Concentration of platelet units into small volumes

To determine the best procedure for concentrating platelets in a smaller volume after storage, we studied platelet loss after concentration at various centrifugation g forces for various times. In vitro studies demonstrated the need to let platelets sit for 1 hour prior to resuspension by gentle kneading. 500 X g gave unacceptable results. Losses were minimal at 1500 X g for 7 minutes, 2000 X g for 10 minutes and 5000 X g for 6 minutes. Reinfusion of 51 Cr-labeled platelets into normal volunteers after concentration at both 2000 X g for 10 minutes and 5000 X g for 6 minutes showed normal viability. Numbers and viability of platelets stored up to 5 days in 50 ml plasma and then concentrated in 10 ml plasma after centrifugation at 1500 X g for 7 minutes, 2000 X g for 10 minutes or 5000 X g for 6 minutes should be clinically acceptable.