ANESTHESIA AND THE QT INTERVAL - EFFECTS OF ISOFLURANE AND HALOTHANE IN UNPREMEDICATED CHILDREN

The effects of isoflurane and halothane on the QT interval were invest igated during induction of anaesthesia. Fifty-one unpremedicated, ASA grade 1 children were studied. Anaesthesia was induced with either iso flurane (n = 25) or halothane (n = 26) and was maintained to the end o f the study with end-tidal concentrations of between 2.5% and 3%. Reco rdings of the electrocardiograph, heart rate and systolic arterial pre ssure were obtained at the following times: before induction of anaest hesia; 1 min and 3 min after stable end-tidal concentrations of anaest hetic agent had been reached; 1 min and 3 min following vecuronium adm inistration; at the time of tracheal intubation and 1 min and 3 min la ter. Isoflurane significantly prolonged the QT interval (p < 0.001), i n contrast to halothane which shortened it (p < 0.01). Heart rate rema ined largely unchanged during isoflurane anaesthesia but it decreased in the presence of halothane (p < 0.001). In bath groups, systolic art erial pressure decreased significantly after induction of anaesthesia (p < 0.001) and remained so to the end of the study. In the isoflurane group, 12 children developed ECG repolarisation abnormalities and in one child an arrhythmia was noticed. In the halothane group, one child developed repolarisation changes while arrhythmias were observed in 1 0 children. There were no adverse sequelae. It is concluded that halot hane may be a better anaesthetic agent than isoflurane for use in chil dren with a prolonged QT interval.