Dr. Azam’s Notes in Anesthesiology Postgraduates appearing 3rd Edition for MD, DNB & DA Exams Regional Anesthesia Edited by: Dr. Azam Consultant Anesthesiologist & Critical Care Specialist www.drazam.com 2 Dr Azam’s Notes in Anesthesiology 2013 Dedication To Mohammed Shafiulla, my father, my oxygen, companion, and best friend; for being my major pillar of support and making this vision a reality. Thank you for your continual sacrifices with boundless love and limitless gratitude, for the sake of your children. I owe you a debt I can never repay. I also would like to thank my mom (Naaz Shafi), my wife (Roohi Azam), my two lovely kids (Falaq Zohaa & Mohammed Izaan), for their support, ideas, patience, and encouragement during the many hours of writing this book. Finally, I would like to thank my teachers (Dr.Manjunath Jajoor & team) & Dr T. A. Patil . The dream begins with a teacher who believes in you, who tugs and pushes and leads you to the next plateau, sometimes poking you with a sharp stick called "truth." 3 Dr Azam’s Notes in Anesthesiology 2013 Dr Azam’s Notes in Anesthesiology 2013 A NOTE TO THE READER Anesthesiology is an ever-changing field. Standard safety precautions must be followed, but as new research and clinical experience broaden our knowledge, changes in treatment and drug therapy may become necessary or appropriate. Readers are advised to check the most current product information provided by the manufacturer of each drug to be administered to verify the recommended dose, the method and duration of administration, and contraindications. However, in view of the possibility of human error or changes in medical sciences, neither the author nor the publisher nor any other party who has been involved in the preparation or publication of this work warrants that the information contained herein is in every respect accurate or complete, and they disclaim all responsibility for any errors or omissions or for the results obtained from use of the information contained in this work. Readers are encouraged to confirm the information contained herein with other sources. It is the responsibility of the licensed prescriber, relying on experience and knowledge of the patient, to determine dosages and the best treatment for each individual patient. Neither the publisher nor the editor assumes any liability for any injury and/or damage to persons or property arising from this publication. Dr. Azam 4 Dr Azam’s Notes in Anesthesiology 2013 Contents Dr Azam’s Notes in Anesthesiology 2013 1. Principles of regional Anesthesia - 5 29. Lumbar Sympathetic Block - 52 2. Describe the course of Sciatic Nerve and any one approach to 30. Inter costal Nerve block - 53 block the nerve - 9 & 65 31. Interpleural block - 56 3. Describe the anatomy of Stellate ganglion. Discuss indications 32. Perineal Anesthesia - 58 technique & implications of stellate ganglion block - 11 & 45 33. Cutaneous innervations of the lower limb - 59 4. Describe Anesthetics concerns for regional anesthesia in a 34. Cutaneous innervations of upper limb - 60 patient on anticoagulants - 13 35. Psoas Compartment block 61 5. Describe the clinical manifestation of LA toxicity & its 36. Femoral Nerve Block - 62 & 100 management - 15 37. Obturator Nerve Block - 63 6. Describe regional block for removal of infected corn foot - 17 38. Inguinal Paravascular technique - 64 7. Anatomy of Epidural Space & the methods of identification - 19 39. Blocks around the Knee Joint - 68 8. Phantom limb pain - 21 40. Saphenous nerve block - 69 9. Cauda Equina Syndrome - 22 41. Common Peroneal Nerve - 70 10. Total Spinal Anesthesia - 23 42. Tibial Nerve - 71 11. Spinal Needles - 24 43. Complications of Spinal & Epidural Anesthesia - 72 12. Post Dural Puncture Headache - PDPH - 25 44. IVRA - 73 13. Differential Blockade - 29 45. Anatomy of vertebral column & physiology of spinal anesthesia - 76 14.Nerve Classification And Sequence Of Block - 31 46. Epidural Anesthesia - 87 15. Supraclavicular Block - 32 & 47 47. Caudal Anesthesia - 92 16. Hernia Block - 33 48. Guidelines on regional anesthesia in patients treated with heparin 17. Field Block for tonsillectomy - 35 oral anti-coagulations, anti platelets and others - 94 18. Celiac Plexus Block - 36 49. FACIAL NERVE BLOCK - 95 19. Interscalene Block - 39 & 46 50. Brachial Plexus - Applied Anatomy - 96 20. Gasserian Ganglion Block - 40 51. Post Operative Analgesia - 101 21. Maxillary Block- 41 52. Patient Controlled Analgesia (PCA) - 102 22. Mandibular Block - 42 53. Assessment Of Pain - 106 23. Glossopharyngeal Nerve block - 43 54. Preemptive Analgesia - 109 24. Superior Laryngeal Nerve block - 44 55. Chronic Pain Management - 112 25. Axillary Nerve Block - 48 56. Mixture of Local Anesthetics - 119 26. Wrist Block - 49 57. Spinal Anesthesia In Children - 121 27. Autonomic Blockade - 50 58. Bromage score - 123 28. Sympathetic Blocks - 51 59. Blocks of Eye - 126 5 Dr Azam’s Notes in Anesthesiology 2013 Contents Dr Azam’s Notes in Anesthesiology 2013 6 Dr Azam’s Notes in Anesthesiology 2013 1. Principles of regional Anesthesia. Dr Azam’s Notes in