What is the treatment for myasthenic crises?

Treatment of Myasthenic Crisis

The most effective treatment for myasthenic crisis requires immediate respiratory support with mechanical ventilation when indicated, discontinuation of cholinesterase inhibitors during the acute phase, and prompt initiation of immunotherapy with either plasma exchange or intravenous immunoglobulin (IVIg). 1, 2

Initial Management

• Assess and secure the airway with early intubation and mechanical ventilation when respiratory failure is present or imminent 2, 3
• Discontinue cholinesterase inhibitors (such as pyridostigmine) during the acute phase of crisis to avoid potential cholinergic crisis and confusion with myasthenic crisis 4, 3
• Monitor vital capacity, negative inspiratory force, and arterial blood gases to evaluate respiratory function 5
• Establish intensive care monitoring with cardiac monitoring due to risk of arrhythmias 6

Immunotherapy Options

• Plasma exchange (PE):

  • Typically 5 exchanges over 7-14 days
  • May provide faster stabilization with median time to extubation of 8 days 1
  • May be more effective than IVIg in respiratory failure, though randomized trials are needed 3

• Intravenous immunoglobulin (IVIg):

  • Standard dose of 2 g/kg divided over 5 days
  • Median time to extubation of approximately 10 days 1
  • Good alternative when PE is not available or contraindicated 1, 2

Supportive Care

• Aggressive treatment of precipitating factors, especially infections which account for 65% of crisis episodes 1
• Vigilant monitoring for and treatment of ventilator-associated pneumonia, which occurs in approximately 30% of cases 1
• Consider temporary cardiac pacing if significant cardiac arrhythmias develop 6
• Resume cholinesterase inhibitors (pyridostigmine) prior to extubation, but at lower doses initially 2
• Maintain adequate nutrition, typically through small-bore duodenal tubes to reduce aspiration risk 3

Corticosteroids and Immunosuppressants

• Corticosteroids can be initiated or increased once the airway is secured 2
• Long-term immunosuppression with agents like azathioprine should be considered after crisis resolution to prevent recurrence 7

Monitoring and Prognosis

• Median duration of mechanical ventilation is approximately 11 days (range 7-39 days) 1
• Median ICU stay is approximately 15 days (range 9-47 days) 1
• Mortality rate is approximately 8% with modern treatment 1
• Thymoma, elevated PCO₂ before mechanical ventilation, and pneumonia are independent risk factors for prolonged mechanical ventilation 5

Special Considerations

• Differentiate between myasthenic crisis (worsening disease requiring more medication) and cholinergic crisis (medication overdose requiring withdrawal of cholinesterase inhibitors) 4
• Edrophonium test may help differentiate between the two types of crisis 4
• Atropine should be readily available to counteract cholinergic effects if needed 4
• Patients with MuSK antibodies may have shorter duration of mechanical ventilation compared to those with AChR antibodies 5

Common Pitfalls to Avoid

• Failure to recognize impending respiratory failure; monitor closely for signs of respiratory compromise 2
• Confusion between myasthenic and cholinergic crisis leading to inappropriate treatment 4
• Inadequate treatment of precipitating factors, especially infections 1
• Insufficient monitoring for cardiac complications, which can be fatal in up to 9.5% of cases 6