title: Hemoglobin concentration and cerebral metabolism in patients with aneurysmal subarachnoid hemorrhage.
abstract: OBJECTIVE
  The optimal hemoglobin (Hgb) target after aneurysmal subarachnoid hemorrhage is not precisely known. We sought to examine the threshold of Hgb concentration associated with an increased risk of cerebral metabolic dysfunction in patients with poor-grade subarachnoid hemorrhage.
  
  
  METHODS
  Twenty consecutive patients with poor-grade subarachnoid hemorrhage who underwent multimodality neuromonitoring (intracranial pressure, brain tissue oxygen tension, cerebral microdialysis) were studied prospectively. Brain tissue oxygen tension and extracellular lactate/pyruvate ratio were used as markers of cerebral metabolic dysfunction and the relationship between Hgb concentrations and the incidence of brain hypoxia (defined by a brain tissue oxygen tension <20 mm Hg) and cell energy dysfunction (defined by a lactate/pyruvate ratio >40) was analyzed.
  
  
  RESULTS
  Compared with higher Hgb concentrations, a Hgb concentration <9 g/dL was associated with lower brain tissue oxygen tension (27.2 [interquartile range, 21.2 to 33.1] versus 19.9 [interquartile range, 7.1 to 33.1] mm Hg, P=0.02), higher lactate/pyruvate ratio (29 [interquartile range, 25 to 38] versus 36 [interquartile range, 26 to 59], P=0.16), and an increased incidence of brain hypoxia (21% versus 52%, P<0.01) and cell energy dysfunction (23% versus 43%, P=0.03). On multivariable analysis, a Hgb concentration <9 g/dL was associated with a higher risk of brain hypoxia (OR, 7.92; 95% CI, 2.32 to 27.09; P<0.01) and cell energy dysfunction (OR, 4.24; 95% CI, 1.33 to 13.55; P=0.02) after adjusting for cerebral perfusion pressure, central venous pressure, PaO(2)/FIO(2) ratio, and symptomatic vasospasm.
  
  
  CONCLUSIONS
  A Hgb concentration <9 g/dL is associated with an increased incidence of brain hypoxia and cell energy dysfunction in patients with poor-grade subarachnoid hemorrhage.
authors.affiliation: Department of Neurosurgery, Clinical Research Division, University of Pennsylvania Medical Center, 3rd Floor Silverstein Building, 3400 Spruce Street, Philadelphia, PA 19104-4283. Peter.LeRoux@uphs.upenn.edu.
authors.forename: Mauro
authors.initials: M
authors.lastname: Oddo
authors.forename: Andrew
authors.initials: A
authors.lastname: Milby
authors.forename: Isaac
authors.initials: I
authors.lastname: Chen
authors.forename: Suzanne
authors.initials: S
authors.lastname: Frangos
authors.forename: Eileen
authors.initials: E
authors.lastname: MacMurtrie
authors.forename: Eileen
authors.initials: E
authors.lastname: Maloney-Wilensky
authors.forename: Michael
authors.initials: M
authors.lastname: Stiefel
authors.forename: W Andrew
authors.initials: WA
authors.lastname: Kofke
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Levine
authors.forename: Peter D
authors.initials: PD
authors.lastname: Le Roux
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006454:Hemoglobins; D006801:Humans; D002534:Hypoxia, Brain / Q000453:epidemiology / Q000378:metabolism*; D015994:Incidence; D008297:Male; D017551:Microdialysis; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011446:Prospective Studies; D012307:Risk Factors; D013345:Subarachnoid Hemorrhage / Q000453:epidemiology / Q000378:metabolism*
chemical_list: D006454:Hemoglobins; D010100:Oxygen