Hebert, P., Wells, G., Blajchman, M., et al. (1999). A Multicenter, Randomized, Controlled Clinical Trial of Transfusion Requirements in Critical Care. The New England Journal of Medicine. 340: 409-417.
The authors compared death rates in critically ill patients from all causes at 30 days and the severity of organ dysfunction to evaluate the difference between restrictive and liberal red-cell transfusion. Thirty-day mortality was similar between the two groups and the authors suggest that the restrictive method is at least as effective as the liberal method.