriccontents Woman Table 10.10

craniotomyforspace-occupyingmassesorheadinjury diagnosticortherapeuticinterventions trauma(whichcomplicates6 spinalsurgery cause ofincidentalmaternaldeathandmorbidity) ranial procedures). acceptable, placethewomanin lateralpositionforlongintrac- Maintaineffectivepelvictiltafter20 weeksgestation(ifsurgically and half-livesofsomeanticonvulsant drugs). erative phase(pregnancychangesthe clearance,unboundfractions, Anticonvulsanttherapyshouldbemaintainedthroughtheperiop- Transfusion-related acutelung injury(TRALI) Associated withoxytocicdrug infusion Associated withtocolyticdrug infusion Over-correction ofhypovolemia Severe mitralstenosis Heart failure Inﬂ uenza andotherviraldisease Systemic sepsis

Etiology ofPulmonaryEdemainthePregnant

% –7 % ofpregnanciesandisaleading

287 Obstetric Anesthesia 288 Coexisting Disease and Other Issues with raisedintracranial pressureisshowninTable and minimizeincreasesincerebral blood ﬂ ow and ICP)inawoman Anapproachtogeneralanesthesia forcesareandelivery(tomodify Anesthetic Techniques • • • • • • • • • • Withrespecttoanesthetictechnique: • • •

tamines, droperidolandserotonin Safe,nonsedatingantiemeticdrugsincludemetoclopramide,antihis- be used. Isonatremic,isotonicandglucose-freeintravenousfl uids should urinary bloodflow, andincreaseplasmasodiumconcentration). (fetal hyperosmolalitycanreducefetallungfluid production,reduce tion, lowtidalvolumes,andfurosemideormannitol0.25–0.5mg/kg Intracranialpressurecanbecontrolledwithaslighthead-upposi- operatively shouldbesuspectedifabdominal painoccurs. Fetalmonitoringmaybeappropriate, andtheonsetoflaborpost- cesarean deliveryorobstetrichemorrhage. tional radiology,andrequiresreversalintheeventofemergency Intravenousheparinmayhavebeenused,especiallyforinterven- ture laboriftheriskoffetallossishigh. anti-infl Postoperativeprophylactictocolysis(nifedipineornonsteroidal bral oxygenmetabolicrate. Volatileanestheticssuchasisofl urane orsevofl urane reducecere- mild metabolicacidosis. Apropofolinfusion,whenusedformanyhours,isassociatedwith enhances rapidwakening. attenuated; remifentanilispopularasitveryeffectiveandalso Intheoperatingroom,responsetolaryngoscopyshouldbe range (PaCO Maintainmaternalarterialcarbondioxidetensioninthelownormal emboli. Usecentralvenousaccessforinotropesoraspirationofair (ICP) israised. maintain highnormalbloodpressureiftheintracranial (aiming topreservecerebralanduteroplacentalperfusion), Havealowthresholdforintraarterialbloodpressuremonitoring Monitor and preserve body temperature (avoid induced hypothermia). Monitorandpreservebodytemperature(avoidinducedhypothermia). the maternaloxyhemoglobindissociationcurve. ventilation-induced uterinearteryvasoconstrictionandleft-shiftof ammatory drugs)isgenerallyonlyusedtopreventprema-

2 25–32mmHg)toreduceICP,whileavoidinghyper-

3 receptor(5-HT3)antagonists.

10.11 .

brain herniationorintracranialhemorrhage. ICP ishigh,duralpuncturedangerous becauseitmayprecipitate alert, cooperative,andhasnormal intracranial pressure.However,if tion, regionalanesthesiacanberecommendedprovidedthepatientis • • for observationorcontinuedventilationmaybeappropriate Admission toaneurosurgicalhigh-dependencyunitorintensivecare • Antithromboembolic stockingsandcalfcompressionperioperatively • • Avoid venoconstrictors • Oxytocin byinfusiononly • • Avoid nitrousoxide if normalICP Total intravenousanesthesia withpropofol(inhalationalanestheticssuitable • Pre-induction opioid Cesarean DeliveryforaPatientwithRaisedICP Table 10.11 • • • Postoperative analgesia Prophylactic antiemetics

Ifcesareandeliveryisscheduledpriortoaneurosurgicalinterven- EpiduralinjectionwillincreaseICP, at leasttransiently. shunt. types ofspinalsurgeryandinthepresence ofventriculoperitoneal Epiduralandspinaltechniqueshave highfailureratesaftersome the potentialhemorrhagiccomplications discuss heparinthromboprophylaxiswiththeneurosurgeonbecauseof contraindicated forfetalreasons neuraxial opioidssuitableafterspinalsurgery e.g., ergotuterotonicsorprostaglandinF hypotension, tachycardiaandincreaseincardiacoutput to minimizebolus-inducedcardiovasculareffectssuchastransient metabolic rate,impairsautoregulation expands airbubbles elevates ICP,increasescerebralbloodﬂ ow andcerebraloxygen 60 mg/kg titrated infusion,withorwithoutpost-inductionIVmagnesium e.g., intravenous(IV)remifentanil1mcg/kgover60seconds then cyclooxygenase and acetaminophen) avoid tramadol multimodal analgesia(localanestheticinﬁ ltration orscalpblocks,opioids Suggested GeneralAnestheticTechniquefor 2 (COX-2)inhibitorsdonot increase bleedingbutmaybe 2 α

289 Obstetric Anesthesia 290 Coexisting Disease and Other Issues months areassociated withhigherratesofrelapse(approximately 30 multiple sclerosisislargelyunaltered, butthefi rst 3postpartum severely affectedindividualsfrequently conceive.Duringpregnancy, over time.Itisnotuncommoninwomen ofreproductiveage,andless • • • • • ized byepisodicsymptoms,thenfi Thisdemyelinatingdiseaseofthecentral nervoussystemischaracter- Multiple Sclerosis not contraindicated. dural andspinalanalgesiaoranesthesia,thatthesetechniquesare preexisting neurologicaldiseasesusuallyexperienceuneventfulepi- Dataarelimited,butthelargestseriessuggestthatmostwomenwith • neuraxial regionalanalgesiaandanesthesia.Problemsinclude: Manyneurologicaldisordersimpactoneithertheeffi cacy orrisksof Neurological DiseaseandAnesthesia

may causematernalhypotension. nimodipine tocontrolintracranialvasospasmappearssafe,but complications. Magnesiumsulfateissafeandsuitableforuse, not beincreasedgiventheriskofeclampsiaandothercerebral in preeclampticpatients,themeanarterialbloodpressureshould volume and,toalesserextent,redcellmass,arebenefi require reassessmentduringpregnancy.Theincreasedplasma ples of“hypertension,hypervolemiaandhemodilution”may 3–6 daysaftertheinitialbleeding,andrecommendedprinci- Cerebralvasospasmcancomplicatesubarachnoidhemorrhage Increasedriskofneurologicaldefi spinal bifi Increasedriskofinadvertentduralpunctureorcordinjury(e.g., Exaggeratedorabnormalresponsestodrugs(e.g.,multiple neurofi Potentialtraumatolesions(e.g.,vascularmalformations, Abnormalautonomicresponses(e.g.,spinalcordinjury) muscular atrophy) neuropathies suchasCharcot-MarieToothdiseaseorperoneal amyotrophic lateralsclerosis,polio,hereditarymotorandsensory Technicaldiffi broma) da)

culties(e.g.,scoliosis)

xed deﬁ xed

cits(e.g.,spinalcanalstenosis)

cits andincreasingdisability cial

sclerosis,

— but %

). ). • • • • • should takeanumberofsteps. consent forregionaltechniquesduringpregnancy,theanesthesiologist Ideally,thesewomenshouldbeseenatanantenatalclinic.Inobtaining • • • crine responsesresultinfeaturessuchas: • process. It isthusveryimportanttoengagethepatientindecision-making absence ofsupraspinalinhibition(Figure to visceralstimulus(especiallylaborandperinealdistension)inthe T related nociception. quadriplegic isautonomichyperreﬂ exia, inducedbylabororsurgery- quadraplegics, themajorconcerninpatientswhoareparaplegicor as poorrespiratoryfunctionandinfectionissues,especiallyinhigh Pregnancyinwomenwithspinalcordinjuryisnolongerrare.Aswell Spinal CordInjury upregulation ofnicotinicacetylcholinereceptors. sensitivity tosuccinylcholine(withpossiblehyperkalemia)due be awarethatmultiplesclerosisandothersimilardiseasesincrease niques (lowerCSFlocalanestheticconcentration). of exacerbationwithepiduraltechniquescomparedtospinaltech- Experimentalbutnotclinicalevidenceindicatesthatthereislessrisk •

8, Thethreemajorconcernsaboutregionalanesthesiaare: Autonomichyperrefl Whengeneralanesthesiaisnecessary,theanesthesiologistshould Unmaskingofsilentdemyelinatedplaquesbylocalanesthetic Exaggeratedblockresponses(especiallyprolongedduration) Documentthecurrentneurologicalconditionofpatient. Higherratesofdiseaserelapse longed block,especiallyinthosewithsignifi Takeintoconsiderationsporadicreportsofmoreintenseorpro- associated withneuraxiallocalanestheticadministration. Informthepatientthatthereisnoevidenceofhigherrelapserates Fetalbradycardiaor placentalabruption rhage orcerebraledema Potentiallyfatalmaternalcomplications includingcerebralhemor- ipine orglyceryltrinitratemayberequired) ing, flushing, andrefl ex bradycardia (vasodilatortherapywithnifed- Severevasoconstrictionleadingto hypertension, headache,sweat- Discussthepossibilityofunmaskingnewdefi andespeciallyT 5 .Itresultsfromsympatheticoutfl ow inresponse exiaprimarilyaffectsthosewithinjuriesabove

10.6

cantdemyelination.

).Neuronalandendo- cits.

291 Obstetric Anesthesia 292 Coexisting Disease and Other Issues resulting inbradycardia. stimulates parasympatheticefferentstothesinusnodeviavagusnerve(5), to thehypertensionwithafferentoutfl ow tothebrainstem,whichinturn provoke severehypertension.Carotidandaorticbaroreceptors(4)respond lesion isaboveT tion ofcontractionsindicatingonsetlabormaybediffi cult ifthe for laboranddeliveryshouldbeinstitutedassoonpossible(detec- (T cord lesion(1),elicitingrefl ex sympatheticoutfl ow to(2)theadrenalmedulla hyperrefl exia. Sensoryafferentsenterthecordbelowlevelofspinal Figure 10.6 • mal autonomicresponse. • •

5 Ifanesthetizingapatientwithspinalcordinjury,regionalanalgesia Repositionthepatientregularlytoprevent pressuresores. block isnotanissue. Adenselocalanestheticblockisrecommended, becausemotor Ifanepiduralisdifﬁ cult toinsert,consider continuousspinalanalgesia. –T 9 ) and(3)theperipheralvasculature(T Mechanism ofcardiovascularresponsetolaborinautonomic 10 )asthisisthebestmethodofobtunding theabnor- 4

1 2 3 Brain 1 –L 1 ). Thesetworesponses Heart andaorta Kidney Blood vessel Vessels

common. Allwomenwithsevererenal diseaseareatincreasedrisk preeclampsia, pretermdeliveryand lowbirthweightaremore • • women ofchildbearingagereceiving dialysis,approximately10 therapy ithasbecomemorecommon, evenforthoseondialysis.Of renal diseasewasunusual,butwith bettermedicalmonitoringand Untilrecently,successfulpregnancyamongpatientswithsevere normal rateofearlypregnancylossandstillbirth. Womenwithmoderateorsevererenaldiseasehaveahigherthan • • • • include: hypertension. Diseasescausingrenalpathologyduringpregnancy tion atconception,theunderlyingdiseaseprocess,anddegreeof with preexistingrenaldiseasedependsonthedegreeofdysfunc- pregnancy (Chapter2),andmaternalfetaloutcomeinwomen Anumberofchangesinrenalanatomyandfunctionoccurduring become pregnantandmorethan50 • •

Renal Disease

Ifgeneralanesthesiaisrequired: hypertension, havebetteroutcomes. creatinine0.8–1.4mg/dlor80to124micromol/l),noestablished Thosewithmildrenaldysfunctionpriortopregnancy(serum three developend-stagerenalfailure. pregnancy, buttwo-thirdsexperiencedeteriorationandonein Patientswithsevererenaldiseasehaveavariablecourseduring continuous arterialbloodpressuremonitoringinthelabilepatient. tension refl ects inadequateblock.Havealowthresholdforusing Monitorbloodpressureandheartrateregularly,assumehyper- Obstetric disorders (e.g., severe preeclampsia, obstetric hemorrhage). Obstetricdisorders(e.g.,severepreeclampsia,obstetrichemorrhage). vasculitides, Goodpasture’ssyndrome). ropathy, systemiclupuserythematosus,connectivetissuedisorders, Systemicdiseases(e.g.,diabeticnephropathy,hypertensiveneph- IgA nephropathy,reflux uropathy,polycystickidneydisease). Renal-specifi c diseases(e.g.,focalsegmentalglomerulosclerosis, 48 hoursforsignsofautonomichyperrefl Maintaingoodanalgesicdepthandmonitorpostdeliveryforupto rapid sequenceinduction). injury tominimizeriskofhyperkalemicarrest(userocuroniumfor Succinylcholinemustbeavoidedinthefirst 6ormoremonthspost-

achievealivebirth,although

exia.

will

293 Obstetric Anesthesia 294 Coexisting Disease and Other Issues tension accountformorethan50 lar ﬁ Chronicrenalfailureisdeﬁ ned asaprogressivedecreaseinglomeru- • • • • • include: common. factant) andpneumonia(impairedresponsetoinfection)aremore Intheperioperativeperiod,postoperativeatelectasis(decreasedsur- • • • • ated with: Acuterenalfailureinpregnancyisrare(rate110,000)andassoci- Renal Failure nephrologists. ment plansmustbeestablishedinliaisonwithobstetriciansand of pregnancy-relatedcomplications,andappropriatemanage- • • • or failureapplyduringpregnancy. Theusualprinciplesofanesthesiaforpatientswithrenalimpairment Anesthesia forPatients withRenalDisease •

Additionalconcernsforanestheticmanagementinclude: Acutefattyliverofpregnancy Obstructiveuropathy Gastricirritationorhemorrhage edema orhypovolemia) Sodiumandwaterretentionhypoalbuminemia(pulmonary arrhythmias), andhypocalcemia(QTintervalprolongation) Hypertension,hyperkalemia(ventriculardysfunctionandacute (nausea andvomiting) Normochromicnormocyticanemia(fatigue,dyspnea)anduremia concentration). etin, althoughthistakesaweekor moretoincreasehemoglobin Anemiamayrequirecorrection(preferably early,witherythropoi- Hemorrhage(e.g.,fromabruption,amnioticﬂ Severepreeclampsia(incidence1 Peripheralneuropathies(documentpriortoregionalblock) Increasedbleedingrisk(defectivevonWillebrandfactor) and reducedrenalelimination) Changesindrugkinetics(lowserumalbumin,metabolicacidosis eratively ifnecessary);largeﬂ taining bloodpressure,renalandplacental perfusion(dialysepreop- Intravascularvolumemustbecarefully assessedwithaviewtomain- ltrationrate(end-stage<5ml/min);diabetesmellitusandhyper-

uid orbloodlossesarepoorlytolerated.

% –2 ofcases.Managementproblems % ) uid embolism)

• • • • • • • • • • tered duringpregnancy.Theseinclude: Anumberofcongenitaloracquiredliverdiseasesmaybeencoun- • • are required. Withrespecttoregionaltechniques,individualrisk-beneﬁ

Hepatic Disease jugated bilirubin(e.g.,Dubin-Johnson andRotorsyndromes) elevations ofunconjugatedbilirubin (e.g.,Gilbert’sdisease)orcon- hyperbilirubinemias(relativelybenign disorderscharacterizedby viralhepatitis(A,B,C,D,E,andGviruses) preeclampsia careful considerationanddiscussionwiththenephrologists. decision toinsertanarterialcannulashouldalsobemadeonlyafter (bandage andpadplaceintravenouscannulawellaway).The Whenpresent,specialcareofarteriovenousfistula shouldbetaken delivery. prophylaxis, andanappropriatechoiceforpostoperativecareafter Othergeneralconsiderationsincludetheuseofheparinthrombo- rupt thebloodbrainbarrier). Exaggeratedresponsestoanestheticdrugsoccur(uremiamaydis- sequence induction. 0.5 mmol/L)maypreventtheuseofsuccinylcholineforrapid- Succinylcholine-inducedserumpotassiumrise(approximately exacerbating hyperkalemia). cellular potassiumtomoveintotheextracellularcompartment, Hypercarbiashouldbeavoided(extracellularacidosiscausesintra- tric aspirationareindicated. Whengeneralanesthesiaisnecessary,fullprecautionsagainstgas- drugs. as shouldnephrotoxicdrugs,includingnonsteroidalanti-infl Drugsthatareprimarilyexcretedbythekidneysshouldbeavoided, and anticoagulantdrugs. ered safe,withtheusualprovisosinrelationtosevererenaldisease Epiduralandspinalanesthesiaanalgesiaaregenerallyconsid- hematologist. preferably bymeansofspecifi c testsinearly consultation witha count andstandardlaboratorycoagulationtestsmaybenormal), Anattempttoassessthebleedingriskshouldbemade(theplatelet

t decisions t ammatory ammatory

295 Obstetric Anesthesia 296 Coexisting Disease and Other Issues dicated becauseoftheriskvertebralcanalhematoma. obtundation. Regionaltechniquesarepreferablebutmaybecontrain- degree ofcoagulopathyorrarely,inveryseveredisease,thestate Thechoiceofanesthetictechniqueisfrequentlydeterminedbythe Principles ofAnesthesia progesterone duringpregnancy. tional changesintheliverinducedbyincreasedserumestrogenand mandate asoundunderstandingoftheanatomic,physiologicandfunc- ous challenges,warrantmultidisciplinarycareledbyphysicians,and Themostcommon(e.g.,severepreeclampsia,Chapter7)poseseri- be maintained,anddrugswhichmayhepatotoxicavoided. • • • • • • • • to aHBsAg hepatitis, especiallyHBV(theriskofseroconversionafterexposure Throughbloodcontact,healthcareworkersareatriskofcontracting Viral Hepatitis high as2 Theprevalenceofthisgeneticdisorder is<1in1,000,butmaybeas Intrahepatic CholestasisofPregnancy attention. and cirrhosis,liverfailure,orhepatocellular carcinoma,needspecial Women intheacutephase,orwhohavedevelopedchronichepatitis HCV andHDV.Theapplicationofuniversalprecautionsisessential.

