Premature infants and neonatal patients who require platelet transfusions may develop circulatory overload when administered a 50-ml unit of platelet concentrate. We evaluated the influence of centrifugation and resuspension steps used to reduce the volume of stored platelet concentrates on platelet properties by in vitro methods and by determining post-transfusion increments in neonatal patients. In vitro studies were conducted with platelet concentrates stored at 20 to 24 degrees C for 1 and 5 days in CLX (Cutter) and PL732 (Fenwal) containers and for 1 and 2 days in PL146 containers (Fenwal). With platelets stored in any of the three containers, platelet morphology, mean platelet volume, hypotonic stress response, synergistic aggregation, and platelet factor 3 activity were not affected by the processing steps. The centrifugation and resuspension steps did not cause an enhanced discharge of lactate dehydrogenase from platelets. Similar results were obtained when the platelet concentrates were stored on either a flatbed or an end-over-end tumbler agitator. The in vitro platelet recovery following volume reduction was at least 85 percent. In vivo studies were conducted with platelets stored in the PL732 and PL146 containers. Infusion of platelet concentrates after volume reduction produced a mean corrected increment of 18,947 +/- 14,824 when platelets were stored in the PL146 container and 16,178 +/- 15,699 when platelets were stored in the PL732 container. These results indicate that the volume of stored platelet concentrates can be reduced in a manner which maintains platelet properties.

The magnitude of the pH change during platelet concentrate storage at 20-24 degree C in polyvinyl chloride containers is not determined solely by platelet count per cubic millimeter of plasma, since a wide variation in pH was observed with similar platelet concentrations. In modified platelet concentrates having lost through centrifugation 3-15% of total platelets and 61-92% of residual leukocytes, the pH was maintained at substantially higher levels than in the paired control platelet concentrates. Leukocyte levels do not appear to determine the magnitude of the pH fall. Continuous oxygen utilization is needed if the pH is to be maintained near 7.0. However, oxygen tension per se is not the factor which influences the extent of pH change. It has been concluded that a specific platelet subpopulation comprising a small proportion of the total platelets in concentrates and having an enhanced capacity to form lactate may be responsible for a major part of the pH reduction which occurs during storage of many platelet concentrates.

Regional blood centers frequently need to hold units of whole blood at 20 to 24 degrees C for several hours after phlebotomy so that sufficient platelet concentrates can be prepared to meet the increasing need. We have evaluated the in vivo viability and in vitro properties of platelets that were prepared from whole blood drawn into citrate-phosphate-dextrose-adenine (CPDA-1) either immediately after phlebotomy or after an 8-hour hold at 20 to 24 degrees C. Platelet concentrates were stored for 5 days at 20 to 24 degrees C in polyolefin containers (PL 732, Fenwal) with end-over-end tumbler agitation. The autologous in vivo recovery (mean +/- SD) and one-half disappearance of 51Cr-labeled platelets prepared immediately after phlebotomy were 44.4 +/- 9.4 percent and 4.0 +/- 0.5 days, respectively. Platelets prepared after the delay of 8 hours showed a recovery of 44.5 +/- 8.4 percent and a one-half disappearance of 4.1 +/- 0.4 days. After 5 days of storage, platelet concentrates showed a mean pH of 7.21 +/- 0.20 when prepared immediately after phlebotomy, and of 7.22 +/- 0.15 when prepared after an 8-hour delay. Mean morphology scores were 280 +/- 33 and 302 +/- 27 for platelets from units prepared immediately after phlebotomy or after a holding period of 8 hours, respectively. Platelets underwent synergistic aggregation after 5 days of storage, independent of the length of time that the units of whole blood were held prior to centrifugation. These studies indicate that platelet concentrates prepared from units of whole blood held initially for 8 hours can be stored for 5 days at 20 to 24 degrees C and survive satisfactorily in vivo and retain in vitro characteristics.

The magnitude of the pH change during platelet concentrate storage at 20-24 °C in polyvinyl chloride containers is not determined solely by platelet count per cubic millimeter of plasma, since a wide variation in pH was observed with similar platelet concentrations. In modified platelet concentrates having lost through centrifugation 3-15% of total platelets and 61-92% of residual leukocytes, the pH was maintained at substantially higher levels than in the paired control platelet concentrates. Leukocyte levels do not appear to determine the magnitude of the pH fall. Continuous oxygen ulilization is needed if the pH is to be maintained near 7.0. However, oxygen tension per se is not the factor which influences the extent of pH change. It has been concluded that a specific platelet subpopulation comprising a small proportion of the total platelets in concentrates and having an enhanced capacity to form lactate may be responsible for a major part of the pH reduction which occurs during storage of many platelet concentrates.