Hypoxic ventilatory responses during thiopentone sedation and anaesthesia in man.

We have assessed the impact of thiopentone on the hypoxic ventilatory reflex, and on the responses to carbon dioxide and doxapram. Thiopentone sedation did not detectably alter any of these aspects of ventilatory control. Thiopentone anaesthesia reduced ventilation and the ventilatory responses to hypoxia, carbon dioxide and doxapram, all approximately in paralle. We conclude that, in contrast to halothane, thiopentone does not selectively reduce the ventilatory response to hypoxia. During light thiopentone anaesthesia, a reasonably brisk hypoxic response is present.