Anesthesiology 2013 Definition: Anatomic consideration: • Is defined as reversible blockade of nerve conduction by L.A. in • Landmarks: the part where it is applied. • Superficial • Deep Types of RA: Nerve Fibres: 4 types: Diameter Velocity Type Myelin Location Function • Topical anaesthesia: Surface application to skin or mucous. μm (m/sex) • Infiltration anesthesia: Injecting LA into the tissue to be cut Aα 15-22 + 70-120 to & from Motor, muscle • Field block: Injecting LA into the area to be operated. muscles and proprioceptors Ex: Inguinal field block. • Aβ 8-13 + 40-70 joints Touch. • Conduction block: (Referred to RA): Accomplished by depositing a solution along the course of nerve supplying a region of the Aγ 4-8 + 15-40 To muscle Touch, pressure, body where elimination of sensory and / or motor innervation is spindles tone of muscle required. Aδ 1-4 + 5-15 Afferent Pain, temp, • Ex: Spinal / Epidural analgesia. sensory nervespressure Pre-block evaluation: B 1-3 + 3-14 Preganglionic Preganglionic Last dose of Heparin & low molecular weight heparin. • sympathetic sympathetic • Patient on T.clopidogrel activity • Aspirin ingestion (consider RA with BT < 10 minutes) CS 0.3-1.3 - 0.7-1.3 Postganglionic Postganglionic • Coagulopathies Pre-medications: sympathetic sympathetic • Benzodiazepines, narcotics, antihistamines, anticholinergics, activity diversion and distraction. γ 0.4-1.2 - 0.1-2 Afferent Pain, temp, • These provide: comfort, protection from CNS toxicity, protection sensory nervestouch from allergy, from reflex bradycardia. • Facilities: proper room, ventilation, light, equipments for CPR etc. Asepsis: • Hexachlorophene or tincture of zephiran used over face, scrotum, perineum. • Betadine, 70% ethyl or isopropyl alcohol used. Skin preparation: • Soap water scrub or 70% ethyl alcohol for 5 min. • Normally skin contains 200-600 bacteria / inch2 of surface area. • Above measure decrease it by 20-40 bacteria / inch2. 7 Dr Azam’s Notes in Anesthesiology 2013 Principles of regional Anesthesia.Continuation: Dr Azam’s Notes in Anesthesiology 2013 Pharmacologic considerations: Summary of chemical factors: • LA blockade depends on 4 factors: • Degree of hydrolysis determines penetrability. 1. Diffusion to nerve and into bundle: Depends on solubility. • Effectiveness is a linear function of pH of tissues. 2. Penetration into nerve cell: Depends on non-ionized (base) • Alkaline pH of solutions increases activity. form. • Buffering to an alkaline pH has a greater effectiveness. 3. Distribution in a nerve fiber cell: Solubility. • Acid media neutralize anesthetic action. 4. Fixation: Affinity of cation form to channel receptors. Minimum anesthetic condition (Cm): Recovery from LA block depends on 4 factors: • Lowest concentration of drug that blocks conduction is called • Absorption: Into circulation. Cm. • Release process: Nerve fibers releases fixed drug as Differential block (Cm): gradient of concentration reverses with time. • Small fibres blocked by low concentration whereas myelinated • Redistribution: to other organs after absorption. ones need high concentration of L.A. This is due to differing Cm • Metabolism and elimination. values of L.A. for different nerve fibres. Transitional block (Wedensky block ): Dissociation constants (pKa): • A latent period required for a L.A. to change the function of a nerve from an unblocked state to the blocked state. During this • It is defined as a pH at which equal concentration of acid and basic forms of a substances exist. time, one conceives of either a partial or threshold block and repetitive stimuli may be conducted. During this time patients • The base or nonionized form is responsible for penetration of nerve and the ionized or cation form is responsible for the feels skin incision but with less intense. action of LA on nerve. Order of block: Amount of base form present is inversely proportional to pKa • • Sympathetic block: of that agent at pH 7.4. Ex: Lidocaine pKa is 7.74 has 65% • Vasomotor ionized and 35% in Non-ionized form at pH 7.4. • Cold • Tetracaine and procaine have high pKa, hence slow onset • Warmth bupivacaine: 8.1 pKa. • Slow pain • Benzocaine: with pKa 3.5 has rapid onset of action. • Fast pain • Outside nerve PH 7.4 à once the base form gets into the • Motor axon where PH is 7.2 à the base form converts into ionized • Joint sense form which is now required for its action on nerve. • Pressure Mechanism of action: • Block of ionic channels: It prevents Na to enter into cells following stimulation hence blocks action potential. • Receptor expansion. • Prior depolarization: also blocks K channels, but its affinity towards Na channels is great. 8 Dr Azam’s Notes in Anesthesiology 2013 Principles of regional Anesthesia.Continuation: Dr Azam’s Notes in Anesthesiology 2013 • Glucose in L.A impair its action due to hypo-osmotic effect. Pharmacokinetics: • Contact of L.A on nerve surface: Atleast 3-4 mm of nerve Absorption: surface has to come in contact with L.A or atleast 3 node of Gets absorbed into blood stream after injection into tissue and depends on: Ranvier blocked.