Peripheral venous and arterial blood gas analysis in adults: are they comparable? A systematic review and meta-analysis.

Peripheral venous blood gas (PVBG) analysis is increasingly being used as a substitute for arterial blood sampling; however, comparability has not been clearly established. To determine if the pH, PCO2 and PO2 obtained from PVBG analysis is comparable with arterial blood gas (ABG) analysis. A search was conducted of electronic databases as well as hand-searching of journals and reference lists through December 2012 to identify studies comparing PVBG with ABG analysis in adult subjects. A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. A meta-analysis using a random effects model was used to calculate the average difference (bias) and the limits of agreement for the venous and arterial pH, PCO2 and PO2 . A total of 18 studies comprising 1768 subjects were included in the meta-analysis. There was considerable heterogeneity between studies with I(2) approaching 100%. There was little difference between the pH obtained from the PVBG and the ABG, with the arterial pH typically 0.03 higher than the venous pH (95% confidence interval 0.029-0.038). The venous and arterial PCO2 were not comparable because the 95% prediction interval of the bias for venous PCO2 was unacceptably wide, extending from -10.7 mm Hg to +2.4 mm Hg. The PO2 values compared poorly, the arterial PO2 typically 36.9 mm Hg greater than the venous with significant variability (95% confidence interval from 27.2 to 46.6 mm Hg). PVBG analysis compares well with ABG analysis for pH estimations in adults but not to the PCO2 or PO2 . These differences are sufficiently large to be of clinical significance.