Fluids,Fluids, ElectrolytesElectrolytes andand AcidAcid--BaseBase BalanceBalance Todd A. Nickloes, DO, FACOS Assistant Professor of Surgery Department of Surgery Division of Trauma/CriticalTrauma/Critical Care University of Tennessee Medical Center - Knoxville ObjectivesObjectives DefineDefine normalnormal rangesranges ofof electrolyteselectrolytes Compare/contrastCompare/contrast intracellular,intracellular, extracellularextracellular,, andand intravascularintravascular volumesvolumes OutlineOutline methodsmethods ofof determiningdetermining fluidfluid andand acid/baseacid/base balancebalance DescribeDescribe thethe clinicalclinical manifestationsmanifestations ofof variousvarious electrolyteelectrolyte imbalances.imbalances. NormalNormal PlasmaPlasma RangesRanges ofof ElectrolytesElectrolytes Cations Concentration Sodium 135-145 mEq/L Potassium 3.5-5.0 mEq/L Calcium 8.0-10.5 mEq/L Magnesium 1.5-2.5 mEq/L Anions Chloride 95-105 mEq/L Bicarbonate 24-30 mEq/L Phosphate 2.5-4.5 mEq/L Sulfate 1.0 mEq/L Organic Acids (Lactate) 2.0 mEq/L Total Protein 6.0-8.4 mEq/L NormalNormal RangesRanges ofof ElectrolytesElectrolytes SodiumSodium (Na(Na+)) RangeRange 135135 -- 145145 mEqmEq/L/L inin serumserum TotalTotal bodybody volumevolume estimatedestimated atat 4040 mEqmEq/kg/kg 1/31/3 fixedfixed toto bone,bone, 2/32/3 extracellularextracellular andand availableavailable forfor transtrans--membranemembrane exchangeexchange NormalNormal dailydaily requirementrequirement 11--22 mEqmEq/kg/day/kg/day ChiefChief extracellularextracellular cationcation NormalNormal RangesRanges ofof ElectrolytesElectrolytes PotassiumPotassium (K(K+)) RangeRange 3.53.5 -- 5.05.0 mEqmEq/L/L inin serumserum TotalTotal bodybody volumevolume estimatedestimated atat 5050 mEqmEq/kg/kg 98%98% intracellularintracellular concentration of 150 mEq/L extracellular concentration of 70 mEq/L NormalNormal dailydaily requirementrequirement 0.50.5 –– 0.80.8 mEqmEq/kg/day/kg/day ChiefChief intracellularintracellular cationcation NormalNormal RangesRanges ofof ElectrolytesElectrolytes IntracellularIntracellular vv ExtracellularExtracellular Electrolyte composition is different + + - - Intracellular - K , Mg , PO4 , SO4 , and proteins + + + - - Extracellular - Na , Ca , Mg , Cl , HCO3 and lactate Compositions of ions are maintained selective permeability of cell membranes active ion pumps Movement of water is passive colloid osmotic gradients intravascular v interstitial spaces (extracellularly) osmolar gradients intracellularly v extracellularly FluidFluid BalanceBalance CalculationCalculation ofof OsmolarityOsmolarity OsmOsm == 22 xx [[NaNas]] ++ [[gluglu // 18]18] ++ [BUN[BUN // 2.8]2.8] NormalNormal osmolarityosmolarity isis 280280--300300 mOsmmOsm/L/L NaNa+ resorptionresorption andand excretionexcretion areare thethe drivingdriving forcesforces forfor osmolarityosmolarity CalculatingCalculating TBWTBW deficitdeficit TBWD males = [(140 – SNa+) x 0.6 x IBW (kg)]/ 140 TBWD females = [(140 – SNa+) x 0.5 x IBW (kg)]/ 140 FluidFluid BalanceBalance HereHere’’ss aa tricktrick ForFor everyevery 3.53.5 mEqmEq thethe NaNa+ isis overover 140,140, therethere isis anan estimatedestimated freefree waterwater deficitdeficit ofof 11 L.L. NormalNormal PhysiologyPhysiology TotalTotal bodybody waterwater 60% IBW of males 50-55% IBW of females directly related to muscle mass (70% water) inversely related to fat content (10% water) This is why witches float CompartmentsCompartments Intracellular Extracellular Interstitial 10 BodyBody FluidFluid CompartmentsCompartments 2/32/3 (65%)(65%) ofof TBWTBW isis intracellularintracellular (ICF)(ICF) 1/31/3 extracellularextracellular waterwater 2525 %% interstitialinterstitial fluidfluid (ISF)(ISF) 55-- 88 %% inin plasmaplasma (IVF(IVF intravascularintravascular fluid)fluid) 11-- 22 %% inin transcellulartranscellular fluidsfluids –– CSF,CSF, intraocularintraocular fluids,fluids, serousserous membranes,membranes, andand inin GI,GI, respiratoryrespiratory andand urinaryurinary tractstracts (third(third space)space) 11 NormalNormal PhysiologyPhysiology 8% Intravascular water 25% Interstitial water 67% Intracellular water 13 NormalNormal PhysiologyPhysiology TwoTwo mainmain compartmentscompartments Intracellular 2/3 of TBW 40% body weight 8% Intravascular water Extracellular 25% Interstitial water Intravascular and Interstitial compartments 67% Intracellular 1/3 of TBW water 20% body weight 15 FluidFluid compartmentscompartments areare separatedseparated byby membranesmembranes thatthat areare freelyfreely permeablepermeable toto water.water. MovementMovement ofof fluidsfluids duedue to:to: hydrostatichydrostatic pressurepressure osmoticosmotic pressurepressure CapillaryCapillary