title: The Impact of Red Blood Cell Transfusion on Cerebral Tissue Oxygen Saturation in Severe Traumatic Brain Injury.
abstract: There are a range of opinions on the benefits and thresholds for the transfusion of red blood cells in critically ill patients with traumatic brain injury (TBI) and an urgent need to understand the neurophysiologic effects. The aim of this study was to examine the influence of red blood cell transfusions on cerebral tissue oxygenation (SctO2) in critically ill TBI patients.
  
  
  
  This prospective observational study enrolled consecutive TBI patients with anemia requiring transfusion. Cerebral tissue oxygen saturation (SctO2) was measured noninvasively with bilateral frontal scalp probes using near-infrared spectroscopy (NIRS) technology. Data were collected at baseline and for 24 h after transfusion. The primary outcome was the applicability of a four-wavelength near-infrared spectrometer to monitor SctO2changes during a transfusion. Secondary outcomes included the correlation of SctO2with other relevant physiological variables, the dependence of SctO2on baseline hemoglobin and transfusion, and the effect of red blood cell transfusion on fractional tissue oxygen extraction.
  
  
  
  We enrolled 24 patients with severe TBI, of which five patients (21 %) were excluded due to poor SctO2signal quality from large subdural hematomas and bifrontal decompressive craniectomies. Twenty transfusions were monitored in 19 patients. The mean pre- and post-transfusion hemoglobin concentrations were significantly different [74 g/L (SD 8 g/L) and 84 g/L (SD 9 g/L), respectively; p value <0.0001]. Post-transfusion SctO2was not significantly greater than pre-transfusion SctO2[left-side pre-transfusion 69 % (SD 7) vs. post-transfusion 70 % (SD 10); p = 0.68, and right-side pre-transfusion 69 % (SD 5) vs. post-transfusion 71 % (SD 7); p = 0.11]. In a multivariable mixed linear analysis, mean arterial pressure was the only variable significantly associated with a change in SctO2.
  
  
  
  The bifrontal method of recording changes in NIRS signal was not able to detect a measurable impact on SctO2in this sample of patients receiving red blood cell transfusion therapy in a narrow but conventionally relevant, range of anemia.
authors.affiliation: Department of Critical Care Medicine, Sunnybrook Health Sciences Center, 2075 Bayview Ave, Room D108, Toronto, ON, M4N 3M5, Canada. Victoria.McCredie@sunnybrook.ca.
authors.forename: Victoria A
authors.identifier: 0000-0002-1590-2846
authors.initials: VA
authors.lastname: McCredie
authors.affiliation: Division of Neuroanesthesia and Neurointensive Care, Department of Anesthesia, Intensive Care and Perioperative Medicine, University of Brescia at Spedali Civili, Brescia, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Piva
authors.affiliation: Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Marlene
authors.initials: M
authors.lastname: Santos
authors.affiliation: Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, ON, M4N 3M5, Canada.
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.affiliation: Department of Medical Imaging, Interventional Neuroradiology, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Airton Leonardo
authors.initials: AL
authors.lastname: de Oliveira Manoel
authors.affiliation: Department of Anesthesia, University of Toronto, Toronto, ON, Canada.|Department of Critical Care Medicine, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Rigamonti
authors.affiliation: Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada.|Department of Anesthesia, University of Toronto, Toronto, ON, Canada.|Department of Physiology, University of Toronto, Toronto, ON, Canada.
authors.forename: Gregory M T
authors.initials: GM
authors.lastname: Hare
authors.affiliation: Department of Critical Care Medicine, Sunnybrook Health Sciences Center, 2075 Bayview Ave, Room D108, Toronto, ON, M4N 3M5, Canada.|Department of Anesthesia, University of Toronto, Toronto, ON, Canada.
authors.forename: Martin G
authors.initials: MG
authors.lastname: Chapman
authors.affiliation: Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada.|Department of Anesthesia, University of Toronto, Toronto, ON, Canada.|Department of Critical Care Medicine, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Baker
mesh_terms: D000328:Adult; D000368:Aged; D000070642:Brain Injuries, Traumatic / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000628:therapy*; D016638:Critical Illness / Q000628:therapy*; D017707:Erythrocyte Transfusion / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D010101:Oxygen Consumption / Q000502:physiology*; D012720:Severity of Illness Index; D019265:Spectroscopy, Near-Infrared
keywords: Brain tissue oxygenation; Oximetry; Transfusion; Traumatic brain injury