Effect of Methadone and Hydromorphone on the QT Interval After Anesthesia and Surgery

A number of drugs used in the perioperative period may cause prolongation of the QT interval on the electrocardiogram (EKG). These drugs include inhalational agents, antiemetic agents, pain medications, and drugs used to reverse the effects of muscle relaxants. Approximately 80% of patients undergoing a general anesthetic will demonstrate significant prolongation of the QT interval on the EKG in the postanesthesia care unit (PACU) following surgery. The concern with QT interval prolongation is that it can result in a potentially lethal ventricular arrhythmia termed torsade des pointes. Despite the concurrent use of several of these medications in a typical general anesthetic, torsade des pointes is a rare event in the perioperative period. In the past decade, the use of intravenous methadone as part of a balanced anesthetic technique has increased significantly. A single dose provided at induction of anesthesia can provide prolonged (24-48 hours) relief from pain. Studies in patients receiving long-term treatment with methadone for addiction therapy or chronic pain have revealed that these patients are at risk for QT prolongation, torsade des pointe, and cardiac death. However, the effect of a single intravenous dose of methadone used in the operating room on the QT interval is uncertain. The aim of this randomized clinical trial is to compare the impact of methadone, when compared to the more commonly-used opioid hydromorphone, on QT prolongation measured with a 12-lead EKG in the PACU and on postoperative day 1. We hypothesize that methadone will not result in significant QT prolongation when used as part of a standardized general anesthetic.