Perioperative factors influencing interleukin-10 release under cardiopulmonary bypass

Background: The cytokine response to cardiopulmonary bypass (CPB) is complex and can be modified. Among several mediators, the anti-inflammatory interleukin-10 (IL-10, 'cytokine-secretion inhibitory factor') is particularly interesting because of its ability to counteract pro-inflammatory cytokines triggering endothelial and leukocyte activation in the immediate immune response to CPB. On the other hand, during the delayed phase of the immune response, IL-10 may act as a promotor of immunodeficiency in complicated courses. Therefore, it is of interest to investigate special conditions of CPB that may influence the extent of perioperative release of IL-10. Methods: We analyzed 20 continuously registered parameters during CPB, including an analysis of subgroups in the case of application of aprotinin or steroids. 30 consecutive adult patients with coronary artery disease (CAD) and normal left-ventricular function undergoing elective CABG were prospectively studied, Arterial blood was sampled perioperatively and levels of IL-10 were determined using ELISA tests. For analysis, the time point of maximum IL-10 release was selected (30min after end of CPB). Simultaneously, CPB-registration protocols were analyzed concerning standard parameters. Results: We could state an exponential relationship between IL-10 levels 30min after end of CPB and the ischemia time (r=0.76), duration of CPB (r=0.73) and the extent of negative base excess (BE, r=0.66) in all subgroups. An inverse relationship could be seen between IL-10 plasma levels and venous O-2 saturation: low values for O-2 saturation correlated with high IL-10 levels as did low mean arterial pressure (MAP). Hypothermia reduced IL-10 release (r=0.80), whereas a long duration correlated with high IL-10 release (r=0.67). In the case of longer duration of hypothermia, the protective effect vanished. Conclusions: The results show a significant rise for IL-10 early after starting CPB. Low values for venous O-2 saturation and low MAP correlated with high IL-10 levels. A good correlation could be seen between IL-10 plasma levels and the duration of CPB, ischemia time, and negative base excess. Because of the ability of persisting IL-10 production to induce a higher incidence of septic complications, all actions for maintaining an optimum of perfusion and oxygenation play an important role.