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When Should ICU Patients Be Transfused?

One of the most controversial issues in critical care medicine is the proper threshold for blood transfusion. This multicenter Canadian trial enrolled 838 patients without active bleeding and with hemoglobin levels of 9.0 g/dl or lower during their first 3 days in intensive care units. Patients were randomized to a "restrictive" strategy (i.e., transfuse when hemoglobin drops below 7.0 g/dl, maintaining a range of 7.0 to 9.0 g/dl) or a "liberal" strategy (i.e., transfuse when hemoglobin drops below 10.0 g/dl, maintaining a range of 10.0 to 12.0 g/dl).

The 30-day mortality rate was 18.7 percent with restrictive transfusion and 23.3 percent with liberal transfusion, a nonsignificant difference. However, in-hospital mortality was significantly lower in the restrictive group (22.2 percent vs. 28.1 percent, p=0.05). In addition, rates of myocardial infarction and pulmonary edema during intensive care were significantly lower with restrictive transfusion. Numerous other subgroups and outcomes were examined, and none favored the liberal strategy. The restrictive group received half as many units of blood as the liberal group (mean, 2.6 vs. 5.6).

Comment: This important study makes a strong case for generally withholding transfusions until the hemoglobin drops below 7.0 g/dl. However, a long list of criteria excluded many patients from this trial, and only a quarter of eligible patients were randomized. Clinicians should thus review the eligibility criteria in this study carefully before applying the results to their patients.

— AS Brett

Published in Journal Watch General Medicine February 12, 1999

Citation(s):

Hebert PC et al. A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. N Engl J Med 1999 Feb 11 340 409-417.

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