Reduction of heparin dose is not beneficial to platelet function

Background. To clarify the effects of the reduction of heparin dose on plat elets, we conducted a prospective trial on patients undergoing cardiopulmon ary bypass. Methods. Twenty-three patients undergoing coronary artery bypass grafting w ere studied. The systemic heparin dose was 300 IU/kg in the control group ( n = 11) and 200 IU/kg in the low-dose group (n = 12). Heparin-coated cardio pulmonary bypass equipment was used for both the groups. Platelet counts, b eta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) concentrations we re measured and the arterial filters in the circuits were observed by elect ron microscopy. Results. Platelet counts were higher in the low-dose group than in the cont rol group (p < 0.01). No significant differences were found in the platelet release reaction (beta-TG and PF4). Electron microscopy demonstrated that cell adhesion on the arterial filters in the control group was significantl y more marked than in the low-dose group (p < 0.01) and that most of the ce lls on the filters were neutrophils. Conclusions. We conclude that the reduction of heparin dose with the use of heparin-coated equipment reduces platelet loss, but does not suppress the platelet release reaction. Furthermore, the reduction of heparin dose reduc es adherence of leukocytes to the filter surface. (Ann Thorac Surg 2000;70: 186-90) (C) 2000 by The Society of Thoracic Surgeons.