Whengeneralanesthesiaisused,liverandrenalbloodﬂ intrahepaticcholestasisofpregnancy acutefattyliverofpregnancy systemicdiseases(e.g.,lupuserythematosusandhemachromatosis) portal hypertension,acuteliverfailureorhepaticrupture Wilson’sdisease,hydatiddiseaseorcysticecchinoccosis,cirrhosis, no alterationofhepaticbloodﬂ Propofolexhibitsnormalpharmacokineticsincirrhosisandcauses associated withencephalopathy). minant hepaticfailure(poormetabolismandcentraldepression Bewareexaggeratedresponsestoanestheticsandanalgesicsinful- nondepolarizing relaxants. Atracuriumandcisatracuriumshowtheleastvariabilityamong metabolism. Amonginhalationalagents,desfluranehasnegligiblehepatic % –15 + womanis1 % insomecountries.Thediseaseis often subclinical % –6

andHBeAg ow.

+ womanis22 ow should ow

–31 % ),

• • plasma mayberequired. and coagulationdisturbance,sincevitaminKtherapyfreshfrozen places toxicbileacidsfromhepaticmembranesandrelievespruritus. commenced withursodeoxycholicacid,ahydrophilicbileacidthatdis- ing. Oncecholelithiasishasbeenexcluded,supportivetreatmentis labor, andtheneonateneedsvitaminKtopreventintracranialbleed- Thefetusisatriskduetothedirecteffectsofbilesaltsorpreterm • • • pregnancy with: and recursinsubsequentpregnancies.Itusuallypresentsaftermid- • • • presentation includes: involvement. because ofsimilaritytoseverepreeclampsiawithhepatic nancy. Ittypicallypresentsclosetoterm,andisdifﬁ cult todiagnose 20,000) oflong-chainfattyacidmetabolismthatisspeciﬁ c topreg- Acutefattyliverisarareandpotentiallyfataldisorder(rate1in Acute FattyLiverofPregnancy • • • • • involves resuscitationandstabilization. Invasivemonitoringisoften Otherthandelivery,therapyismainly supportive.Initialtherapy •

Theanesthesiologistshouldassesstheseverityofliverdysfunction Aconﬁrmed diagnosisrequirespromptdeliveryofthefetus.Clinical Malaise,nausea,abdominaldiscomfortandsubclinicalsteatorrhea. serum aminotransferases,resolvingwithin24hoursofdelivery. A10–100timesincreaseinserumbileacidsandmildlyelevated Cesareandeliverymaybenecessary. Patientsareatincreasedriskofpostpartumhemorrhage. Mildjaundice(in50 (from reducedbileﬂow, bileandsaltexcretion). Pruritusintheextremities(palmsandsoles),thentrunkface Mildlyelevatedaminotransferasesand bilirubin creatinine andammonia Oliguriawithserumelectrolyteabnormalities,includinghigh with thrombocytopenia,anddisseminatedintravascularcoagulation Markedneutrophilleucocytosis,microangiopathichemolyticanemia Malaise,nauseaandvomiting,abdominalpain,feverjaundice Metabolicacidosisfromhighserum lactate levels Severehypoglycemia Renalfailure,acuterespiratorydistress, anddiabetesinsipidus Pancreatitis,pseudocystformation, and retroperitonealbleeding

ofcases,usuallyafter1–2weeks).

297 Obstetric Anesthesia 298 Coexisting Disease and Other Issues • • • • • cholecystitis isuncommon,andpresentswith: motility predisposewomentocholelithiasisandcholecystitis.Acute trations, slowingofbileacidexcretionanddecreasedsmallintestinal Latepregnancyandearlypostpartumincreasesinserumlipidconcen- Disease oftheBiliaryTract • • is severe. associated withgoodmaternalandfetaloutcome,evenwhendisease nongynecologic conditionrequiringsurgeryduringpregnancy. able. Complicationsofgallstonesrepresentthesecondmostcommon agement, buttherelapserateisoverathirdandsurgerymaybeprefer- Mostwomenwithacutecholecystitisaresuitableforconservativeman- ﬂ necessary, andregularassessmentofbloodpressure,glucose, anesthesia oftenrequiresmodiﬁ cians. Regionalanesthesiaisusually welltolerated,butgeneral tions foranesthesiaandrequireclose liaisonwithappropriatephysi- paralysis), whethermyopathicormyotonic, haveimportantimplica- myotonia congenita,paramyotonia congenita, hyperkalemicperiodic myopathies suchasmitochondrial myopathy,myotonicdystrophy, Thesediseases(e.g.,myastheniagravis,themusculardystrophies, uid andelectrolyte,coagulation acid-basestatusisessential.

Disease Muscle, Neuromuscular andMusculoskeletal Cholecystectomyisnecessaryin1–8per10,000pregnancies,but Hypoglycemiashouldbecorrected. Rightupperquadrantpainandtenderness H2-receptor antagonistsshouldbeinstituted. products), andprophylaxisagainstgastrointestinalhemorrhagewith Coagulopathyusuallyrequirescorrection(vitaminKandblood tis, whichisalsoassociatedwithalcoholorviralillness). Backpainandraisedserumamylase(thelatterindicatingpancreati- Feverandleucocytosis with pneumoperitoneum(Chapter6). to placentalperfusionandgasexchangeduringlaparoscopicsurgery Anestheticmanagementfollowstheusualprinciples,withattention fetal exposuretoradiationwhencholangiographyisnecessary. Itcanbeperformedwithleadshieldingoftheuterustominimize

cation.

• • Generalanesthesiainthesepatientsischallenging. • • • • • • • • • nance andmonitoringareimportant. Neuraxialblockinduced Coldorshiveringmayprecipitatemyotonia, sotemperaturemainte- • and rigidity),whichisdifﬁ because anesthesiaandsurgerymayinducemyotonia(musclespasm risk ofpostpartumhemorrhage. Prolonged laboranduterineatonyaremorecommon,increasingthe when itoccurs,mayexacerbateallmanifestationsofthedisease. Pregnancyislesslikelyinthesediseasesbecauseofovarianfailure,but Myotonic Disorders

Anesthesiologistsmustbefamiliarwiththesemyotonicdiseases Muscleweaknessandextramuscularfeaturesmayberelevant. mal reactiontoothers. Patientsmaydisplayextremesensitivitytosomedrugsandabnor- • • aspiration. gastrointestinal problemscontributetoanincreasedriskof Pharyngealweaknessordelayedgastricemptyingandother cough, orsleepapneamaybepresent. Ventilationmaybeimpaired,withrestrictivedefectsandpoor valve prolapsecanoccur. common (heartblock,longQT),asareseptaldefects,andmitral Inmyotonicdystrophy,cardiacconductionabnormalitiesare Thediseasesmayaffectanumberofsystems: patients (e.g.,myotoniacongenita). Susceptibilitytomalignanthyperthermiamaybeincreasedinsome Treatmentoptionsforamyotoniccrisisare: Anticholinesterasesmayprecipitate myotonia. that maypreventintubationandventilation forupto5minutes. Succinylcholinecausesdose-dependent myotoniaofthejawandchest romuscular blockingdrugs(ifmuscle weaknessisafeature). Prolongedresponses(2–3fold)occurwithnondepolarizingneu- and opioids. Unduesensitivitymaybepresenttosedativeandanestheticdrugs, drugs usedwheneverpossible. Dosesofmanymedicationsshouldbemodiﬁ ed andshort-acting

the muscle dantrolene,phenytoin,ordirectinjectionoflocalanestheticinto conduction procainamide1000mgat100mg/min,watchingforslowingof

culttoabolish.

299 Obstetric Anesthesia 300 Coexisting Disease and Other Issues common. improving whileothersdeteriorate.Prematurelaborismore thymectomy. receptors. Treatmentiswithoralanticholinesterases,steroids,or IgG antibodiesacceleratebreakdownandpartiallyblockacetylcholine voluntary muscles,ismostprevalentinfemalesofchildbearingage. Thischronicdisease,characterizedbyweaknessandfatigueofcertain Myasthenia Gravis meperidine). opioids)andtreatedpromptly(e.g.,IVclonidine,tramadolor shivering shouldbeprevented(withwarmsolutionsandneuraxial • • • • • controlled patientswithminimalweakness. protect theairway,thoughregionalanesthesiaissuitableforwell- Forcesareandelivery,generalanesthesiamayberequiredto • option ifnoepiduralcatheterispresent. Ifcesareandeliveryisnecessary,spinal anesthesiaisthepreferred • aspiration prophylaxisdrugsaresafe. adrenergic drugs,opioids,intravenousanesthetics,nitrousoxide,and MH susceptibilityshouldbecounseledintheantenatalperiod. the restofpopulation,makingitextremelyrare.Thewomanwith Malignanthyperthermia(MH)occurslessofteninpregnancythan Malignant Hyperthermia •

Duringpregnancythecourseisunpredictable,withsomewomen Earlyepiduralanalgesiaduringlaborisadvisable.Localanesthetics, Epiduralanalgesiaduringlaborisusuallysuitable. Alldrugsshouldbegiveninminimaleffectivedoses. remifentanil). doses or,preferably,beavoided(e.g.,intubateusingpropofoland Neuromuscularblockingdrugsshouldbeusedinverysmall Respiratorymuscleweaknessmaybepresent. with speech)andopthalmoplegiacanguidetherapy. Observationforbulbarweakness(suchasdifﬁ culty swallowing,or neostigmine 0.7–1.5mgforpyridostigmine60PO). cholinesterases aresubstitutedforequivalentoraldoses(e.g.,IV Duringlaborortheperioperativeperiod,intravenousanti- Prophylacticdantroleneisnotnecessary. drugs thatcausetachycardia. Ifpossibleavoidprostaglandins,which increasetemperature,and

• • • • complications. the needformultipleattempts,subsequent backpain,andother Despitecarefulplanning,thepatient shouldbewarnedabout • or cardiacanomalies,andtreatedaccordingly. reviewed intheantenatalclinic. with bothregionalandgeneralanesthesia,sopatientsshouldbe associated withahigherriskofcesareandeliveryandposesproblems mentation ofthespine.Scoliosisfromanyspinalmusculardisorderis may havebeenarrestedduringadolescencebyHarringtonrodinstru- encountered isidiopathicscoliosis(incidence1–4per1,000),which are rareinthepregnantpopulation.Amorecommonproblem Osteogenesisimperfecta,spinalmuscleatrophicdiseaseanddwarﬁ Musculoskeletal Disorders the precedingprecautionsarestillnecessary. • • • • IfthefatherisMHsusceptible,fetushasa50

Patientsshouldbeassessedforassociatedrespiratoryimpairment blocks, especiallyforcesareandelivery. catheters insomecases,canbeusedtoimplementsuccessful Subarachnoidtechniques,includingmicrospinalormacrospinal forming regionaltechniques. Instrumentedvertebralinterspacesmustbeavoidedwhenper- including X-raysandultrasoundwhenavailable. on surgicalhistory,examinationofthespine,andanatomicimaging, and safety.Acarefulassessmentofspinalanatomyshouldbebased increased. Theriskofunintentionalduralpuncture withanepiduralneedleis Regionaltechniquesmayneedtobemodifi ed tomaximizeeffi accordingly. Evaluatepatientscarefullyforpossiblediffi cult intubationandplan AlwaysmonitorforanMHreaction(end-tidalPCO used forgeneralanesthesia,withorwithoutmidazolam. Atotalintravenousanesthetictechniquewithpropofolshouldbe must beavoidedifgeneralanesthesiaisrequired. Succinylcholineandvolatileinhalationalanestheticsaretriggers regional anestheticisplanned. oxygen, newcircuitry,andcarbondioxideabsorbent),evenwhena Usea“clean”anestheticmachine(novaporizers,fl ushed with guidelines. etc.) andifnecessary,treatanMHcrisisasperrecommended

riskofMH,soall 2 ,temperature,

cacy sm

301 Obstetric Anesthesia 302 Coexisting Disease and Other Issues • • • during pregnancy). infl well totreatmentwithsteroidsandantimalarialdrugs(someanti- of youngwomen.Itisusuallymild,andfl ares ofdiseaserespond Systemiclupuserythematosus(SLE)isachronicmultisystemdisease Systemic LupusErythematosus temic lupuserythematosus,rheumatoidarthritis,andscleroderma. below), themostcommondiseasesofrelevanceencounteredaresys- purpura andantiphospholidsyndrome(seehematologicdisease nia gravis(seemusculardiseaseabove),idiopathicthrombocytopenic InadditiontoMarfan’ssyndrome(seecardiacdiseaseabove),myasthe- • • management. and continuingthoseconsideredrelativelysafe(e.g.,azathioprine). avoiding contraindicateddrugs(anti-infl deteriorate postpartum.Treatmentmustbemanagedappropriately, Mostwomenwiththischronicdiseaseimproveduringpregnancybut Rheumatoid Arthritis ated withincreasedriskofpreeclampsia. SLEfollowsanunpredictablecourseduringpregnancy,butisassoci-

Autoimmune orConnectiveTissueDisease Themainanestheticissueinrheumatoidarthritisisairway Alupusanticoagulantantibodyispresentin5 chiatric abnormalities. respiratory disease,mildthrombocytopenia,neurologicalandpsy- ammatory orotherimmunosuppressivedrugsarecontraindicated or subsequentdrugmaldistribution,ismorelikely. Failureofregionalblockduetofailurelocatethecorrectspace, patient islupusanticoagulantpositive. hematological disease).Thrombosisriskmustbemanagedifthe renal impairment,hypertension,cardiacdisease(presentin50 SLEhasvariablepresentation,especiallyarthritis,cutaneouslesions, lary incisors. patient cannotprotrudethemandibular incisorsinfrontofmaxil- Considerawakeintubationifinterincisor gapis<4–5cmandthe dysfunction). and temporomandibularjointinvolvement, andcricoarytenoid Lookcarefullyforrestrictionofneck extension(atlanto-occipital

ammatory drugs, penicillamine)

% –10

% ofcases(see %

), • • • during pregnancy. and fi brosis oftheskinandviscera,runsanunpredictable course infl ammation, vascularsclerosis(includingRaynaud’sphenomenon) steroids andotherimmunosuppressivedrugs.Itischaracterizedby Sclerodermaisararediseaseinpregnancy,sometimestreatedwith Scleroderma cations. access orintubation,aspiration,andpostoperativerespiratorycompli- longed). Preparationsshouldbemadeforpotentialdiffi cult venous anesthesia isusuallyindicated(althoughblocksmaybepro- comorbidities anddiseasemanifestations,regionalanalgesia Althoughindividualdecisionsarebasedonconsiderationofall • • • • of theAnticoagulatedWoman”below. receiving aspirinandunfractionated heparin (UFH);see“Management events. preeclampsia, andamoderateto severeriskofthromboembolic associated withincreasedfetalloss, amodestincreaseinriskof S andproteinCdefi ciency, andhyperhomocysteinemia.Theseare prothrombin genemutationvariant,antithrombindefi homozygosity forfactorVLeidenmutation,heterozygositya anticardiolipin antibodyandlupusanticoagulant,heterozygosityor Theinheritedthrombophiliasencompassavarietyofdisorders Thrombophilias

Hematologic Disease Anestheticconsiderationsinclude: Basedonriskassessment,womenwith theseconditionsareoften Restrictivepulmonarydiseaseiscommon. Checkforgastroesophagealincompetenceandrefl Restrictedmouthopeningmakesairwaymanagementdiffi abnormalities. Lookforandtreathypertensioncardiacconduction insuffi Distalarterialcannulationisbestavoidedduetocirculatory Venousaccessmaybediffi cause acutecordinjury). Beverycarefulduringintubation(atlanto-axialsubluxationmay ciency.

cult.

ux. ciency, protein ciency,

cult.

