The contribution of anticoagulants to platelet dysfunction with extracorporeal circulation

This investigations evaluates the effects of anticoagulants on platelet function. Fresh human blood from 40 nonmedicated volunteers was anticoagulated with 4.3 units per milliliter heparin and/or acid-citrate-dextrose (ACD) solution 1:9. Retention of platelets from whole blood on glass beads was performed by the method of Bowie. Platelet retention of heparinized blood averaged 88.1 +/- S.E. 1.5 per cent; ACD platelets averaged 24.6 +/- S.E. 2.8 per cent. Platelet retention with citrate-phosphate-dextrose (CPD) and ethylenediaminetetraacetic acid (EDTA) yielded 26.0 +/- S.E. 3.9 per cent and 19.1 +/- S.E. 7.5 respectively. The addition of ACD to heparinized blood decreased platelet retention (19.7 +/- S.E. 3.1 per cent). The addition of heparin to ACD or CPD blood did not alter the original decreased retention. Calcium added, even in excess, to blood containing heparin and ACD did not reverse the depressed retention (29.3 +/- S.E. 4.6 per cent). The substitution of CPD gave similar results. With mixtures of separately collected ACD and heparininzed blood, depression of platelet retention was directly proportional to the amount of ACD blood present. Altering the pH of the ACD blood did not affect its depressed retention of platelets. Neutralizing heparinized blood 50 per cent with protamine or Polybrene also significantly depressed platelet retention 34.6 +/- S.E. 5.8 per cent and 35.5 +/- S.E. 4.0 per cent, respectively. Neither protamine nor Polybrene had any effect upon ACD blood. These data indicate that anticoagulants may play a significant role in the depressed platelt function observed during and following extracorporeal circulation.