filtrationfiltration (hydrostatic)(hydrostatic) pressurepressure CapillaryCapillary colloidcolloid osmoticosmotic pressurepressure InterstitialInterstitial hydrostatichydrostatic pressurepressure TissueTissue colloidcolloid osmoticosmotic pressurepressure 16 17 Cell in a hypertonic solution 18 Cell in a hypotonic solution 19 20 BalanceBalance FluidFluid andand electrolyteelectrolyte homeostasishomeostasis isis maintainedmaintained inin thethe bodybody NeutralNeutral balance:balance: inputinput == outputoutput PositivePositive balance:balance: inputinput >> outputoutput NegativeNegative balance:balance: inputinput << outputoutput 21 SolutesSolutes –– dissolveddissolved particlesparticles ElectrolytesElectrolytes –– chargedcharged particlesparticles CationsCations –– positivelypositively chargedcharged ionsions NaNa+,, KK+ ,, CaCa++,, HH+ AnionsAnions –– negativelynegatively chargedcharged ionsions - - 3- ClCl ,, HCOHCO3 ,, POPO4 NonNon--electrolyteselectrolytes -- UnchargedUncharged Proteins,Proteins, urea,urea, glucose,glucose, OO2,, COCO2 22 BodyBody fluidsfluids are:are: ElectricallyElectrically neutralneutral OsmoticallyOsmotically maintainedmaintained SpecificSpecific numbernumber ofof particlesparticles perper volumevolume ofof fluidfluid 23 HomeostasisHomeostasis maintainedmaintained by:by: IonIon transporttransport WaterWater movementmovement KidneyKidney functionfunction 24 Basic Definitions MW (Molecular Weight) = sum of the weights of atoms in a molecule mEq (milliequivalents) = MW (in mg)/ valence mOsm (milliosmoles) = number of particles in a solution 25 Movement of body fluids “ Where sodium goes, water follows.” Diffusion – movement of particles down a concentration gradient. Osmosis – diffusion of water across a selectively permeable membrane Active transport – movement of particles up a concentration gradient ; requires energy 26 27 NormalNormal PhysiologyPhysiology NaNa+ resorptionresorption secondarysecondary toto aldosteronealdosterone OccursOccurs inin distaldistal convolutedconvoluted tubulestubules ActiveActive exchangeexchange forfor KK+ andand HH+ ionsions MaintainsMaintains extracellularextracellular volumevolume andand osmolarityosmolarity WaterWater resorptionresorption secondarysecondary toto antidiureticantidiuretic hormonehormone OccursOccurs inin collectingcollecting ductsducts ModulatedModulated byby intracranialintracranial osmoreceptorsosmoreceptors andand atrialatrial stretchstretch receptorsreceptors NormalNormal PhysiologyPhysiology NaNa++ modulationmodulation Renal perfusion decreases JG apparatus secretes renin Renin cleaves angiotensinogen Renin secretion ceases to angiotensin I Angiotensin I converted to Renal perfusion increases II by ACE Angiotensin II stimulates aldosterone Extracellular volume secretion from adrenal cortex expansion as water follows Na+ Aldosterone increases Na+ resorption in exchange for K+ in DCT 30 NormalNormal PhysiologyPhysiology Na+Na+ modulationmodulation Result: increased water consumption increased water conservation Increased water in body increased volume and decreased Na+ concentration 31 Dysfunction and/or Trauma Leads to: Decreased amount of water in body Increased amount of Na+ in the body Increased blood osmolality Decreased circulating blood volume 32 RegulationRegulation ofof bodybody waterwater ADHADH –– antidiureticantidiuretic hormonehormone ++ thirstthirst DecreasedDecreased amountamount ofof waterwater inin bodybody IncreasedIncreased amountamount ofof Na+Na+ inin thethe bodybody IncreasedIncreased bloodblood osmolalityosmolality DecreasedDecreased circulatingcirculating bloodblood volumevolume StimulateStimulate osmoreceptorsosmoreceptors inin hypothalamushypothalamus ADHADH releasedreleased fromfrom posteriorposterior pituitarypituitary IncreasedIncreased thirstthirst 33 NormalNormal PhysiologyPhysiology FreeFree HH22OO modulationmodulation Intracranial osmoreceptors detect increased plasma osmolarity Adenohypophysis (posterior Plasma osmolarity increases pituitary) secretes ADH Renal collecting ducts become Renal collecting ducts become less permeable to water more permeable to water Adenohypophysis ceases ADH Plasma osmolarity decreases secretion Intracranial osmoreceptors detect decreased osmolarity Acid/BaseAcid/Base BalanceBalance TheThe managementmanagement ofof HydrogenHydrogen ionsions measuredmeasured asas pHpH maintainedmaintained atat 7.47.4 +/+/-- 0.050.05 ThreeThree mechanismsmechanisms (differing(differing effectiveeffective intervals)intervals) bufferingbuffering systemssystems inin plasmaplasma ventilatoryventilatory changeschanges forfor COCO2 excretionexcretion RenalRenal tubulartubular excretionexcretion ofof HydrogenHydrogen ionsions Acid/BaseAcid/Base