Postoperative anemia and exercise tolerance after cardiac operations in patients without transfusion: What hemoglobin level is acceptable?

Background: Restrictive transfusion strategies have been suggested for cardiac surgical patients, leading to various degrees of postoperative anemia. This study investigates the exercise tolerance during rehabilitation of cardiac surgical patients who did not receive transfusions, with respect to their level of postoperative anemia. Methods: This observational study started in January 2010 and ended in May 2010 in 2 rehabilitation hospitals and 2 large-volume cardiac surgical hospitals. The study population was 172 patients who did not receive transfusions during cardiac surgical operations with cardiopulmonary bypass and subsequently followed a rehabilitation program in 1 of the 2 rehabilitation hospitals. No patient received a transfusion during the rehabilitation hospital stay. Exercise tolerance was measured using the 6-minute walk test at admission and discharge from the rehabilitation hospital. The level of anemia at admission to the rehabilitation hospital was tested as an independent predictor of exercise tolerance within a model inclusive of other possible confounders. Results: Patients with values of hemoglobin less than 10 g/dL at admission to the rehabilitation institute had a significantly (p = 0.007) worse performance on the 6-minute walk test than patients with higher values (258 ± 106 vs 306 ± 101 meters). This functional gap was completely recovered during a normal rehabilitation period. Other independent factors affecting exercise tolerance were age, sex, and albumin concentration. Conclusions: Postoperative anemia with hemoglobin levels of 8 to 10 g/dL is well tolerated in patients who have not received a transfusion and induces only a transient impairment of exercise tolerance.