Circulating cytokines in patients undergoing normothermic cardiopulmonary bypass

To determine the cytokine release during normothermic cardiopulmonary bypass, we have measured plasmatic levels of tumor necrosis factor-alpha and interleukins-1 beta, 6, and 8 in 10 patients during the first 24 hours after the start of bypass. Arterial blood samples were collected at intervals before, during, and after bypass. Interleukin-1 beta was not detectable in the plasma, and traces of tumor necrosis factor-alpha were detected in only three patients at times independent of the cardiopulmonary bypass procedure. Circulating endotoxin remained undetectable. Plasma interleukin-6 and interleukin-8 rose significantly from 2 until 24 hours after the start of bypass (p < 0.05) and peaked respectively at 4 and 2 hours after the beginning of bypass (interleukin-6, 268.1 +/- 131.43 pg/ml; interleukin-8, 370 +/- 420 pg/ml; mean peak +/- standard deviation). Peak values of interleukin-6 and interleukin-8 were correlated neither with the duration of aortic crossclamping or the bypass procedure nor with the hemodynamic parameters recorded at the same times. This study shows that normothermic cardiopulmonary bypass does not induce systemic release of tumor necrosis factor-alpha and interleukin-1 beta. A local production of these cytokines cannot be excluded, because interleukin-6 and interleukin-8 are produced by stimulated macrophages and monocytes in response to tumor necrosis factor-alpha and interleukin-1 beta. Our results, at normothermia, show a similar pattern of interleukin-6 and interleukin-8 release when compared with release during hypothermic cardiopulmonary bypass. Interleukin-8, an important chemotactic neutrophil factor, might play a role in reperfusion injuries observed in lungs and heart after cardiopulmonary bypass.