Management of Myasthenia Gravis Crisis
Initial Assessment and Treatment
- For patients with suspected myasthenia gravis crisis with acute muscle weakness, intravenous pyridostigmine is the recommended parenteral medication for immediate administration, with neostigmine intramuscular as an alternative when IV access is unavailable, as recommended by the American College of Physicians 1, 2
- Rapidly assess for respiratory compromise by measuring negative inspiratory force and vital capacity, as respiratory failure is the defining feature of myasthenic crisis, according to the American Thoracic Society 1, 3
- Evaluate for bulbar symptoms (dysphagia, dysarthria, facial weakness) which may indicate impending respiratory compromise, as suggested by the American Academy of Neurology 4, 3
- Check for pattern of weakness: typically fluctuating, exercise-dependent weakness of proximal extremities or bulbar muscle groups, as described by the American College of Physicians 1, 3
Parenteral Medication Options
- Intravenous pyridostigmine can be administered when oral administration is not possible, with a dosing equivalent of 1 mg IV pyridostigmine corresponding to 30 mg oral pyridostigmine, as recommended by the American College of Physicians 1
- Intramuscular neostigmine can be used as an alternative when IV access is unavailable, with 0.75 mg IM neostigmine corresponding to 30 mg oral pyridostigmine, according to the American College of Physicians 1, 2
Management Algorithm for Myasthenic Crisis
- Initiate IVIG 2 g/kg IV over 5 days (0.4 g/kg/day) or plasmapheresis for 5 days, as recommended by the American Society for Clinical Oncology 4, 2
- Administer high-dose corticosteroids (methylprednisolone 1-2 mg/kg/day), as suggested by the American College of Physicians 1, 4
- For severe symptoms, consider pulse corticosteroid dosing (methylprednisolone 1 g/day for 5 days), according to the American College of Physicians 1
Important Precautions
- Avoid medications that can worsen myasthenia gravis, including β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, macrolides, and anticholinergic medications, as recommended by the American Academy of Neurology 4, 5
- Monitor closely for respiratory function, cardiac involvement, and concurrent myositis, as suggested by the American Thoracic Society 4, 2
- Neurological consultation is essential for management of myasthenic crisis, according to the American Academy of Neurology 4, 2
Respiratory Failure in Myasthenic Crisis
Pathophysiology and Risk Factors
- Bulbar and diaphragm weakness in myasthenic crisis directly threatens airway protection and ventilation, making respiratory failure a critical and immediate risk, with bulbar weakness compromising the patient's ability to protect their airway, clear secretions, and maintain upper airway patency 6, 7, 8
- Diaphragm weakness directly impairs ventilation and can lead to rapid respiratory decompensation, with deterioration in neuromuscular disease patients being very sudden 6, 9
Clinical Recognition and Monitoring
- Bulbar dysfunction makes non-invasive ventilation failure more likely and may make it impossible, with the presence of bulbar dysfunction and more profound hypoxemia or rapid desaturation suggesting ICU placement is indicated 6, 7, 8
Management Implications
- Intubation should not be delayed if non-invasive ventilation is failing in neuromuscular disease patients, unless escalation to invasive mechanical ventilation is not desired by the patient or deemed inappropriate, with inability to clear secretions being a common cause of non-invasive ventilation failure 6, 7, 8, 9
- Intubation is indicated in respiratory arrest or peri-arrest unless there is rapid recovery 9