Once thought to be an isolated perioperative phenomenon, QTc prolongation seems to be common during surgery under general and spinal—but not local—anesthesia, a study has found. Additionally, the relative risk for extended QTc prolongation is more than five times greater with general anesthesia than with spinal.
“QTc prolongation is an indicator of abnormal cardiac repolarization,” explained Andreas Duma, MD, one of a team of researchers at Washington University of St. Louis in Missouri; Dr. Duma is now a resident at the Medical University of Vienna in Vienna, Austria. “If longer than 450 msec, it increases the risk of potentially life-threatening arrhythmia. That brought us to the key questions in this study: Does QTc prolongation occur regularly in the intraoperative period and does the type of anesthesia influence the incidence of QTc prolongation?”
To help answer those questions, Dr. Duma and his colleagues enrolled 300 patients into a prospective cohort study. QTc duration was continuously recorded by 12-lead Holter electrocardiogram from 30 minutes preoperatively to up to 60 minutes postoperatively. Additionally, QTc prolongation was compared between patients undergoing general (n=101) or spinal (n=99) anesthesia for orthopedic surgery, or local anesthesia for biopsy (n=53) or diagnostic coronary angiography (n=47). Although the trial’s primary outcome was intraoperative QTc increase (defined as the intraoperative-to-preoperative QTc duration difference), the researchers also determined the incidence of long QTc episodes, defined as those greater than 500 msec for at least 15 minutes.
“Within all cohorts, the general anesthesia cohort had the most pronounced intraoperative QTc prolongation, with a median of 33 msec [range, 22-46 msec],” Dr. Duma reported at the 2014 annual meeting of the American Society of Anesthesiologists (abstract A1020). “This declined postoperatively but never went back to baseline.” Significant QTc prolongation also occurred during spinal anesthesia (mean 22 msec; range, 12-29 msec). By comparison, no QTc prolongation was observed during local anesthesia: mean 4 msec during biopsy (range, –4 to 7 msec) and 6 msec during coronary angiography (range –5 to 16 msec).
“We also performed a secondary analysis to see if those patients who had a QTc prolongation greater than 500 msec already had prolonged QTc duration at baseline,” Dr. Duma said. It was found that the relative incidence risk for a long QTc episode—defined as QTc greater than 500 msec for at least 15 minutes—was 5.3 (95% confidence interval, 0.7-43) times greater with general than with spinal anesthesia.
Finally, the investigators analyzed the incidence of moderate (>0 to ≤30 msec), marked (>30 to <60 msec) and substantial (≥60 msec) QTc prolongation by anesthesia type (Figure). “In the general anesthesia group, 64% had either marked or substantial QTc prolongation,” Dr. Duma said. This compared with 21% for the spinal anesthesia group, 0% for the local anesthesia biopsy group and 11% for the local anesthesia angiography group. “Nine percent of patients in the general anesthesia group even had a QTc prolongation longer than 500 msec,” Dr. Duma added.
“In conclusion,” he said, “QTc prolongation is not an isolated postoperative phenomenon, but starts early during anesthesia and surgical care. Moreover, marked QTc prolongation is common under general and spinal anesthesia.”
Bruce D. Spiess, MD, professor of anesthesiology and director of the Virginia Commonwealth University Reanimation Engineering Shock Center in Richmond, found the study intriguing. “Perhaps the QTc prolongation is a factor of whole-body generalized inflammation rather than anesthesia,” he said. “It strikes me that short procedures and local procedures do not have the event-related QTc prolongation. Many things get ascribed to anesthesia, but perhaps they are really part of the entire process of a major operation. As a result, general and spinal anesthesia may be preferable for a surgical event that involves more inflammatory processes than just a local excision.”
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