Prolongation of QTc interval after postoperative nausea and vomiting treatment by droperidol or ondansetron

BACKGROUND: At dosages above 0.1 mg/kg, droperidol induces a dose-dependent QTc interval prolongation. Although subject to controversy, low-dose droperidol has recently been suspected to induce cardiac arrhythmias. Hence, 5-hydroxytryptamine type 3 antagonists have become the first-line drug for management of postoperative nausea and vomiting. These drugs are also known to prolong the QTc interval at high dosages. This study describes QTc interval changes associated with postoperative nausea and vomiting treatment by droperidol or ondansetron at low doses. METHODS: Eighty-five patients with postoperative nausea and vomiting were included in this prospective, single-blind study. Patients received either 0.75 mg intravenous droperidol (n = 43) or 4 mg intravenous ondansetron (n = 42). Electrocardiographic recordings were obtained before administration of antiemetic drug and then 1, 2, 3, 5, 10, and 15 min after. Electrocardiographic monitoring was maintained for 3 h in eight patients in each group. RESULTS: The QTc interval was prolonged (> 450 ms in men, > 470 ms in women) in 21% of the patients before antiemetic drug administration. This was significantly correlated with lower body temperature and longer duration of anesthesia. Compared with predrug QTc measurement, both antiemetics were associated with a significant QTc interval prolongation (P < 0.0001). The mean maximal QTc interval prolongation was 17 +/- 9 ms after droperidol occurring at the second minute and 20 +/- 13 ms after ondansetron at the third minute (both P < 0.0001). Compared with predrug measurement, the QTc interval was significantly lower after the 90th minute in both groups. CONCLUSIONS: Droperidol and ondansetron induced similar clinically relevant QTc interval prolongations. When used in treatment of postoperative nausea and vomiting, a situation where prolongation of the QTc interval seems to occur, the safety of 5-hydroxytryptamine type 3 antagonists may not be superior to that of low-dose droperidol.