Boulain et al reported equations for estimating arterial blood concentrations from central venous blood analysis in critically-ill patients. This may obviate the need for an arterial blood sample. The authors are from multiple hospitals in France.

Patient selection: circulatory failure



(1) pH of central venous blood

(2) oxygen saturation of central venous blood in percent

(3) lactate concentration of central venous blood in mmol/L

(4) partial pressure of carbon dioxide of central venous blood in kPa


arterial lactate concentration in mmol/L =

= (0.952 * (lactate in central venous blood)) – (1.8323 * (pH of central venous blood)) – (0.0139 * (partial pressure of CO2 of central venous blood)) – (0.0023 * (oxygen saturation of central venous blood)) + 13.8923



The accuracy of the equation was suboptimal. It may be sufficient for making clinical decisions over time but further studies are required.

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