Improved exercise performance after exchange transfusion in subjects with sickle cell anemia.

Ten patients with sickle cell anemia underwent partial exchange transfusion with hemoglobin-A-containing cells using a technique that allowed hemoglobin concentration and blood volume to remain constant. The mean fraction of hemoglobin-A in these patients increased from 9% to 55%, but the mean hemoglobin concentration increased by only 1.44 g/dl. The exchange resulted in a large improvement in submaximal exercise capacity: the mean of the anaerobic threshold (the work at which lactic acid begins to accumulate in the blood) increased from 68 to 114 W. The mean work performed at a heart rate of 170/min, an estimation of maximal work capacity, increased from 128 to 187 W. Improved exercise performance after partial exchange transfusion may result from the superior flow properties of hemoglobin-A-containing red cells. Furthermore, we believe that exercise testing in sickle cell anemia has great potential utility as a means to monitor therapy and to evaluate the benefits of exchange transfusion.