Red-cell transfusion for the critically ill – is fresh best?

Anemia is a common feature of critical illness and roughly a third of all patients being cared for in intensive care units are given red-cell transfusion. Although such transfusions are unequivocally lifesaving for some patients, e.g. the exsanguinating trauma victim, the benefit is less clear-cut for others. 

There is much epidemiological evidence to suggest that for some undefined critically ill patients, red-cell transfusion may do more harm than good. This has led to more restrictive transfusion policies. The observed variable clinical effect of red-cell transfusion may be due in part to the variable length of time red cells are stored (currently up to 42 days) before being transfused. 

In a recently published article the authors review an ever-growing body of research directed at establishing the nature and clinical significance of the changes that occur in donated red cells during storage. In so doing the authors describe progress towards settling a long-standing controversy that can be summarized in the question: is transfusion of freshly donated red cells more beneficial to the critically ill than transfusion of red cells stored for up to 6 weeks?

The review begins with consideration of the “red-cell storage lesion”, which is the sum of the metabolic and biochemical changes occurring during storage that affect the structure and function of red cells. This is followed by a summary of the evidence that suggests that critically ill patients are particularly susceptible to the deleterious effects of the red-cell storage lesion. 

A major part of the review focuses on 32 clinical studies conducted over the past 2 decades that compared outcome of ICU patients who were transfused fresh red cells with outcome of ICU patients transfused older red cells. 

In summary, the results of these studies are conflicting, with 18 finding a clinically deleterious effect of transfusing older red cells, and 14 suggesting that the age of transfused red cells has no effect on outcome. In discussion of the merits and shortcomings of these conflicting clinical studies, the authors highlight the importance of three large muticenter randomized clinical trials that are currently underway. 

The results of these studies, which will involve close to 10,000 critically ill patients requiring transfusion around the world, will hopefully settle the controversy and provide the stimulus for change – if change is warranted – to current transfusion policy. A useful review of what is currently a very “hot topic” in transfusion and critical care medicine.