What is the treatment for myasthenia gravis crisis?

Treatment of Myasthenia Gravis Crisis

Myasthenia gravis crisis requires immediate ICU admission with high-dose corticosteroids (methylprednisolone 1-2 mg/kg/day IV) and rapid immunotherapy using either plasmapheresis (5 sessions over 5 days) or IVIG (2 g/kg total dose at 0.4 g/kg/day over 5 days), with plasmapheresis potentially being more effective for respiratory failure. 1, 2

Immediate Stabilization and Monitoring

Respiratory Assessment and Support

• Perform immediate pulmonary function testing with negative inspiratory force (NIF) and vital capacity (VC) measurements upon presentation 1
• Apply the "20/30/40 rule" to identify patients requiring intubation: vital capacity <20 ml/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O 1
• Early intubation via orotracheal approach is the most critical intervention when respiratory parameters deteriorate 2
• Consider non-invasive ventilation (NIV) only for patients with APACHE II score <6 and serum bicarbonate <30 mmol/L, as 57% may avoid intubation with these favorable parameters 3

ICU-Level Monitoring

• Establish continuous monitoring with pulse oximetry, ECG, and blood pressure 1
• Perform daily neurological evaluations to assess treatment response 1
• Monitor frequently for respiratory function deterioration, as pulse oximetry and arterial blood gases may not reliably detect early respiratory failure 1

Immunotherapy Initiation

First-Line Rapid Immunotherapy

Choose one of the following:

• Plasmapheresis: 5 sessions over 5 days (preferred for respiratory failure based on superior efficacy data) 1, 2
• IVIG: 2 g/kg total dose administered as 0.4 g/kg/day for 5 consecutive days (alternative when plasmapheresis contraindicated) 1, 4

Critical distinction: Plasmapheresis may be more effective than IVIG specifically for myasthenic crisis involving respiratory failure, though a definitive randomized trial is needed 2

Corticosteroid Administration

• Methylprednisolone 1-2 mg/kg/day IV or prednisone 1-1.5 mg/kg/day orally 1
• Continue corticosteroids concurrently with plasmapheresis or IVIG 4
• Begin steroid taper 3-4 weeks after initiation based on symptom improvement 1

Diagnostic Workup During Crisis

Antibody Testing

• Check acetylcholine receptor (AChR) antibodies and anti-striated muscle antibodies 1
• If AChR antibodies negative, test for muscle-specific kinase (MuSK) and lipoprotein-related protein 4 (LRP4) antibodies 1

Cardiac and Inflammatory Markers

• Measure CPK, aldolase, ESR, and CRP to evaluate for concurrent myositis 1
• Perform ECG and transthoracic echocardiogram if respiratory insufficiency present or elevated CPK/troponin T to rule out life-threatening concurrent myocarditis 1

Critical Medication Management

Immediately Discontinue These Medications

• Beta-blockers 1, 5
• IV magnesium (absolutely contraindicated) - if severe hypomagnesemia requires treatment, mandatory neurology consultation before administration 1
• Fluoroquinolones 1, 4
• Aminoglycosides 1, 4
• Macrolide antibiotics 1, 4

Pyridostigmine Considerations

• Discontinue or withhold pyridostigmine in intubated patients 6
• For non-intubated patients with myasthenic symptoms, pyridostigmine may be used starting from 30 mg orally up to 600 mg daily 6
• In IV application, 30 mg oral pyridostigmine corresponds to 1 mg IV or 0.75 mg neostigmine IM 6

Respiratory Care and Ventilator Management

Aggressive Pulmonary Interventions

• Implement aggressive respiratory treatment including frequent suctioning, intermittent positive-pressure breathing, bronchodilator treatments, and chest physiotherapy to reduce atelectasis and pneumonia risk 7
• Place small-bore duodenal feeding tubes rather than nasogastric tubes to decrease aspiration risk 2

Extubation Criteria

• Maximal expiratory pressure (Pemax) ≥40 cmH₂O is a good predictor of successful extubation 3
• Assess cough strength adequacy, as sputum impaction from poor cough is the most common cause of extubation failure (61.5% of failures) 3
• Extubation failure leads to significantly poorer outcomes, so ensure adequate respiratory muscle strength before attempting 3

Common Pitfalls and Caveats

Avoid These Errors

• Do not use IVIG for chronic maintenance therapy - it is only indicated for acute crisis situations 4
• Do not delay intubation waiting for immunotherapy to work - early mechanical ventilation is paramount 2
• Do not rely solely on pulse oximetry to assess respiratory status, as it may not detect early failure 1

Special Considerations

• Patients with immune checkpoint inhibitor-associated myasthenia gravis may have monophasic disease requiring less prolonged immunosuppression 1
• Current mortality rate for myasthenic crisis is 4-8% with appropriate management 8
• Approximately 15-20% of myasthenia gravis patients will experience crisis during their lifetime 2, 8

Minimum Monitoring Duration

• Monitor for minimum of 24 hours in ICU, HDU, or recovery unit even after apparent stabilization 6