—

303 Obstetric Anesthesia 304 Coexisting Disease and Other Issues • • prolonged surgicalbleeding. defects offunction. more severevariants(typesIIandIII)whichalsohavequalitative type Idisease(70 adherence ofplateletstovascularsubendotheliallayers.Inaddition duced byendothelialcellsandplateletsthatcarriesfactorVIIIaids abnormal productionofvonWillebrandfactor(vWF),aproteinpro- order, andaffects1 Thisisthecommonestinherited(autosomaldominant)bleedingdis- Von Willebrand’sDisease peutic dosesofheparinareindicatedwithwarfarin. usually prescribed.Ifthereisprevioushistoryofthrombosis,thera- If thereisnothrombosishistory,prophylacticheparinpluswarfarin vention ofhypothermia. pregnancy lossandthromboses,antithromboticstockings,pre- Managementduringpregnancyinvolvesaspirinandheparintoprevent • • • hypercoagulable states. systemic lupuserythematosus),andisoneofthemostcommon Thissyndromeiseitherprimaryorsecondary(e.g.,associatedwith Antiphospholipid Syndrome •

Thediseaseischaracterizedbymucosalbleeding,easybruising,and Postoperativeanticoagulationisanimportantpartofmanagement. Thereisnocontraindicationtotheuseofregionalanesthesia. (15–60 units/dL)andfactorVIIIc coagulation protein(40 Laboratorytestsshowlowconcentrations ofvWFantigen reduced by40 vWF toplateletglycoprotein,with ristocetinasacofactor,is Plateletfunctionisabnormalintype IIandIIIdisease(bindingof normal). Venousthrombosisoccursinupto60 placental trophoblastiscommon. Recurrentearlypregnancylossduetoantibodyactivityatthe activated partialthromboplastintimebylupusanticoagulant. positivity tolupusanticoagulant,with LaboratorytestsrevealIgGandManti-cardiolipinantibodies hypertension (includingpulmonary)arecommon. Thrombocytopenia,livedoreticularis(mottlingoftheskin),and infarction canalsooccur. sis in10 % ; lowerlimbsaremostcommonlyaffected,butcerebral % ). % % –2 ofallcasesandaquantitativedefect)thereare

% ofthepopulation.Itismostoftendueto

% in vitroprolongationofthe , butalsoarterialthrombo-

% of • • • exact typeofdiseaseandpreviousresponsetomanagement. Managementincludesconsultationwithahematologistaboutthe • • • concentration. pregnancy. Thereareanumberofcauseslowplateletcountduring Thrombocytopenia • disease risesubstantially,usuallyexceeding100 Duringpregnancy,thelevelsoffactorVIIIcandalsovWFintypeI • •

disease maybenecessary. qualitative defectsofvWFantigenorsevereautosomalrecessive PredeliveryadministrationoffactorVIIIconcentratestothosewith tachyphylaxis. normal i.e., (0.3 mcg/kgIV)toincreasevWFconcentrationsby2–4fold IntravenousDDAVPcanbegiven90minutespriortosurgery or undertakingneuraxialregionaltechniques. Ideally,factorconcentrationsshouldbemeasuredpriortodelivery should notberetained. Factorconcentrationsfallrapidlypostdelivery,soepiduralcatheters disease. RegionalanesthesiatechniquesarenotcontraindicatedintypeI blood lossisexpected. cause plateletreleaseofvWFmaybeappropriate,especiallyif Treatmentwith1-deamino-8-D-argininevasopressin(DDAVP)to Gestationalthrombocytopenia • • Preeclampsia(Chapter7) Idiopathicorautoimmunethrombocytopenicpurpura(ITP) • • • • •

incidence5 countsoften120–150x10 postdelivery observetheneonate,asplatelet countnadiris2–5days to surgery use platelettransfusiontoachievethese levelsimmediatelyprior incidence2–6per100,000 associatedwithantiphospholipidsyndrome aimforcounts unresponsive treatmentwithsteroids,thenhigh-doseIVimmunoglobulinif >

% 100units/dL.DailyrepeatdosesofDDAVPshow > 50x10

/Ltoavoidprimarybleedingrisksand 9 /Lbutrarely<100x10

ofthenonpregnant 9 /L

305 Obstetric Anesthesia 306 Coexisting Disease and Other Issues • • • globin CorEalsousuallyhavemilddisease,withchronichemolysis. who compensatewellfortheirmildanemia.Homozygoteshemo- tion ofglobinchainsubunits)arecarrierswithasymptomaticdisease, ity. Mostwomenwithathalassemia(quantitativedefectsintheproduc- maternal anemia,throughtoseverediseasewithhighperinatalmorbid- structure (hemoglobinopathies)mayproducemildasymptomatic nancy. Inheriteddisordersofhemoglobinsynthesis(thalassemias)or loblastic anemia,andrequireadditionalironfolateduringpreg- Pregnantwomenarepredisposedtobothirondefi ciency andmega- Anemia when plateletcountsareextremelylow. spective seriesindicatethatneuraxialblockmaybeuneventfuleven (see Chapters3and7).Suchaneventisexceptionallyrare,retro- defi there isnospecifi c plateletcountatwhichregionalanesthesiacanbe Inmostbleedingdisorders,includingthoseinvolvingplatelets, (e.g., aplasticanemia)orplateletdysfunction (e.g.,uremia) Regional techniquesmaybecontraindicatedbythrombocytopenia leukocytosis) Treat coexistingbloodfactorabnormalities(e.g.,thrombocytopenia, Give supplementaloxygenasrequired Only treatcompensatedanemiaifthereisongoingbleeding unnecessary ifhemoglobinconcentration isabove7g/dl If wellcompensatedchronicanemia,bloodtransfusionisusually Consider theimplicationsofunderlyingdisease (consult withhematologistorphysicianifrequired) Check thatadiagnosishasbeenmadeandappropriatetherapyintroduced Pregnant Patient Table 10.12

molecular-weight heparin) Heparin-inducedthrombocytopenia(raretoveryrarewithlow- drome (bothrare) Thromboticthrombocytopeniapurpuraorhemolyticuremicsyn- • chronic anemiaonoxygencarriageandcardiacfunction(Table Anestheticconsiderationsarebasedonassessmentoftheimpact • • ned as“safe”withrespecttotheriskofvertebralcanalhematoma

plateletfactor4antibodies associatedwithseriousthromboses commences5–10daysafterexposureoronreexposure Anesthetic ManagementoftheAnemic

10.12

). ).

• • • reproductive period. Anumberofmentalhealthdisorderspeakinincidenceduringthe • • pregnancy, suchas: cell diseaseduetoHbSSandSC)havesigniﬁ cant implicationsduring Sicklecelltraitisbenign,butsomesicklingdisorders(e.g.,sickle disorders orschizophrenia. technical skillstested,especiallybywomenwithmajorpersonality Theobstetricanesthesiologistmayhavehisorhertechnicalandnon- • • • Anti-anxiety drugs • • • Antidepressants • • Major tranquilizers(e.g.,haloperidol,thioridazine,ﬂ Psychiatric Patients Table 10.13 • • • •

Psychiatric Disease

Goodantenatalmanagementrequires: Fetalgrowthretardationandincreasedfetalloss Increasedinfectionrisk common causes of indirect maternal death in developed countries. common causesofindirectmaternaldeathindevelopedcountries. that postnataldepressionleadingtosuicideisnowoneofthemost Thereisa5-foldincreaseindepressiontheyearafterdelivery,such Vaso-occlusivecrises Severeanemia (Table Considerationoftheimplicationsandinteractionsmedications. for panicattacks consider dexmedetomidine forproceduralsedation use intravenousmidazolam 1mgrepeatedorclonidine25mcg tramadol interaction withselectiveserotoninreuptake inhibitors[SSRIs]) awareness of serotoninsyndromefromthecombinationofSSRIsand avoid meperedine(pethidine)inthoseonmoclobemide(butno lowered seizurethresholdfromtricyclicantidepressants condition withsimilaritiestomalignanthyperthermia) neuroleptic malignantsyndrome(rare,potentiallyfataldrug-induced cardiac conductionchanges(heartblock,prolonged QTinterval) poor responsetobloodloss( orthostatic hypotension sedation extrapyramidal sideeffects 10.13 ) Implications ofMedicationsPrescribedfor

α 1 -adrenergic antagonism)

uphenazine)

307 Obstetric Anesthesia 308 Coexisting Disease and Other Issues and anestheticprinciplesareshowninTable with electroconvulsivetherapy(ECT).ECTissafeduringpregnancy Anesthesiamaybeneededtosupporttreatmentofseveredepression • • • • Depression,includingmanic-depressiveillness,isassociatedwith: Depression • • • • • services duringpregnancyandchildbirth. Upto80 place highdemandsonobstetric,anesthetic, andpainmanagement have notaccessedantenatalcareshould raisesuspicion. threatening maternalcomplications. Acuteadmissionsofwomenwho mental confusion,poorfetaloutcomes,andseriousorevenlife- and thepathophysiologyofpregnancy-relateddiseaseoftenleadsto manifestations ofdrugabuse,thephysiologicalchangespregnancy, zodiazepines andtoluene-basedsolvents.Acombinationoftheclinical are alcohol,nicotine,marijuana,opioids,cocaine,amphetamines,ben- per 1000).Polysubstanceabuseiscommon,andfrequentlyuseddrugs (30 per1000deliveriesinAustralia,withopioiddependencealone11 and substanceabuseduringpregnancyisprevalentinmanysocieties Nearly90 thetic servicesintheperinatalperiod.

Pregnant Woman Management oftheDrug-Dependent Womenwhoaredependentonillicit drugspresentchallengesand fears aboutfetaleffects. Poorcompliancewithmedicationbecauseof(mainlyunfounded) Poorhealthandlackofantenatalcare Increasedratesofcesareandelivery Nauseaandvomiting sulting patients. Empathyanduseofsuitablyquietprivateenvironswhencon- guardianship. TheneedtoinvolveotherpartieswithPowerofAttorneyorlegal behavior. Facingchallengesbecauseofaggressive,paranoidoruncooperative Seekinginformedconsentearly. ment plansbeforetheonsetoflabororneedforsurgery. Consultationwithpsychiatristsandphysicianstodevelopmanage- % ofwomenwhoabusedrugsarechildbearingage,

10.14 . % willrequireanes-

• • • • • • signiﬁ Regional analgesiaforlaborandpostoperativeregionalhave function (opioidreceptor“downregulation”fromcocaineabuse). dependency, naltrexoneuseorabnormalopioidreceptordensityand Anesthesiaandanalgesiarequirementsmaybealteredduetoopioid • • • poor dietanduntreatedcoexistingdisease. obtaining consentforprocedures.Thesewomenoftensufferfrom Theassessmentoftheacutelyintoxicatedparturientisdifﬁ cult, asis Monitor thefetusafterECT ( until extubation Ventilate tonormocapniafor pregnancy(30–32mmHg)aftertheECTand • warrant Use arapidsequenceinduction ifsymptomsorgestation( Give aspirationprophylaxis Prevent aortocavalcompression if Continue usualantidepressantmedicationbutconsiderdruginteractions Table 10.14 ECT =electroconvulsivetherapy Monitor foruterinecontractions orbloodlossaftertheECT •

cesarean deliveryareoftenrequired (consistentwiththetheoryof Additionalanalgesicinterventions during regionalanesthesiafor Cautionmustbeexercisedwhenhandlingneedlesandbodyfl Specifi that maybepositiveforhepatitisandothertransmissibleviruses. Earlyantenatalreferraltoananesthesiologyclinicisrecommended. lack ofeffectindirect-acting sympathomimetic stimulationbycocaine oramphetamine,anda Adversedrugreactions(orinteractions) duringanesthesiainclude unsatisfactory. Despiteverylargedosesofsystemicopioids,analgesiaisoften Peripheralvenousaccessisoftendiffi tory infections,untreatedabscesses,andendocarditis. Co-morbiditiesincludehepatitis,cellulitis,poordentition,respira- groups, andmedicalservicespersonnel. midwives, familypractitioners,psychologists,communitysupport Careplansshouldbeorganizedbyteamsincludingobstetricians, e.g., propofol2mg/kgandsuccinylcholine(suxamethonium)0.5–1 transient severefetalbradycardiaoccursrarely cantadvantages. cpharmacologicaleffectsofthedrugsusedmaybeevident. Anesthesia forElectroconvulsiveTherapy

> 24weeks) > 20weeks α 1 -adrenergicagonists. cultorimpossible.

> 20weeks)

uids

309 Obstetric Anesthesia 310 Coexisting Disease and Other Issues • perinatal periods(Table most pregnantwomenreceiveheparin duringtheantenataland patients whorequiremaintenance anticoagulation.Consequently, Therapywithheparinisusuallysubstituted priortopregnancyin • effects.These are: during pregnancybecauseitcrossestheplacentaandhasadversefetal Warfarinisoftenusedinthepostpartumperiod,butinfrequently Anticoagulant Therapy • • • • • • anticoagulation: and pregnancy-speciﬁ c conditionsmeritprophylacticortherapeutic likely duringpregnancy(seeChapter13).Anumberofprepregnancy prothrombotic, makingthromboemboliceventsupto5timesmore risk ofobstetricorsurgicalbleeding.Thenormalpregnantstateis on peripartumandperioperativecare,includinganesthesiathe who areonantiplateletoranticoagulantdrugs.Thesedrugsimpact Theobstetricanesthesiologistisverylikelytoencounterwomen • •

Pregnant Woman Management oftheAnticoagulated sure inthesecondorthirdtrimesters. system andopthalmologicalabnormalities) associatedwithexpo- Fetalhemorrhage(leadingtoacuteorsubacutecentralnervous (5 chondral calciﬁcation) unlessstoppedwithin6weeksofconception Embryopathy(facialhypoplasia,scoliosis,shortlimbsandphalanges, Malignancy Mechanicalprostheticheartvalves Certaincardiacdiseases Prolongedbedrest mine, iswarranted. approach, whichmayincludetheuseofgabapentinoidsandketa- Postoperativepainreliefisofteninadequate.Amultimodal algesia”). opioid-induced abnormalpainsensitivityor“opioid-inducedhyper- Highriskofthromboembolicdisease Recentdeepveinthrombosisand/orpulmonaryembolism Inheritedthrombophilias % riskwithexposurebetween6–9weeksgestation).

10.15

).Managementdecisionsshouldbe

[aPTT] 2–3.5timesnormal). anticoagulation (aimingforanactivatedpartialthromboplastintime Unfractionatedheparin(UFH)isadministeredIVforacutetherapeutic • • • reduced monitoringrequirements. greater efﬁ cacy forprophylaxis,morereliablepharmacokinetics,and bocytopenia andosteoporosisthan LMWH. when usedintravenously,andhigher ratesofheparin-inducedthrom- DisadvantagesofUFHincludehigher ratesofmaternalhemorrhage • • • in differentcircumstances. heparin (UFH)andlow-molecular-weight(LMWH)areused placenta duetotheirhighmolecularweight,andbothunfractionated regarding theoptimumdurationoftherapy.Heparinsdonotcross made incollaborationwithobstetriciansandhematologists,including Enoxaparin Drug Table 10.15 heparin Unfractionated Dalteparin thromboplastin time. SC =subcutaneous.iuinternationalunits.aPTTactivatedpartial

LMWH(e.g.,enoxaparin,dalteparin)isoftenpreferredbecauseof thrombocytopenia (<1 LMWHisassociatedwithalowerincidenceofheparin-induced cutaneous administrationofenoxaparin. tion; UFHmustbeadministeredintravenously,asopposedtosub- Dosingismoreconvenientwhenusedfortherapeuticanticoagula- bility thanUFH. LMWHhasalongerdurationofactionandhigherpatientaccepta- LMWH. Reversalofanticoagulation(withIV protamine)iseasierthanwith tein binding,andincreasedrenalclearance). cokinetics inpregnancy(placentalheparinases,alteredplasmapro- Uptitrationofdosesmaybenecessarybecausealteredpharma- in patientswithamechanicalheartvalve. Totreatacutethrombusorthromboembolus,priortodelivery Typical DosesofHeparin Prophylaxis 0m Cdiy 1 mg/kgSCbdor1.5mg/kg 40 mgSCdaily 00i Cdiy 100 iu/kgSCbd 5,000–10,000 iuIVthen 7,500–10,000 iuSCbd 5000 iuSCdaily

% ).

Therapeutic SC daily range foraPTT infusion tomaintaintherapeutic

311 Obstetric Anesthesia 312 Coexisting Disease and Other Issues • • • • • • • bral canalhematoma. which willalsoallowneuraxialblockbydecreasingtheriskofverte- labor anddeliverytoavoidsevereobstetricoroperativebleeding, Anticoagulationshouldbereversedfullyorminimizedatthetimeof Peripartum Management of clotandthusepiduralbleeding). 2 hoursafterepiduralcatheterremoval(toavoidpotentialbreakdown be delayedforatleast4hoursandnotrestarteduntil Aftersurgicaldeliveryorprocedures,reintroductionofLMWHshould • coagulation. gesia inpatientsonantiplateletand anticoagulant drugs. societies havepublishedguidelinesabout regionalanesthesiaandanal- The AmericanSocietyofRegionalAnesthesiaandsimilarEuropean bolism, thrombophiliaandantithrombotictherapyduringpregnancy. duced practiceguidelinesforthemanagementofvenousthromboem- Physicians andtheObstetricMedicineGroupofAustralasiahavepro- AnumberoforganizationssuchastheAmericanCollegeChest

Medicationsotherthantheheparins mayhavesigniﬁ cant effectson partum removalatatimeofminimalanticoagulantactivity laxis isplanned,butstepsmustbetakentoensurescheduledpost- Anepiduralcathetermayberetainedifthromboembolismprophy- tion isplanned. Anepiduralcathetershouldberemovediftherapeuticanticoagula- negligible withprophylacticsubcutaneousUFH). regional blockordelivery(althoughepiduralhematomariskappears SubcutaneousUFHmaybestoppedatleast4hourspriorto approximately 4–6hoursbeforelabororsurgery. shorter-acting andreversibleIVUFHthiscontinueduntil TherapeuticanticoagulationwithLMWHshouldbechangedto prior toplannedregionalblock(toensurelowanti-Xaactivity). TherapeuticLMWHshouldbestoppedatleast24hoursormore planned regionalblockoranticipatedlaboranddelivery. ProphylacticLMWHshouldbestoppedatleast12hourspriorto the internationalnormalizedratio(INR)hasreturnedto<1.5. K-dependent coagulationfactorconcentrationsarerestored,and Warfarinneedstobestopped4–5daysprior,untilvitamin 12 hoursafteraprophylacticdoseofLMWH. roidal anti-inﬂ ammatory drugs)ora mildtomoderateirreversible Drugswithmild,reversibleeffectson plateletfunction(e.g.,nonste-

— at least

11. 10.

