Association of lactate to Po2 ratio (LPR) with 28-day mortality in ICU sepsis: A retrospective cohort study based on the MIMIC-IV database.

The high mortality rate among patients with sepsis continues to be a major hurdle in critical care environments, and metabolic imbalances are a defining feature of the underlying pathophysiology of this disease. However, the association between the lactate-to-oxygen tension ratio (LPR) and patient outcomes in sepsis remains underexplored, with insufficient research to fully elucidate its clinical significance. In the context of assessing a patient's metabolic health, lactate alone might not be sufficient to fully capture their physiological condition, as it is influenced by non-hypoxic factors including hepatic dysfunction, catecholamine administration, and renal clearance impairment. The integration of lactate and arterial partial pressure of oxygen (PaO2) into the LPR offers a composite measure that simultaneously reflects tissue metabolic stress and systemic oxygenation status, potentially providing a more comprehensive representation of the metabolic-oxygenation mismatch characteristic of sepsis. This research examines the relationship between LPR and 28-day mortality rates among patients with sepsis admitted to the intensive care unit. According to ICD-9 diagnosis codes, patients diagnosed with sepsis in the Medical Information Mart for Intensive Care IV (v.2.2) database were selected. The receiver operating characteristic (ROC) curve, Kaplan-Meier (K-M) survival curve, logistic regression analyses, sensitivity analysis, and subgroup analysis were used to assess the predictive power of LPR. Based on the MIMIC-IV database, patients with sepsis admitted to the ICU for the first time (n = 14,921) were included. The 28-day mortality was 17.26%. The area under the ROC curve (AUC) for LPR was 0.725 (95% confidence interval [CI], 0.714-0.73), which was comparable to that of OASIS (0.765; 95% CI, 0.755-0.775) and SAPSII (0.772; 95% CI, 0.762-0.781), and superior to SOFA (0.624; 95% CI, 0.612-0.636; P = .500). The cutoff value of LPR was 0.137 based on the ROC curve. The high LPR group showed a poor prognosis in the K-M analysis (P < .001). Multivariate logistic regression showed that LPR10 was significantly associated with poor outcome (odds ratio, 1.61; 95% CI, 1.42-1.84; P < .001), after adjusting for lactate alone and established severity scores. Net Reclassification Improvement analyses confirmed incremental prognostic value of LPR beyond SOFA (NRI 0.142; P < .001), SAPS II (NRI 0.118; P < .001), and OASIS (NRI 0.095; P < .001). Subgroup analysis showed no significant interaction between LPR and any subgroup (P for interaction: 0.065-0.867). LPR is a rational and easily accessible marker that is strongly associated with 28-day mortality in ICU patients with sepsis. The integration of lactate and PaO2 into a single ratio captures prognostic information beyond that provided by either parameter alone or by established severity scores, offering a practical bedside tool for early risk stratification.