title: Hemoglobin levels and transfusions in neurocritically ill patients: a systematic review of comparative studies.
abstract: BACKGROUND
  Accumulating evidence suggests that, in critically ill patients, a lower hemoglobin transfusion threshold is safe. However, the optimal hemoglobin level and associated transfusion threshold remain unknown in neurocritically ill patients.
  
  
  METHODS
  We conducted a systematic review of comparative studies (randomized and nonrandomized) to evaluate the effect of hemoglobin levels on mortality, neurologic function, intensive care unit (ICU) and hospital length of stay, duration of mechanical ventilation, and multiple organ failure in adult and pediatric neurocritically ill patients. We searched MEDLINE, The Cochrane Central Register of Controlled Trials, Embase, Web of Knowledge, and Google Scholar. Studies focusing on any neurocritical care conditions were included. Data are presented by using odds ratios for dichotomous outcomes and mean differences for continuous outcomes.
  
  
  RESULTS
  Among 4,310 retrieved records, six studies met inclusion criteria (n = 537). Four studies were conducted in traumatic brain injury (TBI), one in subarachnoid hemorrhage (SAH), and one in a mixed population of neurocritically ill patients. The minimal hemoglobin levels or transfusion thresholds ranged from 7 to 10 g/dl in the lower-Hb groups and from 9.3 to 11.5 g/dl in the higher-Hb groups. Three studies had a low risk of bias, and three had a high risk of bias. No effect was observed on mortality, duration of mechanical ventilation, or multiple organ failure. In studies reporting on length of stay (n = 4), one reported a significant shorter ICU stay (mean, -11.4 days (95% confidence interval, -16.1 to -6.7)), and one, a shorter hospital stay (mean, -5.7 days (-10.3 to -1.1)) in the lower-Hb groups, whereas the other two found no significant association.
  
  
  CONCLUSIONS
  We found insufficient evidence to confirm or refute a difference in effect between lower- and higher-Hb groups in neurocritically ill patients. Considering the lack of evidence regarding long-term neurologic functional outcomes and the high risk of bias of half the studies, no recommendation can be made regarding which hemoglobin level to target and which associated transfusion strategy (restrictive or liberal) to favor in neurocritically ill patients.
authors.affiliation: Department of Anesthesiology, Division of Critical Care Medicine, Faculty of Medicine, Université Laval, 1050, Avenue de Médecine, Pavillon Ferdinand-Vandry, Québec, QC, G1V 0A6, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Desjardins
authors.forename: Alexis F
authors.initials: AF
authors.lastname: Turgeon
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Tremblay
authors.forename: François
authors.initials: F
authors.lastname: Lauzier
authors.forename: Ryan
authors.initials: R
authors.lastname: Zarychanski
authors.forename: Amélie
authors.initials: A
authors.lastname: Boutin
authors.forename: Lynne
authors.initials: L
authors.lastname: Moore
authors.forename: Lauralyn A
authors.initials: LA
authors.lastname: McIntyre
authors.forename: Shane W
authors.initials: SW
authors.lastname: English
authors.forename: Andrea
authors.initials: A
authors.lastname: Rigamonti
authors.forename: Jacques
authors.initials: J
authors.lastname: Lacroix
authors.forename: Dean A
authors.initials: DA
authors.lastname: Fergusson
mesh_terms: D001803:Blood Transfusion / Q000706:statistics & numerical data*; D001927:Brain Diseases / Q000097:blood*; D016638:Critical Illness; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data; D007902:Length of Stay / Q000706:statistics & numerical data; D009102:Multiple Organ Failure / Q000097:blood; D012121:Respiration, Artificial
chemical_list: D006454:Hemoglobins