title: Low-shear red blood cell oxygen transport effectiveness is adversely affected by transfusion and further worsened by deoxygenation in sickle cell disease patients on chronic transfusion therapy.
abstract: BACKGROUND
  Simple chronic transfusion therapy (CTT) is a mainstay for stroke prophylaxis in sickle cell anemia, but its effects on hemodynamics are poorly characterized. Transfusion improves oxygen-carrying capacity, reducing demands for high cardiac output. While transfusion decreases factors associated with vasoocclusion, including percent hemoglobin (Hb)S, reticulocyte count, and circulating cell-free Hb, it increases blood viscosity, which reduces microvascular flow. The hematocrit-to-viscosity ratio (HVR) is an index of red blood cell oxygen transport effectiveness that varies with shear stress and balances the benefits of improved oxygen capacity to viscosity-mediated impairment of microvascular flow. We hypothesized that transfusion would improve HVR at high shear despite increased blood viscosity, but would decrease HVR at low shear.
  
  
  METHODS
  To test this hypothesis, we examined oxygenated and deoxygenated blood samples from 15 sickle cell patients on CTT immediately before transfusion and again 12 to 120 hours after transfusion.
  
  
  RESULTS
  Comparable changes in Hb, hematocrit (Hct), reticulocyte count, and HbS with transfusion were observed in all subjects. Viscosity, Hct, and high-shear HVR increased with transfusion while low-shear HVR decreased significantly.
  
  
  CONCLUSIONS
  Decreased low-shear HVR suggests impaired oxygen transport to low-flow regions and may explain why some complications of sickle cell anemia are ameliorated by CTT and others may be made worse.
authors.affiliation: Division of Cardiology, Children's Hospital Los Angeles, California 90027, USA. jdetterich@chla.usc.edu
authors.forename: Jon
authors.initials: J
authors.lastname: Detterich
authors.forename: Tamas
authors.initials: T
authors.lastname: Alexy
authors.forename: Miklos
authors.initials: M
authors.lastname: Rabai
authors.forename: Rosalinda
authors.initials: R
authors.lastname: Wenby
authors.forename: Ani
authors.initials: A
authors.lastname: Dongelyan
authors.forename: Thomas
authors.initials: T
authors.lastname: Coates
authors.forename: John
authors.initials: J
authors.lastname: Wood
authors.forename: Herbert
authors.initials: H
authors.lastname: Meiselman
mesh_terms: D000293:Adolescent; D000328:Adult; D000755:Anemia, Sickle Cell / Q000097:blood* / Q000378:metabolism / Q000628:therapy*; D001692:Biological Transport; D001809:Blood Viscosity / Q000502:physiology; D002648:Child; D003430:Cross-Sectional Studies; D004526:Efficiency / Q000502:physiology; D017707:Erythrocyte Transfusion / Q000009:adverse effects*; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006451:Hemoglobin, Sickle / Q000378:metabolism; D006801:Humans; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D033081:Shear Strength; D013997:Time Factors; D055815:Young Adult
chemical_list: D006451:Hemoglobin, Sickle; D010100:Oxygen