What is the recommended plasma exchange regime in myasthenia crisis?

Plasma Exchange Regime in Myasthenia Crisis

Standard Treatment Protocol

For myasthenic crisis, perform 5 plasma exchange sessions over 5 days, exchanging 1.5 liters of plasma per session (20-25 ml/kg, representing 0.5-0.6 plasma volumes). 1

This regimen is equally effective as IVIG (2 g/kg over 5 days) and should be initiated immediately upon ICU admission alongside high-dose corticosteroids. 2, 1

Alternative Extended Regimen

• For severe or refractory cases, an extended protocol of 7 exchanges over 14 days may be considered. 1
• Research demonstrates that 3-5 treatment sessions using the low plasma volume dosage of 20-25 ml/kg are adequate to achieve significant clinical improvement in most patients. 3

Critical Concurrent Management

• Administer high-dose corticosteroids concurrently: methylprednisolone 1-2 mg/kg/day IV or prednisone 1-1.5 mg/kg/day orally. 1, 4
• Discontinue or withhold pyridostigmine in intubated patients; for non-intubated patients, pyridostigmine may be continued at 30 mg orally up to 600 mg daily. 1
• Monitor respiratory function frequently with negative inspiratory force (NIF) and vital capacity (VC) measurements, applying the "20/30/40 rule" to identify patients at risk: VC <20 ml/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O. 1

Medication Timing Considerations

• When using rituximab: Hold plasma exchange for 48-72 hours after rituximab infusion to prevent antibody removal. 1
• When using cyclophosphamide: Administer the infusion after the plasma exchange session. 1

Important Precautions

• Do NOT combine sequential therapy (plasma exchange followed by IVIG), as this is no more effective than either treatment alone and should be avoided. 2
• Immediately discontinue medications that worsen myasthenia: β-blockers, IV magnesium (absolutely contraindicated), fluoroquinolones, aminoglycosides, and macrolide antibiotics. 1, 4
• Plasma exchange carries risks including hemodynamic shifts, coagulation disorders, electrolyte imbalances, and line-related bacteremia, requiring careful monitoring and expertise in apheresis procedures. 1

Clinical Monitoring During Treatment

• Daily neurological evaluation to assess treatment response. 1
• Frequent pulmonary function assessment with NIF and VC measurements. 1
• Monitor for complications of immunotherapy and apheresis-related adverse events. 1
• Research shows that substantial reduction of acetylcholine receptor antibodies occurs after each session, with clinical improvement typically evident by Day 14 of the post-treatment phase. 3

Choosing Between Plasma Exchange and IVIG

• Both modalities are equally effective for myasthenic crisis. 2, 3
• IVIG may be preferred in pregnant women, as plasma exchange requires additional monitoring considerations. 2
• Plasma exchange requires specialized equipment and expertise, often necessitating transfer to tertiary academic centers. 1
• Research demonstrates that immunoadsorption is equally effective compared with plasma exchange, with fewer serious adverse events (1 vs. 7 in one controlled trial). 3