Post-op Prolonged QT in Non-Cardiac Surgery

Dr. C. Chon

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

Nagele, Peter, et al. Anesthesiology. August 2012 – Vol 117 – No. 2, pp 321-8

Summary:

12-lead EKG’s were performed on 469 adult patients undergoing major noncardiac surgery in the immediate preoperative period (baseline), within 30 minutes of arriving to the PACU, and on postoperative days 1 and 2. A single experienced anesthesiologist analyzed all of the EKG’s.

At the end of surgery, 51% of the patients demonstrated a prolonged QTc interval -- defined as greater than 440 ms. Moreover, 80% of study participants had significant increases in their QTc interval as compared to their preoperative baseline values. At later time points (ie, postoperative days 1 and 2), QTc intervals were unchanged from baseline. The perioperative QTc interval prolongation, then, can be attributed in large degree to medications administered in the perioperative period. Surgical stress may have also been an important contributing factor, although there was no correlation between increased heart rate and QTc prolongation.

The study found that isoflurane, methadone, ketorolac, calcium and ephedrine, in addition to the antibiotics cefoxitin, unasyn and zosyn, caused the most pronounced QTc prolongation. Surprisingly, neither ondansetron nor droperidol caued postoperative QTc prolongation.

One of the most important points discussed by the authors is the association between QTc prolongation and torsades de pointes. For each 10-ms increase in QTc interval, the risk of developing torsades de pointes increases by 5-7%. Therefore, the anesthesiologists must be ever-vigilant to catch the development of perioperative QTc interval prolongation.