Physicians understand the inherent risks of transfusion, and most hospitals have mechanisms in place to avoid overuse of this expensive intervention. In some situations, however, transfusions may decrease the mortality rate among hospitalized patients. Wu and colleagues report data from a retrospective analysis of 78,974 elderly patients hospitalized for myocardial infarction.

The authors attempted to discover whether transfusion has an effect on 30-day mortality. The study population was drawn from a larger group of 234,769 patients whose discharge diagnosis was myocardial infarction. The authors excluded patients younger than 65 years, those whose entire hospitalization could not be followed because of transfer to another hospital, those with hematocrit levels above the upper limit of normal, and patients whose hospitalizations were readmissions after the acute myocardial infarction. Anemia was defined as a hematocrit measurement of 39 percent or lower. The principal study outcome was mortality within 30 days after hospital admission.

Anemia was present in 43.4 percent of the study patients, and more severe degrees of anemia correlated with higher rates of 30-day mortality, congestive heart failure, and shock. Transfusions were performed in 4.7 percent of patients. Curiously, family physicians were more likely than cardiologists to order transfusions.

In patients with hematocrits of 33 percent or lower, the 30-day mortality rate was improved by use of transfusion, and the beneficial effect was more pronounced in those with greater degrees of anemia. In patients with hematocrits above 33 percent, transfusion was associated with an increased mortality rate.

The authors conclude that in elderly patients with myocardial infarction, the use of blood transfusions in those with hematocrits of 33 percent or lower is associated with decreased mortality.

editor's note: Transfusion appears to be a relatively low-tech, low-cost means of reducing mortality in the substantial number of patients with myocardial infarction who are also anemic. The chief caution to mention about this article, before touting it as “evidence-based proof” of benefit, is that it is a retrospective analysis excluding 67 percent of the total study group. The possibility of an unrecognized bias factor is not small, and a prospective trial that confirms a beneficial effect to transfusion would be helpful.—b.z.