Interaction of the effects of domperidone and sub-anaesthetic concentrations of isoflurane on the immediate and sustained hypoxic ventilatory response in humans.

Abstract

Twenty normal male subjects with brisk hypoxic ventilatory responses were recruited and ventilatory responses to sustained isocapnic hypoxia (SaO2 80.4 (SD 1.3)% for 20 min) were studied on separate days under four conditions: hypoxia alone, with or without domperidone, and 0.1 MAC of end-tidal isoflurane, with or without domperidone. Ventilatory variables were subjected to analysis of variance with estimation of the effects of isoflurane and domperidone, and their interaction. Isoflurane reduced the initial increase in ventilation significantly by 3.12 (95% confidence limits 1.69, 4.55) litre min-1 (P < 0.05) and domperidone increased the initial increase in ventilation by 1.78 (0.35, 3.21) litre min-1 (P < 0.05). Neither isoflurane nor domperidone affected the subsequent ventilatory decline. No interaction was found between these agents. These results confirm that 0.1 MAC of isoflurane suppressed the initial hypoxic ventilatory response but not the subsequent ventilatory decline when hypoxia was sustained. Domperidone offset the suppressive effect of isoflurane on the hypoxic ventilatory response but no interaction was detected.