VBG vs. ABG

CLINICAL BOTTOM LINE


pH

Excellent agreement between VBG and ABG

pCO2

Moderate agreement between VBG and ABG but wide confidence interval

            Excellent screening test for hypercarbia

If pCO2 on VBG < 45 mmHg, very unlikely that patient has hypercarbia and ABG can be safely avoided



Kelly A. A Review: Can venous gas replace arterial in emergency medical care? EMA 2010;22:493.


pH   

12 studies, n = 1252

         Mean difference venous/arterial: 0.035

         Confidence Interval small

         Agreement good w DKA and COPD

   

pCO2

6 studies, n = 760

        Mean difference venous/arterial: 5.7 mmHg

            (wider range in agreement, 95% CI +/- 20 mmHg)

4 studies

        Venous pCO2 as a screening test for arterial hypercarbia (Table 3 below)

            Using venous pCO2 45 mmHg

                100% sensitivity (using 3 studies w lab-based analyses)

                Potentially avoid 36% of ABGs


Thanks, Jason Chu, MD