UMEM Educational Pearls

Title: Neuromuscular Blocker Dosing in Patients With Myasthenia Gravis

Category: Pharmacology & Therapeutics

Keywords: Myasthenia gravis, Myasthenic crisis, neuromuscular blocker, paralytic, rocuronium, vecuronium, succinylcholine (PubMed Search)

Posted: 4/1/2023 by Matthew Poremba
Click here to contact Matthew Poremba

Myasthenia gravis is an autoimmune disease of the neuromuscular junction, most commonly due to antibodies attacking acetylcholine receptors in the postsynaptic membrane. Up to 30% of patients with myasthenia gravis will experience a myasthenic crisis during their disease course. If rapid sequence intubation is indicated, the unique characteristics of this patient population must be considered in the event use of a paralytic is necessary. All paralytic agents can be expected to last significantly longer, and an unpredictable response may be seen with depolarizing agents - therefore non-depolarizing agents are preferred in this population.

Non-Depolarizing Agents (Rocuronium, Vecuronium)

MG patients have increased sensitivity to non-depolarizing agents and require lower doses than typically used
It is reasonable to dose non-depolarizing agents at one-half the standard dose used. For example, rocuronium would be dosed at 0.5-0.6 mg/kg instead of the standard 1-1.2 mg/kg

Depolarizing Agents (Succinylcholine)

MG patients have decreased expression of normal acetylcholine receptors which are required for depolarizing agents to work effectively and require higher doses than typically used
Succinylcholine is typically dosed at 1.5-2.0 mg/kg (roughly double the dose used in other patient populations)

References

Roper J, Fleming ME, Long B, Koyfman A. Myasthenia Gravis and Crisis: Evaluation and Management in the Emergency Department. J Emerg Med. 2017;53(6):843-853.

Abel, Mark, and James B Eisenkraft. “Anesthetic implications of myasthenia gravis.” The Mount Sinai journal of medicine, New York vol. 69,1-2 (2002): 31-7.