Platelet damage caused by the centrifugal pump: Laser-light scattering analysis of aggregation patterns

Platelets are damaged by shear force during centrifugal pumping; however, t he mechanism of this damage has not been fully investigated. A new laser-li ght scattering (LS) assay method enables quantification of realtime chan-es in the number of platelet aggregates of different sizes. Using this method , we assessed the kinetics of platelet damage caused by the centrifugal pum p from the standpoint of platelet aggregation capacity. Conventional optica l density (OD) and LS methods were used to measure platelet aggregation wit h a Kowa AG-10 aggregometer. Platelet aggregation in fresh human blood was evaluated in a mock circuit for 3 h under a flow rate of 5.0 L/min and a pr essure head of 100 mm Hg. Test samples were obtained before pumping for con trol, and at 1, 2, and 3 h after the start of pumping. The test series was begun 8 times. Aggregation after stimulation by 2.0 mug/ml collagen was det ermined; small (9 to 25 mum), medium (25 to 50 mum), and large (50 to 70 mu m) aggregates were counted by the LS method. OD measurement at hourly inter vals showed significant reduction in platelet aggregation. The LS method sh owed that generation of small and medium aggregates was not suppressed duri ng pumping, but that generation of large aggregates was significantly reduc ed at 2 and 3 h of pumping. Platelet aggregation is significantly suppresse d during centrifugal pumping, and the resulting platelet dysfunction is due mainly to inhibited development of small aggregates into larger aggregates .