The agreement between arterial and venous lactate in patients with sepsis

Arterial sampling, which is the gold standard for measuring lactate levels in sepsis, is more painful, requires experience and is associated with a higher incidence of morbidity, when compared with venous sampling. This study attempted to measure the correlation and agreement between arterial and peripheral venous (PV) lactate and between arterial and central venous (CV) lactate, with the objective to test interchangeability of the two and possibly support the use of venous lactate levels in resuscitating patients with sepsis.

Eighty-seven patients admitted to the critical care unit of our hospital with the diagnosis of sepsis or septic shock were included in the study after taking informed consent. The arterial, PV and CV samples were taken within the first 24 hours following admission and within 10 minutes of each other. Lactate levels, CV oxygen saturation (ScvO₂ ) and base excess of each sample type were reported within 15 minutes of collection. Patients were followed up for a period of 28 days to record the need for organ support (newly diagnosed renal failure, need for renal replacement therapy [RRT], liver failure, coagulopathy and need for ventilation) and mortality.

Pearson correlation for arterial versus PV lactate was 0.76 and for arterial versus CV lactate was 0.992. The mean difference between arterial and PV lactate was found to be -0.30 (95% confidence interval [CI], -0.38 to -0.21). The upper and lower limits of agreement were 0.51 and -1.10, respectively. Mean difference between arterial and CV lactate was found to be -0.13 (95% CI, -0.21 to -0.05). Upper and lower limits of agreement were 0.63 and -0.89, respectively.

Our study demonstrates a high level of agreement in the lactate levels as measured on venous samples and arterial samples. Venous lactate levels are reliable in resuscitation of patients with sepsis.