• • •

Further Reading 7. 6. 5. 9. 8. 4. 3. 1. 2.

contraindicate neuraxialtechniqueswhileactive. cross theplacenta,conferanunknownriskofbleeding,andalso ThrombininhibitorsandfactorXa(e.g.,fondaparinux) raxial blockforaweek. are rarelyencounteredinpregnantwomenbutcontraindicateneu- Drugswithprofoundeffectsonplateletfunction(e.g.,clopidogrel) bleeding risk. ginkgo) alsoshownoevidenceofasigniﬁ cant increaseinclinical Herbalmedicationsthatalterplateletfunction(garlic,ginseng, techniques orsurgery. effect (e.g.,low-doseaspirin)donotalonecontraindicateregional

Horlocker TT , 2001 ; 75 Wedel : Australasia. 258 DJ - , Anticoagulation inpregnancyandthepuerperium 263 . Rowlingson A WorkingGrouponbehalfoftheObstetricMedicine JC, guidelines (3rdedition). Society ofRegionalAnesthesiaandPain Medicine evidence-based patient receivingantithromboticorthrombolytic therapy:American 35 : 881 - during pregnancy:anaestheticissues 893 . . AnesthAnalg. 2009 ; 108 : 572 - 575 . antiphospholipid syndrome . Madan R Analg. , 2006 Khoursheed ; in patientswithpreexistingcentralnervoussystemdisorders 103 M . : , 223 - 228 Kukla . R, Hebl JR Analg. , 2008 Horlocker ; 107 TT ; , Wang 193 - LP 200 Schroeder , . DR Paech . MJ Neuraxial anesthesiaandanalgesia . Neuroanaesthesia forthepregnantwoman . Ludlow J , 648 - 660 Whybrow . patients withcommonbleedingdiatheses T . , Paech MJ Choi , S , Brull R . Neuraxial techniquesinobstetricandnon-obstetric Galvagno SM , 2009 ; 18 Camann : 156 - Madden 164 . BP . Pulmonary hypertensionandpregnancy . ContinuingEducationinAnaesthesia,CriticalCareandPain. Burt CC , Durbridge J . Management ofcardiacdiseaseinpregnancy . congenital heartdisease . Dob DP , Yentis SM . Practical managementoftheparturientwith

Reg AnesthPainMed. 2010 ; 35 : 64 - 101 .

Int JObstetAnesth. 2005 ; 15 : 137 - 144 . . Sepsis andacuterenalfailureinpregnancy . Anaesthesia. 1997 ; 52 : 72 - 76 . et al et al . The anaesthetist andthe Anaesth IntensiveCare . 2007 ; . Drug abuseanddependency et al . Regional anesthesiainthe Anesth Analg. 2009 ; 109 :

Int JObstetAnesth. 2009 ; 9 : 44 - 47 . Anesth MJA . Anesth

313 Obstetric Anesthesia Chapter 11 Complications of Labor and Delivery

Craig M. Palmer , MD

Introduction 314 Prematurity and Preterm Labor 314 Multiple Gestation 325 Abnormal Presentation 329 External Cephalic Version 332 Shoulder Dystocia 333 314 Vaginal Birth After Cesarean Delivery (VBAC) 334 Amniotic Fluid Embolism 336 The Febrile Parturient 338 Summary 340

Introduction

Despite the best efforts and intentions of obstetricians and anesthesiologists in caring for the parturient, complications can arise which impact the management of labor and delivery, and have implications for anesthesia care. As with complications such as hemorrhage (Chapter 8), understanding the underlying pathophysiology improves our approach to anesthetic management.

Prematurity and Preterm Labor

Defi nitions Preterm labor is defi ned as regular uterine contractions occurring at least once every 10 minutes and resulting in cervical change prior to 37 weeks gestation. A preterm infant is any infant delivered before 37 weeks of gestation. • • regression equation. Figure 11.1 infants sufferandsubsequentimpactontheirlives.Whileadvancesin Neonatalmortalityfi At29weeksgestation,over90 • nations ininfantmortality. major reasonstheU.S.rankssolow(28thin1998)amongdeveloped the UnitedStates.Thehighincidenceofpretermdeliveryisone Prematurityistheleadingcauseofperinatalmorbidityandmortalityin Incidence 1500 grams. Perinatalmortalityapproaches90 Neonatal MorbidityandMortality • • • gestation; by30weeksgestation,survivalexceeds90 have asignifi Within this6-weektimeframe,evenminimaldelaysindeliverycan

% Survival (VLBW) infant,regardlessofgestationalage. Anyinfantbelow1500gramsatbirthisaverylowweight weight (LBW)infant. Anyinfantweighinglessthan2500gramsatbirthisalow groups — 12.7 TheoverallincidenceofpretermdeliveryintheUnitedStateswas in blackparturients. improves neonatalsurvivalratefromjustover15 Delayofdeliveryfromagestationalage25weeksto31 By34weeksgestation,neonatalsurvivalshouldexceed98 delayed improvessurvivalratebyupto5percentagepoints. Between25and26weeksgestation,eachdaythatdeliverycanbe 100 25 50 75 0 % 22 in2007,buttherewasasigniﬁ cant disparitybetweenracial 23 the incidencewas11.6

cantimpactonneonatalsurvival. Predicted survivalbygestationalagederived fromlogistic 24 25 guresshedlittlelightonthecomplicationsthese

27 Gestational a % 28 ofestimatedfetalweightsarebelow % % forinfantsbornbefore24weeks 29 inwhiteparturients,and18.3 g e ( 30 weeks

31 )

32 % % toalmost95 33 (Figure11.1). 34 % . 35

36 % % .

315 Obstetric Anesthesia 316 Complications of Labor and Delivery • ing delivery (Figure 11.2). infants, suchneonatesstillusuallyencounterastormycoursefollow- neonatology havedecreasedmortalityforverylowbirthweight • • whether toinstitutepharmacologic tocolytic therapy. to assessfetallungmaturityandrule outinfection. to establishgestationalage;onoccasion, amniocentesiswillbeused conservative measuresareineffective,ultrasonographyisundertaken alone areeffectiveinasubstantialportionofpatients.Ifthese tocography arealmostuniversallyindicated.Bedrestandhydration intravenous hydration,continuousfetalheartratemonitoring,and pelvic examtoruleoutprematureruptureofmembranes.Bedrest, treatable medicalconditionsthatmayhaveprecipitatedlabor,anda with PTLconsistsofathoroughphysicalexaminationtoeliminate who developpretermlabor(PTL).Theinitialassessmentofapatient Currentobstetricalpracticefocusesondelayingdeliveryinpatients Obstetric Management for allinvolvedtodowhateverispossibleavoidpretermdelivery. infants, theirfamilies,andthehealthcaresystem,itbecomesimperative disturbances (Figure11.3).Becauseofthisoverwhelmingimpactonthe with neurologicabnormalities,chronicpulmonaryproblems,andvisual Evenbeyondtheimmediateperinatalperiod,survivorsareoftenleft ing staysofseveralmonthsinaneonatalintensivecareunitsetting. Treatmentoftheseproblemsistremendouslyexpensive,oftenrequir-

Oncethediagnosisisestablished, theobstetricianmustdecide • bidity fromanumberofcomplications,including: • • Verylowbirthweight(VLBW)infantsareatriskofsigniﬁ and thepresenceorabsenceoffetal distressandinfection. Thisdecisionisbasedontheestimated gestationalage,fetalweight, lifetime earningspersurvivor. gestational age,thetotalcostpersurvivorexceedsexpected Ithasbeenestimatedthatforinfantsof900grams,about26weeks

near 90 Respiratorydistresssyndrome(RDS).TheincidenceofRDSis almost linearlytonear0 (Grade IIIandIV)IVHexceeds30 Intraventricularhemorrhage(IVH).Theincidenceofserious and necrotizingenterocolitisaregestationalagerelated. Necrotizingenterocolitisandsepsis.Theincidenceofbothsepsis declines rapidlytonear0 % ininfantsbornbefore27weeksgestation,anddeclines

% % by36weeks.

by31weeks. % at26weeksgestation,but

cant mor-

Copyright Elsevier(1992). tertiary carecentersintheUnitedStates,1983–1986,pp.1629–1645, Neonatal morbidityaccordingtogestationalageandbirthweightfromﬁ AmericanJournalofObstetricsandGynecology,Vol.166 (NEC) relatedtogestationalageatbirth. This articlewaspublishedinthe intraventricular hemorrhage(IVH),sepsis,andnecrotizingenterocolitis Figure 11.2 % Incidence % Incidence % Incidence 100 25 50 75 10 20 30 40 10 20 30 40 0 0 0 25 26 25 26 The incidenceofrespiratorydistresssyndrome(RDS), 27 26 27 28 27 Gestational age(weeks) 28 29 28 Sepsis RDS IVH 29 30 29 Gestational age(weeks) Gestational age(weeks) 30 30 31 31 31 32 32 33 33 34 , RobertsonPAetal. 34 35 343332 35 36 36 738 37 ve 3837

317 Obstetric Anesthesia 318 Complications of Labor and Delivery • and ClinicalPractice . 1999,Elsevier. pp. 1071–1086.In:RodeckCHandWhittleMJ, and MarlowN.Thecontributionofpretermbirthtooutcomesinchildren, age atbirthinpreterminfants. Reprinted withpermissionfromWoodN Figure 11.3 spreads throughout the myometrium via gap junctions between cells. spreads throughoutthemyometriumviagapjunctionsbetweencells. metrium arecapableofinitiatingspontaneouscontractileactivity,which that generatethecontractileforce.Pacemakercellswithinmyo- smooth muscle,themyometriumcontainsmyosinandactinﬁ the physiologyofuterinecontractioniswellunderstood.Likeall Whiletheprocessesthatinitiatelaborareincompletelyunderstood, Physiology andTreatmentofPretermLabor myosin, inhibitstheactin-myosininteraction, causingrelaxation. intracellular calciumconcentration, ordephosphorylationof myosin elementsandmyometrial contraction.Areductionin ATPase, releasingtheenergythatcauses movementoftheactin- with actin.Adenosinetriphosphate(ATP) ishydrolyzedbymyosin (MLK). ActivatedMLKphosphorylates myosin,whichthenbinds latory enzyme),whichinturnactivatesmyosinlight-chainkinase across thesarcolemma.Calciuminteractswithcalmodulin(aregu- to releaseofcalciumfromthesarcoplasmicreticulumand/orﬂ contraction,theintracellularcalciumconcentrationincreases,due Calciumplaysacriticalroleinuterinecontractility.Priorto indicationsfortocolytictherapy. weight lessthan2500gmandareassuringfetalheartrateare Ingeneral,agestationalagebetween20and34weeks,withfetal

Percentage Estimated ratesofmajorpermanentdisabilityversusgestational 25 50 75 0 23 24 Gestation (weeks)

25 Mean +95%C.I. Fetal Medicine:BasicScience 26 27 28 laments laments ux

• • • • • and uterinecontractility(Table11.1): and each agent possesses side effects that can limit its usefulness. and eachagentpossessessideeffects thatcanlimititsusefulness. Nosingleagentisuniformlysuccessful astocolytictherapyforallpatients, Anesthetic Implications blockers Calcium channel M geimslae Intracellular Magnesium sulfate Agent Preterm Labor Table 11.1 Ritodrine Terbutaline β -agonistagents agents (NSAIDs) anti-inﬂ Nonsteroidal

Thereareseveralpharmacologicavenuestoinhibitpretermlabor Prostaglandinsynthetaseinhibitors. the concentrationoffreecalciumwithinmyometrium. and releasemechanisms),calciumchannelblockingagentsdecrease cium channelsinthecellmembrane(oralteringintracellularuptake Calciumchannelblockers cyclic-AMP. sites. Itmayalsoactivateadenylcyclase,increasingsynthesisof competitively inhibitingcalciumthroughcompetitionforbinding probably bydecreasingintracellularfreecalciumconcentration,and Magnesium. inhibiting MLKanddecreasingcontractileactivity. cyclic-AMP. Increasedcyclic-AMPdecreasesintracellularcalcium, within themyometriumactivatesadenylcyclase,convertingATPto Adrenergicagents signifi Eachofthetocolyticagentscurrently inusehasthepotentialfor synthetase caninhibittheproductionoftheseprostaglandins. nonsteroidal anti-infl ammatory agentsthatinhibitprostaglandin concentration increasesinmaternalbloodandamnioticfl are potentstimulatorsofuterineactivity.Duringlabor,their ammatory cantinteractions with commonlyusedanestheticagents. Pharmacological AgentsforControlof Magnesiumsulfatedecreasesuterineactivity, cyclase Possibly Adenylate calcium channels Voltage-dependent ieo cin Mechanism Site ofaction Ca β P otgadnsnhts Inhibit productionof Prostaglandin synthetase 2 -Adrenergic receptors . 2 Activationofbeta-2adrenergicreceptors + bindingsites . Byblockingvoltagedependentcal-

ProstaglandinsF increases cAMP Activatesadenylatecyclase, Increases cAMPsysthesis binding sites Direct competitionfor Decrease intracellularCa concentration prostaglandins F

2 α 2 andE

uid. The uid. α andE

2 α 2 +

319 Obstetric Anesthesia 320 Complications of Labor and Delivery • probably because of a relatively low incidence of serious side effects. probably becauseofarelativelylowincidenceserioussideeffects. Magnesiumistheintravenoustocolyticagentofchoiceinmanycenters, Magnesium Sulfate • • • • • hypotension mayresult,butaretransient. experiencewarmth,fl ushing, andnausea.Maternaltachycardia Magnesiumcausesperipheralvasodilation,andparturientsoften Physiologic Effects • • • • patients duringregionalanesthetics. Duetovasodilation,hypotensiontends tooccurmoreofteninthese Management ofRegionalAnesthesia magnesium therapy. tone havebeenreportedinneonatesfollowingprolongedmaternal Chapter 12).Respiratorydepression,hyporefl exia, anddecreased has beenreported,asareducedbiophysicalprofi le score(see Fetaleffectsareinfrequent;decreasedfetalheartratevariability •

Athigherserumconcentrations,othereffectsareseen(Table11.2): for therouteofdelivery(i.e.,vaginalorabdominal). Thedegreeofprematuritytheinfantitselfmayhaveimplications effi the careofpreterminfant,ithasprovendifficult tocomparethe Becauseofthehighstakesandlong-termconsequencesinvolvedin Thenormalserummagnesiumlevelrangesfrom1.4to2.2meq/l. and increasessideeffects. Increasingtheserumconcentrationisnotusuallymoreeffective, this concentration,magnesiumisnotalwayssuccessful. 5–8 mg/dL;whileoftensuffi cient toinhibituterineactivity,evenat Theinfusionistitratedtomaintainaserumconcentrationof venous bolusof4–6gm,followedbyacontinuousinfusion. Therapyforterminationofpretermlaborisinitiatedwithanintra- 10 –12 meq/l:Deeptendonrefl PR intervalareuncommon,butcanbeseenattherapeuticlevels. <10meq/l:WideningoftheQRScomplexandprolongation 15 –18 meq/l:Respiratoryarrestcanoccur. can befollowedasaroughclinicalmeasureofserumconcentration). either epiduralorspinalanesthesia. Carefulattentiontomaternalblood pressureallowstheuseof 25meq/l:Cardiacarrestmayoccur. cacyofagentsinrandomizedclinicaltrials.

exes arelost(deeptendonreﬂ

exes exes

• • are tocolytic,butonlyritodrineisFDA approvedfortocolysis. Bothritodrineandterbutaline(byvirtueoftheir b -2AdrenergicAgents • • • monitored. receiving magnesium,theresponsetoanyrelaxantmustbecarefully to acetylcholine.Whengeneralanesthesiaisnecessaryinaparturient of acetylcholineanddecreasessensitivitythepostsynapticendplate relaxants. Attheneuromuscularjunction,magnesiuminhibitsrelease Parturientsreceivingmagnesiumaremoresusceptibletomuscle Management ofGeneralAnesthesia at therapeuticlevels,thisisnotaclinicallysigniﬁ WhilemagnesiumhasbeenshowntodecreasetheMACofhalothane 25 15–18 10–12 6–10 5–8 1.4–2.2 (mEq/l) Serum concentration Table 11.2

taneous dose for prompt but temporary inhibition of uterine activity. taneous doseforpromptbuttemporary inhibitionofuterineactivity. Terbutalineissometimesadministered asasingleintravenousorsubcu- titrated inresponsetotheuterinecontraction pattern. Bothareusuallyadministeredbycontinuous intravenousinfusion, tain maternalbloodpressure. to spinalanesthetics,asintravenousﬂ uids canbetitratedtomain- Thesloweronsetofepiduraltechniquesmaymakethempreferable small dosesbecauseoftheirexaggeratedeffect. Whennecessary,furtherrelaxantsshouldbeadministeredinvery guide furtheruseofrelaxants. must becloselyfollowedwithaperipheralnervestimulatorto Followingtheuseofsuccinylcholine,train-of-fourresponse Clinical EffectsofMagnesiumSulfateTherapy Cardiac arrest on ECG Respiratory arrest;S-AandA-Vblock Loss ofdeeptendonreﬂ on ECG Widening ofQRScomplexandPRinterval of pretermlabor Therapeutic concentrationforinhibition Normal serumconcentrations Clinical effects

canteffect. exes β -2 receptoractivity)

321 Obstetric Anesthesia 322 Complications of Labor and Delivery Bothritodrineandterbutalinehavesigniﬁ cant Physiologic Effects • • • • of leading toincreasedcardiacoutput.Themostsigniﬁ cant sideeffects Direct accounting forthemajorityoftheirsideeffects. • • • Unfortunately, adelayofthismagnitudemayjeopardizethefetus. short half-lifeoftheseagents,thisallowstheiracuteeffectstosubside. discontinuation oftherapyandtheanestheticisideal;because Whenanesthesiaisrequired,aperiodof60–90minutesbetween Management ofAnesthesia a Hypokalemia Table 11.3 Pulmonary edema Hypotension Cardiac arrhythmias 10 “Ischemic” ECGchange Shortness ofbreathorchestpain Hyperglycemia Side effect

Transient (lessthan24hours). Pulmonaryedemaoccursinupto1 frequently seeninthesepatients,asistremulousness(Table Hyperglycemia(oftenrequiringinsulintherapy)andhypokalemiaare β-1activitycancausevasodilation(resultinginhypotension). Thevasodilationaccompanying and ECG change; this also resolves with discontinuation of therapy. and ECGchange;thisalsoresolveswithdiscontinuationoftherapy. Myocardialischemiahasalsobeenreported,manifestingaschestpain tion ofthepulmonaryedema. of therapybut,fortunately,discontinuationusuallyleadstoresolu- cardiogenic ornoncardiogenicinnature.Itrequiresdiscontinuation edema. but aggressivehydrationmayprecipitateorexacerbatepulmonary Intravenousﬂuids canbeusedtosupportmaternalbloodpressure, spinal anesthesia. Epiduralanesthesia,withitssloweronset,isprobablypreferableto hypotension whenregionaltechniquesareused. β -agonist therapyareduetothesecardiaceffects. β -1activityincreasesmyocardialcontractilityandheartrate, a

