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Arterial versus venous lactate
Summarized from Mikami A, Ohde S, Deshpande G et al. Can we predict arterial lactate from venous lactate in the ED. Am J Emerg Med 2013; 31: 1118-20
Blood lactate concentration, a parameter often available at the point of care on blood gas analyzers, is useful for assessment of global tissue oxygenation among acutely/critically ill patients. The ”gold standard” sample for this assessment, as for blood gas analysis, is arterial blood.
Sampling of venous blood is technically less demanding, safer and less painful for the patient than sampling arterial blood, and in some clinical situations it has been demonstrated that it is appropriate to use venous blood for some parameters (e.g. pH, pCO2 and bicarbonate) measured during blood gas analysis.
But is it appropriate to use venous rather than arterial blood if lactate is the parameter of interest? Can we predict arterial blood lactate by measuring venous blood lactate? These are the questions addressed by a recently published clinical study conducted at a tertiary care hospital in Tokyo.
The study population comprised 72 acutely/critically ill adult patients (aged >17 years) whose clinical condition required that they be submitted for arterial blood gas analysis. Arterial and venous blood was collected simultaneously from each study participant, and both samples were analyzed at the same time using the same blood gas analyzer that included lactate in its test repertoire.
Statistical analysis of the paired results revealed a high level of correlation between venous and arterial lactate concentration, although mean venous lactate concentration of all 72 patients was higher (2.42 mmol/L) than mean arterial lactate concentration (2.15 mmol/L).
Difference between arterial and venous samples ranged from –0.4 mmol/L to +1.1 mmol/L; mean difference was 0.268 mmol/L. Univariate linear regression analysis allowed construction of the following equation for predicting arterial lactate concentration from measured venous lactate concentration:
Arterial lactate (mmol/L) = –0.259 + venous lactate (mmol/L) × 0.996
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