The antithrombin III-saving effect of reduced systemic heparinization and heparin-coated circuits

Objective: To investigate the perioperative changes of antithrombin III (AT-III) activity using reduced systemic heparinization and the possible role of AT-III in determining a better postoperative outcome. Design: Prospective randomized study. Setting: University hospital. Participants: Patients undergoing elective coronary revascularization with cardiopulmonary bypass (n = 90). Interventions: Of patients, 30 were treated with heparin-coated circuits and reduced systemic heparinization; 30, with heparin-coated circuits and full systemic heparinization; 30, with conventional circuits and full systemic heparinization. Measurements and Main Results: Heparin-coated circuits with full systemic heparinization did not exert any effect on coagulation parameters. Low systemic heparinization resulted in a significantly (p <0.01) higher hematocrit value on arrival in the intensive care unit and in significantly higher values of AT-III activity during cardiopulmonary bypass (66 ± 12% v 57.4 ± 13% and 59.1 ± 12% in the full systemic heparinization groups; p <0.05), on arrival in the intensive care unit (69.7 ± 13% v 60.7 ± 13% and 60.8 ± 11% in the full systemic heparinization groups; p <0.01), and on the first postoperative day (81.3 ± 15% v 67.4 ± 13% and 70.2 ± 12% in the full systemic heparinization groups; p <0.01). No differences were observed in the clinical outcome. Conclusion: Reducing systemic heparinization determines an AT-III-saving effect that could be responsible for the decrease in thromboembolic complications already observed by other authors. It induces higher hematocrit levels immediately after the operation, probably reducing the unmeasurable intraoperative blood loss.