Regional Anesthetics

Question 1

1. Name 2 chemical classes of local anesthetics.

Answer 1

esters: metabolized by plasma psuedocholinesterase (short acting novocaine to long acting tetracain)
amides: lidocaine bupivicaine etc

Question 2

2. Describe the metabolism of the ester local anesthetics and how the metabolic product relates to their allergenic potential.

Answer 2

local anesthetics metabolized by plasma pseudocholinesterase resulting in para-aminobenzoic acid PABA which can provoke allergic reactions

Question 3

3. Give advantages of amide local anesthetics.

Answer 3

less likely allergy

high temp sterilization w/o losing potency

Question 4

4. Name intermediate and long acting locals and their dose limits.

Answer 4

intermediate: lidocaine 5mg/kg w/o epi, 7 with

long acting: bupivicaine 2mg/kg w/o epi 3 with

Question 5

5. List the reasons epi is added to local.

Answer 5

prolongs action
blunts systemic uptake (limits tox)
decreases bleeding
serves as a marker of injection
improves quality of spinal blockade probably by action on a2 receptors

Question 6

6. Give signs and sx of local anesthetic toxicity.

Answer 6

perioral numbness
metallic taste in mouth
tinnitus
dizziness
respiratory depression
coma 
seizure
CV depression

Question 7

7. Describe the equipment that should be available where blocks are performed.

Answer 7

oxygen, ET tube, bag/mask, laryngoscope, suction, hypotension/seizure/pain/bradycardia rx, monitors, IV start 20% fat emulsion (bupivvacaine tox) adjustable bed ant assistant

Question 8

8. Explain why local anesthetics will not cause numbness if injected into an abscess?

Answer 8

positively charge local anesthetics can only enter nerves when buffered which but there are no molecules to accept an excess hydrogen ions to buffer in an abscess

Question 9

9. Identify nerves that transmit pain.

Answer 9

myelinated A-delta fibers- fast pain

unmyelinated C fibers- secondary dull aching pain

local anes only works at breaks in myelin in a delta fibers but all along the C fibers

Question 10

10. Describe 4 methods to ID nerve location.

Answer 10

• look for accompanying artery
• seek parathesia
• use electric nerve stimulator
• visualize nerves with U/S

Question 11

11. Explain how to perform an IV or Beir block.

Answer 11

IV inserted to distal vein in extremity; Esmarch is tightly wrapped starting distally to proximally to exsanguinate the limb and tourniquet is inflated;
50-60mL of lidocaine 0.5% ;
tourniquet can stay in place for up to 2 hours

Question 12

12. Compare and contrast spinal and epidural anesthesia.

Answer 12

anatomy: spinal is a subarachnoid block into CSF, epidural does not pierce the dura

drug dose: spinal is small dose, epidural is larger amount

onset: spinal is very rapid, epidural has longer onset

Question 13

12. What are side effects of spinals

Answer 13

decreased afterlaod, hyptension, bradycardia and respiratory depression due to sympathetic block

Question 14

13. Describe sx, pathophys and tx of PDPHA

Answer 14

sx: diplopia CNVI compression, positional headache (11-30 at highest risk)
pathphys: low CSF pressure due to leaking fluid (higher risk bevel or larger needle)

tx recumbency, hydration, caffeine or epidrual blood patch

Question 15

14. List absolute and relative contraindications to regional anes.

Answer 15

absolute: pt refusal, infection at site, coagulopathy or increased ICP
relative: sepsis, hypotension, neurologic disease, psychiatric instability, antiplatelet drugs, long surgery, aortic stenosis

Question 16

How many grams of lidocaine are in 1mL of 1% lidocaine

Answer 16

10mg