title: Physiopathology of anemia and transfusion thresholds in isolated head injury.
abstract: BACKGROUND
  Blood transfusion strategies among patients with critical illness use a restrictive hemoglobin threshold. However, among patients with head injury, no outcome differences have been shown between either liberal or restrictive strategies. Several studies and literature reviews suggest that anemia is associated with markers of tissue ischemia. The paucity of prospective data confuses the association between surrogates of tissue ischemia and neurological outcome.
  
  
  METHODS
  A narrative review of transfusion practices among patients in the acute phase of head injury was performed using PubMed, MEDLINE, EMBASE, Cochrane, and WEB of Science databases. A total of 104 articles were reviewed.
  
  
  RESULTS
  There are few data to guide clinical practice. Clinicians use blood hemoglobin concentrations to trigger transfusion. Markers of potential cerebral injury are not in regular use despite experimental and observational data rising from histologic examination, microdialysis, oximetry, and flow-based multimonitoring systems recommending their use to titrate blood transfusion in neurotrauma.
  
  
  CONCLUSIONS
  The generalization of transfusion triggers is common practice. Evidence-based approaches to transfusions strategies in head injury are lacking and not based on an understanding of cerebral physiopathology.
authors.affiliation: Department of Intensive Care Medicine, Royal Brisbane and Women’s Hospital, Butterfield St, Herston, Queensland, Australia. 30489jbr@comb.es
authors.forename: Judith
authors.initials: J
authors.lastname: Bellapart
authors.forename: Rob
authors.initials: R
authors.lastname: Boots
authors.forename: John
authors.initials: J
authors.lastname: Fraser
mesh_terms: D000740:Anemia / Q000209:etiology / Q000503:physiopathology*; D001803:Blood Transfusion / Q000592:standards*; D006259:Craniocerebral Trauma / Q000150:complications* / Q000503:physiopathology; D006801:Humans