Hypothermia and the stress response to cardiopulmonary bypass.

There is no consensus on the optimal level of intraoperative hypothermia during cardiopulmonary bypass (CPB). To assess the effect of systemic cooling on the stress response to CPB, the acute phase and endocrine responses were measured in 20 male patients undergoing elective coronary artery surgery and randomised to an intraoperative blood temperature of 28 degrees C or 20 degrees C. The acute phase response was assessed by changes in the plasma concentration of C-reactive protein (CRP) and the endocrine response by the urinary excretion of the counter-regulatory hormones adrenaline, noradrenaline and cortisol. The groups were comparable with respect to age, anthropometric indices, cross clamp and bypass times. There was no significant difference in the groups in the acute phase response but the endocrine response was attenuated in the 20 degrees C group. These findings may have implications for the severely stressed preoperative patient.