Acute neuromuscular respiratory failure: Case

Case discussion

Why this is a time-critical neuromuscular respiratory emergency

This boy has acute neuromuscular respiratory failure from probable Guillain-Barre syndrome. The most dangerous feature is the one that looks reassuring: his oxygen saturation is 98 percent. Neuromuscular failure is a failure of the respiratory pump, not the lungs, so the lung tissue is normal and oxygenation is preserved early while the weak pump fails to clear carbon dioxide. The normal saturation therefore hides a rising carbon dioxide, and the child can arrest with a calm monitor. The clinical lesson is to drive the airway decision from the bedside forced vital capacity and the bulbar assessment, never from the saturation or a single blood gas. ^[4][1]

The thresholds that force the decision

His numbers already meet every Lawn threshold for ventilation. His forced vital capacity of 16 mL per kilogram is under the 20 mL per kilogram threshold, it has fallen by a third in six hours, his maximum inspiratory pressure of minus 24 cmH2O is weaker than the minus 30 cmH2O trigger, and his bulbar weakness with a weak cough and pooled secretions predicts aspiration. Any one of these would justify intensive care; together they make intubation the immediate decision, made before the blood gas decompensates. ^[1][2]

Airway management: intubate, avoid suxamethonium

Because bulbar weakness has developed, non-invasive ventilation will not protect his airway, and pushing a mask in an aspirating child only delays the intubation that was always going to be needed. I would proceed to elective intubation. I would preoxygenate, set up continuous cardiac and haemodynamic monitoring for the autonomic instability of Guillain-Barre syndrome, and perform a rapid sequence induction with rocuronium one milligram per kilogram intravenously. I would avoid suxamethonium entirely, because in denervating disease it upregulates extrajunctional acetylcholine receptors and can trigger life-threatening hyperkalaemia and cardiac arrest. ^[9][10]