BACKGROUND: Guidelines for allogeneic transfusion emphasize minimizing use to avoid transmission of serious illness. However, there is little information on the risks associated from withholding transfusion.

STUDY DESIGN AND METHODS: A retrospective cohort study of patients who declined RBC transfusions for religious reasons was performed. This analysis was restricted to consecutive patients ≥18 years old, who underwent surgery in the operating room from 1981 to 1994 and had a postoperative Hb count of 8 g per dL or less. The primary outcome was defined as any in-hospital death occurring within 30 days of the surgery. Secondary outcome was 30-day mortality or in-hospital 30-day morbidity. Morbidity was defined as myocardial infarction, arrhythmia, congestive heart failure, or infection.

RESULTS: Of 2083 eligible patients, 300 had postoperative Hb counts of 8 g per dL or less. The study population was predominantly female (70.3%) with a mean age of 57 years (SD, ± 17.7). In patients with a postoperative Hb level of 7.1 to 8.0, 0 died (upper 95% CI, 3.7%), and 9.4 percent (95% CI, 4.4-17.0%) had a morbid event. In patients with a postoperative Hb level of 4.1 to 5.0, 34.4 percent (95% CI, 18.6-53.2%) died and 57.7 percent (95% CI, 36.9-76.6%) had a morbid event or died. After adjusting for age, cardiovascular disease, and Acute Physiology and Chronic Health Evaluation II score, the odds of death in patients with a postoperative Hb level of ≤8 g per dL increased 2.5 times (95% CI, 1.9-3.2) for each gram decrease in Hb level.

CONCLUSIONS: The risk of death was low in patients with postoperative Hb levels of 7.1 to 8.0 g per dL, although morbidity occurred in 9.4 percent. As postoperative blood counts fall the risk of mortality and/or morbidity rises and becomes extremely high below 5 to 6 g per dL.