| Abstract: | Platelet aggregation by adenosine diphosphate (ADP) is a self-limited and reversible process. An application of this phenomenon is described which allows removal of the platelets from large volumes of fresh platelet rich plasma (PRP) for the preparation of platelet concentrates. The macroscopic platelet clumps resulting from a concentration of 10 μgm ADP per ml of PRP are removed by centrifugation at 50 × g for 10 minutes. Resuspension of these platelets in 20 cc of native plasma results in a platelet concentrate that is 80 to 90 per cent as effective per unit as PRP in its ability to elevate the platelet count in recipients. Such concentrates are superior to concentrates prepared by other methods. The posttransfusion survival of ADP platelets compares favorably with the survival of platelets administered as PRP. There is evidence of minor sequestration but there is no apparent irreversible damage to platelets handled in this manner. Alkaline plasma and increase in plasma ionized calcium enhance the ADP aggregation and improve the efficiency of in vitro separation of platelets from PRP. However, the resulting concentrate is less effective in vivo, because of prolonged and slowly reversible clumping, and failure of these platelets to circulate. |
