What is the recommended plasma exchange regime for a patient in myasthenia crisis?

Plasma Exchange Regime for Myasthenia Crisis

For myasthenia crisis, perform 5 sessions of plasma exchange over 10 days (every other day), exchanging 200-250 mL plasma/kg body weight (or 1-1.5 L exchanges per session), using fresh-frozen plasma or 5% albumin as replacement fluid. 1

Standard Protocol Details

The established plasma exchange regimen for myasthenic crisis involves:

• Number of sessions: 5 treatments 1
• Frequency: Every other day over 10 days 1
• Volume per session: 200-250 mL plasma/kg body weight, or 1-1.5 L exchanges 1
• Total plasma volume exchanged: Twice the patient's blood volume 1
• Replacement fluid: Fresh-frozen plasma or 5% albumin 1

This protocol should be initiated 10-30 days before planned surgery in preoperative optimization, but in acute crisis, begin immediately upon ICU admission. 1

Alternative Dosing Regimens

For severe cases requiring extended treatment, an alternative regimen of 7 exchanges over 14 days may be used. 2 However, the standard 5-session protocol is typically adequate for most patients in myasthenic crisis. 3

A shorter protocol of 3-5 treatments using lower plasma volume dosage (20-25 mL/kg or 0.5-0.6 plasma volumes) has proven equally effective in controlled studies, with significant clinical improvement in most patients. 3 This lower-volume approach may be preferred when minimizing hemodynamic shifts is critical.

Clinical Context and Monitoring

Plasma exchange must be performed in conjunction with:

• Immediate ICU-level monitoring with frequent respiratory function assessment 2
• High-dose corticosteroids: Methylprednisolone 1-2 mg/kg/day IV or prednisone 1-1.5 mg/kg/day orally 2
• Discontinuation of pyridostigmine in intubated patients 2
• Application of the "20/30/40 rule" to assess respiratory failure risk: vital capacity <20 mL/kg, maximum inspiratory pressure <30 cmH₂O, or maximum expiratory pressure <40 cmH₂O 1, 2

IVIG as Alternative

IVIG (2 g/kg total dose over 5 days at 0.4 g/kg/day) is equally effective as plasma exchange and may be preferred due to easier administration, wider availability, and fewer complications. 1 However, plasma exchange remains the treatment of choice when IVIG is contraindicated or unavailable. 4

Sequential therapy (plasma exchange followed by IVIG) is no more effective than either treatment alone and should be avoided. 5

Critical Medication Management During Plasma Exchange

When administering concurrent immunosuppressive therapy:

• Cyclophosphamide: Administer the infusion after the plasma exchange session 2
• Rituximab: Hold plasma exchange for 48-72 hours after rituximab infusion to prevent antibody removal 2

Safety Considerations and Pitfalls

Plasma exchange carries significant risks requiring specialized expertise:

• Hemodynamic shifts, coagulation disorders, electrolyte imbalances, and line-related bacteremia necessitate careful monitoring 2
• Specialized equipment and apheresis expertise are required, often necessitating transfer to tertiary academic centers 2
• Monitor for a minimum of 24 hours in ICU even after apparent stabilization 2

Immediately discontinue medications that worsen myasthenia gravis before initiating plasma exchange: beta-blockers, IV magnesium (absolutely contraindicated), fluoroquinolones, aminoglycosides, and macrolide antibiotics. 2

Expected Clinical Response

Substantial reduction of acetylcholine receptor antibodies occurs after each session, with uniform, significant clinical improvement including successful extubation in most patients. 3, 4 Clinical improvement typically stabilizes patients to Oosterhuis Classes 1 and 2 within 14 days post-treatment. 3

The average of 7-8 plasma exchange procedures (range 1-16) has been reported in consecutive crisis cases, with uniform improvement and hospital discharge in all patients. 4