What are the considerations for anesthesia in a patient with myasthenia gravis (MG)?

From the Guidelines

Anesthesia in patients with myasthenia gravis requires careful planning and medication adjustments, with a preference for short-acting neuromuscular blocking agents like rocuronium at reduced doses (50-75% of standard dose) and close monitoring of neuromuscular blockade. When considering anesthesia for patients with myasthenia gravis, it is essential to take into account the potential risks and complications associated with neuromuscular blocking agents. According to the most recent guidelines on muscle relaxants and reversal in anesthesia 1, patients with myasthenia gravis may exhibit significant pharmacodynamic changes, including increased sensitivity and duration of action of non-depolarizing muscle relaxants.

Key Considerations

• The use of long-acting neuromuscular blocking agents should be avoided, and instead, short-acting agents like rocuronium should be used at reduced doses (50-75% of standard dose) 1.
• Regional anesthesia is preferred when possible to minimize respiratory complications.
• Preoperative optimization includes continuing anticholinesterase medications (pyridostigmine) until the morning of surgery, as discontinuing them may increase the risk of respiratory distress 1.
• During induction, propofol (1.5-2.5 mg/kg) or etomidate (0.2-0.3 mg/kg) can be used, while volatile anesthetics like sevoflurane or desflurane are suitable for maintenance at reduced concentrations.
• Opioids should be used cautiously, with remifentanil (0.05-0.1 mcg/kg/min) being a good option due to its short half-life.
• Postoperatively, patients require close monitoring in a high-dependency unit with access to ventilatory support, as they are at increased risk for respiratory failure.
• Reversal agents like neostigmine should be used cautiously as they may cause cholinergic crisis.

Monitoring and Dosing

• Monitoring of neuromuscular blockade is recommended to avoid overdosing, and the train-of-four (TOF) ratio by EMG in the hypothenar hand muscles prior to muscle relaxant administration can predict sensitivity to non-depolarising muscle relaxants 1.
• A 50-75% reduction in the recommended dose of non-depolarizing muscle relaxants like atracurium and cisatracurium is common, and this reduction correlates with the severity of myasthenia 1.

From the FDA Drug Label

In patients with myasthenia gravis or myasthenic (Eaton-Lambert) syndrome, small doses of nondepolarizing neuromuscular blocking agents may have profound effects. In such patients, a peripheral nerve stimulator and use of a small test dose may be of value in monitoring the response to administration of muscle relaxants. In patients who are known to have myasthenia gravis or the myasthenic (Eaton-Lambert) syndrome, small doses of vecuronium bromide may have profound effects. In such patients, a peripheral nerve stimulator and use of a small test dose may be of value in monitoring the response to administration of muscle relaxants

The considerations for anesthesia in a patient with myasthenia gravis (MG) include:

• Using small doses of nondepolarizing neuromuscular blocking agents to avoid profound effects
• Utilizing a peripheral nerve stimulator to monitor the response to administration of muscle relaxants
• Administering a small test dose to assess the patient's response to the muscle relaxant 2 3 Key considerations for patients with MG include careful dose adjustment and close monitoring to minimize the risk of prolonged neuromuscular blockade and other complications.

From the Research

Considerations for Anesthesia in Myasthenia Gravis Patients

• Patients with myasthenia gravis (MG) are at risk of postoperative residual curarization (PORC) if nondepolarizing muscle relaxants are used, which can result in hypoventilation and postoperative bronchopneumonia 4.
• The use of sugammadex as a neuromuscular blockade reversal agent has been shown to be effective in MG patients, allowing for rapid and predictable recovery from neuromuscular blockade 4, 5, 6.
• However, there have been cases where sugammadex failed to reverse neuromuscular blockade in MG patients, highlighting the importance of monitoring neuromuscular blockade and considering alternative reversal agents such as neostigmine 7.
• Anesthesia recommendations for MG patients include:
  • Reversal of nondepolarizing neuromuscular blockade agents with sugammadex 8.
  • Obtaining sufficient spontaneous breathing with absolutely no residual curarization before extubation 8.
  • Limited use of opioids and sedatives 8.
  • Avoidance of routine admission to the intensive care unit 8.
  • Consideration of peripheral nerve blocks for adjunct pain control 8.
• The pharmacology of acetylcholinesterase inhibitors versus sugammadex should be considered in the perioperative management of MG patients 8.
• Extubation criteria and pain management should also be carefully considered in MG patients to minimize the risk of postoperative complications 8.