title: Agreement between central venous and arterial blood gas measurements in the intensive care unit.
abstract: OBJECTIVE
  Venous blood gas (VBG) analysis is a safer procedure than arterial blood gas (ABG) analysis and may be an alternative for determining acid-base status. The objective of this study was to examine the agreement between ABG and central VBG samples for all commonly used parameters in a medical intensive care unit (ICU) population.
  
  
  METHODS
  We performed a single-center, prospective trial to assess the agreement between arterial and central VBG measurements in a medical ICU. Adult patients who were admitted to the ICU and required both a central venous line and an arterial line were enrolled. When an ABG was performed, a central venous sample was obtained to examine the agreement among the pH, Pco(2), and bicarbonate. Data comparing central and peripheral VBG values were also obtained.
  
  
  RESULTS
  The mean arterial minus venous difference for pH, Pco(2), and bicarbonate was 0.027, -3.8, and -0.80, respectively. Bland-Altman plots for agreement of pH, Pco(2), and bicarbonate showed 95% limits of agreement of -0.028 to 0.081, -12.3 to 4.8, and -4.0 to 2.4, respectively. Regression equations were derived to predict arterial values from venous values as follows: Arterial pH = -0.307 + 1.05 x venous pH, arterial Pco(2) = 0.805 + 0.936 x venous Pco(2), and arterial bicarbonate = 0.513 + 0.945 x venous bicarbonate. The mean central minus peripheral differences for pH, Pco(2), and bicarbonate were not clinically important.
  
  
  CONCLUSIONS
  Peripheral or central venous pH, Pco(2), and bicarbonate can replace their arterial equivalents in many clinical contexts encountered in the ICU.
authors.affiliation: West LA Veterans Affairs Medical Center, 11301 Wilshire Boulevard, W111A, Los Angeles, CA 90073, USA. richard.treger@va.gov
authors.forename: Richard
authors.initials: R
authors.lastname: Treger
authors.forename: Shahriar
authors.initials: S
authors.lastname: Pirouz
authors.forename: Nader
authors.initials: N
authors.lastname: Kamangar
authors.forename: Dalila
authors.initials: D
authors.lastname: Corry
mesh_terms: D000328:Adult; D000368:Aged; D001639:Bicarbonates / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D001784:Blood Gas Analysis / Q000379:methods*; D002245:Carbon Dioxide / Q000097:blood*; D002405:Catheterization, Central Venous; D002406:Catheterization, Peripheral; D003422:Critical Care; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007362:Intensive Care Units; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results
chemical_list: D001639:Bicarbonates; D015415:Biomarkers; D002245:Carbon Dioxide