Presentation for a lecture on_Anesthesia_part_3.pptx

Presentation for a lecture on_Basics of Anesthesia part 3

1. Anesthesiology Local anesthetics & regional anesthesia Anesthesiology , Reanimatology & Intensive care Faculty with Ambulance/Paramed course. TSMU of RF Health ministry

2. Anesthesiology History of local anaesthetics Erythroxylon coca Albert Niemann inventor of cocaine Vassily von Anrep

3. Anesthesiology History of local anaesthetics Karl K¨oller ophthalmologist

4. Anesthesiology History of local anaesthetics

5. Anesthesiology Structure and function of nerve fibres

6. Anesthesiology Structure and function of nerve fibres Diagram showing transverse section of (a) myelinated nerve fibres and (b) unmyelinated nerve fibres. A – axon or dendrite; m – myelin sheath; sn – nucleus of Schwann cell.

7. Anesthesiology Structure and function of nerve fibres Myelinated axon. A – The diagram shows a cross section of an axon and its coverings formed by a Schwann cell: the myelin sheath and neurilemma . B – Transmission electron micrograph showing how the densely wrapped layers of the Schwann cell’s plasma membrane form the fatty myelin sheath

8. Anesthesiology Structure and function of nerve fibres Compound Aα, Aδ , and C fiber action potentials recorded after supramaximal stimulation of a rat sciatic nerve. Note the differing time scale of the recordings. In peripheral nerves, Aδ and C fibers have much slower conduction velocities, and their compound action potentials are longer and of less amplitude when compared with those from Aα fibers.

9. Anesthesiology A – Action potential propagates continuously along the unmyelinated axon by sequential depolarization of the nerve membrane. B – In myelinated axon, the action potential is conducted only at the nodes of Ranvier, skipping the distance between adjacent nodes (saltatory conduction) . Structure and function of nerve fibres

10. Anesthesiology Structure and function of nerve fibres

11. Anesthesiology Structure and function of nerve fibres

12. Anesthesiology Ionic (sodium ion [Na + ]) currents measured by voltage-clamp technique by depolarization applied infrequently (“tonic” test). After equilibration with 0.2 mM lidocaine, the currents measured tonically are reduced significantly compared with control currents. Application of repeate depolarizations results in a dynamic reduction of currents after each depolarization (use-dependent inhibition). Modified from Butterworth JF, Strichartz GR. Molecular mechan isms of local anesthesia: a review. Anesthesiology 1990;72:711–734. Structure and function of nerve fibres

13. Anesthesiology Nerve fiber classification Structure and function of nerve fibres

14. Anesthesiology LOCAL ANESTHETICS Drugs that produce transient and reversible loss of sensation or feeling in circumscribed areas in the body without loss of consciousness

15. Anesthesiology Structure activity relationships R R R - R R N / - \ ---- + H

16. Anesthesiology Structure activity relationships

17. Anesthesiology Metabolism

18. Anesthesiology Relative potency of Local Anesthetics

19. Anesthesiology Relative potency of Local Anesthetics

20. Anesthesiology Relative potency of Local Anesthetics

21. Anesthesiology Differential blockade

22. Anesthesiology Decremental decay A – Current flow along an axon, showing the flow across the membrane and within the cytoplasm gradually dissipating ( arrow width is proportional to current flow). B – Depolarization of the nerve membrane is strongest at the site of activation and dissipates decrementally as an inverse first-order exponential with increasing distance from the site of activation.

23. Anesthesiology Toxicity

24. Anesthesiology Toxicity

25. Anesthesiology Toxicity

26. Anesthesiology Toxicity

27. Anesthesiology Anesthesiology Toxicity * With epinephrine

28. Anesthesiology Regional Anesthetic techniques Infiltration Anesthesia Central neuraxial anesthesia Spinal anesthesia Epidural Anesthesia Combined Epidural and Spinal Anesthesia IV Regional Block Peripheral Nerve Blocks

29. Anesthesiology Infiltration anesthesia Dose: volume depends on the area to be anesthetized More volume may be given in dilute concentrations Particular attention to toxic dose of the local anesthetic . Onset: almost immediate Duration of action: depends on the agent and might be prolonged by epinephrine as an adjuvant Extravascular (intra- or subdermal) injection of LA to the area to be anesthetized

30. Anesthesiology Central Neuraxial Anesthesia Subarachnoid Blocks (Spinal Block) Injection of LA into the subarachnoid space Epidural Blocks Injection of LA into the epidural space Combined Spinal and Epidural Anesthesia

31. Anesthesiology Indications Might be u sed alone or in conjunction with GA for most procedures below the neck M ost useful for : lower abdominal inguinal urogenital rectal lower extremity surgery * Lumbar spinal surgery may also be performed under spinal anesthesia Upper abdominal procedures difficult to achieve a sensory level adequate for patient comfort yet avoid the complications of a high block Spinal anesthesia for neonatal surgery

32. Anesthesiology Mechanism of Action P rincipal site of action - nerve root Local anesthetic bathes the nerve root in the subarachnoid space or epidural space S pinal anesthesia : D irect injection of LA into CSF R elatively small dose and volume to achieve dense sensory and motor blockade Epidural/Caudal anesthesia: I njection of LA (with or without opiates) into the lumbar or thoracic epidural space Controlled local anesthetic delivery “ Redosing ” of anesthetic for long procedures Post-operative analgesia with local anesthetics and opiates