Side Effectsof a

b -agonist Therapy

β % -agonisttherapycanaggravate <2 3 3 5 30 Reported incidence(approx.) 50 ofpatients,andmaybeeither

β -1receptoreffects,

11.3

maternal sideeffects. Incontrasttomagnesiumandbeta-agonists,indomethacinhasfew Physiologic Effects • • into theactiveprostaglandins. synthetase inhibitors(PSIs)preventtheconversionofarachidonicacid activity, andalsocausesofteningofthecervixnearterm.Prostaglandin Theseagentsmayhavesigniﬁ ers reducemyometrialcontractility. Nifedipineismostwidelyused Byinhibitingtransmembranecalcium ﬂ ux, thecalciumchannelblock- Calcium ChannelBlockers limited to48hoursorless. thicin is400mg;thislimitationmeans indomethicintherapyisusually Becauseofthesesideeffects,thetotal recommendeddoseofindome- ProstaglandinsE Prostaglandin SynthetaseInhibitors • • • •

weeks. limit thedurationoftherapy.Therapycanbecontinuedforseveral tered bothorallyandrectally,butfetalsideeffects(below)usually is widelyusedinthetreatmentofpretermlabor.Itcanbeadminis- Whilealldrugsinthisclasspossesscapacity,onlyindomethacin status isgenerallynotindicated. impaired hemostasis,furtherevaluationofmaternalcoagulation In anotherwisehealthyparturientwithoutclinicalevidenceof parturients, thisdoesnotseemtobeofmajorclinicalimportance. Itmayaffectmaternalcoagulation,butdespitewidespreadusein continuously monitored. pressor ofchoiceformostpatients;thefetalheartrateshouldbe already elevatedmaternalheartrate,phenylephrineisthevaso- maintain maternalbloodpressure;duetothelikelihoodofan Vasopressortherapymayneedtobeusedmoreaggressively neonates followinginuteroindomethacintherapy(Table hemorrhage, andbronchopulmonarydysplasiahasbeennotedin Anincreasedincidenceofnecrotizingenterocolitis,intracranial oligohydramnios and,rarely,neonatalrenalfailure. Indomethacinmaycausedecreasedfetalurineexcretion,leadingto a problempriorto32weeks’gestation. in utero;thiseffectappearsrelatedtogestationalage,andislessof PSIsmayresultinprematureclosureofthefetalductusarteriosus 2 α andF

2 cantfetaleffects,however. α

arepotentstimulatorsofuterine

11.4 ).

323 Obstetric Anesthesia 324 Complications of Labor and Delivery Maternalsideeffectsofnifedipinetherapyaregenerallymild. Physiologic Effects tration, andtherapyismaintainedviatheoralroute. for tocolysis.Thedrughasarapidonsetfollowingsublingualadminis- • little evidencetosupportthisposition. head traumaandsubsequentintracranial hemorrhage,butthereis infants withanestimatedgestational weightbelow1500g,toreduce around 24weeksgestationalage. delivery mustbemade.Currently,thelowerlimitofviabilityhovers When deliverybecomesinevitable,achoiceastothebestrouteof Despiteaggressivetherapy,tocolysisoftenfailsandlaborprogresses. • • these agentsdonotstopwithdelivery. Itisimportanttorememberthattheuterinerelaxantpropertiesofall Management ofDelivery • • • • • Increased neonatalincidence of: Neonatal renalfailure Oligohydramnios Pulmonary hypertension Premature closureoffetalductusarterious Therapy forPretermLabor Table 11.4

Someobstetricianshaveadvocated routine cesareandeliveryforall delivery, compared withcesareandelivery. orrhage ininfantsunder1500gwith vertexpresentationandvaginal Nodifferencehasbeenshowninthe incidenceofintracranialhem- Chapter 8). uterine toneandpreventsignificantmaternalbloodloss(see Vigorouspharmacologictherapymaybenecessarytorestore all maycontributetouterinehypotonia. Dependingonthedurationoftherapyandhalf-lifeagent, Ithasfewclinicallysigniﬁ tachycardia, headache,andnausea. blood pressuremaybeseen.Thisassociatedwithareﬂ Nifedipinehasfewcardiaceffects,butvasodilationanddecreased bronchopulmonary dysplasia intracranial hemorrhage necrotizing enterocolitis Reported FetalEffectsofIndomethacin

cantfetaleffects.

ex • • used tothesameends. Likewise, ifdeliveryisknowntobeimminent,spinalanesthesiacan Eachofthesegoalscanbeachievedwithsolidepiduralblockade. • • • anesthesia hasseveraltheoreticaladvantages. Whenthevaginaldeliveryofapreterminfantisplanned,epidural • • in theUnitedStates,3 technology andincreaseduseofovulation-inducing drugs.Currently 15 yearsdueprimarilytotheproliferationofassistedreproduction Theincidenceofmultiplegestationhasbeenincreasingoverthelast Incidence

Multiple Gestation viability tothepointwhereitstandstoday. and facilitiesareresponsibleforloweringthegestationalageof intensive careunitforsubsequentcare.Suchneonatalexpertise personnel forresuscitation,andreadyaccesstoaneonatal very prematureinfant,toensurethepresenceoftrainedneonatal Itisprobablymostimportant,whenplanningforthedeliveryofa 4 per1000inJapan. twin pregnanciesis50per1000 inNigeria,whileonly Considerablegeographicandethnic variationexists is triplet,andonlyabout1in70,000are higherordergestations. Naturally,about1in90pregnanciesis atwingestation,about1in9800 infant’s head. Awell-relaxedperineumallowsforcontrolleddeliveryofthe avoided. “Pushing”effortsbythemotherbeforefullcervicaldilationmustbe intracranial hemorrhage. Itcanhelpavoidaprecipitousdeliverythatmayincreasetheriskof delivery. be weighedagainsttheincreasedmaternalmorbidityofcesarean delivery; theadvantagesofsurgicaldeliveryforinfantmust evidence toindicatethatacesareandeliveryissaferthanvaginal Inthepreterminfantwithbreechpresentation,however,thereis forcepsprovidesprotectionagainstheadtrauma. Thereisnoevidencetosuggestthattheroutineuseofoutlet

ofallpregnanciesaremultiple.

— the rateof

325 Obstetric Anesthesia 326 Complications of Labor and Delivery • • • • • gestation,whichcanincreasematernalrisk(Table11.5). Anumberofphysiologicchangesareassociatedwithmultiple Physiologic Effects • Metabolic Respiratory Reproductive Hemotologic Cardiovasular System (Compared withSingletonPregnancies) Table 11.5

stomach, placingparturientsatgreaterriskofaspiration. Thelargersizeoftheuterusincreasescephaladpressureon induction ofgeneralanesthesia). an increasedriskofhypoxemiaduringapnea(asoccurs rate andgreateroxygenconsumption,thesefactorscontributeto an elevatedclosingvolume.Togetherwithincreasedmetabolic capacity(TLC),adecreasedfunctionalresidual(FRC),and Thelargersizeoftheuteruscontributestoalowertotallung hypotension syndromeandaortocavalcompression. earlieringestation,placingtheparturientatgreaterriskofsupine- Thesizeoftheuterusislarger,andincreaseinoccurs volume. in bloodvolumebutarelativelysmallerincreaseredcell Thereisanincreasedincidenceinanemia,duetoagreaterincrease pregnancies, andtheincreaseoccursearlieringestation. Cardiacoutputincreasesmoreinmultiplegestationthansingleton of higherparity. Multiplegestationismorecommoninolderparturientsandthose Maternal ConsequencesofMultipleGestation ↑ O ↑ ClosingVolume capacity ↓ Functionalresidual ↓ Totallungcapacity Larger uterus anemia Increased incidenceof Occurs earlieringestation Increased cardiacoutput Consequence ↑ Metabolicrate

2 consumption

anesthesia on inductionofgeneral All increaseriskofhypoxemia Greater riskofaspiration lung capacityandFRC Contributes tolowertotal compression whensupine Increased incidenceofaorta in RBCmass relatively greaterthanincrease Increase inbloodvolume hypoxemia Also increasesriskof Comments

• pregnancy-related risks. Apartfromthephysiologicchanges,multiplegestationentailsother Obstetric Implications • • pregnancies. fetal mortalityis5–6timeshigherintwinpregnanciesthansingleton Fetalmortalityisincreasedinmultiplegestation;theriskof • • tions ofpresentationarepossiblewithtwins: Vaginaldeliveryispossibleformosttwingestations.Severalcombina- • • • precisely aspossibletheirorientation. presentation ofthefetuses.Ultrasonographyisusedtodetermineas Thecourseofobstetricmanagementdependsupontheintrauterine Obstetric Management

Pretermlaborcomplicates40 tion areallincreasedwithmultiplegestation. Theriskofplacentalabruption,placentaprevia,andmalpresenta- common inmultiplegestationthansinglegestation. Pregnancy-inducedhypertensionisasmuch5timesmore distention oftheuterusatterm. increased byboththeuseoftocolyticagentsand risk ofuterineatonyandpostpartumhemorrhageafterdeliveryare pulmonary edema,arealsolikelyincreasedinthispopulation.The The inherentrisksoftocolytictherapyfortheparturient,suchas the riskoftocolyticinteractionswithanestheticagentsnotedabove. requirement fortocolytictherapyislikewiseincreased,increasing Mostofthisriskisduetoagreaterincidenceprematurity. • TwinAvertex/TwinBvertex(occurringinabout42 Mortalityofthesecondtwinisalsoincreasedoverthatﬁ cesarean section. With tripletorhighergestations,deliverywillalmostalwaysbe the expertiseofindividualobstetricianattendingdelivery. Therouteandmethodofdeliveryarealsohighlydependenton prolapse orentrapment,andmalpresentation. twin, duetointrapartumeventsincludingplacentalabruption,cord TwinAvertex/TwinBnon-vertex(about 38 accomplished with eitherpartialorcompletebreechextraction. to turnTwinBafter deliveryofTwinA; Bmaybe external cephalicversionorinternal podalicversionmaybeused either avertexorbreechpresentation. Maneuversincluding 1500 gestimatedfetalweight.Twin Bmaybedeliveredfrom Thesecondtwin(TwinB)mustbesmaller thanTwinA,butover

–50

% ofmultiplegestations.The

% )

% ofcases)

rst via

327 Obstetric Anesthesia 328 Complications of Labor and Delivery • • • necessary. a methodofinducingsurgicalanesthesiaifcesareandeliverybecomes anesthesia willfacilitateanymanipulationsnecessary,aswell a verystrongindicationforepiduralanesthesia.Effective Theanticipatedvaginaldeliveryofaparturientwithtwingestationis Anesthetic Considerations necessary fordeliveryofthesecondtwin. accomplished. Onoccasion,surgicaldelivery(i.e.,cesareansection)is fetal heartratemonitoringofTwinBisnecessaryuntildelivery Thetimeintervalbetweendeliveriesisnotcritical,thoughcontinuous • • fetal oxygenation. applied totheparturient.Oxygenviasimplefacemaskmayimprove thetic standpoint)isreadilyavailable.Routinemonitorsshouldbe necessary forsurgicalintervention(bothfromanobstetricandanes- Deliveryshouldtakeplaceinanoperatingroomwhereeverything induce generalanesthesia. cesarean delivery.Incasesofdirefetal distress,itmaybenecessaryto omy orapplicationofforceps,for internal versionofTwinB,orfor block isnecessary.Itcanbeusedfor perinealanesthesiaforepisiot- is thelocalanestheticofchoicewhen rapidestablishmentofasurgical allow obstetricmanipulationsasnoted above.2-chloroprocaine,3 Twin Ahowever,itmaybenecessary torapidlydensentheblock suppliedtoanyotherroutinevaginaldelivery.Afterdeliveryof epidural blockshouldnotdiffergreatlyfromanalgesia DuringlaborandthroughthedeliveryofTwinA,nature

• pression mustbecarefullyavoided. Becauseoftherelativelygreatersizeuterus,aortocavalcom- sent fortypeandcrossmatch. (16-g orlarger)intravenousaccessshouldbeestablished,andblood Duetotheincreasedriskofpostpartumhemorrhage,largebore catheterexists,itshouldbereplaced. and itsfunctionassured;ifanydoubtastothereliabilityof Theepiduralcathetershouldbeplacedasearlyinlaborpractical, TwinAnon-vertex(about19 save valuablemoments. course ofthedelivery,andanticipatingobstetricinterventionscan obstetric plancanchangequicklyanddramaticallydependingonthe Communicationwiththeobstetricianisofvitalimportance:

in thiscase,cesareandeliveryisusuallyperformed. Intheformertwocases,vaginaldeliveryisusuallyfeasible,while

% ).

provide % , delivery isattemptedwithbreechpresentation: It haslongbeenknownthatthefetus isatincreasedriskwhenvaginal • • either vertex(cephalic)orbreech(caudal). infant; longitudinalliesarebyfarthemostcommon,buttheymaybe “presenting”) partoftheinfant.The“lie”referstolongaxis The“presentation”oftheinfantreferstomostdependent(or Defi ing onthepositionoflowerextremities (Figure11.4). further classified ascomplete,frank,orincomplete(footling),depend- Breechpresentationisthemostcommon malpresentation.Itmaybe Breech Presentation chance ofasuccessfulspontaneousvaginaldelivery. (“occiput anterior”or“OA”).Thispresentationgivesthegreatest (the fetalchinonitschest)andthefaceturnedposteriorly Innormallabor,thefetalheadpresentswithafl • • atony; aggressivetherapyincludingmethergineandprostaglandinF Followingdelivery,bealertforexcessivebleedingduetouterine aspiration risk,makesavoidanceofgeneralanesthesiapreferable. and, togetherwiththepropensitytorapiddesaturationandincreased contribute toahigherincidenceofdiffi perspective, greaterweightgainassociatedwithmultiplegestationcan in parttodecreasetheriskofneonataldepression.Fromamaternal anesthesia, eitherepiduralorspinal,ispreferabletogeneral may benecessary.

Abnormal Presentation Atterm,about3 Forinternalmanipulations,uterinerelaxationmaybenecessary. Forelectivecesareandeliveryofmultiplegestations,regional Theriskoffetaldeath is16timesgreaterthanvertex presentation. common presentation Vertexpresentation,withinfant’sheaddeliveringﬁ rst, isthemost and rotation of the fetal head, may still constitute a malpresentation. and rotationofthefetalhead,maystillconstituteamalpresentation. uterine relaxation,thoughtheyareeffectiveathighconcentrations. Itshouldrarelybenecessarytouseinhalationalagentssolelyfor sary, upto500ug. initial doseof100ugshouldbeused,andcanincreasedasneces- Intravenousnitroglycerinisaneffectiveagentforthispurpose; nitions

ofsingletonfetusesareinbreechpresentation. — but, dependingontheﬂ exion, extension, cult intubationinthesepatients

exed cervicalspine

2 α

329 Obstetric Anesthesia 330 Complications of Labor and Delivery Maternalriskisalsoincreased: • • • bidity ofasurgicaldelivery. stance alsodoesnottakeintoaccounttheincreasedmaternalmor- fetal risk;deliveryofthefetuscanbedifﬁ cult evenatsurgery.This cases ofbreechpresentation,butthisdoesnotcompletelyeliminate Thisincreasedriskhasledsometoadvocatecesareandeliveryforall • Pregnancies . 1986,Elsevier. from SeedsJW.In:GabbeSG,NiebylJR,andSimpsonJL, Figure 11.4 • • • delivery. Therearethreemainmethodstoaccomplishavaginalbreech Anesthetic Considerations • •

Com Thelikelihoodofperinealtraumaisincreased. often arenecessarywithvaginaldelivery. Infectiousriskincreasesduetheintrauterinemanipulationsthat use oftocolyticagents. Theriskofuterineatonyandpostpartumbleedingresultingfrom Regardless,atpresentover90 Theriskofasphyxiaisover3timesgreater. United Statesare delivered bycesareansection. Birthtraumais13timesmorecommon. either manuallyor withPiperforceps. the obstetricianassistswithdelivery ofthethoraxandhead, infant isallowedtodeliverthelevel oftheumbilicus,andthen Partialbreechextraction obstetric interventionormanipulation involved. Spontaneousdelivery. presentation, and 5 times with complete breech presentation. presentation, and5timeswithcompletebreechpresentation. Theriskofcordprolapseisincreased15timeswithincompletebreech p lete breech Classiﬁ cation ofbreechpresentation. Reprinted withpermission

Incom

Withaspontaneousdelivery,there isno

p .Withpartialbreechextraction,the lete breech % ofbreechpresentationsinthe

Normal andProblem Frank breech

block shouldnotneedtoexceedT 2 or epidural)areequallyefﬁ • severaladvantages: strong indicationforepiduralanesthesia.Epiduralanesthesiahas Theattemptedvaginaldeliveryofabreechpresentationisvery bupivacaine 0.25 inhibit maternalpushingurges. analgesia shouldproveadequate,unlessadeeperblockisnecessaryto Duringlabor(untilfullcervicaldilation),standardregimensof • • • • Vertexmalpresentationsinclude Other AbnormalPresentations persistent fails toﬂex withdescenttothepelvic brim; inafacepresentation,the %

