Cardiopulmonary bypass over 24-hours using heparin surface coated equipment, without systemic heparinization was analyzed in comparison to standard equipment with systemic heparinization in 8 open-chest canine experiments (37 +/- 7 kg). Mean duration of perfusion was 21 +/- 2 hours for the group perfused without versus 21 +/- 6 hours with systemic heparinization. The group without systemic heparinization could be perfused for 13 +/- 1 hours without transfusion of blood components whereas the pumpsucker was necessary during the whole procedure with systemic heparinization. Hematocrit dropped with systemic heparinization from 40 +/- 7% to 18 +/- 5% at 12 h versus a decrease from 38 +/- 4% to 15 +/- 1% without (with versus without: ns). Free plasma hemoglobin increased with systemic heparinization from 0.1 +/- 0.0 g/l to 1.4 +/- 1.2 g/l at 12 h compared with an increase 0.1 +/- 0.0 g/l to 0.3 +/- 0.1 g/l without (with versus without: p less than 0.05). Platelet levels dropped with systemic heparinization from 100 +/- 36% to 41 +/- 17% at twelve hours versus from 100 +/- 29% to 82 +/- 14 without (with versus without: p less than 0.05). Mean aortic pressure dropped with systemic heparinization from 73 +/- 12 mmHg to 53 +/- 4 mmHg at 22 hours whereas it remained at the same level without (83 +/- 6 mmHg). Improved hemostasis during long term open-chest cardiopulmonary bypass without systemic heparinization resulted in superior hemodynamics.