Can Peripheral Venous Lactate Levels Substitute for Arterial Lactate Levels in The Emergency Department? An Observational Study

Background: Arterial lactate (AL) level is an important parameter used to predict patients’ prognosis. AL and peripheral venous lactate (PVL) in blood gas analysis have a low concordance rate, and PVL cannot be used as a substitute for AL. However, if the AL range can be predicted from PVL, PVL may be an alternative method of predicting patient prognosis, and the risk of arterial puncture complications with AL may be reduced. This could become a safe and rapid test method.Methods: This was a retrospective observational study of 143 cases in which blood gas analysis was performed on both arterial blood and venous blood in an emergency department. Spearman's rank correlation coefficient (r) and Bland–Altman analysis were performed. Sensitivity, specificity, and the area under the curve (AUC) were calculated for PVL to predict AL < 2 mmol/L or < 4 mmol/L.Results: The median [interquartile range] AL and PVL were 1.82 [1.25–2.58] vs 2.09 [1.57–3.29], respectively, r was 0.799 (p<0.0001), and a strong correlation was observed; however, Bland–Altman analysis showed disagreement. When AL < 2 mmol/L was used as the outcome, AUC was 0.974, the PVL cutoff value was 2.55 mmol/L, sensitivity was 87.9%, and specificity was 94.1%. If PVL < 2 mmol/L was the outcome, the sensitivity for AL < 2 mmol/L was 100%, and for PVL levels ≥ 3 mmol/L, the specificity was 100%. When AL < 4 mmol/L was used as the outcome, AUC was 0.970, the PVL cutoff value was 3.4 mmol/L, sensitivity was 100%, and specificity was 84.5%. When PVL < 3.5 mmol/L was the outcome, the sensitivity for AL < 4 mmol/L was 100%, and for PVL levels ≥ 4 mmol/L, the specificity was 93.8%.Conclusions: This study revealed that PVL and AL levels in the same critically ill patients do not perfectly agree with each other but are strongly correlated. Furthermore, the high accuracy for predicting AL ranges from PVL levels explains why PVL levels could be used as a substitute for AL level ranges.