The use of venous blood gas in assessing arterial acid-base and oxygenation status - an analysis of aggregated data from multiple studies evaluating the venous to arterial conversion (v-TAC) method.

BACKGROUND: Several methods exist to reduce the number of arterial blood gases (ABGs). One method, Roche v-TAC, has been evaluated in different patient groups. This paper aggregates data from these studies, in different patient categories using common analysis criteria. RESEARCH DESIGN AND METHODS: We included studies evaluating v-TAC based on paired arterial and peripheral venous blood samples. Bland-Altman analysis compared measured and calculated arterial values of pH, PCO2, and PO2. Subgroup analyses were performed for normal, chronic hypercapnia and chronic base excess, acute hyper- and hypocapnia, and acute and chronic base deficits. RESULTS: 811 samples from 12 studies were included. Bias and limits of agreement for measured and calculated values: pH 0.001 (-0.029 to 0.031), PCO2 -0.08 (-0.65 to 0.49) kPa, and PO2 0.04 (-1.71 to 1.78) kPa, with similar values for all sub-group analyses. CONCLUSION: These data suggest that v-TAC analysis may have a role in replacing ABGs, avoiding arterial puncture. Substantial data exist in patients with chronic hypercapnia and chronic base excess, acute hyper- and hypocapnia, and in patients with relatively normal acid-base status, with similar bias and precision across groups and across study data. Limited data exist for patients with acute and chronic base deficits.

Correlation between acid-base parameters measured in arterial blood and venous blood sampled peripherally, from vena cavae superior, and from the pulmonary artery.

OBJECTIVE: In intensive care units arterial blood sampling is routine for analysing acid-base and oxygenation status. In nonintensive departments arterial blood sampling is seldom performed. Venous blood sampling is routine but not usually analysed for acid-base and oxygenation status. This study describes the correlation between arterial and peripheral, central and mixed venous pH, PCO2 and PO2 in a wide range of adult patients. METHODS: Arterial and venous blood samples were taken anaerobically and simultaneously. The values of pH, PCO2 and PO2 were compared using Bland-Altman plots. RESULTS: A total of 103 patients were included. The arteriovenous difference (bias+/-SD) for pH was 0.026+/-0.023 and for PCO2 -0.60+/-0.57 kPa (peripheral venous blood), 0.036+/-0.014 and -0.79+/-0.26 kPa (central venous blood) and 0.026+/-0.010 and -0.67+/-0.22 kPa (mixed venous blood). The arteriovenous difference for PO2 for peripheral, central and mixed venous blood was 6.27+/-4.36, 8.33+/-3.94 and 11.00+/-4.87 kPa, respectively. CONCLUSION: The venous values of pH, corrected for bias, can give arterial values which are within reasonable laboratory and clinical acceptance criteria. For PCO2 this is also true, except for peripheral blood, where the standard deviation is outside laboratory acceptance criteria but within clinical acceptance criteria. For PO2 the arteriovenous differences are not randomly distributed and even for PO2