Preservation of platelets and blood products by intravenously administered dipyridamole in patients who undergo coronary artery bypass grafting.

The combination of dipyridamole and acetylsalicylic acid has been proven effective in preventing coronary artery bypass graft occlusion, but the benefits of dipyridamole alone have not yet been evaluated. In order to assess the value of dipyridamole alone, the authors randomized 24 patients (age range from 47 to 76 years) who underwent coronary artery bypass grafting to treatment with either dipyridamole (120 mg/d) by constant intravenous infusion or isotonic dextrose solution. They recorded platelet counts and aggregates, hemoglobin levels, total blood loss, blood products and intravenous fluids given and dipyridamole plasma levels, starting 8 hours before operation and continuing for 3 days after. The two groups were similar with respect to pump time, cross-clamp time and baseline demographic factors. Platelet counts during cross-clamping and 1 hour postoperatively were similar, but those on days 1, 2 and 3 postoperatively were significantly (p = 0.01 to 0.02) higher in the dipyridamole group. Mean blood losses in this group were 22% to 30% lower, but the difference was not significant. However, administration of erythrocytes and plasma was 49% to 58% less in the dipyridamole group (p = 0.005 to 0.048) over the same period. Dipyridamole plasma concentrations varied from 0.37 micrograms/ml before and during bypass to 1.5 micrograms/ml in the 3 days after. The authors conclude that dipyridamole administered intravenously to patients who undergo coronary artery bypass grafting may preserve hemostatically effective platelets so that fewer blood products are required.