What is the immediate management for a patient with myasthenia gravis (MG) experiencing an exacerbation?

Immediate Management of Myasthenia Gravis Exacerbation

For patients experiencing myasthenia gravis exacerbation, immediate hospitalization with ICU monitoring is recommended, with treatment consisting of either IVIG 2 g/kg over 5 days or plasmapheresis for 5 days. 1

Assessment and Monitoring

1. Respiratory Function Evaluation:

   • Measure Negative Inspiratory Force (NIF) and Vital Capacity (VC) immediately
   • Critical values requiring intervention:
     • NIF between -20 to -60 cm H₂O: Close monitoring and potential intervention
     • NIF > -60 cm H₂O: Continue routine monitoring 1

2. Differentiate between myasthenic crisis and cholinergic crisis:

   • Myasthenic crisis: Worsening weakness due to disease progression
   • Cholinergic crisis: Weakness due to anticholinesterase overdose
   • Edrophonium (Tensilon) test may be required for differentiation 2
   • This distinction is crucial as treatment approaches differ radically 2

Treatment Algorithm

Step 1: Stabilize Respiratory Function

• Intubation and mechanical ventilation if respiratory compromise is severe
• Monitor pulmonary function tests regularly

Step 2: Initiate Rapid-Acting Immunotherapy

• First-line options (choose one):
  • IVIG: 2 g/kg divided over 5 days
  • Plasmapheresis: Daily for 5 days 1

Step 3: Adjust Anticholinesterase Medication

• If myasthenic crisis is confirmed:

  • Continue or increase pyridostigmine dosage
  • Starting dose: 30 mg orally three times daily
  • Can increase up to 120 mg four times daily (maximum 600 mg/day) 1

• If cholinergic crisis is confirmed:

  • Immediately withdraw all anticholinesterase drugs
  • Administer atropine to counteract cholinergic effects 2

Step 4: Initiate or Adjust Immunosuppressive Therapy

• Corticosteroids:

  • Prednisone 1-1.5 mg/kg PO daily 1
  • Response rate: 66-85% of patients 1

• Consider steroid-sparing agents:

  • Methotrexate: 15 mg weekly
  • Azathioprine: 2 mg/kg of ideal body weight in divided doses
  • Mycophenolate mofetil: Start at 500 mg twice daily, increase to 1000 mg twice daily 1

Important Considerations and Pitfalls

Medication Precautions

• Avoid medications that can worsen myasthenia:
  • β-blockers
  • IV magnesium
  • Fluoroquinolones
  • Aminoglycosides
  • Macrolides 1

Anesthetic Considerations (if procedures needed)

• Safe agents:

  • Propofol, Sevoflurane, isoflurane
  • Fentanyl, remifentanil
  • Lidocaine, bupivacaine
  • Rocuronium (preferred as it can be antagonized with sugammadex) 1

• Avoid:

  • Atracurium
  • Mivacurium
  • Succinylcholine 1

Common Pitfalls

1. Misdiagnosis of crisis type:

   • Incorrectly increasing anticholinesterase medication during cholinergic crisis can be fatal 2
   • Withdrawal of medication during myasthenic crisis will worsen symptoms

2. Overlooking respiratory compromise:

   • Regular assessment of respiratory function is essential
   • Early intervention prevents respiratory failure

3. Masking cholinergic crisis:

   • Using atropine to treat gastrointestinal side effects without recognizing overdose can lead to inadvertent cholinergic crisis 2

4. Inadequate monitoring:

   • Continuous monitoring in ICU setting is necessary during acute exacerbation

By following this structured approach to managing myasthenia gravis exacerbation, clinicians can effectively stabilize patients and prevent life-threatening complications while working toward disease control.