The effect of inhalational anaesthetics on QTc interval.

BACKGROUND AND OBJECTIVE

The aim of this study was to assess time dependent cumulative effects of three different inhalation anaesthetics on QTc interval during the maintenance of anaesthesia.

METHOD

Seventy-five ASA I-II male patients undergoing inguinal herniorrhaphy were randomly allocated into three groups. No premedication was given. Anaesthesia was induced with thiopental and tracheal intubation was facilitated by vecuronium in all groups. Anaesthesia was maintained with 0.8% halothane (Group I) (n = 25), 1% isoflurane (Group II) (n = 25), or 2% sevoflurane (Group III) (n = 25) and 66% nitrous oxide in oxygen. Three lead electrocardiogram recordings were taken before induction, 2, 5, 10, 15, 30 and 45 min after induction and after extubation. Heart rate, systolic, diastolic, mean arterial pressure and SpO2 were recorded at the same time. Heart rate and corrected QT interval were evaluated by using Bazett's formula. Multivariate analysis of variance for repeated measures was used to determine intergroup and intragroup differences.

RESULTS

There was no statistically significant difference in the baseline QTc values of the groups. There was no difference between QTc values with halothane and sevoflurane. There was a difference between QTc values with isoflurane and those with the other two inhalation anaesthetics (P < 0.05). Although QTc values in the isoflurane group were higher at all times, the critical value of 440 ms was not exceeded.

CONCLUSION

We conclude that halothane 0.8%, isoflurane 1% and sevoflurane 2% do not prolong QTc interval.