title: Anemia and brain oxygen after severe traumatic brain injury.
abstract: OBJECTIVE
  To investigate the relationship between hemoglobin (Hgb) and brain tissue oxygen tension (PbtO(2)) after severe traumatic brain injury (TBI) and to examine its impact on outcome.
  
  
  METHODS
  This was a retrospective analysis of a prospective cohort of severe TBI patients whose PbtO(2) was monitored. The relationship between Hgb-categorized into four quartiles (≤9; 9-10; 10.1-11; >11 g/dl)-and PbtO(2) was analyzed using mixed-effects models. Anemia with compromised PbtO(2) was defined as episodes of Hgb ≤ 9 g/dl with simultaneous PbtO(2) < 20 mmHg. Outcome was assessed at 30 days using the Glasgow outcome score (GOS), dichotomized as favorable (GOS 4-5) vs. unfavorable (GOS 1-3).
  
  
  RESULTS
  We analyzed 474 simultaneous Hgb and PbtO(2) samples from 80 patients (mean age 44 ± 20 years, median GCS 4 (3-7)). Using Hgb > 11 g/dl as the reference level, and controlling for important physiologic covariates (CPP, PaO(2), PaCO(2)), Hgb ≤ 9 g/dl was the only Hgb level that was associated with lower PbtO(2) (coefficient -6.53 (95 % CI -9.13; -3.94), p < 0.001). Anemia with simultaneous PbtO(2) < 20 mmHg, but not anemia alone, increased the risk of unfavorable outcome (odds ratio 6.24 (95 % CI 1.61; 24.22), p = 0.008), controlling for age, GCS, Marshall CT grade, and APACHE II score.
  
  
  CONCLUSIONS
  In this cohort of severe TBI patients whose PbtO(2) was monitored, a Hgb level no greater than 9 g/dl was associated with compromised PbtO(2). Anemia with simultaneous compromised PbtO(2), but not anemia alone, was a risk factor for unfavorable outcome, irrespective of injury severity.
authors.affiliation: Department of Neurosurgery, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA. mauro.oddo@chuv.ch
authors.forename: Mauro
authors.initials: M
authors.lastname: Oddo
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Levine
authors.forename: Monisha
authors.initials: M
authors.lastname: Kumar
authors.forename: Katia
authors.initials: K
authors.lastname: Iglesias
authors.forename: Suzanne
authors.initials: S
authors.lastname: Frangos
authors.forename: Eileen
authors.initials: E
authors.lastname: Maloney-Wilensky
authors.forename: Peter D
authors.initials: PD
authors.lastname: Le Roux
mesh_terms: D018806:APACHE; D000328:Adult; D000740:Anemia / Q000209:etiology* / Q000473:pathology; D001921:Brain / Q000098:blood supply*; D001930:Brain Injuries / Q000150:complications* / Q000473:pathology; D016001:Confidence Intervals; D005260:Female; D015600:Glasgow Coma Scale; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D006454:Hemoglobins