PLATELET CONCENTRATES PROMOTE PROCOAGULANT ACTIVITY - EVIDENCE FROM EXPERIMENTAL STUDIES USING A PERFUSION TECHNIQUE

Background: Evaluation of the hemostatic effectiveness of platelet tra nsfusions is difficult. Perfusion methods have been employed to test t he quality and function of platelet concentrates, allowing differentia tion between platelet-platelet and platelet-surface interactions. Stud y Design and Methods: A study was performed to investigate platelet ad hesive and cohesive properties as well as the formation of fibrin when aliquots of platelet concentrates were added to thrombocytopenic bloo d. Blood previously anticoagulated with low-molecular-weight heparin ( 20 U/mL) underwent platelet and white cell reduction by filtration. Pe rfusates were prepared by adding to filtered blood platelets obtained from standard concentrates (stored for 1, 3, and 5 days). The final pl atelet count in these perfusates was standardized at 80,000 per mu L. After perfusions, platelet-subendothelium interaction and fibrin forma tion were analyzed morphometrically. Results were always compared with those obtained in unfiltered blood (>150,000 platelets/mu L). Results : A slight impairment in the ability of stored platelets to interact w ith the subendothelium was noticed during the storage period. However, the presence of fibrin was significantly greater than that observed i n studies with unfiltered blood (Day 1 = 23.48 +/- 9.43%(); Day 3 = 2 6.99 +/- 6.74%(); Day 5 = 17.95 +/- 9.06% vs. unfiltered blood = 12.6 0 +/- 3.08%; ()p<0.05). The lower platelet counts (80,000/mu L) in th e perfusates containing platelets from concentrates could account for the reduced platelet-subendothelium interactions, but they cannot expl ain the increments in fibrin formation. Conclusion: While the preparat ion and storage of platelets have a detrimental effect on platelet adh esiveness, such procedures can positively influence the platelet proco agulant activity necessary to platelet hemostasis.