Early blood lactate as a biomarker for cardiovascular collapse in experimental sepsis

Cecal ligation and puncture (CLP) is the gold standard model for studying septic shock, which is characterized by hypotension and hyporeactivity to vasoconstrictors. However, approximately 30% of CLP animals do not exhibit cardiovascular changes, requiring more replicates because of the high variability of the model. Therefore, biomarkers enabling the early prediction of cardiovascular collapse in sepsis would greatly benefit sepsis nonclinical studies, refining experimental models and improving clinical translation. Thus, this study aimed to test whether the early increase in lactate levels could predict hypotension and hyporesponsiveness to vasoconstrictors in a rat model of sepsis. Male and female Wistar rats were subjected to CLP or sham procedure. Tail blood lactate was measured 6, 12, and 24 h after surgery. Then, inflammatory, biochemical, and hemodynamic parameters were evaluated. Rats subjected to CLP developed hypotension, hyporesponsiveness to vasoconstrictors, an intense inflammatory process, and increased plasma markers of organ dysfunction. By using receiver operating characteristics curve analysis, we have established that a lactate value of 2.45 mmol/L can accurately discriminate between a rat exhibiting a normal vasoconstrictive response and a vasoplegic rat with 84% accuracy (area under the curve: 0.84; confidence interval [CI]: 0.67-1.00). The sensitivity, which is the ability to identify a diseased rat (true positive), was 75% (CI: 41-95), and the true negative rate was 81% (CI: 57-93). Therefore, early measurement of lactate levels in sepsis could serve as a valuable biomarker for distinguishing vasoplegic rats from those exhibiting normal vasoconstrictive responses.