Moderate hypothermia during cardiopulmonary bypass reduces myocardial celldamage and myocardial cell death related to cardiac surgery

OBJECTIVES The goal of this study was to test the hypothesis that moderate hypothermia during cardiopulmonary bypass (CPB) provides myocardial protect ion by enhancing intramyocardial anti-inflammatory cytokine balance. BACKGROUND Moderate hypothermia during experimental CPB stimulates producti on of interleukin-10 (IL10) and blunts release of tumor necrosis factor-alp ha (TNF Phi). METHODS Twelve young pigs were assigned to a temperature (T degrees) regime n during CPB: moderate hypothermia (T degrees: 28 degreesC; n = 6) and norm othermia (T degrees: 37 degreesC; n = 6). Intra-myocardial TNF alpha- and I L10-messenger RNA were detected by competitive reverse transcriptase polyme rase chain reaction and quantification of cytokine synthesis by Western blo t. Levels of cardiac troponin I (cTnI) in cardiac lymph and in arterial and coronary venous blood were examined during and after CPB. Myocardial cell damage was assessed by histologic and ultrastructural anomalies of tissue p robes taken 6 h after CPB. RESULTS Synthesis of IL10 was significantly higher, while that of TNF alpha was significantly lower, m pigs that were in moderate hypothermia during s urgery than in the others. In contrast with normothermia, moderate hypother mia was also associated with significantly lower cumulative cardiac lymphat ic flow during and after CPB, significantly lower lymphatic cTnI concentrat ions after CPB, significantly lower percentages of myocardial cell necrosis and a significantly lower score of ultrastructural anomalies of myocardial cells. While die percentage of apoptotic cells was not different between g roups, the apoptosis/necrosis ratio tended to be higher in animals that wer e in moderate hypothermia during surgery. In all animals, TNF alpha synthes is correlated positively while IL10 production correlated negatively with n ecrosis and total cell death, respectively. CONCLUSIONS Our results suggest that moderate hypothermia. during CPB provi des myocardial protection by enhancing intra-myocardial anti-inflammatory c ytokine balance. (C) 2001 by the American College of Cardiology.