Perfusion during cardiopulmonary bypass with low-dose heparin (activated clotting time, > 180 sec) versus full-dose heparin (activated clotting time, > 480 sec) combined with high-dose aprotinin was evaluated prospectively. Fifteen patients undergoing elective myocardial revascularization were randomly assigned to 1 of 2 groups. No significant differences between the groups were found for age, sex, body surface area, preoperative hematocrit level, duration of cardiopulmonary bypass, aortic cross-clamp time, mean number of bypasses per patient, or mean number of arterial grafts per patient. In all patients, heparin-coated cardiopulmonary bypass equipment was used, including heparinized hollow-fiber membrane oxygenators and tubing sets. In each group, protamine sulfate was given equivalent to the heparin loading dose; additional doses were administered according to the ACT. The mean total dosage of heparin was 9.5 +/- 1.4 x 10(3) IU for the group given low systemic heparinization (Group 1) compared with 34.6 +/- 3.4 x 10(3) IU for the group given full systemic heparinization in combination with high-dose aprotinin (Group 2) (p < 0.0001). The mean amount of aprotinin administered in Group 2 was 5.6 +/- 0.3 x 10(6) KIU; aprotinin was not used in Group 1. The mean protamine dosage necessary in Group 1, 7.0 +/- 0.9 x 10(3) IU, was significantly less than the 22.9 +/- 3.2 x 10(3) IU needed in Group 2 (p < 0.0001). In Group 1, shed blood recovery was achieved by a red-cell spinning device; in Group 2, cardiotomy suction was used. The total chest tube drainage (i.e., postoperative blood loss) per patient in Group 1 totaled 432 +/- 162 mL/m2; in Group 2, it was 311 +/- 111 mL/m2 (difference not significant). Transfusion requirements comprised a mean volume of 143 +/- 165 mL/m2 concentrated homologous red blood cells per patient in Group 1 and 416 +/- 128 mL/m2 in Group 2 (p < 0.01). Heparin-coated perfusion equipment allowed a significantly lower dosage of systemic heparin and protamine in Group 1 than that in Group 2, and a lower dosage in Group 2 than that in previous studies. Postoperative blood loss appeared to be similar between groups. The combination of heparin-coated perfusion equipment with low systemic heparinization and a red-cell spinning device provides promising results.