title: Skin pigmentation interferes with the clinical measurement of regional cerebral oxygen saturation.
abstract: BACKGROUND
  Devices utilizing near-infrared (NIR) spectroscopy have been used to assess regional intracerebral oxygen saturation (rSO2) during anaesthesia for a decade. The presence of wide differences among individuals reduces their applicability to steady-state measurements. Current devices may not adequately account for variations in skin pigmentation.
  
  
  METHODS
  From our ongoing departmental registry, 3282 consecutive patients underwent cardiac surgery between 2010 and 2012 and their pre-induction measurements of rSO2 were available. Of these, 2096 identified themselves as Caucasian (Cauc) and 1186 as African-American (AA). Pre-induction rSO2, clinical and operative features were compared.
  
  
  RESULTS
  Clinical and operative details of these patients differed widely between the two populations. High-risk features were more common in AA patients, but no difference in mortality was observed (4.8% in AAs vs 4.7% in Caucs, P=0.87). Preprocedure rSO2 was systematically higher in Cauc (65.5% vs 53.3%, P<0.001). After multivariate linear regression adjustment, AA ethnicity proved to be associated independently with low rSO2 [odds ratio (OR) -8.28, 95% confidence interval (CI) -9.12 to -7.44, P<0.001]. Multivariate logistic regression analysis showed that preprocedural rSO2 was independently associated with operative mortality both in the Cauc group (OR 0.97, 95% CI 0.96-0.99, P=0.001) and in the AA group (OR 0.97, 95% CI 0.95-0.99, P=0.01).
  
  
  CONCLUSIONS
  AAs have a lower rSO2 than Caucs as measured by the INVOS 5100C cerebral oximeter. Reasonably, this could be attributed to attenuation of the NIR light by skin pigment. Despite this limitation, in both ethnic groups, lower preoperative rSO2 was predictive of greater operative mortality.
authors.affiliation: Department of Cardiac Surgery, sxmdcg@gmail.com.
authors.forename: X
authors.initials: X
authors.lastname: Sun
authors.affiliation: Department of Cardiac Surgery.
authors.forename: J
authors.initials: J
authors.lastname: Ellis
authors.affiliation: Department of Cardiac Surgery.
authors.forename: P J
authors.initials: PJ
authors.lastname: Corso
authors.affiliation: Department of Cardiac Surgery.
authors.forename: P C
authors.initials: PC
authors.lastname: Hill
authors.affiliation: Medstar Cardiovascular Research Network, and.
authors.forename: F
authors.initials: F
authors.lastname: Chen
authors.affiliation: Department of Cardiology, Medstar Washington Hospital Center, 110 Irving Street, Room Suite 1E RM1223, Washington, DC 20010, USA.
authors.forename: J
authors.initials: J
authors.lastname: Lindsay
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044383:Black People; D001923:Brain Chemistry; D006348:Cardiac Surgical Procedures / Q000379:methods* / Q000401:mortality; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000097:blood*; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D018570:Risk Assessment; D012880:Skin Pigmentation / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared; D044465:White People; D055815:Young Adult; D001741:Black or African American
chemical_list: D010100:Oxygen
keywords: cardiovascular anaesthesia; regional cerebral oxygen saturation; skin pigmentation