Cardiopulmonary Bypass Is the Main Predictor of Gastrointestinal Complications after Cardiac Surgery

To the Editor:

We read with great interest the recent article of D'Ancona and colleagues ¹ about the determinants of gastrointestinal complications in cardiac surgery, and we congratulate them for presenting the largest experience on the topic. However, we tend to disagree with the comment of the authors that variables such as cardiopulmonary bypass time and ischemic time are marginal factors in the development of gastrointestinal complications. To date, we are the only group to have published a randomized controlled trial comparing patients undergoing off-pump coronary artery bypass surgery (OPCAB) with those undergoing conventional myocardial revascularization on cardiopulmonary bypass (CABG). ²

The stepwise multivariate regression analysis in our prospective randomized controlled trial comparing 150 OPCAB and 150 CABG patients, none of whom had undergone previous abdominal surgery, identified cardiopulmonary bypass (CPB) including cardioplegic arrest as the only predictor of postoperative gastrointestinal complications (OR, 7.4; CI, 3.4–17.9). We attribute the high incidence of gastrointestinal complications to the period of visceral ischemia or to the inflammatory response after CPB itself, and to the adverse effects of cardioplegia. Cardiac surgery with CPB is associated with a low-flow state, with subsequent hypoperfusion of end-organs. Perioperative hypotension, hypovolemia, prolonged CPB time, use of vasoconstrictors, and postoperative arrhythmias all aggravate this end-organ hypoperfusion and could well explain the relatively high number of gastrointestinal complications in the group undergoing conventional surgery. ² We acknowledge the conclusion of D'Ancona and co-authors ¹ that prolonged mechanical ventilation, acute renal failure, sepsis, valve surgery, chronic renal failure, and sternal wound infection are major determinants of gastrointestinal complications after cardiac surgery. However, we maintain that cardiopulmonary bypass including cardioplegic arrest is the main independent predictor of postoperative gastrointestinal complications in patients undergoing cardiac surgery.