Effect of different intra-abdominal pressure levels on QT dispersion in patients undergoing laparoscopic cholecystectomy

Background

Hemodynamic changes caused by carbon dioxide (CO₂) insufflation occur frequently in patients who undergo laparoscopic surgery. One indicator of these changes is corrected QT dispersion (QTcd), an index of myocardial function. Prolongation of QTcd has been associated with cardiovascular morbidity and mortality. We compared the effects of high-pressure (15 mmHg) and low-pressure (7 mmHg) CO₂ pneumoperitoneums on the QT interval, the rate-corrected QT interval (QTc), the QT dispersion (QTd), and the corrected QT dispersion (QTcd) during laparoscopic cholecystectomy.

Methods

Twenty consecutive patients were in a low-pressure pneumoperitoneum group and 32 were in a high-pressure pneumoperitoneum group. A 12-lead electrocardiogram was used to monitor cardiac variables. In all patients, serial electrocardiograms were recorded before anesthesia induction (baseline), immediately after the pneumoperitoneum had been created, every 15 minutes during CO₂ insufflation, and 5 minutes after deflation. Two observers measured the QT intervals independently, and the QTcd was calculated using Bazett’s formula.

Results

The QT interval and the QTc interval did not change significantly during the study in either group. The QTd and QTcd in the high-pressure pneumoperitoneum group increased significantly during CO₂ insufflation and were significantly higher in the high-pressure pneumoperitoneum group compared with the low-pressure pneumoperitoneum group. Changes caused by CO₂ insufflation were reversible.

Conclusions

Statistically significant increases of QTd and QTcd, which are associated with an increased risk of arrhythmias and cardiac events, occur during CO₂ insufflation in both high-pressure and low-pressure pneumoperitoneums. QTd and QTcd were significantly higher in the high-pressure pneumoperitoneum group than they were in the low-pressure pneumoperitoneum group. QT interval changes were not related to anesthetic agents, surgical stress, hypercapnia, or duration of CO₂ insufflation. Increased intra-abdominal pressure may have caused these changes.