Elective Transfusions

A growing number of randomised trials are reporting on the effects of different transfusion thresholds for red cells or platelets - the two commonest cellular blood products for transfusion. Most threshold studies for ‘elective’ (or non-emergency) transfusions of red cells and platelets compare outcomes for interventions defined by different haemoglobin (Hb) concentrations or platelet counts, typically using two-arm designs of trials testing liberal or restrictive transfusion strategies. Overall, the findings from these trials do not find evidence to support benefits with higher thresholds for transfusion practices (liberal), as defined and tested in the trials. For clinical use of platelets, a number of trials outside the population of haematological malignancies have reported harm with the use of liberal platelet strategies. Given blood components are biological products with risks, international guidelines therefore recommend restrictive thresholds for clinical use of red cells and platelets for transfusion. However, very recent red cell transfusion threshold trials now also suggest that some selected patients - such as those with acute myocardial infarction and neurological injury such as traumatic brain injury or subarachnoid haemorrhage - might benefit from liberal strategies. This reinforces the importance of considering the clinical context for each red cell transfusion, in addition to the Hb concentration. A number of clinical populations remain poorly studied for clinical use of platelets, which remain areas of research need, such as cardio-vascular surgery and adult critical illness, including pre-procedure. Finally, the randomised trial data for the clinical practice of plasma transfusions raises uncertainties regarding the effectiveness of the widespread use of plasma, including specifically as prophylaxis, although the lack of high-quality randomised trial data precludes strong recommendations.