Objective: Cardiopulmonary bypass (CPB) is known to cause part of the systemic inflammatory reaction after cardiac surgery that can be responsible for organ failure. A novel technique based on a minimal extracorporeal circulation (MECC(R)) system has been evaluated with regard to the inflammatory response in a prospective study involving patients undergoing coronary artery bypass grafting.
Methods: Sixty consecutive patients were randomly assigned to either standard normothermic CPB (n=30) or the MECC system, with a reduced priming volume, no aortic venting and no venous reservoir, excluding the blood-air interface (n=30). Specific evaluation of cytokine release (IL-1beta, IL-6, TNF-alpha), as well as neutrophil elastase secretion and beta-thromboglobulin release from platelets and S100 protein assay were performed. Serial blood samples were taken prior to the onset, after initiation, at the end and after weaning of the CPB; further samples were collected 6 and 24h after the end of the CPB.
Results: All patients were similar with regards to pre- and intra-operative characteristics and clinical outcomes were comparable for both groups. MECC system allowed a reduced hemodilution with a mean drop of the hematocrit of 8.5 vs. 15.3% (P<0.05). Mononuclear phagocytes dropped in a more important manner under standard CPB conditions (247+/-151 vs. 419+/-168, P=0.002), but both groups demonstrated a rise in monocyte count at the end of the CBP. No significant release of IL-1beta was observed in either group. By the end of CPB, IL-6 levels were significantly lower in the MECC group (38.8+/-19.6 vs. 87.9+/-78.9, P=0.04), despite a higher monocyte count. Plasma levels of TNF-alpha rised significantly more during standard CPB than with the MECC system (17.8+/-15.4 vs. 10.1+/-5.6, P=0.002). With MECC, the neutrophil elastase release was reduced (72.7+/-47.9 vs. 219.6+/-103.4, P=0.001). Platelet count remained at higher values with the minimal compared to standard CPB. It is noteworthy to consider that beta-thromboglobulin levels showed slightly lower platelet activation in the MECC group at all times of CPB (110.5+/-55.6 vs. 134.7+/-46.8, P=0.10). The pattern of release of S100 protein showed higher values in patients undergoing standard CPB than after MECC.
Conclusions: The MECC system is suitable to maintain total extracorporeal circulation and demonstrates a lower inflammatory reaction when compared to standard CPB.