Effect of prostacyclin on the circulatory histamine during cardiopulmonary bypass

Changes in plasma histamine levels were studied in sixteen dogs under cardiopulmonary bypass (CPB) or bypass with the addition of prostacyclin (PGI2) infusion. In both groups, plasma histamine rose immediately after anaesthetic induction (median above pre-induction: 0.4 ng/ml) and following heparin infusion (median above pre-induction: 0.7 ng/ml). During CPB, plasma histamine levels were elevated throughout the 90 minute period of perfusion (median above pre-induction: 0.5-1.2 ng/ml). PGI2 infusion reduced the elevation in plasma histamine levels (median above preinduction: 0-0.7 ng/ml). These data support the hypothesis that histamine release occurs during CPB. Platelet aggregation in the extracorporeal circuit may be contributory since prostacyclin premedication reduces histamine release.