title: Non-invasive assessment of muscle oxygenation may aid in optimising transfusion threshold decisions in ambulatory paediatric patients.
abstract: OBJECTIVE
  To assess the potential utility of a novel non-invasive muscle oxygen measurement to determine the presence of muscle hypoxia in patients with anaemia.
  
  
  BACKGROUND
  Recent assessment of the risk/benefit ratio of blood transfusion has led to clinical strategies optimising transfusion decisions. These decisions are primarily based on haematocrit (Hct) but not oxygen delivery, the primary function of red blood cells (RBCs). We hypothesised that muscle oxygenation (MOx) would correlate with Hct in patients with anaemia and may be a physiologically relevant determinant of the transfusion threshold.
  
  
  METHODS
  MOx was non-invasively determined in children in the Cancer and Blood Disorders Center ambulatory clinic at Seattle Children's Hospital using a custom-designed optical probe and spectrometer. MOx was compared with contemporaneous Hct. In subjects receiving RBCs, MOx and Hct were also determined following transfusion.
  
  
  RESULTS
  MOx ranged from 36·7 to 100%, and Hct ranged from 17·0 to 38·6% in 27 measurements from 16 patients. High MOx values were associated with high Hct. Mean MOx for patients with normal Hct for age (n = 5) was 95·9 ± 2·9%. RBC transfusion increased mean Hct from 19·1 ± 1·5% to 29·3 ± 2·0 and mean MOx from 67·9 ± 21·1% to 89·9 ± 9·8%. Among six transfusion episodes (in five patients) with initial Hct < 22, only three had a pre-transfusion MOx of <70%. Patients with the lowest pre-transfusion MOx had the largest increase in MOx after transfusion.
  
  
  CONCLUSIONS
  These preliminary data suggest that MOx may aid in making transfusion decisions when used in combination with Hct.
authors.affiliation: Department of Pediatrics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA.|Department of Anesthesiology, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA.|Department of Bioengineering, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Schenkman
authors.affiliation: Department of Pediatrics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Hawkins
authors.affiliation: Department of Pediatrics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Ciesielski
authors.affiliation: Department of Pediatrics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA.|Department of Laboratory Medicine, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA.
authors.forename: M
authors.initials: M
authors.lastname: Delaney
authors.affiliation: Department of Pediatrics, University of Washington, Seattle Children's Hospital, Seattle, Washington, USA.
authors.forename: L S L
authors.initials: LS
authors.lastname: Arakaki
mesh_terms: D000293:Adolescent; D000740:Anemia / Q000097:blood* / Q000503:physiopathology / Q000628:therapy; D002648:Child; D002675:Child, Preschool; D017707:Erythrocyte Transfusion; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption
chemical_list: D010100:Oxygen
keywords: anaemia; muscle oxygenation; optical spectroscopy; red blood cell transfusion