Subanaesthetic halothane: its effect on regulation of ventilation and relevance to the recovery room.

Ventilation and the ventilatory response to a steady-state of isocapnic hypoxaemia were measured in six healthy volunteers, both awake and while sedated with low doses of halothane (0.05 and 0.1 MAC). Halothane sedation markedly reduced ventilatory responses to sustained hypoxaemia, in a dose-related fashion. We estimated the length of time after anaesthesia that halothane 0.1 MAC would be present in patients in the recovery room. In five healthy patients who had halothane anaesthesia with a mean duration of one hour, halothane 0.1 MAC or more persisted for approximately one hour. We conclude that, during emergence from halothane anaesthesia, patients may have a significant impairment of the ventilatory response to hypoxaemia, which persists for some time even after regaining consciousness.