To investigate the predictive value of baseline blood lactate, lactate clearance, and lactate-to-albumin ratio for 28-day all-cause mortality in patients with necrotizing fasciitis (NF) admitted to the intensive care unit (ICU), and to inform early clinical risk stratification and dynamic monitoring.

Data of 156 patients with NF were extracted from the Medical Information Mart for Intensive Care Ⅳ (MIMIC-Ⅳ) database and retrospectively analyzed. The associations of baseline blood lactate, lactate clearance, and lactate-to-albumin ratio with 28-day all-cause mortality were evaluated. Univariate and multivariate logistic regression, receiver operating characteristic (ROC) curves, likelihood ratio tests, and sensitivity analyses were used to compare the predictive performance of each indicator.

The initial lactate level measured within 24 hours of ICU admission was associated with 28-day all-cause mortality in patients with NF (OR=1.67, 95%CI: 1.39-2.10, P<0.001). After adjusting for lactate, lactate clearance ≥10% was an independent protective factor for 28-day all-cause mortality (OR=0.23, 95%CI: 0.05-0.77, P=0.028). Models constructed using cutoff values of 10%, 15%, and 20% for lactate clearance showed similar assessment efficacy, the area under the curve (AUC) values were 0.826 (95%CI: 0.714-0.937), 0.824 (95%CI: 0.711-0.938), 0.817 (95%CI: 0.701-0.932), respectively, with no statistically significant differences (all P values were >0.05). Likelihood ratio tests indicated that combining lactate and lactate clearance significantly improved model goodness-of-fit (χ²=5.753, P=0.016). The lactate-to-albumin ratio was an independent predictor in the multiple imputation model (OR=2.92, 95%CI: 1.03-9.14, P=0.049), and a consistent trend was observed in the complete case analysis, although it did not reach statistical significance (OR=2.31, 95%CI: 0.81-7.52, P=0.128). After 1∶1 propensity-score matching, 36 well-balanced patients were obtained. Upon further adjusting for the Charlson comorbidity index, both baseline lactate (OR=1.39, 95%CI: 1.10-1.91, P=0.017) and lactate-to-albumin ratio (OR=2.05, 95%CI: 1.23-4.21, P=0.020) remained independent risk factors for 28-day all-cause mortality in patients with NF, and the lactate-to-albumin ratio showed a stronger association.

The initial lactate level measured within 24 hours of ICU admission serves as a core prognostic indicator for 28-day all-cause mortality in patients with NF. The lactate clearance dynamically reflects treatment response, while the lactate-to-albumin ratio offers additional predictive value.