Are Central Venous Lactate and Arterial Lactate Interchangeable? A Human Retrospective Study

Abstract

In Brief BACKGROUND: In critically ill patients, arterial blood lactate concentration (Lacta) and Lacta clearance are used for the diagnosis of shock, for prognosis assessment, and to guide therapy. In recent years, central venous oxygen saturation (ScvO2), a surrogate for mixed venous blood saturation, either measured by fiberoptic catheters or from central venous blood samples, was used in shock to estimate the global balance between oxygen delivery and consumption. When central venous blood is drawn for ScvO2 measurement, it also could be used to measure central venous lactate concentration (Lactcv). In this study, we evaluated the utility of Lactcv and Lactcv clearance as predictors of Lacta and Lacta clearance, respectively, in critically ill patients. METHODS: This retrospective study was performed in an intensive care unit of a regional and teaching hospital. Using the electronic registry of our blood gas analyzer from March 2007 to December 2009, we identified patients with circulatory or respiratory failure who had pairs of Lactcv and Lacta obtained within a 30-minute interval. To assess the utility of Lactcv as a predictor of Lacta above 2 and 4 mmol/L, we calculated the area under receiver operating characteristic curves (AUCs) for these thresholds. We also calculated AUC of Lactcv clearance to detect a Lacta clearance <10% or >10%. RESULTS: Six hundred seventy-three Lactcv/Lacta pairs in 188 patients were analyzed. AUC of Lactcv to predict a Lacta above 2 and 4 mmol/L was 0.98 (95% confidence interval: 0.97–0.99) and 0.98 (95% confidence interval: 0.96–0.99), respectively. Lactcv with the cutoff value of 2 mmol/L can predict a Lacta above 2 mmol/L with sensitivity >92% and specificity >90%. AUC for Lactcv clearance to detect a Lacta clearance <10% or >10% was 0.93 or 0.94, respectively. CONCLUSION: Lactcv and Lacta collected within a 30-minute range are interchangeable for clinical practice. Published ahead of print June 28, 2012