Improved in-vitro quality of platelet concentrates stored in a dextrose-free synthetic medium

Increased in vitro Aggregation of Stored Platelets at Room Temperature in Contrast to 37°C

Platelet concentrates were stored at room temperature and the reactivity of platelets to aggregating agents was studied at temperatures between 23 and 39°C. Fresh platelets showed increased reactivity at higher temperatures. When stored platelets were considered, maximal aggregation was not statistically different when compared with fresh platelets in the temperature range of 23-29°C (5 μM ADP). In addition, platelets stored either in Terumo or Baxter (PL 146 and PL 732) plastic bags at room temperature, showed an increased ADP-induced aggregation (10 μM) when studied at room temperature compared to 37°C. This pattern was confirmed by the difference in released ATP during aggregation. Collagen, although not resulting in detectable aggregation at 25°C, caused a similar release of ATP as that observed at 37°C. Since the observed differences in platelet reactivity seem to be similar using different types of plastic bags, the increased aggregation observed at room temperature is unlikely to be due to a special effect of a storage bag. Since the recovery of ADP aggregability is better at room temperature than at 37°C, ADP-induced aggregation determined at room temperature might be a better index of the clinical results expected when using stored platelets.

In vitro and in vivo properties of various types of platelets

The most popular procedures used to prepare platelet concentrates (PC) can be categorized into methods using platelet rich plasma (PRP) obtained by soft centrifugation of whole blood units, methods using buffy coats (BC) obtained by hard centrifugation of whole blood units, and apheresis procedures. The main feature that differentiates apheresis PC from whole blood unit derived PC is that apheresis reduces the number of donors necessary to support a recipient, although the advantages related to this feature have not been conclusively documented. From the biochemical point of view, a limited number of comparative studies and a large series of non-comparative studies indicate that differences in PC obtained with different protocols depend more on the performances of the production laboratory rather than the preparative approach--PRP, BC or apheresis--itself. Similarly, the clinical effectiveness of PC seems to depend more on PC age, storage modalities and recipient's conditions rather than primarily on the method of PC preparation. Despite the basic differences in the three preparative approaches, all methods share a number of key elements that are necessary pre-requisites for a successful platelet transfusion therapy: minimization of the risk of bacterial contamination by careful donor skin disinfection and temperature control during PC production and storage; protection of aerobic metabolism during PC storage; laboratory quality control including at least pH and volume determinations, platelet and white cell counts and visual inspection of the swirling phenomenon at time of release. Future directions in the field of PC production include the development of new products such as infusible platelet membranes, thrombospheres, thromboerythrocytes and reconstituted freeze-dried platelets.

Quantitative study of starving platelets in a minimal medium: maintenance by acetate or plasma but not by glucose

The requirement of donor platelets for fuels, plasma and calcium were studied using platelets washed, filtered to remove leucocytes and resuspended in a new glucose-free minimal platelet storage medium with low citrate (3 mmol/l), low buffer capacity and no calcium. This is the first study of platelets stored without plasma, glucose or calcium and it was shown that platelets continued to aggregate with collagen plus adrenaline for 48 h and showed only a 50% fall in 'swirl index', an objective morphology score, after 3 days, showing that by these criteria human platelets do not require glucose. Sodium acetate extended the storage time by between 2 and 4 days, depending on the index parameter. This is the first evidence showing that failure of platelets in these conditions is at least partly due to exhaustion of fuel, and the first evidence that acetate prolongs in vitro survival. As little as 10% low-glucose plasma extended the storage time, but it was no better than acetate. New observations using this system included a very rapid fall in pH during resuspension of the washed platelet pellet, a rising pH in the absence of added fuel and an increased pH with added acetate.

Red cell and platelet concentrates from blood collected into half-strength citrate anticoagulant: improved maintenance of red cell 2,3-diphosphoglycerate in half-citrate red cells

This study confirms previous work suggesting equivalent in vitro properties in blood components prepared from donations collected into half-citrate preservative (HCPD) compared to components derived from donations collected into standard citrate-phosphate-dextrose (CPD) preservatives. In addition, red cell products harvested from HCPD donations showed significantly improved maintenance of pH over storage, and this was reflected in improved maintenance of intracellular 2,3-diphosphoglycerate (2,3-DPG). This effect was observed in whole blood and in red cells suspended in a phosphate-containing additive solution (Tuta AAS). Collection into HCPD also improved 2,3-DPG maintenance in red cell concentrates processed following an 18-hour hold at 22 degrees C. These improvements were less pronounced in red cells suspended in a non-phosphate-containing medium (Fenwal Adsol) in which a higher pH was maintained even in units collected in CPD. Platelets harvested from HCPD blood and suspended in plasma showed equivalent quality to platelets from standard donations. Some deterioration of platelet properties was observed when HCPD platelets were stored in a non-citrate synthetic medium. Together with data indicating improved coagulation factor stability, these results suggest that collection into HCPD improves stored blood quality and may also allow logistical benefits in blood component preparation.