• discussed beforehand. is essential!Ideally,theobstetricalplanofmanagementshouldbe Aswithtwindeliveries,clearcommunicationtheobstetrician Foranelectivecesareandelivery,regionaltechniques(eitherspinal Asurgicalblock(asobtainedwith2-chloroprocaine3 Duringtheactualdelivery,adeeperblock,suchasobtainedwith Faceandbrowpresentationsresult whenthefetalcervicalspine the deliveryofasecondtwininbreechpresentation. delivers theentirefetalbody;thismaneuverisrarelyusedexceptin obstetrician beginswithtractiononthefetallegsandfeet, Totalbreechextraction Itprovidesexcellentmaternalpaincontrol. delivery ifnecessary. maneuvers notedabove,ortoconvertanesthesiaforcesarean rapidly increasethedensityofblockadetofacilitateobstetric Anin-situepiduralcatheterprovidesaquickandeffectiverouteto delivery. Itprovidesexcellentperinealrelaxationtofacilitateacontrolled achieved. Itcaninhibitthematernalurgetopushuntilfullcervicaldilationis

) ishelpfulforforceps-assisteddeliveries,thoughthelevelof nous nitroglycerin,shouldbereadilyathand. Ameansofrapidlyprovidinguterinerelaxation,suchasintrave- occiput posterior % , isusuallyhelpful.

cacious. (“OP”)presentation. . Withtotalbreechextraction,the face andbrowpresentations

8 .

orlidocaine epidural , and

331 Obstetric Anesthesia 332 Complications of Labor and Delivery cesarean delivery. when regionalanesthesia isused. have shownanincreasedsuccessrate withnoincreaseinmorbidity maternal comfortduringtheprocedure, andseveralrecentseries to beincreasing.Epiduralorspinal anesthesiacertainlyincreases of regionalanesthesiaforECVissomewhat controversial,butappears Atocolyticisoftenadministeredto facilitatetheprocedure.Theuse Anesthetic Considerations preterm labor,andevenfetaldemise. Complicationsarerare,butincludeplacentalabruption,hemorrhage, Complications • • • • • weeks gestationfor several reasons: successful in50 the abdominalwall.Whenperformedclosetoterm,maneuveris breech tovertexpresentationbymanipulationoftheuterusthrough Externalcephalicversion(ECV)istherotationoffetusfrom larger diameterispresentedtothepelvicinlet. is neutral.Eitherofthesepresentationsposesproblemsbecausea cervical spineisinanextendedposition,andbrowpresentation,it will be the same as for a routine occiput anterior presentation and labor. will bethesameasforaroutineocciputanteriorpresentationandlabor. discomfort thanusualandhavealongerlabor. can usuallybeexpected,thoughtheparturientmayexperiencemore Vaginaldeliverywithapersistentocciputposteriorpresentation

External CephalicVersion A Generallyspeaking,managementoflaboranalgesiainthesesituations delivered. Ifcomplicationsarise,theinfantiscloseenoughtotermbe (reversion rateisaslow2 Riskofreversionasuccessfulversionislowerafter36weeks would likelyhavehappenedby36weeks. Ifspontaneousversiontoacephalicpresentationwasoccur,it course oflabortoeitherafaceorocciputanteriorpresentation. Browpresentationsusuallyconvertspontaneouslyduringthe if thefetusisinamentumanterior(chinanterior)position. Withafacepresentation,successfulvaginaldeliveryismostlikely transverse lieorshoulderpresentation % –80

% ofcases.Themaneuverisattemptedafter36 % ).

usuallymandatea

• • • • for theinfant. Shoulderdystociacanresultinsignificant morbidityandeven Implications the anteriorshoulderbecomeslodgedbehindpubicsymphysis. delivery oftheshoulders.Inmostcases,afterfetalhead, vers beyondmodestdownwardtractiononthefetalheadtoeffect Shoulderdystociaisdefined asadeliverythatrequiresadditionalmaneu- Defi Amongidentifi Risk Factors partum hemorrhageandfourthdegree lacerationsoftheperineum. Parturientsdevelopingshoulderdystocia areatincreasedriskofpost- • • • •

Shoulder Dystocia version. make anyrecommendationsfororagainsttheuseofanesthesia TheAmericanCollegeofObstetriciansandGynecologistsdoesnot proves inadequate. allowing epiduralextensionoftheblockifintrathecalinjection for providinganesthesiaprobablyprovidesthegreatestﬂ epidural blockade.Theuseofacombinedspinal-epiduraltechnique high successrates,comparabletothoseobtainedwithextensive or bupivacaine2.5mgwithanopioid)hasalsobeenassociated Spinalanesthesiawithlessextensiveblock(i.e.,sufentanil10ug utilized extensiveblockade,totheT ReportsofthesuccessfuluseepiduralanesthesiaforECVhave which canbeappliedduringtheprocedure. maternal discomfortisanimportantgaugeoftheamountforce Useofanesthesiaisresistedbysomeobstetricianswhofeelthat Ifdeliveryisnotaccomplishedpromptly,umbilicalcord fetal humerus. Maneuverstoeffectdeliverymayresultinfractures,mostoftenthe plexus (“Erb’spalsy”);thisdamagecanbepermanent. Tractiononthefetalheadmaycausedamagetobrachial may resultinasphyxia. concentrations oflocalanesthetics(i.e.,2 macrosomia nition

edrisksforshoulderdystociaare:

6 level,andtheuseofsurgical % lidocaine).

compression mortality exibility,

333 Obstetric Anesthesia 334 Complications of Labor and Delivery • poses 2distinctproblems: of laboraftercesareandelivery,or“TOLAC.” Laborinthesepatients substantialnumberwillattempttodelivery vaginally,optingforatrial parturients willoptforanelective repeatcesareandelivery,buta a previouscesareandeliveryhassteadily risenalso.Manyofthese 50 years,thenumberofwomenpresentingfordeliverywhohavehad Astherateofcesareandeliveryhasclimbedsteadilyinlast • • • obstetric optionsare: ric, thoughpromptanestheticinvolvementcanbehelpful.Among Themajorityofmanagementoptionsforshoulderdystociaareobstet- Anesthetic Management • • • • • • • lidocaine 2 tate eachoftheseoptions.Surgicalanesthesia,ascanbeachievedwith Ifanepiduralcatheterisinplace,goodperinealanesthesiawillfacili- throughout induction. cult, andthefetalheartrateshouldbecontinuouslymonitored anesthetic wouldlikelyslowdelivery;positioningusuallyprovesdifﬁ sia willbenecessary.Attemptingtopositionthepatientforaspinal tional epiduralcatheter,butmorelikelyinductionofgeneralanesthe- is essential.Conceivablythiscanbedonewithrapiddosingofafunc- necessary toattemptacesareandelivery,rapidinductionofanesthesia

Vaginal Birth After CesareanDelivery(VBAC) the previouspregnancy mayreoccur. Thesamecircumstancewhichprevented theirvaginaldeliverywith historyofapreviousmacrosomicinfant historyofapriordeliverywithshoulderdystocia. maternaldiabetes maternalobesity Suprapubicpressuretodislodgetheimpactedanteriorshoulder Extensionofepisiotomy Attempteddeliveryoftheposteriorshoulder maternal pelvis Rotationoftheshoulderstoanobliquepresentationwithin pubic symphysis(“McRobertsmaneuver”) Hyperﬂ exion ofthematernalthighsinanattempttoelevate infant withanabdominalcesareandelivery(“Zavanellimaneuver”). Replacingthefetalheadinvaginaandpelvisrescueof % orchloroprocaine3

% ,isindicated.Shoulditbecome

• successful vaginal delivery byallayingmaternalpainand anxiety. anesthesia besafelyemployed,itcan actuallyincreasethechanceof labor andusuallyreadilydistinguished. further, whenpresent,thepainassociated withruptureisatypicalof most prominent,symptomofintrapartum ruptureinTOLACpatients; However, experiencehasshownthat painisnottheonly,oreven mask thepainassociatedwithuterineruptureanddelaydiagnosis. anesthesia wascontraindicated,fearingthatepiduralblockwould be widelyemployedinthe1980s,someobstetriciansbelievedregional Whentrialoflaboraftercesareandeliveryproceduresﬁ rst beganto Anesthetic Considerations

allowed toproceedinfacilitieswithlowerstaffi informed of,andaccepts,therisksofaTOLAC,sheshouldbe availability” representsoptimalpractice,butifapatientisfully pressure, ACOGhasreaffi rmed itspositionthatthe“immediate women whoappearedat“lowrisk.”Partiallyinresponsetothis ACOG’s positionhaslimitedaccesstotheprocedureformany VBAC rates,whichurgedACOGtorevisittheirposition,as in theU.S.convenedaconsensusconferenceonTOLACand round-the-clock staffing. In2010,the NationalInstitutesofHealth in TOLACgenerallybeingofferedonlylargerfacilitieswithsuch available” toperformoperativedeliveryifindicated.Thisresulted have obstetrical,anesthesia,andnursingservices“immediately that theprocedureshouldbeattemptedonlyinfacilitieswhich due touterinerupture.ThisriskledACOGadopttheposition increase inmorbidityandmortalityforbothmotherinfant attempting TOLACentailsasmall,butsignifi cant andserious Subsequent reviewshaveindicatedthateveninthesepatients, could safelyundergoatrialoflaborandvaginaldelivery. all parturientswithapriorlow-uterine-segmentcesareandelivery Obstetricians andGynecologists(ACOG)determinedthatalmost over thepastdecade.Inmid1980s,AmericanCollegeof had apreviouscesareandelivery(TOLAC)hasbeencontroversial Thepracticeofofferinga“triallabor”toparturientswhohave Severallargeserieshaveindicated thatnotonlycanregional fetal mortality(seealsoChapter8). Theuterinescarmayrupture,signifi cantly increasingmaternaland

nglevels.

335 Obstetric Anesthesia 336 Complications of Labor and Delivery • • specifi reviews todateislikelybetween1in13,00020,000pregnancies.No ThetrueincidenceofAFEisunknown,butbasedononethelargest Risk Factors • • • specifi made basedonpresentingsymptomsandclinicalcourse,ratherthan immunologic basisforthesyndrome,andatpresentdiagnosisis pulmonary circulation.Morerecentinvestigationshaveproposedan be definitively madebyidentifying fetalsquamouscellsinthematernal into thematernalcirculation.Formanyyears,diagnosiscouldonly originally thoughttobeanembolicevent,thepassageofamnioticfl plications ofpregnancy,labor,anddelivery.ThecauseAFEwas Amnioticfl uid embolism(AFE) isoneofthemostcatastrophiccom- Defi •

Amniotic FluidEmbolism artifact ofchangingdiagnosticcriteria andreportingmethods. less resuscitation andcriticalcareofthese patientsorrecognitionthat this changeinmaternalmortalityrepresents improvementinthe in maternalmortalityassociatedwith AFE.Itisnotclearwhether Reportsoverthelastseveraldecades appeartoindicateadecrease suffering signifi Neonatalmortalityisprobablyabout25 Survivorsmaybeleftwithsevereandpermanentdisability. Itmayoccurintrapartumorintheimmediatepostpartumperiod. Maternalmortalityhasbeenreportedashigh80 attempted, aTOLACisconsideredstrongindication InmanylargepracticeswhereVBACdeliveriesarecommonly but morerecentreportsindicateitisbetween20 allow verylowconcentrations(bupivacaine0.0625 patients; combinationtechniquesusingopioidsandepinephrinecan thetic thatprovidesadequateanalgesiashouldbeusedinthese Prudencestilldictatesthatthelowestconcentrationoflocalanes- regional analgesia. ropivacaine 0.5 nition catastrophiccasescanoccur;the decreasemayalsobean c riskfactorshavebeenidentifi ed, makingprediction claboratoryorpathologicfi

cantneurologicdeﬁ % ) tobeused.

ndings. cit.

% ,with50 % –30 % % insomeseries, % orlower, ofsurvivors % . for impossible. impossible. epidural

uid

• • • • • • • • described incasereports. ventions associatedwithsuccessfulresuscitationofAFEhavebeen obvious reasonswillnotlikelyeverbeperformed),anumberofinter- Whilerandomizedclinicaltrialshavenotbeenpublished(andfor • outcome. die, andevenheroiceffortsmaybeunsuccessfulorhaveapoor Withoutaggressiveresuscitation,apatientsufferingAFEwilllikely Anesthetic Management Table thy ispresentinallcases.ThediagnosticcriteriaforAFEarelisted unresponsive andmayexhibitseizureactivity.Eventually,coagulopa- tory arrest,andrapidonsetofhypoxia.Awakepatientsbecome dramatic dropinbloodpressureandcirculatorycollapse,respira- Typically,theonsetofsymptomsisabruptandincludesasudden Symptoms andPresentation Onset within30minofevacuationtheuterus - or Onset duringlabor,cesareandeliveryordilationandevacuation Coagulopathy Acute hypoxia Acute hypotension orcardiacarrest Embolism (AFE)(Allmustbepresent fordiagnosis.) Table 11.6

Ingeneral,managementisstraightforwardbutchallenging: Inhalednitricoxide Plasmaexchange Hemoﬁ Intra-aorticballooncounterpulsation Aggressivelytreatalterationsincoagulation. necessary, especiallyinlightofalteredmentalstatus. Maintainmaternalarterialoxygensaturation.Intubationisusually tropes ifnecessary. Maintainmaternalbloodpressurewithﬂuids, vasopressorsandino- • Cardiopulmonarybypass Extracorporealmembraneoxygenation

developing clinicaldisseminatedintravascularcoagulation(DIC). AllcasesofAFEexhibitcoagulationabnormalities,withoverhalf 11.6 ltration . Diagnostic CriteriaforAmnioticFluid

337 Obstetric Anesthesia 338 Complications of Labor and Delivery allow timeforthemyocardiumtorecover. symptom inthesepatients,andtemporarymechanicalsupportmay concerns are the same as they would be in a nonpregnant patient. concerns arethesameastheywouldbeinanonpregnantpatient. general anestheticisplannedinanacutelyill,febrilepatient, cord andmeninges,duringabacteremicorviremicepisode.When the theoreticalriskofspreadinginfectiontoneuraxis,spinal give risetoconcernwhenaregionaltechniqueisplanned.Thereason variety ofcauses,fromananestheticstandpointinfectiouscausesusually lenges foranestheticmanagement.Whilefevercanresultfromawide Feverisnotuncommonlaboringorpregnantwomen,andcanposechal- • • • Herpes Simplex • • • Amongcommonvirusesencounteredduringlaborare: Viral Causes

The FebrileParturient indicators, whenextraordinaryeffortshavebeenapplied. comes havebeenachieveddespiteotherwisedismalprognostic patient populations.Casereportshaveshownthatgoodout- when theymightotherwisebeabandonedashopelessinother tion ofresuscitativeeffortsanduseextraordinaryinterventions healthy withexcellentphysiologicreserve.Thisjustiﬁ underestimated isthatpriortotheinsult,theywereyoungand AnattributeofparturientswhosufferAFEwhichshouldnotbe Heartfailure,particularlyrightheartappearstobeacommon Feverintheparturientmaybeviralorbacterialorigin. of eithertype,soregionalanesthesia canbesafelyemployed. Herpessimplextypes1and2 Generallyspeaking,viremiaisuncommon during the genitaltract,andisspreadthrough sexualcontact. HSV2isassociatedwithlesionson mucous membranesorskinof occurs throughoralsecretions. HSV1isassociatedwithorallesions (coldsores)andtransmission HIV Hepatitis

recurrent es continua- es

outbreaks

• • • Hepatitis • • • • • Urinary TractInfection • • in origin.Commonbacterialsourcesoffeverparturientsinclude: Feverofinfectiousorigininthelaboringparturientisusuallybacterial Bacterial Causes Human Immunodeﬁciency Virus(HIV) • • • •

anesthesia isinduced;asingledoseof antibioticsissuffi Intravenousantibioticsshouldbe administered beforeregional tion andvomiting. account potentialhemodynamicinstability secondarytodehydra- Inductionofregionalanesthesiainpatients withUTImusttakeinto treatment withantibiotics. PyelonephritisisthemostsevereformofUTI,andrequiresprompt patients. Atleast5varietiesofhepatitis(A,B,C,D,E)havebeenidentifi Urinarytractinfection(UTI) the sameasthoseinanonpregnantpatient. Ifaparturientwithacutehepatitisrequiresanesthesia,concernsare anesthesia inpatientswithchronicdisease. count andclottingstudiesshouldbecheckedbeforeregional Ashepaticfunctionmayimpactmaternalcoagulation,aplatelet encountered, thoughonlyacuteinfectionswilltypicallybefebrile. ParturientswithchronichepatitisBandCaremostfrequently and asymptomaticbacteruriamayoccurin10 UTIisprobablythemostcommonbacterialinfectioninparturients, Chorioamnionitis HIVseropositivityalonehaslittleanestheticimplication. HIV ( Ifnecessary,epiduralbloodpatchcanbesafelyperformedin spread HIVtotheCNS. there isnovaliditytotheconcernthataneuraxialanestheticmay CNSinfectionoccursearlyintheprocesswithHIV,so anesthetics duringprimaryinfectionshasnotbeenconfi outbreaks shouldbeuncommonduringlabor.Thesafetyofregional Primaryinfectionisassociatedwithatransientviremia,butsuch purpose. + ) parturients.

% ofpregnant cient forthis rmed.

ed.

339 Obstetric Anesthesia 340 Complications of Labor and Delivery

Further Reading excellent one. standing separatetheaverageobstetricanesthesiologistfrom time inanurgent situation. Communication, anticipation,andunder- necessaryintermsofanesthesiatoaccomplishit,cansavevaluable Anticipating whattheobstetricianneedtodo,andknowingis the obstetriciancanbekeytoensuringasuccessfuloutcome. a multiplegestationorabnormalpresentation,communicationwith thetic planaccordingly.Finally,duringdeliveryofthepatientwith must understandtheseinteractions,andprepareoraltertheanes- must beawareofthemedicationsparturientmaytaking, with commonanestheticagentsandtechniques;theanesthesiologist preterm laborisessential,asmosthavethepotentialforinteraction optimaloutcome.Familiaritywiththemedicationsassociated a moreaggressiveanestheticapproachisnecessarytoensurean Whenabnormalitiesoccurintheprocessoflaboranddelivery, • • • • Chorioamnionitis

2. 4. 3. 1.

