Hyperhemolysis during the evolution of uncomplicated acute painful episodes in patients with sickle cell anemia

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Abstract
Some patients with sickle cell anemia (SS) experience significant decrease in their hemoglobin (Hb) level and significant increase in reticulocyte count during the progression of uncomplicated acute painful episodes. These changes have been attributed to, but not proven, hyperhemolysis. This study provides evidence of hyperhemolysis in this group of patients. Hospitalized patients who met the above criteria were identified and followed prospectively, and the measures of red blood cell (RBC) survival were determined. The latter included 1) laboratory measures of hemolysis: Hb level, reticulocyte count, nucleated RBC count, RBC distribution width (RDW), total bilirubin, lactate dehydrogenase (LDH), and aspartate transaminase (AST); 2) determination of RBC survival in vivo by the (51)Cr method in selected patients; and 3) the determination of the RBC Hb:reticulocyte Hb ratio. Baseline values of these measures were also obtained and compared to the crisis data. During the evolution of the painful episode in the selected patients, there was a significant increase in total bilirubin, LDH, AST, nucleated RBC count, and RDW that are indicative of hyperhemolysis. There was a significant decrease in RBC Hb:reticulocyte Hb and (51)Cr RBC survival, which is diagnostic of hyperhemolysis. Together, the data indicate that hyperhemolysis occurs during uncomplicated acute painful episodes in some patients with SS. The presence of free plasma Hb, consequent to hyperhemolysis, reduces nitric oxide bioavailability, promotes endothelial dysfunction, and contributes to the development of pulmonary hypertension and vasoocclusion.