Neuromuscular Blockers

Question 1

Succinylcholine MOA

Answer 1

Mimics Ach to stimulate nicotinic receptors at post synaptic cell membranes in the NMJ. It depolarizes the post synaptic cell membrane causing an EPP, action potential, and muscle cell contraction. This causes wide spread fasciculations and subsequent paralysis. Although Ach is rapidly broken down by acetylcholinesterase, Succs must diffuse away from the receptor, back into the ECF to be broken down by pseudocholinesterases and therefore prevents another Ach from binding and causing an AP for several minutes.

Question 2

Succinylcholine indications

Answer 2

“Optimize conditions for laryngoscope and intubation.
RSI for pt at risk for aspiration.
Optimize mechanical ventilation with a gtt.
Optimize surgical paralysis with a gtt.”

Question 3

Succinylcholine onset, E 1/2t, DOA, & Vd

Answer 3

"Onset = 30-60sec
E1/2t = short (2-4mins)
DOA = 5-8 mins
Vd = 200mL/kg
Not highly PB – no clinical significance"

Question 4

Succinylcholine Adverse Effects

Answer 4

“Without controlled airway, conscious pts
Cardiac dysrhythmias (sinus brady, juncitonal, sinus arrest) – mimicking of Ach at cardiac muscarinic receptors
↑hyperK+ 0.5-1.0mEq/L = dysrhythmias (response exaggerated in pts with upregulated or extrajunctional receptors, ie 3rd* burns, muscle atrophy, upper motor lesions, SCI, CVA, prolonged mobility)
Masseter spasm and MH
Phase II block
Myoglobinemia – rhabdomylosis
↑IOP and ICP
Myalgia (fasciculations)
MOST COMMON TRIGGER FOR ALLERGIC RXN!”

Question 5

Succinylcholine Metabolism

Answer 5

Plasma pseudocholinesterase when diffused away from NMJ into the ECF

Question 6

Succinylcholine Contraindications

Answer 6

“abnormal plasmacholinesterase (dibucaine#)
Hyperkalemia, renal failure, Burn pts
Neurologic injury or disease = muscular dystrophy
Severe sepsis
MH history
Pediatrics (give with atropine if emergency)
(lithium prolongs sch)”

Question 7

Succinylcholine Dosage

Answer 7

“Laryngospasm = 20-40mg IV or 0.3mg/kg
Intubation = 1-1.5mg/kg
Infusion = 2.5mg/min (0.5-10mg/min) (1-2mg/ML)
IM intubation = 2.5-4mg/kg (onset 2-3mins doa 10-30mins)
NO REVERSAL AGENT!”

Question 8

Sccinylcholine Class

Answer 8

Depolarizing Neuromuscular blocker