NMJ Blockers Flashcards
Uses of NMJ blockers
tracheal intubation
orthopedic manipulations
balanced anesthesia (less general anesthetic)
skeletal muscle paralysis
Major use of spare receptors
reversal of clinical blockade with drug still present.
How are NMJ blockers used as adjuncts during general anesthesia
relax skeletal muscle w/ no sedative effect, especially the abdominal wall, given IV
What do competitive NMJ blockers prevent
Motor end plate depolarization,
muscle weakness followed by flaccid paralysis
Curare
NMJ blocker, causes death form skeletal muscle paralysis.
Competitive ACh antagonist at nicotinic receptors in the NMJ
Pancuronium
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)
Atracurium
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
Mivacurium
Competitive NMJ blocker
-short duration of action (15min)
-rapid hydrolysis (1/2 life not increased w/ renal disease)
-promotes histamine release
How do you pharmacologically reverse NMJ blockers?
Acetylcholinesterase inhibitors:
Physostigmine or neostigmine
-ACh outcompetes the competitive antagonists
What do non-competitive (depolarizing) NMJ blockers do?
Cause prolonged motor end plate depolarization by stimulation of NMJ nicotinic receptors.
AKA initial muscle fasciculations followed by relaxation
Succinylcholine
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
Succinylcholine and wildlife
Used to dart wildlife
Paralysis w/ out CNS effect
Potential problems w/ NMJ blockade
Monitoring depth of anesthesia
Loss of reflexes and muscle tone
Watch HR, resp response