How should myasthenia (myasthenia gravis) be managed in a surgical patient?

Perioperative Management of Myasthenia Gravis in Surgical Patients

Surgical patients with myasthenia gravis require careful perioperative management with continued pyridostigmine on the day of surgery, avoidance of certain medications that exacerbate neuromuscular blockade, and respiratory monitoring to prevent complications. 1, 2

Preoperative Management

Medication Management

• Pyridostigmine (first-line treatment):

  • Continue pyridostigmine on the day of surgery 1, 2
  • Continuing pyridostigmine helps prevent respiratory discomfort and reduces sensitivity to neuromuscular blocking agents 3
  • Standard dosing: 30 mg orally three times daily, can be increased to maximum 120 mg four times daily as tolerated 4

• Medications to avoid:

  • Methocarbamol (contraindicated in myasthenia gravis) 5
  • Orphenadrine (contraindicated in myasthenia gravis) 5
  • β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides 4

Respiratory Assessment

• Perform pulmonary function tests including Negative Inspiratory Force (NIF) measurements 4
  • Normal NIF values: more negative than -60 cm H2O
  • Values between -20 and -60 cm H2O warrant close monitoring
  • Forced Vital Capacity (FVC) values <80% predicted with symptoms or <50% without symptoms indicate respiratory compromise

Intraoperative Management

Anesthetic Considerations

• Neuromuscular blocking agents:

  • Use reduced titrated doses of non-depolarizing agents if necessary 6
  • Rocuronium is preferred as it can be antagonized with sugammadex 2
  • Avoid atracurium, mivacurium, and succinylcholine 5

• Safe anesthetic agents:

  • Propofol for induction
  • Sevoflurane or isoflurane for maintenance
  • Fentanyl or remifentanil for analgesia
  • Lidocaine or bupivacaine for local anesthesia 5

• Precautions:

  • Avoid temperature extremes (hypothermia or hyperthermia)
  • Minimize unnecessary trauma during positioning 5
  • Use anxiolytic agents (benzodiazepines) with caution 2
  • Limited use of opioids and sedatives 7

Postoperative Management

Extubation Criteria

• Ensure sufficient spontaneous breathing with absolutely no residual neuromuscular blockade before extubation 7
• Consider sugammadex for reversal of non-depolarizing neuromuscular blockade 7, 2

Pain Management

• Consider peripheral nerve blocks for adjunct pain control 7
• Use opioids with caution due to risk of respiratory depression 7

Monitoring

• Regular neurological assessments
• Monitor for signs of respiratory compromise
• Continue pulmonary function assessment with NIF and vital capacity 4

Risk Factors for Postoperative Myasthenic Crisis

• Bulbar symptoms
• High doses of pyridostigmine preoperatively
• History of myasthenic crisis
• Thymoma
• Concurrent lung disease 4, 8

Special Considerations

Differentiating Myasthenic vs. Cholinergic Crisis

• Myasthenic crisis: Increased disease severity requiring more intensive anticholinesterase therapy
• Cholinergic crisis: Overdosage of anticholinesterase drugs requiring prompt withdrawal of these medications 1
• Edrophonium test may be needed for differentiation 1

Multidisciplinary Approach

• Involve surgical, anesthesia, and perioperative medical teams 5
• Regular follow-up with a neuromuscular specialist 4

Implementation of a standardized perioperative protocol for myasthenia gravis patients has been shown to reduce ICU admissions by 73.5% and decrease the use of neuromuscular blocking agents by 80% 8.