Capillary lactate as a prognostic marker in sepsis: correlation with venous lactate and prediction of outcomes.

Abstract

Introduction: Venous lactate (VL) measured by a blood‒gas analyser is not widely available despite its importance in the management of sepsis. Capillary lactate (CL) measured via a hand-held lactate analyser is a feasible and less expensive option. The aim of this study was to determine the correlation between CL and VL in sepsis patients at 0 h (t₀) and 6 h (t₆) and identify the best CL and lactate clearance cut-off values that predicts a poor outcome.

Methods: A descriptive study was conducted recruiting all patients with suspected sepsis (qSOFA ≥ 2 with evidence of infection) admitted to a tertiary care hospital in Sri Lanka between March and June 2022. "Lactate-plus", a hand-held lactate analyser, was used to measure CL and VL at t₀ and t₆ of admission. The lactate analyser was tested for accuracy and calibrated in a pilot study of 30 patients by correlating to laboratory lactate values. Patient demographics, clinical data and outcomes during hospitalization and at 28 days were assessed.

Results: There were 102 patients with suspected sepsis and a median age of 71.5 (interquartile range: 62-77) years were recruited. Majority were females (n = 52, 51%). Majority of the source of infection was pulmonary (n = 57, 55.9%) and urological (n = 19, 18.6%). Paired CL and VL values significantly correlated at both t₀ and t₆ (p < 0.001). CL at t₀ predicted 28-day mortality with a ROC curve AUC of 0.89 (95% CI: 0.82-0.95, p < 0.05) and 3.5 mmol/L was the best cut-off value with an 85% sensitivity and 78% specificity. CL ≥ 3.5 at t₀ was associated with increased intensive care unit (ICU) admission (p < 0.01), vasopressor requirement (p < 0.0001), and a higher mortality rate (p < 0.001) compared to CL < 3.5. Additionally, a capillary lactate clearance greater than 64% predicted a good outcome, with a 97% sensitivity and 91% specificity.

Conclusions: CL measured by a lactate meter correlates well with VL and effectively predicts sepsis outcomes. A CL cut-off ≥ 3.5 mmol/L at admission increases the risk of mortality, vasopressor requirement and ICU admission, making CL a useful tool for risk assessment in sepsis.