Neuromuscular blockers in myasthenia gravis and Lambert-Eaton

This is a review of how neuromuscular blocking agents (both depolarizing like succinylcholine and non-depolarizing like rocuronium) might behave in patients that have neuromuscular disorders, myasthenia gravis and Lambert-Eaton.
Images adapted from Wikimedia Commons.
ADDITIONAL TAGS:
Neuromuscular blockers in myasthenia gravis and Lambert-Eaton
Myasthenia gravis: Autoimmune loss of postsynaptic proteins (nicotinic AchR) of NMJ
Generally avoid NMBA in MG, unless ndNMBA and sugammadex available
MG has ↓ Ach receptors → resistant to depolarizing NMBAs
2.6-fold ↑ in ED95 of succ
Tx with anticholinesterase meds (-stigmines, donepezil, galantamine) may ↑ effects of succ
MG: very sensitive to ndNMBA
Administer ndNMBA in small doses (0.1*ED95) w ToF monitor
Reverse with sugammadex; anticholinesterase reversal (neostigmine) can induce a cholinergic crisis
Lambert-Eaton myasthenic syndrome: Autoimm destruction of presynaptic voltage-gated Ca_v → ↓ Ach release at NMJ
Sensitive to both dNMBA and ndNMBA: Requires ↓ succ or roc
Patients with LEMS are more sensitive to ndNMBAs than patients with MG
Reversal with neostigmine might be ineffective
Only use ndNMBAs if sugammadex is available: admin small titrated doses and monitor
Condition sensitivity to:
dNMBA (succ)
ndNMBA (roc)
MG:
↓
↑
LEMS:
↑
↑
If the goal is surgical paralysis …
Amnt drug required in:
dNMBA (succ)
ndNMBA (roc)
MG:
↑
↓
LEMS:
↓
↓
Normal neuromuscular junction:
O = acetylcholine (ACh)
Lambert-Eaton myasthenic syndrome: Autoimmune destruction of presynaptic voltage-gated Ca_v → ↓ Ach release at NMJ
Myasthenia gravis: Autoimmune loss of postsynaptic nicotinic AchR of NMJ
Depolarizing neuromuscular blocking agent (dNMBA = O) mimics acetylcholine, causing initial twitch then blocks further muscle action.
Nondepolarizing neuromuscular blocking agent (ndNMBA = X) competes with acetylcholine for receptor sites, preventing muscle activation.
Adapted from TrueLearn, Wikipedia, UpToDate. By Paul Hege - Own work, CC BY-SA 4.0, commons.wikimedia.org/w/index...