Postoperative QT Interval Prolongation in Patients Undergoing Noncardiac Surgery under General Anesthesia

ABSTRACTBackground: Abnormalcardiacrepolarization,indicatedbya prolongation of the QT interval, increases the risk fortorsadesdepointes,apotentiallylife-threateningarrhyth-mia. Many perioperatively administered drugs and condi-tions prolong the QT interval. Despite several reports ofperioperative torsades de pointes, systematic evidence re-gardingperioperativeQTintervalprolongationislimited. Methods: Serialpostoperative12-leadelectrocardiogramswere obtained from 469 adult patients undergoing majornoncardiac surgery under general anesthesia. Heart ratecorrected QT-interval duration (Fridericia formula) wasthe primary outcome. All perioperatively administereddrugs were recorded. Emphasis was placed on absoluteQTc prolongation greater than 500 ms and relative in-creases of 30 and 60 ms. Results: At the end of surgery, 80% of the patients (345 of429) experienced a significant QTc interval prolongation( QTc 23 26 ms (mean and SD), 95% CI 20–25 ms, P less than 0.001). Approximately 51% (219 of 429) had aQTcgreaterthan440ms,and4%(16of429)aQTcgreaterthan 500 ms. In 39% (166 of 429), the QTc was greaterthan 30 ms, in 8% (34 of 429) 60 ms, and in greater than0.5% (2 of 429) 100 ms. No changes in QTc occurredatsubsequenttimepoints.Onepatientdevelopedtorsadesde pointes with a QTc: 29 ms (0.4% incidence rate).Several drugs had a large effect on QTc: isoflurane,methadone, ketorolac, cefoxitin, zosyn, unasyn, epineph-rine, ephedrine, and calcium. Postoperative body temper-ature had a weak negative correlation with QTc (r 0.15,