The aim of this study was to determine whether elderly patients (aged > or = 65 years, n = 20) in comparison with younger patients (aged < or = 55 years, n = 23) demonstrate a different biochemical and hemodynamic response to coronary artery bypass operations. In the elderly group, we calculated a smaller body surface area (p < 0.01) than that in the younger group, and more female patients were included in this group (p < 0.05). During cardiopulmonary bypass, the elderly had higher endotoxin plasma concentrations (p < 0.01) than the younger patients, and significantly more circulating tumor necrosis factor-alpha was found after operation (p < 0.04). In the intensive care unit, the elderly patients had a significantly higher pulmonary capillary wedge pressure (p < 0.001), a higher mean pulmonary artery pressure (p < 0.01), and a lower calculated left ventricular stroke work index (p < 0.05). Multivariate analysis for the postoperative outcome showed that the intergroup differences in tumor necrosis factor-alpha, mean pulmonary artery pressure, and pulmonary capillary wedge pressure could be explained mainly by the difference in age between the groups and that the calculated left ventricular stroke work index difference could be explained by the difference in circulating tumor necrosis factor-alpha levels. Thus in elderly patients higher circulating endotoxin and tumor necrosis factor-alpha concentrations were detected than in younger patients, which clinically resulted in a suppressed myocardial performance.