In coronary artery revascularization, low systemic heparinization was compared to full systemic heparinization during perfusion with heparin surface-coated cardiopulmonary bypass equipment. Twelve patients were randomly assigned to two groups and perfused with low [activated clotting time (ACT) greater than 180 s] or full (ACT greater than 480 s) systemic heparinization. A standard battery of blood samples was taken before the procedure, after heparinization, and at regular intervals during and after cardiopulmonary bypass. No differences were seen between the two groups in regard to age, body surface area, preoperative hematocrit, duration of bypass, bypass hypothermia, cross-clamp time, and number of bypasses per patient. However, there were more internal thoracic artery (ITA) grafts in the group with low systemic heparinization (1.5 +/- 0.8 ITA grafts per patient versus 0.8 +/- 0.4 ITA grafts per patient with full heparinization; p less than 0.05). The oxygenator gradient at the end of perfusion (before weaning) was 107 +/- 40 mmHg for low versus 110 +/- 10 mmHg for full heparinization (difference not significant). The total amount of heparin used was 7200 +/- 1030 IU for low versus 51400 +/- 9700 IU for full (p less than 0.05). Postoperative hematocrit was 35.0 +/- 2.0% for low versus 24.7 +/- 2.7% for full (p less than 0.05). Total chest tube drainage was 428 +/- 153 ml/m2 for low versus 935 +/- 414 ml/m2 for full (p less than 0.05). Homologous transfusions of blood products were necessary in 3/6 patients for low versus 6/6 patients for full (p less than 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)