Is single-unit blood transfusion bad post-coronary artery bypass surgery?

This report on transfusion practice in a single-unit cardiac center regarding the effects of one, as opposed to two units of blood, examines the effects of a very important “bad habit” in practical transfusion medicine. The article questions the dogma: “When blood transfusion is needed, give two units to be sure to have a measurable effect”. Not only following cardiac surgery, but in almost all disciplines, whether it be in intensive care, on the ward, in the emergency unit or in the operating theater, in most countries of the world the current practice is to order and give 2 units whenever transfusion is necessary, even when the transfusion indication is not ongoing (such as in the presence of heavy bleeding).

Analysis of the database including 4615 CABG patients by Warwick el al. used various complex statistical methods. Postoperative transfusion requirements and long-term (8 years) survival of patients were analyzed. Not surprisingly, preoperative anemia was a confounding factor. Kaplan Meier survival by univariate analysis resulted in a decreased 8-year survival for both overall transfusion and one-unit blood transfusion. Using a more sophisticated propensity analysis, survival was not different in patients who received one unit only and had a hemoglobin concentration above 10.5 g/dL (p=0.7). On the other hand, those who received two units or more (p=0.0001) still had reduced long-term survival.

Whether we accept these tricky statistical results or not, the message is clear and in agreement with other transfusion guidelines: the administration of double units should be avoided since this practice appears to have a negative effect on long-term survival.

– Thomas Frietsch