Prognostic value of lactate-to-hemoglobin ratio in nontraumatic critically ill patients presenting to the emergency department: a retrospective cohort study

BACKGROUND: Nontraumatic critically ill patients constitute a substantial cohort of individuals presenting to the emergency department (ED). However, reliable parameters to predict early mortality in these patients are limited. Lactate and base deficit (BD) are commonly used markers reflecting tissue hypoxia and metabolic acidosis, respectively. This study aimed to evaluate the prognostic value of the lactate-to-hemoglobin ratio (LHR), a novel parameter that concurrently reflects imbalances in oxygen delivery and utilization, for predicting in-hospital mortality. METHODS: This retrospective observational study was conducted in the ED of a tertiary care hospital between January 1 and December 31, 2023. Patients aged ≥ 18 years with a lactate level ≥ 4 mmol/L and BD ≤ − 2 mmol/L at presentation were included. Patients with a history of trauma or incomplete data were excluded. Demographic, clinical, and laboratory data were recorded. LHR, lactate clearance, and BD clearance were calculated. The primary endpoint was in-hospital mortality. Logistic regression and receiver operating characteristic curve analysis were used for statistical analysis. RESULTS: A total of 693 patients were included in the study, of whom 180 (26%) died in the hospital. The median age of the patients was 69 years, and 55.8% were aged ≥ 65 years. Compared to survivors, nonsurvivors had significantly higher lactate levels (6.47 vs. 5.24 mmol/L), higher LHR values (0.62 vs. 0.42), lower lactate clearance (13.35% vs. 51.84%), and more pronounced base deficits (− 10.55 vs. −6.10 mmol/L) (p < 0.001 for all). Multivariate analysis identified age (odds ratio OR = 1.043), LHR (OR = 9.033), and BD clearance as independent predictors of mortality. In ROC analysis, the predictive power of LHR (AUC = 0.749) was comparable to lactate clearance (AUC = 0.762) and superior to initial lactate level. CONCLUSIONS: The LHR is a readily accessible and reliable predictor of in-hospital mortality in nontraumatic critically ill patients. Its prognostic performance is comparable to lactate clearance and superior to initial lactate levels. These findings warrant confirmation by prospective, multicenter studies. CLINICAL TRIAL NUMBER: Not applicable.