The effects of volatile anesthetics on the Q-Tc interval

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 hospi tal. 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-tida l concentrations of 3 minimum alveolar concentration was 6 to 10 minutes. W hen compared with preinduction values, heart rate decreased after halothane (p < 0.01) and sevoflurane (p < 0.05) administration; in contrast, heart r ate increased after induction of anesthesia with isoflurane (p < 0.05). The mean QRS intervals were not significantly changed after halothane, isoflur ane, or sevoflurane. The Q-Tc interval was increased with isoflurane compar ed with baseline (465 +/- 23 <nu> 441 +/- 18 msec, p < 0.01), not changed w ith sevoflurane (441 +/- 17 <nu> 434 +/- 19 ms, p > 0.05), and shortened wi th halothane (426 +/- 23 nu 445 +/- 21 msec, p < 0.01). Conclusions: Sevoflurane or halothane may be preferred to isoflurane patien ts 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 fu rther investigation. Copyright (C) 2001 by W.B. Saunders Company.