Myasthenic crisis may be defined as respiratory failure or delayed postoperative extubation
for more than 24 hours resulting from myasthenic weakness. Myasthenic crisis results
from weakness of upper airway muscles leading to obstruction and aspiration, weakness
of respiratory muscles leading to reduced tidal volumes, or from weakness of both
muscle groups. About one-fifth of patients with myasthenia gravis experience crisis,
usually within the first year of illness. Over the last four decades, prognosis from
myasthenic crisis has dramatically improved from a mortality rate of 75% to the current
rate of less than 5%. Common precipitating factors for myasthenic crisis include respiratory
infections, aspiration, sepsis, surgical procedures, rapid tapering of immune modulation,
beginning treatment with corticosteroids, exposure to drugs that may increase myasthenic
weakness, and pregnancy. Myasthenic crisis should not be fatal, as long as patients
receive timely respiratory support and appropriate immunotherapy to reduce myasthenic
weakness of the upper airway and respiratory muscles. Myasthenic patients with oropharyngeal
or respiratory muscle weakness should receive preoperative plasma exchange or intravenous
immunoglobulin therapy to a minimal level of weakness to prevent postoperative complications.
KEYWORDS
Myasthenia gravis - myasthenic crisis - respiratory failure
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