Reduction of heparin dose is not beneficial to platelet function

Background. To clarify the effects of the reduction of heparin dose on platelets, we conducted a prospective trial on patients undergoing cardiopulmonary bypass. Methods. Twenty-three patients undergoing coronary artery bypass grafting were 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 cardiopulmonary bypass equipment was used for both the groups. Platelet counts, β-thromboglobulin (β-TG) and platelet factor 4 (PF4) concentrations were measured and the arterial filters in the circuits were observed by electron microscopy. Results. Platelet counts were higher in the low-dose group than in the control group (p< 0.01). No significant differences were found in the platelet release reaction (β-TG and PF4). Electron microscopy demonstrated that cell adhesion on the arterial filters in the control group was significantly more marked than in the low-dose group (p< 0.01) and that most of the cells 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 reduces adherence of leukocytes to the filter surface.