Prospective correlation of arterial vs venous blood gas measurements in trauma patients

Am J Emerg Med. 2012 Oct;30(8):1371-7. doi: 10.1016/j.ajem.2011.09.027. Epub 2011 Dec 12.


Objective: The objective of this study is to assess if venous blood gas (VBG) results (pH and base excess [BE]) are numerically similar to arterial blood gas (ABG) in acutely ill trauma patients.

Methods: We prospectively correlated paired ABG and VBG results (pH and BE) in adult trauma patients when ABG was clinically indicated. A priori consensus threshold of clinical equivalence was set at ± less than 0.05 pH units and ± less than 2 BE units. We hypothesized that ABG results could be predicted by VBG results using a regression equation, derived from 173 patients, and validated on 173 separate patients.

Results: We analyzed 346 patients and found mean arterial pH of 7.39 and mean venous pH of 7.35 in the derivation set. Seventy-two percent of the paired sample pH values fell within the predefined consensus equivalence threshold of ± less than 0.05 pH units, whereas the 95% limits of agreement (LOAs) were twice as wide, at -0.10 to 0.11 pH units. Mean arterial BE was -2.2 and venous BE was -1.9. Eighty percent of the paired BE values fell within the predefined ± less than 2 BE units, whereas the 95% LOA were again more than twice as wide, at -4.4 to 3.9 BE units. Correlations between ABG and VBG were strong, at r(2) = 0.70 for pH and 0.75 for BE.

Conclusion: Although VBG results do correlate well with ABG results, only 72% to 80% of paired samples are clinically equivalent, and the 95% LOAs are unacceptably wide. Therefore, ABG samples should be obtained in acutely ill trauma patients if accurate acid-base status is required.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Alkalosis / blood
  • Arteries*
  • Blood Gas Analysis / methods*
  • Female
  • Humans
  • Hydrogen-Ion Concentration
  • Injury Severity Score
  • Male
  • Middle Aged
  • Prospective Studies
  • Trauma Centers
  • Veins*
  • Wounds and Injuries / blood*
  • Young Adult