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From the *Department of Pediatric Anesthesia, British Columbia Children’s Hospital and the Department of Anesthesiology, Pharmacology and Therapeutics, Division of Pediatric Cardiology, British Columbia Children’s Hospital and the Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada.
Address correspondence and reprint requests to Dr. S. D. Whyte, Department of Pediatric Anesthesia, Room 1L7, British Columbia Children’s Hospital, 4480 Oak St., Vancouver, BC, V6H 3V4, Canada. Address e-mail to swhyte{at}cw.bc.ca.
Abstract
BACKGROUND: QT interval prolongation on the electrocardiogram (ECG) may be drug-induced and is traditionally associated with torsades des pointes. A better predictor of torsades des pointes is the time interval between the peak and the end of the T-wave (Tp-e). Older studies of propofol’s effect on the corrected interval (QTc) are conflicting and confounded by polypharmacy. It was recently shown that target-controlled infusion of propofol at 3 µg/mL has no effect on QTc or Tp-e. This plasma concentration of propofol is at the extreme lower end of the range for surgical anesthesia. In this randomized, double-blind, clinical study, we investigated the dose–response relationship between propofol, QTc, and Tp-e in a range of doses clinically relevant for surgical anesthesia.
METHODS: Sixty healthy unpremedicated children, aged 3–10 yr, were recruited. Subjects were randomized to receive target-controlled infusions of propofol, to achieve 1 of 3 plasma concentrations: 3, 4.5, and 6 µg/mL. A preoperative 12 lead ECG was performed and repeated 5 min after induction. Two investigators, blinded to group allocation and to the timing of the ECG traces, independently measured QTc and Tp-e within and between each group. Paired t-tests were used to compare QTc and Tp-e within groups. One-way analysis of variance was used for intergroup analysis. The primary outcome measure was a change of >25 ms in Tp-e both within and between groups.
RESULTS: ECG recordings were obtained in 51 children. There were no demographic or ECG differences at baseline, at which time QTc and Tp-e values were within normal limits. There were no differences in QTc or Tp-e after induction within or between the three different groups.
DISCUSSION: Propofol has no effect on myocardial repolarization in healthy children at clinically relevant doses. This suggests that propofol would be a rational choice for children with a preexisting repolarization abnormality.
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