Red-cell transfusion in the critically ill

Anemia and consequent need for red-cell transfusion is a common feature of critical illness. According to a recently published review of the topic, nearly all (95 %) patients who have been in an intensive care unit for longer than 3 days become anemic. 

For close to 50 % of these patients, anemia is considered of sufficient severity to warrant red-cell transfusion, and a mean of 5 red-cell units are transfused to each during their stay in intensive care. Having set the background for this wide-ranging review directed primarily at critical care nurses, the author begins with a discussion of the many factors that predispose critically ill patients to anemia. 

There follows a discussion of the research directed at defining the changes that occur in red cells during storage. This is currently a hot topic in blood-transfusion medicine because it remains controversial to what extent, if any, these storage-related changes (lesions) affect the clinical efficacy/safety of red-cell transfusion. 

The author includes in this section the rationale for the now widespread policy of leukoreduction (removal of white cells) of red-cell units for transfusion. There is a brief consideration of the trial evidence that the hemoglobin trigger for red-cell transfusion in the critically ill should be set at less than 7 g/dL (70 g/L). 

The rest (bulk) of the review is a detailed discussion of six clinical studies conducted between 2004-2008 involving close to 18,000 critically ill patients, the aim of which was to assess the efficacy of red-cell transfusion. These studies compared morbidity and mortality among patients who received red-cell transfusion with morbidity and mortality of those who did not receive red-cell transfusion. 

In very broad terms the results of these studies indicate that it remains unclear if red-cell transfusion, as delivered during the study period, improves the chance of surviving critical illness. The significance of the results of these studies for the current restrictive policy of red-cell transfusion is discussed. 

Future research directed at improving the safety (clinical effectiveness) of red-cell transfusion is hinted at. This review, which includes 40 references, provides a valuable resource for nurses interested in understanding the current controversies surrounding the use of red-cell transfusion during critical illness.