title: Obesity is associated with reduced brain tissue oxygen tension after severe brain injury.
abstract: BACKGROUND
  Obesity has been associated with compromised tissue oxygenation and reduced organ perfusion. The brain is critically dependent on oxygen delivery, and reduced brain tissue oxygen tension (P(bt)O(2)) may result in poor outcome after brain injury. We tested the hypothesis that obesity is associated with compromised P(bt)O(2) after severe brain injury.
  
  
  METHODS
  Patients with severe brain injury (GCS score ≤ 8) who underwent continuous P(bt)O(2) monitoring were retrospectively identified from a prospective single-center database. Patients, were classified by body mass index (BMI = weight (kg)/m(2)) and were included if they were obese (BMI ≥ 30) or non-obese (BMI = < 30).
  
  
  RESULTS
  Sixty-nine patients (mean age 46.4 ± 17.0 years) were included. Mean daily P(bt)O(2) was 25.8 (9.6) mmHg for the 28 obese and 31.8 (12.3) mmHg for the 41 non-obese patients (P = 0.03). Initial P(bt)O(2) and mean daily maximum P(bt)O(2) measurements also were significantly lower in obese patients than in non-obese patients. Univariate predictors of compromised P(bt)O(2) (defined as minutes P(bt)O(2) < 20 mmHg) included elevated BMI (P = 0.02), presence of ARDS (P < 0.01), mean PaO(2) (P < 0.01), maximum FiO(2) (P < 0.01), mean PaO(2):FiO(2) (P < 0.01), and mean CVP (P < 0.01). In multivariable analysis, BMI was significantly associated with compromised P(bt)O(2) (P = 0.02). Sex, age, and mean CVP were also identified as significant predictors of compromised P(bt)O(2); ARDS and PF ratio were not.
  
  
  CONCLUSIONS
  In patients with severe brain injury, obesity was found to be an independent predictor of compromised P(bt)O(2). This effect may be mediated through obesity-related pulmonary dysfunction and inadequate compensatory mechanisms.
authors: Department of Neurosurgery, Clinical Research Division, University of Pennsylvania Medical Center, Philadelphia, PA, USA.
authors: Monisha A
authors: MA
authors: Kumar
authors: Rishi
authors: R
authors: Chanderraj
authors: Ryan
authors: R
authors: Gant
authors: Christi
authors: C
authors: Butler
authors: Suzanne
authors: S
authors: Frangos
authors: Eileen
authors: E
authors: Maloney-Wilensky
authors: Jennifer
authors: J
authors: Faerber
authors: W Andrew
authors: WA
authors: Kofke
authors: Joshua M
authors: JM
authors: Levine
authors: Peter
authors: P
authors: LeRoux
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D001930:Brain Injuries / Q000150:complications* / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000378:metabolism* / Q000503:physiopathology; D010100:Oxygen / Q000378:metabolism*; D012189:Retrospective Studies
chemical_list: D010100:Oxygen