Effects of sevoflurane versus propofol on QT interval.

BACKGROUND: Prolongation of the QT interval is an alteration of the electrocardiogram (ECG) that may result in a potentially dangerous polymorphic ventricular tachycardia known as torsade de pointes. Michaloudis et al. investigated the effect of isoflurane and halothane on the QT interval in premedicated and non premedicated children, and in premedicated adults. Isoflurane significantly prolonged the QTc interval, in contrast to halothane, which shortened the QTc interval. The aim of the study was to evaluate the effect of sevoflurane on the QT interval in patients undergoing non-cardiac surgery.

METHODS: One hundred and eighty patients classified as ASA physical status I-III were enrolled and 102 were excluded. Patients had been scheduled for elective non cardiac surgery. Exclusions criteria were: cardiovascular impairment or chronic obstructive lung disease, medication affecting QT interval, and an abnormal prolongation of the QTc interval (440 ms). The patients were then randomly allocated to one of two groups, one receiving sevoflurane anesthesia and the other receiving propofol anesthesia. In all patients, a 12 lead ECG was recorded before surgery, after intubation, after extubation. The investigators reading the ECG were blinded to the type of induction and anesthesia used. The following variables were recorded or calculated: heart rate, P-R interval, QRS interval, QT interval, QTc interval according to Bazett's formula, systolic, diastolic and mean blood pressure.

RESULTS: The sevoflurane significantly prolongs the QT and the QTc interval, whereas the induction and total intravenous anesthesia with propofol significantly shortens the QT but not the QTc interval.

CONCLUSIONS: The amount the sevoflurane-associated QT prolongation may possibly be of clinical significance in some patients presenting long QT syndrome, hypokalemia, or in presence of other agents or factors that lengthen QT.