QT interval prolongation after oxytocin bolus during surgical induced abortion

Background. Although oxytocin, a uterotonic agent, may cause short-term vasodilation that results in severe hypotension, it is still routinely given as an intravenous bolus injection during surgical suction curettage. Two reported cases of ventricular tachycardia after oxytocin bolus in patients with long QT interval syndrome led us to assess the effect of oxytocin on QT interval. Methods: Thirty-eight healthy women scheduled for a surgical suction curettage with general anesthesia were enrolled. General anesthesia was induced by propofol and maintained by either propofol (n = 18) or sevoflurane (n = 20). Electrocardiographic recordings were obtained before and at 1, 2, 3, and 5 minutes after a 10-U intravenous bolus of oxytocin. Results. Intravenous oxytocin induced a pronounced QTc interval prolongation of 41 +/- 21 ms (P <.0001), which was maximal 1 minute after administration. The QTc interval returned to control values 3 minutes after oxytocin bolus. Oxytocin bolus also induced an increase in heart rate of 19 +/- 10 beats/min and a significant decrease in systolic arterial pressure of 11 +/- 9 mm Hg (both P <.0001). The drug used to maintain anesthesia was not an independent factor of QTc interval prolongation in ANOVA analysis. Conclusions. Oxytocin intravenous bolus induced a large and transient QTc interval prolongation, suggesting that it may lead to proarrhythmia in circumstances favoring QTc interval increase.