Effects of red blood cell transfusion on resting energy expenditure in adolescents with sickle cell anemia

Background: Previous studies indicate that resting energy expenditure is el evated in children with sickle cell anemia, possibly caused in part by hemo lysis and increased erythropoietic activity. The purpose of the present inv estigation was to determine whether erythrocyte transfusion normalizes rest ing energy expenditure in sickle cell anemia. Methods: Five adolescents with sickle cell anemia (12-16 years old; 4 boys, 1 girl) were studied before and 1 week after erythrocyte transfusion befor e elective surgery or at the initial transfusion for growth failure. Restin g energy expenditure was measured by indirect calorimetry, and laboratory m easures were determined by routine, validated methods. Data comparisons wer e by nonparametric analysis. Results: After erythrocyte transfusion, total hemoglobin levels increased ( difference (D) = 15 g/l; p < 0.05), whereas hemoglobin S (D = -0.36; p < 0. 05) and reticulocyte count (D = -0.12; p < 0.05) decreased. Mean pretransfu sion resting energy expenditure was elevated to 124% above predicted levels (p < 0.05) and increased further to 134% above prediction (p < 0.05 vs. pr etransfusion levels). Plasma triiodothyronine (T3) levels increased(D = 0.1 7 nmol/l; p < 0.05), reverse T3 (rT3) levels tended to decline (D = -0.04 n mol/l; p = 0.14), and rT3/T3 decreased (D = -0.03; p < 0.05). Plasma insuli n-like growth factor-I (IGF-I) levels were low-normal before transfusion an d did not change, despite the change in resting energy expenditure. Conclusions: The results confirm that resting energy expenditure is elevate d in patients with sickle cell anemia. However, resting energy expenditure further increased after transfusion, despite decreased erythropoietic activ ity. A posttransfusion decrease in rT3/T3 may contribute to the increased r esting energy expenditure, That there was no change in IGF-I implies that t he growth hormone-IGF system is not involved in posttransfusion regulation of resting energy expenditure. Therefore, our data are nor consistent with the hypothesis that increased resting energy expenditure in sickle cell ane mia is directly related to erythropoietic activity. The mechanisms by which resting energy expenditure increases after transfusion in sickle cell anem ia require additional investigation.