Summary therapy isbegun. AswithUTI,regionalanesthesiacanbeinducedafterantibiotic promptly. Oncethediagnosisissuspected,antibioticsshouldbeadministered palsy. respiratory tractinfections,andanincreasedincidenceofcerebral Neonatalcomplicationsofchorioamnionitisincludeneonatalsepsis, partum uterineatonyandhemorrhage. Intra-amnionoticbacterialinfectionhasbeenassociatedwithpost-

1999 ; 180 : morbidity inextremelylowbirthweightinfants 665 . - 669 . neonatal survival:antenatalpredictorsofsurvivaland gynecology . Childress CH , Katz VL . Nifedipine anditsindicationsinobstetrics 1995 ; 38 : 725 - Hill 745 . Gynecol. 1999 ; 42 : 802 Katz - 819 VL . , Farmer RM . Controversies intocolytic therapy . Bottoms SF , Paul RH , Mercer BM , WC . Risks andcomplicationsoftocolysis .

Obstet Gynecol. 1994 ; 83 : 616 - 624 .

et al . Obstetric determinantsof

Clin ObstetGynecol. Am JObstetGynecol. Clin Obstet

11. 10. 12. 8. 7. 6. 5. 9.

indication forepiduralanalgesia? WilliamsObstetrics , Preterm birth . In Cunningham Philadelphia, PA FG : , W.B. Saunders , 2006 Gant : Palmer 763 NF - , CM 765 . 340 Leveno : . 1234 Preterm labor KJ - . In: , morbidity andmortalityamongnewborninfants 1238 . . Atlee JL McIntire (ed.): DD Livingstone, , 2002 : Bloom 473 - SL JL, 501 , . eds. Casey BM Lanni , SM etal. , Birth weightinrelationto Seeds Wilkins IA , Van Zundert , A , Vaes , L , Soetens , M, 2010 ; 116 : 450 American CollegeofObstetricians andGynecologists - . 63 . Vaginal Birthafterpreviouscesareandelivery . Practice BulletinNo.115 . Clinical Practice . London : children Churchill Livingstone . In: , 1999 : Rodeck 1071 - CH 1086 Wood , . N , Whittle MJ, Marlow N eds. . The contributionofpretermbirthtooutcomesin ritodrine astocolyticagents Obstetrics: NormalandProblemPregnancies . New York : Churchill et al . Efﬁ JW 21st Edition . New York : McGraw-Hill , 2001 : 689 - 727 . . Malpresentations . In Gabbe SG , Niebyl JR , Simpson cacy andsideeffectsofmagnesiumsulfate . Am JObstetGynecol. 1988 ; 159 : 685 - 689 . Anesth Analg. 1991 ; 72 : 399 - 403 . et al . Are breechdeliveriesan Fetal Medicine:BasicScienceand Complications inAnesthesia . New EnglJMed. 1999 ; Obstet Gynecol. et al. (eds.)

341 Obstetric Anesthesia Chapter 12 Fetal Assessment and Care

Laura S. Dean , MD Robert D’Angelo , MD Craig M. Palmer , MD

Introduction 342 Normal Fetal Growth and Development 343 Uteroplacental Physiology 344

342 Fetal Circulation 346 Prepartum Fetal Assessment 346 Intrapartum Fetal Heart Monitoring 351 In Utero Resuscitation 357

Introduction

Obstetric anesthesia is unique among anesthetic subspecialties in its responsibility to not one, but two patients: the parturient and the fetus. Not only must anesthetic interventions be in the best interests of the mother but they must also, as far as possible, be in the best interests of the unborn infant. Often, the “best” interests of these two patients are at odds with each other, and there is no single “best” course of action. The appropriate anesthetic interventions will depend upon the clinical circumstances, and the judgment and experience of the individual anesthesiologist. Obstetric anesthesiologists need to be familiar with available means of fetal assessment for two reasons. • All maternal anesthetic interventions have at least the potential to impact fetal well-being. • • • • • • • • • preeclampsia. strict. Abnormaltrophoblastationisintegraltothepathophysiologyof supply theendometriumlosesmoothmuscleandabilitytocon- Duringgestationandtrophoblasticinvasion,thespiralarteriesthat

Normal FetalGrowthandDevelopment are termedan“embryo.” diately; oncethisdevelopmentbegins,theproductsofconception Development oftheplacentaandchorionicvillibeginalmostimme- related temporally)theblastocystimplantsinuterinelining. Aboutoneweekafterovulationandfertilization(whichareclosely milestones. trimestersof3monthseach,correspondingtovariousobstetrical 9 months.This9-monthgestationperiodisoftendividedinto the lastmenstrualperiod,amountingto40weeks,orroughly Onaverage,deliveryoccursabout280daysfromthefi rst dayof of fertilizationisabouttwoweekslater. time fromthefirst dayofthelastmenstrual period.Theactualtime Estimatedgestationalage(EGA)isdefi ned byobstetriciansasthe anesthesiologist toexerciseappropriatejudgment. and limitationsoffetalassessmentistheknowledgethatallows taken onthemotherbecauseoffetus:understandingrole Inmostemergentsituations,anestheticinterventionsareunder- weight isabout3400g(Table with skilledneonatalcare.Atterm, 40weeksEGA,averagefetal is small,survivalafterdeliveryatthis gestationalageisalmost100 and passes1000g(2.2lbs.)byanEGA of28weeks.Whilethefetus Overthenextfourweeks,weightmorethandoublestoover600g, roughly 300g. Atmidpointofthepregnancy,20weeksEGA,fetusweighs enlarged enoughtobepalpableabovethepubicsymphysis. By12weeksEGA(10afterfertilization),theuterushas after fertilization. Mostmajorstructuresoftheembryohavebeenformedby8weeks oped, andmaternalbloodsupplytotheplacentaisestablished. Bythreeweeksafterfertilization,atrueintervillousspacehasdevel-

12.1 ).

343 Obstetric Anesthesia 344 Fetal Assessment and Care those ofhighmolecular weight. actively speedorslowthetransfer ofmanysubstances,particularly Transfer acrossthisbarrierisnotstrictly passive;thetrophoblastcan the intravillousspace,andfetal capillarywall,orendothelium. between theintervillousspaceand the chorionicvilli),stromaof lation, itmusttraversethetrophoblast (cellsthatformtheboundary placenta. villi, andmaternalbloodstayswithintheintervillousspaceof tions. Fetalbloodstayswithinthefetalcapillariesofchorionic There isnodirectcommunicationbetweenmaternalandfetalcircula- and wasteproductspassfromthefetalcirculationtomother. pass fromthematernalcirculationtofetus,andcarbondioxide the motherandfetus;throughplacenta,oxygennutrients Theplacentaistheorganofinterfaceandcommunicationbetween — Weight (grams) Average Fetal Table 12.1 <1 14 45 200 460 820 1000 1700 3400 pp. 165–207.In: et al.Themorphologicalandfunctionaldevelopmentofthefetus, Reprinted withpermissionfrom CunninghamFG,MacdonaldPC,GantNF, Uteroplacental Physiology Inorderforasubstancetopassfrom thematernaltofetalcircu-

Fetal DevelopmentalMilestones Williams Obstetrics,19 th ed. 1993,McGraw-Hill. 2 (weeks) Gestational Age Estimated 3 12 14 18 22 26 28 32 40 Fertilization Characteristics Implantation Eyes closed Intestines inabdomen. Identifi able externalgenitalia well-developed Prominent ears.Lowerlimbs present Lanugo (hair)visible.Vernix adipose tissue Fingernails present.Little Eyelashes present descending Toenails present.Testes Testes inscrotum Fingernails beyondfi ngertips. tion offetalbloodintheumbilicalveinisaboutsame,butPO tissue level: grow andthriveinutero.Thesefactorsincreaseoxygendeliveryatthe • • • saturation (about70 blood intheintervillousspaceislowerthanmaternalarterialoxygen of bloodwithintheintervillousspace,oxygensaturationmaternal fetal bodyweightofoxygentothedevelopingfetus.Becausemixing fetal bloodfl ow. Theplacentasuppliesapproximately8ml/min/kg rate ofoxygentransferacrosstheplacentaislimitedbymaternaland small molecules,alsotraversetheplacentaviapassivediffusion.The dioxide, water,andelectrolytes.Anestheticgases,beingrelatively simple diffusion;thisisthemechanismfortransportofoxygen,carbon Moleculeswithamolecularweightunder500dmoveprimarilyby • • • • is lower(Table Obstetrics, 19thed ., Norwalk,CT:Appleton&Lange, 1993:165–207. morphological andfunctionaldevelopment ofthefetus.In: Based onCunninghamFG,MacDonaldPC,GantNF,etal.(eds.)The PO Maternal andFetalBlood Table 12.2 pH SaO Hemoglobin(g/dl) CO HCO O O Variable PCO

Otherimportantfactorsthatimpactplacentaltransportinclude: DespitethislowPO Highercardiacoutputperbodyweightthanadults Increasedoxygenafﬁ totalsurfaceareaoftheplacenta Higherhemoglobinconcentrationthanadults thedegreeofproteinbinding therateofbothmaternalandfetalbloodﬂ concentrationgradients 2 2 Capacity(mlO Content(ml/dl)

2 2 (mmHg) 2 Content(mM/L) 2 ( 3 (mmHg) (mM/L) % Saturation)

Oxygen, CarbonDioxide,andpHValuesin

12.2 ).

/dl) %

2 ) withaPO nityoffetalhemoglobin ,thefetushasseveraladaptationsallowingitto

2 of30to35mmHg.Oxygensatura-

Uterine Artery 18.8 95 15.8 32 19.6 98 12.0 16.1 7.40 ow Vein 20.7 40 12.2 40 21.8 76 12.0 16.1 7.34

Umbilical Artery 25.0 15 48 26.3 30 16.0 21.4

Williams 6.4 7.35

Vein 24.0 27 14.5 43 25.2 68 16.0 21.4 7.38

345 Obstetric Anesthesia 346 Fetal Assessment and Care pCO dioxide crossestheplacentafasterandmorereadilythanoxygen.The the superiorvenacava(SVC). heart fromtheIVCisstillconsiderablyhigherthanthatreturning in alowerPO to theheartfromlowerhalfoffetalbody.Whilemixingresults oxygenated placentalbloodmixeswithdeoxygenatedreturning division joinstheinferiorvenacava(IVC).Incava, carries bloodtotheportalsinusandhepaticveins,whilemajor the abdominalwalltoliver,whereitdivides.Thesmallerdivision the umbilicalvein;veinentersabdomenandfollows (Figure Thefetalcirculationishighlyadaptedtothismetabolicenvironment partum testwouldbe: demise, orstillbirth,andtodecrease neonatalmorbidity.Anidealpre- Theprimarygoalofintrauterinefetal surveillanceistopreventfetal ies isslightlyhigherthanmaternalvenouspCO • • respiratoryalkalosisinthethirdtrimester. diffusion,asdoesthemildmaternalhyperventilationandresulting content offetalblood. times thatofanadultatrest),andhelpscompensateforthelowerO ment contributestoahighercardiacoutputperweight(asmuchas3 while to returntheplacenta. ing aorta.Aportionofthisbloodﬂ artery, beforebeingshuntedviatheductusarteriosustodescend- brain. BloodfromtheSVCentersrightventricleandpulmonary oxygenated bloodtotheleftventricle,andthenceheart through theforamenovale;thishaseffectofdeliveringbetter-

Fetal Circulation Prepartum FetalAssessment Carbondioxidetransferisbysimplepassivediffusion. Thispatternofshuntsallowsthefetalventriclestopumpinseries Uponenteringtheheart,bloodfromIVCisshuntedprimarily quickandsimpletoperform inexpensive 2 infetalbloodreturningtotheplacentaviaumbilicalarter- in utero,ratherthanparallelasadults.Thisseriesarrange- 12.1 ).Oxygenatedfetalbloodreturnsfromtheplacentavia 2 ,theoxygencontentofbloodreturningtofetal

owsthroughtheumbilicalarteries

2 ,whichfacilitates 2

McGraw-Hill. Macdonald PC,GantNF,etal. development ofthefetus. Reprinted withpermissionfromCunninghamFG, and theductusarteriosus(3).After:The morphologicalandfunctional the fetalcirculationareductusvenosus (1),theforamenovale(2) to theheartandbrainviaascendingaorta.Thethreemajorshuntsof Well-oxygenated bloodreturningfromtheplacentaisselectivelyshunted Figure 12.1 Placenta Umbilical vein Inferior Portal Portal vein sinus vena cava Fetal circulation.Seetextforcompleteexplanation. vena cava Superior arteries Umbilical Williams Obstetrics,19 th ed , pp.165–207.1993, blood Deoxygenated blood Oxygenated 3 Ductus arteriosus 1 Ductus venosus 2 ovale Foramen arteries Hypogastric Aorta

347 Obstetric Anesthesia 348 Fetal Assessment and Care • • • • • • late decelerations. hypoxia andasphyxiawithcertainfetalheartratepatterns,particularly the useofintrapartumfetalheartmonitoring,whichlinked rate anduterinecontractionmonitoring;itwasadirectoutgrowthof Contractionstresstestingcombinestheuseofcontinuousfetalheart Contraction StressTest with signifi heart rate.Incontrast,fetalactivityremainsnormalifnotassociated during uterinecontractionsthatareassociatedwithdecreasesinfetal ment isdecreasedbyhypoxia.Fetalmovementsdecreasesignifi large numbersofpatients.Theunderlyingpremiseisthatfetalmove- of beingsimpleandcheaptoperform,canthereforebeapplied earliest prepartumfetalassessmenttestsdevised.Ithastheadvantage Quantifi Fetal Movement urgency ofdelivery,andarereviewedbelow. may haveimplicationsfortheanesthesiologistintimingand tions, toimprovetheoutcomeofpregnancy.Theresultsthesetests of prepartumtestsareusedbyobstetricians,ofteninselectedpopula- Thereisnosingletestthatmeetsthesecriteria.However,anumber • •

within onehour,furtherfetalevaluationisindicated. takes forhertofeel10movements;ifshefailsmovements Toperformthetest,motherrecordsamountoftimeit ments isgreaterthan3standarddeviationsbeyondthemean. trimester isabout18minutes;aone-hourtimeperiodfor10move- Theaveragetimeittakestofeel10fetalmovementsinthethird turn, orotherwisemoveduringasettimeperiod. instructed tocountthenumberoftimesshefeelsfetuskick, Inthesimplestformoffetalactivitymonitoring,motheris with nodecelerationsassociated contractions;apositivetest Inaconfusingtwistofterminology, anegativetestisreassuring, while thefetalheartrateiscontinuously recorded. Asatisfactorytestrequiresthreecontractions within10minutes nous oxytocinadministration. during thethirdtrimesterbyeither nipplestimulationorintrave- Uterinecontractionscanbeinducedinthenonlaboringpatient abletoproduceobjectiveresults accurate cation offetalactivityperceivedbythemotherwasone cantfetalheartratechangesduringuterinecontractions.

cantly

• • • movement. as longfetalheartrateaccelerationswereassociatedwith it wasobservedthatcontractionstresstestswererarelyabnormal Thenonstresstestwasderivedfromthecontractionstresswhen Nonstress Test • when indicatedforongoingevaluation. prepartum fetalsurveillanceandistypicallyperformedtwiceweekly Duetoitssimplicity,thenonstresstestiscurrentlymainstayof • • • • • • • fetal well-being. it anessentialtoolintheprepartumandintrapartumevaluationof Thewidespreadavailabilityandaccuracyofultrasonographyhasmade Ultrasonography •

Maternalandfetalindicationsfornonstresstestinginclude: ated withfetalmovement. tions of15beatsperminuteormore,lastingsecondsandassoci- rate, adequatevariability,andatleasttwofetalheartrateaccelera- Anormal,orreactive,testexhibitsanormalbaselinefetalheart 40 minutes,whilethemothersimultaneouslynotesfetalmovement. Thefetalheartrate(andusuallyuterineactivity)ismonitoredfor20to contractions. Thissimplifiesthetestandeliminatesneedforuterine must beavoided. centa previaandprematureruptureofmembranes,wherelabor necessary; further,itiscontraindicatedinconditionssuchaspla- Disadvantagesofthetestincludetime,effort,andequipment evaluation. indicates thepresenceofdecelerationsandneedforfurther Collagenvasculardisorders Diabetesmellitus Intrauterinegrowthretardation Decreasedfetalmovement Multiplegestation Chronicdisease means availableof determininggestationalage. measurementsobtainedwithultrasound arethemostaccurate Particularlyinthelatefirstandearly secondtrimesters,fetal provide isanestimateofgestational age. Amongthemostvaluableinformation whichultrasonographycan

349 Obstetric Anesthesia 350 Fetal Assessment and Care performed asearly28weeks. Testing isusuallyperformedat34to36weeksgestation,butmaybe are assessedforthebiophysicalprofile (Table ment ofthefetus’soveralldevelopmentandwell-being.Fiveelements parameters, inconjunctionwithanonstresstest,toprovideanassess- Thebiophysicalprofi le utilizesultrasonographytomeasureseveral Biophysical Profi • • mining acourseofactionwithintermediatevalues(Table Theamnioticfl uid volumetendstoreceivegreaterweightindeter- • • score ofeither0or2. ∗ Test Nonstress Table 12.3 Variable Movements Breathing Fetal Movements Body GrossFetal FetalTone Volume AmnioticFluid

10 totalpointsavailable. to improvementwith optimize outcome;onoccasion,suchanomaliesmaybeamenable allows planningforappropriatepostpartumcareoftheneonate,to Identiﬁ cation ofseriousbutnonlethalanomaliespriortodelivery mits rationalchoicestobemaderegardingrouteofdelivery. As withaccuratedating,identiﬁ cation oflethalfetalanomaliesper- Ultrasonographyisalsohighlyusefulinidentifyingfetalanomalies. marginal. pregnancy isthreatenedbeforefetalviability,orwhenviability Accuratedatingisespeciallyusefulfordeterminingoptionswhen requires intervention. Ascoreof0to6indicatesahighperinatalmortalityratethatusually (Table Ascoreof8to10isgenerallyassociatedwithafavorableoutcome 12.4 )

Elements ofBiophysicalProfi Reactive test Description duration At leastoneepisodeofbreathing60s At leastthreeepisodes to fl exion ofextremitiesorspine At leastoneepisodeofextensionandreturn depth At leastonefl uid pocketofatleast1cmin le

in utero therapy.

