Beginning Neuraxial Anesthesia (an overview) Local Anesthetics (an introduction)

1. Beginning Neuraxial Anesthesia(an overview)Local Anesthetics(an introduction)

2. Neuraxial Anesthesia Indications • Any operation in the lower abdomen and below

3. Contraindications • Absolute • Patient doesn’t want it • Infection at site of puncture • Increased ICP • Uncorrected hypovolemia • Uncorrected coagulopathy • Relative • Systemic infection • Neuruologic diseases like MS

4. Spinal vs. Epidural • Spinal • More definite endpoint • Easier to do • Faster onset • More intense sensory and motor block • Limited duration • Fewer failures • Epidural • Less definite endpoint • More difficult to do • Slower onset • Less intense sensory and motor block possible (labor) • Unlimited duration • Postop analgesia possible • More failures

5. Sedation/Analgesia

6. Position

7. ABSOLUTELY NO RITUALS!

8. Where? Spinal - L2-3 and below Epidural - anywhere

9. Skin anesthesia • Do a good intradermal skin wheal • Other, deeper soft tissues are not painful • The periostium is painful but impossible to anesthetize easily, so don’t try

10. Please memorize this image. When you are performing an epidural or spinal puncture use the image of the ligaments as a guide to imagine where the needle tip is at all times.

13. If at any time you think the plunger is stuck, STOP. Remove the syringe and check that the plunger moves freely. Pay attention to what you are FEELING as the needle advances. If you feel as though the ligamentum flavum has been penetrated but there has been no LOR to injection, STOP. Reassess plunger action and resistance to injection. Pay attention to DEPTH as the needle advances. If you feel as though you should have penetrated the ligamentum flavum by now but there has been no LOR to injection, STOP. Reassess plunger action and resistance to injection.

16. Spinal Anesthesia We do it the same as we do an epidural except we use flimsy needles and we don’t stop in the epidural space

17. Because the needles are so flimsy, we use an introducer needle

19. CSF Dura Epidural space Ligamentum flavum Interspinous lig

20. FAILURE!

23. So, we’re in!What do we inject?

24. Ask your attending

25. Epidural injections: Chloroprocaine Lidocaine Bupivacaine

26. Epidural injections: What concentration? How much?

27. Ask your attending

28. Epidural injections: What concentration? Chloroprocaine – 3% Lidocaine – 1-2% Bupivacaine – 0.625-0.5% (low conc. for labor) How much? Roughly 10-20 ml

29. Spinal injections: What solution? How much?

30. Ask your attending

31. Spinal injections: What solution?Chloroprocaine – 2-3% (no dextrose)Lidocaine – 5%/0.75% dextroseBupivacaine – 0.75%/0.825 dextrose

32. Spinal injections: How much?Chloroprocaine – 2 ml (40-60 mg)Lidocaine – 1-2 ml (50-100 mg)Bupivacaine – 1-2 ml (7.5-15 mg)

33. Conversion of % concentration to mg/ml:1% solution = 1gm per 100 ml (1000 mg per 100 ml) = 10 mg/ml % solution X 10 = mg/ml e.g., 0.5% bupivacaine X 10 = 5 mg/mlDose is volume X concentration:10 ml of 0.5% bupivacaine = 50 mg dose Dose is important in determining toxicity

34. Manufacturer Maximum Recommended Doses • Chloroprocaine • 800 mg no epinephrine • 1000 mg with epinephrine • Lidocaine • 300 mg no epinephrine • 500 mg with epinephrine • Bupivacaine • 175 mg no epinephrine • 225 mg with epinephrine

35. Concept of baricity • Baricity is the relationship of the density of the local anesthetic solution to the density of the cerebrospinal fluid. If the LA solution is: • Less dense than CSF it is hypobaric (floats) • Equal in density to CSF it is isobaric (stationary) • More dense than CSF it is hyperbaric (sinks) • As a concept, baricity refers only to spinal anesthesia and not to epidural anesthesia

36. Spinal solutions • Hyperbaric solutions (with dextrose) • Intra-abdominal operations (including inguinal hernia and vaginal procedures) • All operations can be done with this solution • Isobaric solutions (epidural solutions without dextrose) • Lower extremity operations (hip and below) • Hypobaric solutions (diluted with DW) • Not really useful

37. 1 ml 5% lido with dextrose immediately after injection 1 ml 5% lido with dextrose during injection

38. The effect of baricity on the distribution of bupivacaine in spinal model Hyperbaric Immediately after injection 20 min. after injection Isobaric • In spite of the crudeness of this model, the levels of anesthesia predicted by the model are remarkably similar to the levels of anesthesia observed in patients Hypobaric

39. Hyperbaric Isobaric Hypobaric

40. What could go wrong?

41. What could go wrong with spinal anesthesia? • It doesn’t work • It goes too high (total spinal) • It doesn’t go high enough • It causes hypotension • It doesn’t last long enough • It causes a spinal headache

42. There must have been a lumbar puncture The headache is related to posture Worst when standing or sitting Gone or improved with recumbency The Two Components of Spinal Headache

46. Effect of Age on the Incidence of Spinal Headache This and AARP discounts are two of the few advantages to aging! Vandam and Dripps, JAMA 1956;161:586-591

48. Needle tip design is important • 25 gauge Quincke or cutting needle has 5% incidence of spinal headache in OB patients. • 25 gauge Whitacre or pencil tipped needle has <1% incidence of spinal headache in OB patients

49. What could go wrong with epidural anesthesia? • It doesn’t work • It goes too high (total spinal) • It doesn’t go high enough • It causes hypotension • It doesn’t last long enough • It causes a spinal headache (but it’s not supposed to) • It produces spinal anesthesia • It goes intravascular causing systemic toxicity

50. Or the catheter could have penetrated the dura and be located intra-thecally