[Comparative effect of halothane and isoflurane on peroperative cardiac arrhythmias]

Cardiac arrhythmias were studied in twenty ASA class 1 patients under general anesthesia using halothane or isoflurane to supplement nitrous oxide in oxygen. The study began during the maintenance period, once the expiratory MAC value had reached a stable level of 1, and stopped one hour later. Both intubation and recovery periods were excluded. The end-tidal gas concentration was measured for carbon monoxide and vapours. The ECG was recorded on a magnetic tape. The incidence of arrhythmias was higher in the halothane group when compared to the isoflurane group (p less than 0.05). The main types of arrhythmias observed were supraventricular and ventricular ectopic beats. None of the arrhythmias observed were serious; in particular the ventricular beats were all unifocal and occasional. Heart rate measured at 10 min intervals tended to be more rapid in the isoflurane group.