12.3 le

); eachisassigneda 2 Score 2 2 2 2 12.4 ∗

). vascular resistanceofintraplacentalvessels(Figure imately 60mmHg,whichisslightlylowerthanpredictedduetothe a slightlyhigherapproximation.Inhealthyparturient,UPPisapprox- mean arterialpressureminusthematernalcentralvenousis arterial pressureminusmeanuterinevenouspressure;thematernal fusion pressure(UPP)isapproximatedasmeanmaternaluterine stand thehemodynamicsofuteroplacentalbloodfl ow. Uterineper- Tounderstandthefetalresponsetolabor,itisnecessaryunder- is aperiodwhere uterinebloodfl ow isessentiallycutoff,andno the contraction;therefore,atpeak ofmostcontractions,there preventing perfusion. flow, andeventuallyuterinearterial pressurewillbeexceeded, ine venouspressurewillbeexceeded, whichconstrictsuterineout- mmHg. Asthepressureincreasesduring acontraction,fi rst theuter- normal uterinecontraction,intrauterinepressurecaneasilyexceed60

0 2 4 Fluid 6:LowAmniotic Amniotic Fluid 6:Normal Fluid 8:LowAmniotic Amniotic Fluid 8:Normal referred high-riskpregnancies,p.880,CopyrightElsevier(1987). Assessment basedonfetalbiophysicalproﬁ le scoring:Experiencein19,221 Gynecology , Vol.157,ManningFA,Morrison I,HarmanCR,etal.Fetal This articlewaspublishedin the ∗ Perinatal 10 BPP Score Proﬁ Table 12.4 Intrapartum Fetal HeartMonitoring Perinatal mortalitywithin1week withoutintervention.

Thefetalcirculationthroughtheplacenta continuesthroughout

le Score Interpretation andManagementofBiophysical

600/1000 125/1000 91/1000 89/1000 Variable 89/1000 1/1000 Mortality <1/1000

∗ American JournalofObstetricsand

Deliver forfetalindications Deliver forfetalindications Deliver forfetalindications Deliver forfetalindications 24 hrsforimmaturity Deliver maturefetus,repeattestin indications membranes, deliverforfetal If functioningrenaltissueandintact Routine Routine Management 12.2 ).Duringa

351 Obstetric Anesthesia 352 Fetal Assessment and Care identify potentiallyominoussignsandtakecorrectiveaction. monitoring, asheorsheisoftenthefi rst physicianinthepositionto important thattheanesthesiologistbefamiliarwithbasicsofFHR tion ofthefetalhearttraceisresponsibilityobstetrician,it the addedstressofuterinecontractions.Whileultimatelyinterpreta- ing fetalstatusduringlabor,specifi cally theresponseoffetusto this stresswithoutproblems. labor. Ahealthytermfetushassufficient metabolicreservetotolerate to “holditsbreath”forafewmomentseveryminutesduring exchange occurs.Theanalogycanbemadethatthefetusisrequired Figure 12.2 • • maintained. does notusuallyrequireurgentintervention, aslongvariabilityis (bpm). FetaltachycardiaisapersistentFHRabove160bpmand ThenormalbaselineFHRisbetween110and160beatsperminute Baseline FHR • • •

ElementsoftheFHRtobeconsideredininterpretationinclude: Monitoringthefetalheartrate(FHR)isprimarymeansofassess- Fetaltachycardiacanbetheresultof: presenceorabsenceofdecelerationsandaccelerations variabilityoftheFHR baselinefetalheartrate Maternalfeverorinfection(particularly chorioamnionitis). ritodrine, oftenused fortocolysis). tachycardia — Medicationsadministeredtothe mothercanalsocausefetal UPP MMUVP –MeanMaternalUterineVenousPressure MMUAP –MeanMaternalUterineArterialPressure Calculation ofUterinePerfusionPressure. UPP –UterinePerfusionPressure atropine andbeta-sympathomimetics (terbutalineor 60 mmHg 70 mmHg–10 (M.M.U.A.P –M.M.U.V.P.)

• • Bradycardiamaybeassociatedwith: FHR monitorstrips(Figure slightly. Thisresultsinthejagged,“sawtooth”patternseennormal ever, withtheresultthatR–Rintervalisconstantlychanging changing balanceofautonomicinfl uences affecttheSA node, how- and theFHRtracewouldappearasastraight,fl at line.Aconstantly absence ofanyotherinfl uences, theR–Rintervalwouldbeconstant, R-waves ofthefetalECG.TheSAnodesetsintrinsicFHR;in VariabilityintheFHRreferstominutefl uctuations betweenthe Variability • • • • increasing strokevolume. has averylimitedabilitytocompensatefordecreasedheartratesby adults, cardiacoutputofthefetusishighlyratedependent; Fetalbradycardiaisdefi ned asaFHRbelow110bpm.Incontrast to They aredefi fetal insults,andmayberelatedto theuterinecontractionpattern. DecelerationsareperiodicFHRchanges thatoccurinresponseto Decelerations taken asasignofCNShypoxia. nerve andcardiacsympathetics.Diminished orabsentvariabilityis through thecerebralcortexandbrainstem,outvagus between aorticarchandcarotidchemoreceptorsbaroreceptors, evidence ofanintact,functionalneuraxis:appropriateCNStraffi c tuation of6–10bpm.ThepresencevariabilityintheFHRistakenas

Somecongenitalheartlesions. low heartrateduringactivelabor. labor describedabove,evenahealthyinfantcannottoleratesuch Duetotheepisodicinterruptionsofuterinebloodﬂ ow during is increased. infant willexperienceprogressivehypoxemiaunlesstheheartrate bpm foraprolongedperiodduetometabolicreserve,stressed Whileahealthyfetuscanprobablytolerateheartrateof90to100 insult. Moresigniﬁ cantly, fetalbradycardiaisoftenaresponsetohypoxic thetics). Maternalmedications(beta-blockersandhighlevelsoflocalanes- become progressivelyanaerobic,andPO ing ofbloodtothebrain,heart,andvitalorgans;othertissuewill AtaFHRbelow90bpm,cardiacoutputfalls,resultingintheshunt- nedas early, variable,

12.3

). Normalvariabilityisdeﬁned asﬂ

and

late . 2 andpHwilldecrease. uc-

353 Obstetric Anesthesia 354 Fetal Assessment and Care shape (Figure abrupt onsetandreturnto baseline,andareirregularin tions isappropriately“variable.”Theyarecharacterizedbyan cal cordcompression.Theirtemporalrelationtouterinecontrac- Variabledecelerationsareconsideredtobeavagalrefl ex toumbili- Variable Decelerations ered benign. • • to “mirror”thecontraction(Figure to baselinebeforetheendofcontraction;theyaresometimessaid contraction, withagradualdecreaseintheFHRandreturn compression duringcontractions.Theybeginwiththeonsetof Earlydecelerationsareconsideredtobeavagalresponsefetalhead Early Decelerations Gynecol. 1984;27(1):84–94. Management ofacutefetaldistressintheintrapartumperiod. infl uences tendtodecreaseit. inflReprinted withpermissionfromHuddlestonJF, uences tendtoincrease the baselineheartrate,whileparasympathetic Figure 12.3 undertaken. progressivefetalacidosis,andefforts toeliminatethemshouldbe Ifrepetitiveandsevere,variable decelerationsmayleadto bpm belowbaselinefor60seconds or more. Theyareconsidered“severe”when theFHRdrops60ormore autonomic Lack of effects Autonomic infl uences andthe fetalheartrate.Sympathetic

12.5 ). FHR 120 150 180 210 240 30 60 90 autonomic Normal effects 12.4 ). Theyaregenerallyconsid- influence FHR FHR influence

: Parasympathetic : Sympathetic Clin Obstet markedlyreducedandfetalPO a briefperiodduringeachcontractionwhenoxygenexchangeis ﬂ to indicateuteroplacentalinsufﬁciency. Asnotedabove, uterineblood Latedecelerationsareconsideredominous,becausetheyassumed Late Decelerations contraction. (Note:Theuterinecontractionpressurescaleisnotaccurate.) contraction pattern,andtheFHRreturnstobaselinebeforeendon parturient inearlylabor.Thedecelerationstendto“mirror”theuterine Figure 12.4 maintained between thedecelerations.) before theendofcontraction.(Note thatFHRvariabilityiswell the uterinecontraction,andfetalheart ratehasreturnedtobaseline year oldparturientinactivelabor.Thedecelerations beginafterthestartof Figure 12.5 10:53 06:00 ow ceasesatthepeakofnormaluterinecontractions;thisleadsto 100 120 150 180 210 240 20 40 60 80 30 60 90 0 120 150 180 210 240 100 30 60 90 20 40 60 80 0 NIBP: 127/67, 92 Hr: Early decelerations.decelerationsina23-year-old Variable decelerations.Severevariabledecelerations ina30 IP 1/1 r 7NB:176,H:9 NIBP: 114/56, 92 Hr: NIBP: 117/62, 91 Hr: NIBP: 116/61, 87 Hr: 120 150 180 210 240 100 30 60 90 20 40 60 80 0 10:57 06.04 120 150 180 210 240 100 30 60 20 40 60 80 90 0 2 fallsslightly(Figure 120 150 180 210 240 100 30 60 90 40 60 80 20 0 100 120 150 180 210 240 12.6 40 60 80 20 30 60 90 0 ). Ahealthy 11:01 06:08

355 Obstetric Anesthesia 356 Fetal Assessment and Care disrupted, resultinginatransientdropfetalpO decreases duringauterinecontraction,placentaloxygenexchangeisbriefl the aorticarchandcarotids. refl and heart,awayfromperipheraltissues.Thisactivatesavagal tions inoxygensupply.Theresultisthatbloodshuntedtothebrain stressed fetusmaynotbeabletotolerateeventhesebriefinterrup- fetus hassuffi cient reservetotoleratethisbrief interruption,buta Figure 12.6 1984;27(1):84–94. of acutefetaldistressintheintrapartumperiod. fetal heartrate. Reprinted withpermissionfromHuddlestonJF,Management fetal pO suffi cient reservetotoleratethisbriefinterruption,butinastressedfetus,the • • • 100 (a) 120 150 180 210 240 20 40 60 80 30 60 90 0 to delivertheinfant asquicklypossible. sign, indicatingseverefetalhypoxemia; everyeffortshouldbemade Latedecelerationswithabsentvariability areaparticularlyominous or todeliverthefetusshouldbemade. and deterioration.Aggressiveefforts toeliminatethedecelerations Ifrepetitive,latedecelerationscanlead toprogressivefetalacidosis to baselineaftertheendofcontraction (Figure from baselineafterthestartofcontraction,andasmoothreturn LatedecelerationsarecharacterizedbyasmoothdecreaseinFHR exduetotransientfetalhypertension,activatingbaroreceptorsof 2 dropsbelowacriticallevelcausing avagally-mediateddecreasein Mechanism oflateFHRdecelerations.Asuterinebloodfl 120 150 180 210 240 100 30 60 90 20 40 60 80 0 Limit offetalreserve

120 150 180 210 240 100 (b) 30 60 90 20 40 60 80 0

Clin ObstetGynecol . 2

. Ahealthyfetushas 120 150 180 210 240 100 30 60 90 20 40 60 80 0 12.7 ). pO venous Umbilical pressure Intra-uterine trace FHR ow 2 y contraction pressurescaleisnotaccurate.) and persistsafterthecontractionhasresolved.(Note:Theuterine contraction pattern:thedropinFHRbeginsafterstartofcontraction, parturient inactivelabor.ThedecelerationstheFHRlagbehinduterine Figure 12.7 compression thatmaybeimpedinguterinebloodﬂ Therationaleformaternalpositionchangeistoeliminateaortocaval Position Change Interventions possible todetermineexactlywhichstepwillalleviatethefetalinsult. ventions thatshouldallbeappliedatthesametime,asitisrarely can beeffected.Inuteroresuscitationconsistsofseveraldistinctinter- or atleastmayimprovefetalstatusduringtheperiodbeforedelivery pected. Itmaypreventtheneedforurgentinterventionanddelivery, that shouldbeattemptedwhenfetalcompromiseordistressissus- Inutero • • 11:31

InUteroResuscitation sion oftheabdominal venacava;inthisinstance, however, the The“supine-hypotensionsyndrome” resultsfromsimilarcompres- blood ﬂow totheplacenta. aorta incertainsituationssomepatients. Thiscanrestrictuterine the massofgraviduterusmay still impingeontheabdominal placement positionshouldberoutine duringallphasesoflabor,but Avoidanceofsupinepositioning,and useoftheleftuterinedis- resuscitation,orfetalistheﬁ rst intervention 100 120 150 180 210 240 20 40 60 80 30 60 90 0 Late decelerations.Repetitivelatedecelerationsina31-year-old Turned totheleftside 11:35

120 150 180 210 240 100 30 60 90 20 40 60 80 0 ow. 120 150 180 210 240 100 20 30 60 90 40 60 80 0

11:39

357 Obstetric Anesthesia 358 Fetal Assessment and Care • • • • room air(FiO blood oxygencontentdoesnotincreasesigniﬁcantly, becauseevenon DespitelargeincreasesinmaternalPO Oxygen Administration • oxygen.

1.0 0.47 ∗ 0.21 Table 12.5 epidural anesthesia. et al.Oxygentransferfrommothertofetus during cesareansectionunder Reprinted withpermissionfromRamanathanS,GandhiArismandy J, FiO Maternal Artery andVeinOxygenGradient

In: mlO increase signifi Unfortunately,itisnotusuallypossibletoincreasematernalFiO (Table increasing fetalbloodoxygencontentmayimprovestatus blood flow, increaseduterinetone,orumbilicalcordcompression), Iffetaloxygendeliverydecreasesforanyreason(decreaseduterine cord compressionorfetalheadatthepelvicbrim. to movethefetus’sweightcephalad,andcandecreaseumbilical knees andupperchestoranteriorshouldersonthebed.Thistends “ Inextremesituations,themothershouldbeplacedin problem, theothershouldbetried. lateral position,eitherleftorright;ifonesidedoesnotrelievethe Witheithersituation,themothershouldbeturnedtofull maternal hypotension. decrease invenousreturnbecauseofcavalcompressionresults available evidenceindicatesthatfetalPO Fetalhemoglobinhasadifferentaffi nity foroxygen,however,and mask athighfl ows (15l/minormore)cansignifi cantly increase with ananesthesiamachine).Administeringoxygenviasimpleface- 1.0 inthestandardlaborsuite(thoughthiscanbeaccomplished knee-chest” position,i.e.,turnedproneandpositionedwithher 2

2 12.5 ). /100 mlblood 17.7 15.9 13.2 oxygen content Umbilical venousblood Relation betweenMaternalFiO 2 =0.21)maternalhemoglobinisnearlysaturatedwith cantlywithincreasesinmaternalFiO + /– 0.1 + /– 0.8 + /– 0.5 Anesth Analg. 1982;61:576–581.

∗

2 withincreasingFiO 11.8 7.9 5.3 oxygen content Umbilical arterialblood + /– 0.4 + /– 0.6 + /– 0.8 2 andoxygensaturation 2 andUmbilical 2 . ∗

2 ,maternal

2 to • • • • • oxygen delivery. between contractionstorecoverfromtheepisodicdecreasein rapid contractionpatternmaynotallowafetussufficienttime recover andtheurgencyorneedfordeliverymaybeavoided.Avery can bestopped,oratleastslowed,thefetusmayhaveachanceto the ﬁ rst stepstotakeisstopthecontractions.Ifcontractions Sincethecauseofdecelerationsisuterinecontractions,one Decreasing UterineTone • • • may improveuterineandplacentalperfusion. decreases inuterinebloodﬂ ow, increasingmaternalbloodpressure Sincedecreasesinmaternalbloodpressurecanclearlyresult Blood PressureSupport

to beeffective.Careful maternalbloodpressuremonitoring is Sublingualnitroglycerin,eithertablets orspray,hasalsobeenshown action (1–2min),soitshouldbeviewed asatemporizingmeasure. glycerin hasarapidspeedofonset(30–45 sec)andashortdurationof 500 mcguntilthedesiredrelaxanteffect isseen.Intravenousnitro- of 50mcg:thedosecanbeescalated upwardstoashigh Intravenousnitroglycerinshouldbeadministered beginningatadose has proveneffectiveforrapidlyproducinguterinerelaxation. Nitroglycerin,eitherintravenousorsublingual,isanotheragentthat intravenous, 0.25mg. uterine contractionsisprobablyterbutaline,eithersubcutaneousor Themostwidelyusedmethodofdecreasinguterinetoneorstopping reduced orstoppedwhenthereisevidenceoffetalcompromise. Ifcontractionsareaugmentedwiththepitocin,infusionshouldbe interventions. Closelymonitorbloodpressureresponseduringandfollowing lactated Ringer’ssolution,orPlasmalyte administration, withnonglucosecontainingﬂ uids (normalsaline, 5–10 mg);thisshouldbeaccompaniedbyvigorousintravenousﬂ intravenous phenylephrine40–80mcg(alternatively,ephedrine Themostrapidmeansofelevatingmaternalbloodpressureiswith compromise isindicated. empirically increasingmaternalbloodpressureinthefaceoffetal pressureisknowntobeexcessive(asinseverepreeclampsia), Exceptinthoseunusualcircumstanceswherematernalblood improvement infetalbloodoxygencontent. maternal FiO

2 ,anditisreasonabletoassumeacorresponding

® ).

uid

359 Obstetric Anesthesia 360 Fetal Assessment and Care 10.