Effects of droperidol and ondansetron on dispersion of ventricular repolarization: A randomized double-blind clinical study in anesthetized adult patients.

BACKGROUND AND OBJECTIVE: Droperidol and ondansetron prolong QT interval, a circumstance that has raised some concerns regarding the possibility of inducing torsades de pointes (TdP). However drug-induced spatial dispersion of ventricular repolarization has been shown to be the principal arrhythmogenic substrate for TdP. The aim of this study is to explore the effects of droperidol and ondansetron on the dispersion of repolarization, measured using the T peak-to-end interval (Tp-e) and Tp-e/QT and Tp-e/RR(1/2) ratios in surgical anesthetized patients.

METHODS: A randomized, double-blind study carried out on sixty-three adult patients without cardiac disease or factors favoring QT prolongation and undergoing non-cardiac surgery were randomly assigned to the droperidol or ondansetron group. Under propofol anesthesia, a 12-lead EKG was obtained, and 1.25mg droperidol or 4mg ondansetron was injected. Five minutes later, a new 12-lead EKG was recorded. EKG analyses were independently performed by two cardiologists blinded to the state of the traces or group allocation. QT, RR and Tp-e intervals were measured by averaging five successive beats in leadII (QT) or V5 (Tp-e). The mean value for each measurement was calculated for statistical analysis.

RESULTS: Thirty-two patients (19 women) received droperidol, and 31 (22 women) ondansetron. Droperidol and ondansetron prolonged the QTcF interval (Fridericia formula) by 6.8 and 7.2ms (mean values) respectively, but neither droperidol nor ondansetron increased the Tp-e interval or Tp-e/QT and Tp-e/RR(1/2) ratios.

CONCLUSION: At antiemetic doses, neither ondansetron (4mg) nor droperidol (1.25mg) increases the dispersion of ventricular repolarization in healthy adult patients anesthetized with propofol.