Fast Five Quiz: Myasthenia Gravis Emergency Management

Richard Nowak, MD, MS


July 07, 2021

Figure 1. Myasthenia gravis (MG) is a condition involving voluntary muscles, most commonly of the eye, mouth, and throat. Normally, acetylcholine, a neurotransmitter (yellow) released by a neuron (turquoise), travels to the neurotransmitter receptors (green), leading to muscle contraction. MG is an autoimmune disease where there are fewer receptors than normal. The few existing receptors are blocked by antibodies (purple).

A negative inspiratory force of 30 cm H2O or less, or a forced vital capacity of 20 mL/kg point to a myasthenic crisis and airway compromise.

Careful monitoring of respiratory status is necessary during an exacerbation. Negative inspiratory force, vital capacity, and tidal volume must be closely monitored. Relying on pulse oximetry alone to monitor respiratory status can be misleading and potentially dangerous. During the initial phase of neuromuscular hypoventilation, carbon dioxide is retained but arterial blood oxygenation is maintained, which can project a false picture of a patient's respiratory status.

Patients who come to the emergency department in myasthenic crisis will often be admitted to an intensive care unit. Even patients with increasing muscle weakness of a less severe degree should be admitted to a monitored setting because their disease course is unpredictable in nature and can further decline despite the initiation of rescue therapy.

Learn more about emergent management of patients with MG.


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