Cold-Stored Platelets: Review of Studies in Humans

Although numerous reviews and editorials have been published about the biologic features of platelets exposed to cold temperature and their in vitro function, none has focused on the data from studies after transfusion in healthy human participants and patients. This may, in part, be due to the paucity of well-controlled in vivo investigations of cold-stored platelets. Although numerous studies are looking into the recovery and survival of cold-stored platelets (ie, the percentage of infused platelets maintained in circulation over time), very few assess in vivo platelet function. Another caveat is that most studies were performed in the 1960s and 1970s, at a time when platelet collection and storage were different compared to today. Despite these limitations, we believe the transfusion community can take valuable information from these studies. This review is limited to data on cold-stored platelets in plasma or additive solution and does not include data on whole blood or resuspended whole blood from components because the hemostatic properties of whole blood are likely very different (the interested reader is referred to the review article focused on the hemostatic properties of platelets stored in whole blood by van der Meer et al in this special edition of Transfusion Medicine Reviews). In this review, we report that room temperature storage consistently results in a longer in vivo platelet circulation time at the expense of bacterial growth and shorter storage duration, resulting in expiration, wastage, and regional and national shortages. Cold storage of platelets universally results in moderately reduced recovery and markedly reduced survival. We found inconsistent data about the efficacy of cold-stored platelets likely due to study design differences. The analysis of the available data suggests that there is a short-lasting hemostatic effect of cold-stored platelets. Storage time or choice of anticoagulant did not have a clear effect on platelet efficacy after cold storage. In summary, more data and clinical trials are needed to better understand the effect of cold-stored platelets after transfusion into humans.