Effects of halothane, isoflurane and enflurane on ventilation in children

The ventilatory effects of halothane in eight children were compared with those of isoflurane in eight children and enflurane in six children. All studies were completed before surgery commenced, and the children received no preoperative medication. The depression of ventilation produced by the three agents increased in a dose-related fashion as the alveolar concentrations were increased, and the depression of ventilation that they produced in oxygen was greater than that produced by equipotent concentrations in nitrous oxide. While the increase in ventilatory frequency and the decrease in TE associated with increasing concentrations of halothane were statistically significant (P less than 0.05), the increase in frequency associated with isoflurane was not, although it was sufficient to maintain the end-tidal and arterialized venous PCO2 in the isoflurane group at a value which did not differ significantly from that in the halothane group. Profound depression of ventilation was produced in the children by enflurane, clearly because no increase in ventilatory frequency was associated with its use. It was evident that the ventilatory effects of the three volatile agents in unstimulated children are very similar to those described elsewhere in the adult. There was no difference of any clinical significance between the degree of depression of ventilation produced by halothane and isoflurane in children.