Platelet transfusions: the science behind safety, risks and appropriate applications.

Platelets are active metabolising cells that are evolved for the tasks of haemostasis, inflammatory reactions and wound healing. When platelet products are stored in the blood bank a complex series of changes occur, leading to partial activation, up-regulation of inflammatory mediators, cellular morphology changes, loss of cell membrane lipids and micro-particle formation, as well as apoptosis. The resultant coagulation transfusion product has a number of potential expected side effects including fever, alloimmunisation, sepsis, thrombosis and transfusion-related acute lung injury. Of course, these events are occasional side effects yet they are some of the most common potential disasters of transfusion. Platelet transfusions in patients bleeding from thrombocytopaenia or severe platelet suppression will most likely benefit from a platelet transfusion. However, outcome data (controversial) have shown in some populations that platelet transfusions are associated with worse patient outcomes. Such associations may be due to the biologic changes that have occurred during storage, lack of HLA matching as well as other causes or it could be a mismatch of the platelet products to patient's needs (over-use). Platelets are administered in the surgical arena often due to 'clinical judgement', which errs on the side of, perhaps, too frequent use.