Should the transfusion trigger and hemoglobin low critical limit be identical?

At this medical center, the transfusion trigger and the hemoglobin low critical limit are identical (< 8.0 g/dL), but should they be the same? To answer this question, over one year all hemoglobin results < 8.0 g/dL (n = 421) were reviewed, physician awareness of and response to various hemoglobin levels were evaluated, and the effect of adopting a lower hemoglobin critical limit assessed. Patients were divided into three groups: (1) 7.5-7.9 g/dL (n = 81); (2) 7.0-7.4 g/dL (n = 53); and (3) < 7.0 g/dL (n = 59). Seventy (86 percent), 47 (89 percent), and 52 (88 percent) patients were transfused in Groups 1, 2, and 3; transfused units, mean (sd), were 2.0 (0.8), 2.3 (1.1), and 2.8 (1.7), respectively. Post transfusion hemoglobin increase, mean (sd) was 2.1 (1.0), 2.4 (1.0), and 3.1 (1.5) g/dL for Groups 1, 2, and 3, indicating an inverse correlation between severity of anemia and number of transfused units and post-transfusion hemoglobin increase. Physicians were aware of anemia for all patients in Groups 1 and 2, but three patients in Group 3, not clinically anemic, had erroneous results (improperly collected specimens). Physicians randomly surveyed (n = 20) indicated that the hemoglobin critical limit could be lowered without adverse clinical consequence. A lower hemoglobin critical limit of 7.5 and < 7.0 g/dL would lead to a 52 percent and 77 percent decrease in phone calls for physician notification. The medical center has now lowered the critical limit for hemoglobin to < 7.0 g/dL. The transfusion trigger and the low critical limit for hemoglobin are distinct entities, need not be identical, and represent a balance between the need for transfusion response and the need to be aware of a highly abnormal lab result.