Nielsen and colleagues performed a small randomized trial (N=50) comparing liberal versus restrictive intraoperative transfusion strategy on subcutaneous oxygen tension over the left deltoid muscle. The mean hemoglobin concentration was 8.9 d/dL in the restrictive group and 10.0 g/dL in the liberal group although there was significant overlap of hemoglobin levels. The proportion of patients who received a transfusion was 52% in the restrictive group and 87% in the liberal group. There were no significant differences in oxygen tension. It is hard to know how to evaluate this trial given the small sample size, uncertain relevance of peripheral oxygen tension, the level of hemoglobin concentration studied , and the modest differences in hemoglobin levels between the groups.

– Jeffrey L. Carson