Effect of normothermic versus hypothermic cardiopulmonary bypass on cytokine production and platelet function

Background. Proinflammatory cytokines and platelets play a key role in the systemic inflammatory response associated with cardiopulmonary bypass (CPB) . The aim of this study was to evaluate the effects of both hypothermic and normothermic CPB on platelet activation, cytokine production, as well as t heir possible correlations. Methods, Twenty patients who underwent CABG were randomly assigned into two groups receiving hypothermic and normothermic CPB, Blood samples were obta ined through a venous catheter at 6 time points. The following parameters w ere measured: in vitro platelet aggregation, in vivo platelet activation, c omplete and differential blood cell counts, plasma soluble P-selectin level s, plasma IL-6, IL-1 beta and TNF alpha levels. Results, The results demonstrated that platelet abnormalities could be obse rved to a greater extent during hypothermic rather than normothermic CPB, T he occurrence of in vivo platelet activation was suggested by the presence of a significantly increased parentage of platelets expressing CD62P on the ir surface, as well as by a decreased in vitro platelet aggregation induced by different agonists, Complete and differential blood cell counts showed no substantial decrease in platelet number without differences between grou ps. The results obtained also showed the presence of a significant release of sP-selectin during CPB, as well as a more pronounced increase of plasma sP-selectin levels in patients undergoing hypothermic compared to normother mic CPB, A comparison of cytokine levels demonstrated a significant elevati on of plasma IL-6 levels during either hypothermic or normothenmic CPB, par alleling the neutrophil rise, while no differences were observed for TNF-al pha levels. Conversely, plasma IL-1 beta levels were significantly elevated during hypothermic, but not during normothermic CPB, Conclusions. Hypothermic CPB is responsible for a greater platelet activati on and endothelial dysfunction than normothermic CPB, leading to more profo und changes in the hemostatic and inflammatory systems, which, in turn, mig ht be responsible for the higher incidence of postoperative complications r eported during hypothermic CPB.