Hemodynamic changes following heparin injection in aortocoronary bypass operations. Sequela of histamine liberation

: Prior to cannulation for extracorporeal circulation, 375 Units of Heparin/kg body weight were applied to 22 patients (group 1) into the right atrium. A few minutes later, characteristic changes in haemodynamics were observed. In a second group of 10 patients, the same amount of heparin was injected directly into the ascending aorta to avoid the passage of an undiluted bolus of heparin through the pulmonary vessels. In this group, the haemodynamic effects of heparin seemed to be slightly weakened. Immediately after administration of heparin, a significant increase of plasma histamine was measured (in 12 patients of group 1). This might be the main reason for the heparin-dependent haemodynamic effects.