Anemia and postoperative rehabilitation

Most of the published data relating anemia to function have come from clinical trials evaluating recombinant human erythropoietin in end stage renal failure, orthopedic surgery, and patients undergoing cancer chemotherapy. While most studies were small and underpowered, the results are consistent in showing measurable improvement in fatigue, exercise capacity, muscle strength, and the performance of activities of daily living. Furthermore, studies are consistent in showing improvement in cardiac and cognitive function as anemia is corrected. What is less clear is whether there is a level of hemoglobin below normal that does not compromise functional outcome. Aerobic exercise capacity improves when hemoglobin values are increased. In the published literature, the initial hemoglobin levels ranged from 6 to 7 g·dL^-1 and hemoglobin levels following treatment with erythropoietin ranged from 9 to 14 g·dL^-1. In two studies no further improvement in exercise performance was found when hemoglobin levels of 9 to 10 g·dL^-1 had been reached.^23,25 In another study, physical performance was reported when hemoglobin levels of 14 g·dL^-1 were reached compared to 10 g·dL^-1.²⁴ While it is likely that normal levels of hemoglobin (12-14 g·dL^-1) are optimal, there could be diminishing return as the hemoglobin concentration approaches normal. Thus, the risks and/or costs of blood transfusion or treatment with erythropoietin become important to consider. Patients undergoing surgery are often elderly and have co-morbidities. Anemia in these patients may impede their ability to recover from basic impairments and participate in postoperative rehabilitation. It is likely that higher blood counts will result in a more active participation in rehabilitation and greater functional independence. How high the hemoglobin levels need to be awaits further study.