Interleukin 6 production during cardiac surgery correlates with increasing age

Cardiac surgery produces a proinflammatory response characterized by cytokine production. Proinflammatory cytokines such as interleukin 6 (IL-6) may contribute to morbidity and mortality after cardiopulmonary bypass (CPB). Elderly patients undergoing CPB are at increased risk of morbidity and mortality. We hypothesized that patients aged >70 y produce more IL-6 during CPB.

Twenty-three patients (ages 23-80) undergoing cardiac surgery had blood sampled from the ascending aorta and coronary sinus on initial cannulation for bypass, at 30 min of aortic cross-clamp time, on release of the aortic cross-clamp, and at 20 min after reperfusion. Group 1 patients (n = 8) were aged <60 y, group 2 patients (n = 7) were aged between 60 and 70 y, and group 3 patients (n = 8) were aged >70 y. Plasma levels of tumor necrosis factor-alpha, IL-1, and IL-6 were analyzed.

The three groups did not differ with respect to preoperative ejection fraction, New York Heart Association classification, mean aortic cross-clamp time, or mean CPB time. IL-6 levels rose throughout myocardial ischemia and reperfusion in all three age groups. The increase in IL-6 during ischemia and reperfusion in the age group >70 was greater than the increase in younger patients. IL-6 was similar in the coronary sinus and the ascending aorta.

These data suggest that patients aged >70 y undergoing cardiac operations generate more IL-6 during CPB. The increased circulating IL-6 in elderly patients may incite a proinflammatory state that could subsequently underlie the associated higher mortality and morbidity of these procedures in elderly patients.