NMJ Blockers

Question 1

Uses of NMJ blockers

Answer 1

tracheal intubation
orthopedic manipulations
balanced anesthesia (less general anesthetic)
skeletal muscle paralysis

Question 2

Major use of spare receptors

Answer 2

reversal of clinical blockade with drug still present.

Question 3

How are NMJ blockers used as adjuncts during general anesthesia

Answer 3

relax skeletal muscle w/ no sedative effect, especially the abdominal wall, given IV

Question 4

What do competitive NMJ blockers prevent

Answer 4

Motor end plate depolarization,
muscle weakness followed by flaccid paralysis

Question 5

Curare

Answer 5

NMJ blocker, causes death form skeletal muscle paralysis.
Competitive ACh antagonist at nicotinic receptors in the NMJ

Question 6

Pancuronium

Answer 6

Competitive NMJ blocker
-long duration of action (2-3 hours)
-renal elimination (1/2 life increased w/ renal disease)
-no histamine release
-blocks muscarinic receptors (tachycardia)

Question 7

Atracurium

Answer 7

Competitive NMJ blockers
-Intermediate duration (o.5-1hr)
-spontaneous elim + hydrolysis + renal elim (1/2 life not increased w/ renal disease)
–rate of spontaneous degradation dependent on temp and pH (reduced w/ hypothermia and acidosis)
-promotes histamine release

Question 8

Mivacurium

Answer 8

Competitive NMJ blocker
-short duration of action (15min)
-rapid hydrolysis (1/2 life not increased w/ renal disease)
-promotes histamine release

Question 9

How do you pharmacologically reverse NMJ blockers?

Answer 9

Acetylcholinesterase inhibitors:
Physostigmine or neostigmine
-ACh outcompetes the competitive antagonists

Question 10

What do non-competitive (depolarizing) NMJ blockers do?

Answer 10

Cause prolonged motor end plate depolarization by stimulation of NMJ nicotinic receptors.
AKA initial muscle fasciculations followed by relaxation

Question 11

Succinylcholine

Answer 11

Depolarizing NMJ blocker
-mimics ACh at the NMJ
-resistant to acetylcholinesterase
-not pharmacologically reversible
-rapid onset and short acting
-useful for rapid and short NMJ blockade ie tracheal intubation
-some histamine release
-hyperkalemia

Question 12

Succinylcholine and wildlife

Answer 12

Used to dart wildlife
Paralysis w/ out CNS effect

Question 13

Potential problems w/ NMJ blockade

Answer 13

Monitoring depth of anesthesia
Loss of reflexes and muscle tone
Watch HR, resp response