Changes in brain natriuretic peptide concentrations following open cardiac surgery with cardioplegic cardiac arrest

Elevated brain natriuretic peptide (BNP) concentration in peripheral blood reflects impaired cardiac ventricular function. We investigated the release pattern of BNP following cardioplegic cardiac arrest during heart surgery. In particular, we sought to discover whether there is an increase in peripheral BNP concentrations following reperfusion of the ischaemic heart. A secondary aim of the study was to investigate whether allopurinol, an anti-oxidant, has any effect on BNP release. A total of 29 patients scheduled for elective coronary artery bypass grafting were recruited, of whom 12 were randomly allocated to receive allopurinol with their pre-medication. Blood specimens were taken at six time points from the indwelling arterial catheter, the first before surgery and the last 2 h following the termination of cardiopulmonary bypass (CPB). BNP was found to decrease markedly when the aortic cross clamp was applied and the heart was isolated from circulation (P=0.0001). There was a slight increase in BNP following cross clamp release and myocardial reperfusion (P=0.04). A more substantial increase occurred with weaning from CPB when ventricular filling occurred (P=0.0015). Only the final BNP value, 2 h after CPB, was elevated compared with baseline (P=0.0013). Allopurinol had no demonstrable effect on changes in BNP.