Synopsis
Recognise impending neuromuscular respiratory failure before oxygen saturation falls, avoid medicines and procedures that worsen transmission, and coordinate ventilation with rapid immunomodulatory treatment.
- Myasthenic crisis is severe myasthenia gravis causing respiratory failure or unsafe bulbar function; it may be the first presentation rather than a complication of known disease.
- Infection is a frequent precipitant, but surgery, pregnancy, aspiration, undertreatment, abrupt immunotherapy change and medicines that impair neuromuscular transmission must also be sought.
- Ask the patient to count aloud on one breath and assess speech, swallowing, neck flexion, cough and accessory-muscle use, then obtain serial forced vital capacity through experienced respiratory staff.
Key red flags
Exhaustion, drowsiness, silent weak cough, rising carbon dioxide or inability to clear secretions mandates immediate definitive airway action.
Investigation priorities
Measure the direction and severity of respiratory-muscle decline.
Management branches
A patient with known or possible myasthenia develops breathlessness, dysphagia or rapidly worsening weakness.
- Call critical care and neurology, position safely, give suction and oxygen only as needed, and assess cough, secretions, speech, swallow, neck flexion and breathing pattern.
- Measure forced vital capacity serially and obtain a blood gas without allowing either result to delay intubation when exhaustion or airway protection is failing.
Key medicines
Intravenous immunoglobulinFor life-threatening myasthenic crisis with intensive-care respiratory or bulbar failure, current NHS England criteria specify a total 2 g/kg over 2–5 days using the commissioned weight and infusion policy.
PyridostigmineUsual oral dosing is individualised through the current BNF; during intubated crisis it may be withheld then cautiously reintroduced by neurology before extubation.