Dense red blood cell and oxygen desaturation in sickle-cell disease

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• 作者：Gaetana Di Liberto ; Laurent Kiger ; Michael C. Marden ; Laurent Boyer ; Florence Canoui Poitrine ; Marc Conti ; Marie Georgine Rakotoson ; Anoosha Habibi ; Sanam Khorgami ; Benoit Vingert ; Bernard Maitre ; Frederic Galacteros ; France Pirenne and Pablo Bartolucci
• 刊名：American Journal of Hematology
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：91
• 期：10
• 页码：1008-1013
• 全文大小：526K
• ISSN：1096-8652

文摘

Production of abnormal hemoglobin (HbS) in sickle-cell disease (SCD) results in its polymerization in deoxygenated conditions and in sickled-RBC formation. Dense RBCs (DRBCs), defined as density >1.11 and characterized by increased rigidity are absent in normal AA subjects, but present at percentages that vary of a patient to another remaining stable throughout adulthood for each patient. Polymerized HbS has reduced affinity for oxygen, demonstrated by the rightward shift of the oxygen-dissociation curve, leading to disturbances in oxygen transport. Ninety-two SCD patients' total RBCs were separated into LightDRBC (LRBC) (d < 1.11 g/mL) and DRBC fractions. Venous blood partial oxygen pressure and RBC-fraction–deoxygenation and –reoxygenation Hb–oxygen-equilibrium curves were determined. All patients took a 6-minute walking test (6MWT); 10 had results before and after >6 months on hydroxyurea. 6MWT time with SpO₂ < 88% (TSpO₂ < 88) assessed the physiological impact of exertion. Elevated mean corpuscular hemoglobin (Hb) concentrations, decreased %HbF, and 2,3-bisphosphoglycerates in DRBCs modulated Hb–oxygen affinity. Deoxygenation and reoxygenation Hb–oxygen equilibrium curves differed between normal Hb AA and SS RBCs and between LRBCs and DRBCs, with rightward shifts confirming HbS-polymerization's role in affinity loss. In bivariate analyses, 50% Hb saturation correlated positively with %DRBCs (P < 0.0001, r² = 0.34) and negatively with %HbF (P < 0.0001, r² = 0.25). The higher the %DRBCs, the longer the TSpO₂88 (P = 0.04). Hydroxyurea was associated with significantly shorter TSpO₂ < 88 (P = 0.01). We report that the %DRBCs directly affects SCD patients' SpO₂ during exertion; hydroxyurea improves oxygen affinity and lowers the %DRBCs. Am. J. Hematol. 91:1008–1013, 2016.