The effects of volatile anesthetics on the Q-Tc interval

Abstract

Objective: To examine the effects of halothane, isoflurane, and sevoflurane on Q-Tc interval (corrected for heart rate) during inhalation induction of anesthesia.

Design: Prospective, double-blind, randomized study.

Setting: Departments of Cardiology and Anesthesiology in a university hospital.

Participants: Patients undergoing noncardiac surgery.

Interventions: A total of 65 American Society of Anesthesiologists physical status I-II patients, aged 16 to 50 years, undergoing general anesthesia, were randomly allocated to receive halothane, isoflurane, or sevoflurane.

Measurements and main results: The time to reach the predetermined end-tidal concentrations of 3 minimum alveolar concentration was 6 to 10 minutes. When compared with preinduction values, heart rate decreased after halothane (p < 0.01) and sevoflurane (p < 0.05) administration; in contrast, heart rate increased after induction of anesthesia with isoflurane (p < 0.05). The mean QRS intervals were not significantly changed after halothane, isoflurane, or sevoflurane. The Q-Tc interval was increased with isoflurane compared with baseline (465 +/- 23 v 441 +/- 18 msec, p < 0.01), not changed with sevoflurane (441 +/- 17 v 434 +/- 19 ms, p > 0.05), and shortened with halothane (426 +/- 23 v 445 +/- 21 msec, p < 0.01).

Conclusion: Sevoflurane or halothane may be preferred to isoflurane in patients with conditions that are known to induce a prolonged Q-Tc interval. The effects of Q-Tc interval changes resulting from different anesthetic agents on morbidity and the incidence of arrhythmias during anesthesia warrant further investigation.