What is the best approach for emergent intubation in a patient with myasthenia gravis (MG) and potential respiratory muscle weakness?

Emergent Intubation in Myasthenia Gravis

For emergent intubation in myasthenia gravis, use rocuronium at standard or slightly increased doses (0.6 mg/kg or higher) as the neuromuscular blocking agent, and strictly avoid succinylcholine due to unpredictable prolonged paralysis from interaction with anticholinesterase medications. 1

Pre-Intubation Medication Management

Immediately discontinue pyridostigmine before intubation. 2 The American Academy of Neurology recommends withholding all anticholinesterase inhibitors in intubated patients, as these medications interfere with neuromuscular blocking agents and provide no benefit during mechanical ventilation. 2, 3

Critical Medications to Avoid

• Succinylcholine is absolutely contraindicated - pyridostigmine inhibits both acetylcholinesterase and plasma cholinesterase, causing excessive ligand accumulation at the neuromuscular junction and unpredictable, prolonged depolarization 1
• IV magnesium is absolutely contraindicated - can precipitate or worsen myasthenic crisis 2, 4
• Avoid corticosteroids during the acute crisis phase in the emergency department 3

Neuromuscular Blocking Agent Selection

Rocuronium is the preferred agent at doses of 0.6 mg/kg or higher because it has mild vagolytic effects and metabolism independent of cholinesterase activity. 1 If nondepolarizing agents must be used, reduce the dose as MG patients demonstrate increased sensitivity to these medications. 3

Key Pharmacologic Considerations

• Patients on pyridostigmine have reduced plasma cholinesterase activity, risking prolonged neuromuscular blockade with succinylcholine 1
• The synergistic effect between pyridostigmine and succinylcholine intensifies and prolongs depolarization unpredictably 1
• Pyridostigmine also inhibits mivacurium metabolism, delaying recovery from this agent 1

Intubation Technique and Airway Management

Follow standard difficult airway protocols with heightened awareness of bulbar weakness and aspiration risk. 5 Second-generation supraglottic airways (PLMA, LMA Supreme, or i-gel) should be immediately available for rescue oxygenation if direct laryngoscopy fails. 5

Intubation Approach

• Pre-oxygenate thoroughly given the high risk of rapid desaturation from respiratory muscle weakness 2
• Consider awake fiberoptic intubation in patients with severe bulbar symptoms to maintain airway reflexes 5
• If rapid sequence intubation is necessary, use rocuronium with reduced or no paralytic dosing if possible 3
• Have equipment ready for front-of-neck access (cricothyroidotomy) as a rescue option 5

Rescue Oxygenation Strategy

If initial intubation fails:

• Place a second-generation SGA immediately for rescue oxygenation 5
• Allow one single attempt at fiberoptic intubation through the SGA 5
• If this fails, proceed directly to surgical cricothyroidotomy rather than repeated laryngoscopy attempts 5

Post-Intubation Management

Patients require ICU-level monitoring for a minimum of 24 hours even after apparent stabilization. 2 Prolonged muscle weakness with breathing difficulties represents the most hazardous complication and can occur as late as 4 days after acute cholinesterase inhibitor exposure. 1

Immediate Post-Intubation Actions

• Initiate high-dose corticosteroids: methylprednisolone 1-2 mg/kg/day IV or prednisone 1-1.5 mg/kg/day 2
• Start either IVIG (2 g/kg total over 5 days at 0.4 g/kg/day) OR plasmapheresis (5 sessions over 5 days) 2
• Perform daily neurological evaluations and frequent respiratory function assessments 2

Extubation Criteria

Patients must be fully awake, clear of secretions, and able to maintain upper airway reflexes before extubation to avoid postoperative upper airway obstruction. 1 Do not use neostigmine for reversal of neuromuscular blockade in patients who were taking pyridostigmine, as this adds further unpredictable cholinesterase inhibition. 1

Common Pitfalls to Avoid

• Never repeat succinylcholine dosing - the cumulative effect with ongoing cholinesterase inhibition becomes completely unpredictable 1
• Do not attempt to "wake the patient" after failed intubation - neurological impairment and residual drug effects make this dangerous and unreliable in critically ill patients 5
• Avoid multiple laryngoscopy attempts - limit interventions to prevent airway trauma and maintain the core principle of safe airway management 5
• Do not delay cricothyroidotomy if cannot intubate/cannot ventilate situation develops - rapid reoxygenation with a cuffed tube through the cricothyroid membrane is life-saving 5