33. Anesthesiology Spinal Anesthesia Factors affecting Spinal Blockade Anesthetic agent Variable pharmacologic properties Volume and dose Increasing the dose: increase the extent of cephalad spread and block duration Patient position and anesthetic agent baricity Influences LA spread and level of the block Addition of opioids Prolong duration of analgesia and increase tolerance for tourniquet pain Anatomic and Physiologic Factors Examples: obesity, pregnancy, increased intraabdominal pressure, previous spine surgery, spine deformities, age Baricity : specific gravity of LA solutions relative to CSF Hypobaric Isobaric Hyperbaric

34. Anesthesiology Spinal Anesthesia Patient positioned Landmarks identified Aseptic Preparation Local infiltration of LA at injection site Lumbar puncture with spinal needle Note presence of CSF, blood, paresthesia Note if CSF is free flowing Intrathecal injection of LA

35. Anesthesiology Central Neuraxial Anesthesia TECHNIQUE - EA Patient positioned Landmarks identified Aseptic Preparation Local anesthesia at injection site Epidural puncture with Tuohy needle Epidural space identified: LossOfResistanceTest , hanging drop technique Note +/- of CSF, blood, paresthesia Epidural catheter threaded into space Test for inadvertent intravascular and intrathecal placement of catheter Epidural injection of LA

36. Anesthesiology Central Neuraxial Anesthesia Epidural versus subarachnoid block

37. Anesthesiology Central Neuraxial Anesthesia Spinal Needles A vailable in an array of sizes (16–30 gauge), lengths, and bevel and tip designs T ightly fitting removable stylet avoid s tracking epithelial cells into the subarachnoid space 2 b road groups S harp (cutting)-tipped Quincke needle is a cutting needle 2. B lunt tip (pencil-point) needles Whitacre – rounded poi nt with side injection Sprotte – rounded point with long side opening markedly decreased the incidence of PDPH

38. Anesthesiology Epidural Needles ( Tuohi ) Central Neuraxial Anesthesia

39. Anesthesiology Caudal Epidural Anesthesia O ne of the most commonly used regional techniques in pediatric patients U sed in anorectal surgery in adults 2 nd stage of labor In children - typically combined with GENA for intra op supplementation and postop analgesia P erformed after induction C ommonly used for procedures below the diaphragm urogenital, rectal, inguinal, and lower extremity Within the sacral canal, the dural sac extends t o…what level? S2 in adults S3 in infants Makes inadvertent intrathecal injection much more common in infants

40. Anesthesiology Caudal Epidural Anesthesia P rone jackknife position Position l ateral or prone with one or both hips flexed

41. Anesthesiology Contraindications

42. Anesthesiology Complications Central Neuraxial block Useful numbers for quoting risk to patients .

43. Anesthesiology Intravenous Regional Anesthesia Intravenous administration of a local anesthetic into a tourniquet-occluded limb. Local anesthetic diffusion from the peripheral vascular bed to axons and nerve endings Retrograde spread of distally injected local anesthetic Indications: Short arm/leg procedures Drug of choice: lidocaine

44. Anesthesiology Intravenous Regional Anesthesia A tourniquet is placed on the proximal arm of the extremity to be blocked. Patency of the cuff is confirmed. A small IV intravenous catheter is introduced in the dorsum of the patient's hand of the arm to be anesthetized The arm is then elevated and at least for 1 minute to allow passive exsanguination, Cuff is inflated (100mmHg above systolic BP) The extremity is then lowered and the local anesthetic is slowly injected through the previously inserted IV catheter

45. Anesthesiology Intravenous Regional Anesthesia COMPLICATIONS OF IV-RA Tourniquet –related complications Local anesthetic toxicity – from inadvertent deflation of tourniquet Increase in systemic blood pressure - prolonged tourniquet time Tourniquet pain Neurologic injury – from compression of nerves Compartment syndrome Loss of limb – from ischemia

46. Anesthesiology Peripheral nerve blocks

47. Anesthesiology Peripheral nerve blocks Nerve simulator technic

48. Anesthesiology Peripheral nerve blocks Upper limb blocks Interscalene block Supraclavicular blocks Infraclavicular blocks Axillary block Ulnar, Radial, Median blocks

49. Anesthesiology Peripheral nerve blocks Lower limb blocks Spinal anesthesia Caudal anesthesia Lumbar plexus block Iliofascial block Obturator block Sciatic blocks Ankle blocks

50. Anesthesiology Peripheral nerve blocks Ultrasound guided blocks

51. Anesthesiology Peripheral nerve blocks

52. Anesthesiology Peripheral nerve blocks Eye Blocks Face Blocks Ophthalmic Nerve Block Maxillary Nerve Block Mandibular Nerve Blocks Cervical Plexus Blocks Cranial Blocks Neurosurgery and Scalp Surgeries Head and Neck

53. Anesthesiology Peripheral nerve blocks Thorax and abdomen Epidural anesthesia Ilioinguinal-Iliohypogastric block Peri-umbilical & Rectus sheath block Pudendal block

54. Anesthesiology Intravenous Regional Anesthesia Why local when I can already afford imported anesthesia?