The effect of halothane and thiopentone on ventilatory responses mediated bythe peripheral chemoreceptors in man.

The activity and responsiveness of the peripheral ventilatory chemoreflex were assessed by the transient depression of ventilation following two breaths of oxygen in air-breathing subjects, and the differing times of onset of the ventilatory response to i.v. sodium bicarbonate in subjects breathing either air or oxygen. In patients premedicated with pethidine, in whom anaesthesia was induced with thiopentone, it was found that halothane, in an inspired concentration of 0.7-0.8%, reduced the activity and responsiveness of the peripheral ventilatory chemoreflex markedly. When halothane was discontinued and anaesthesia was maintained wtih intermittent injections of thiopentone (0.2 mg/kg/min) evidence of peripheral chemoreceptor activity and responsiveness returned.