A 45-year-old man with known myasthenia gravis (AChR antibody positive) develops worsening ptosis, dysphagia, and progressive respiratory distress over 24 hours. He was recently started on azithromycin for a respiratory infection. On examination, deep tendon reflexes are intact. PFTs show FVC 1.1 L (26% predicted). What is the most critical immediate intervention?
- A IV pyridostigmine 2 mg
- B Intubation and mechanical ventilation ✓
- C IV neostigmine and atropine
- D Plasmapheresis as first intervention
Explanation
This is myasthenic crisis, triggered by azithromycin (a macrolide that impairs neuromuscular transmission by inhibiting acetylcholinesterase and reducing muscle action potential). The critical threshold for intubation in MG crisis is FVC <15–20 mL/kg or <1 L (20/30/40 rule: intubate when FVC <20 mL/kg, MIP >−30 cmH2O, or MEP <40 cmH2O). With FVC of 1.1 L (26% predicted) and rapid deterioration, immediate intubation takes priority over any immunotherapy. Pyridostigmine IV during crisis is actually withheld to avoid cholinergic secretions complicating airway management.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.