[Elevated serum lactic acid level is an independent risk factor for the incidence and mortality of sepsis-associated acute kidney injury].

To explore the effect of serum lactic acid (Lac) level on acute kidney injury (AKI) in patients with sepsis and whether Lac level affects the in-hospital mortality of patients with sepsis-associated AKI.A retrospective cohort study was conducted. Clinical data of patients with sepsis admitted to the internal intensive care unit (ICU) of the First Affiliated Hospital of Guangxi Medical University from March 2014 to June 2019 and the ICU of the Second Affiliated Hospital of Guangxi Medical University from January 2017 to June 2020 were collected. According to the first quartile of Lac within 24 hours of admission to ICU, the patients were divided into Lac ≤ 1.4 mmol/L group (group Q1), Lac 1.5-2.4 mmol/L group (group Q2), Lac 2.5-4.0 mmol/L group (group Q3), and Lac ≥ 4.1 mmol/L group (group Q4). The incidence of sepsis-associated AKI after admission to ICU and hospital mortality were compared among four groups. The effect of elevated Lac on the incidence and mortality of sepsis-associated AKI was investigated by binary Logistic regression analysis. The receiver operator characteristic curve (ROC curve) was drawn to analyze the predictive value of Lac on the incidence and mortality of sepsis-associated AKI, and the cut-off value was obtained to analyze the incidence and death risk of sepsis-associated AKI at different Lac levels.A total of 655 sepsis patients were enrolled, of which 330 patients (50.4%) developed AKI and 325 patients (49.6%) did not. Among 330 patients with sepsis-associated AKI, 134 (40.6%) died and 196 (59.4%) survived. With the increase of Lac level, the incidence of sepsis-associated AKI increased gradually (34.5%, 41.0%, 58.4%, 66.3%, respectively, in group Q1-Q4), meanwhile, the in-hospital mortality also increased gradually (23.4%, 29.2%, 33.1%, 43.4%, respectively, in group Q1-Q4), the differences were statistically significant (both P < 0.01). Compared with the non-AKI group, the Lac level in the AKI group was significantly increased [mmol/L: 3.08 (1.84, 5.70) vs. 1.91 (1.20, 3.10), P < 0.01]. After adjustment for factors such as gender (male), site of infection (abdominal cavity), vasoactive drugs, basal mechanical ventilation, mean arterial pressure (MAP), basal renal insufficiency, uric acid, procalcitonin (PCT), platelet count (PLT), basal serum creatinine (SCr) and basal estimated glomerular filtration rate (eGFR), and other influencing factors, multivariate Logistic regression analysis showed that elevated Lac was an independent risk factor for sepsis-associated AKI [odds ratio (OR) = 1.096, 95% confidence interval (95%CI) was 1.022-1.175, P = 0.010]. Compared with the survival group, the Lac level in the death group was significantly increased [mmol/L: 3.55 (2.00, 6.76) vs. 3.00 (1.70, 4.50), P < 0.01]. After adjusting for age, diabetes, vasoactive drugs, basal eGFR, and other factors, multivariate Logistic regression analysis suggested that increased Lac was an independent risk factor for in-hospital mortality in sepsis-associated AKI patients (OR = 1.074, 95%CI was 1.004-1.149, P = 0.037). ROC curve analysis showed that the area under the ROC curve (AUC) of Lac for predicting the incidence and mortality of sepsis-associated AKI was 0.653 (95%CI was 0.611-0.694) and 0.593 (95%CI was 0.530-0.656, both P < 0.01), respectively, and the cut-off values were 2.75 mmol/L (sensitivity was 57.8%, specificity was 69.2%) and 5.95 mmol/L (sensitivity was 56.7%, specificity was 83.7%). When the Lac ≥ 2.75 mmol/L, the risk of sepsis-associated AKI was 2.772 times higher than that of < 2.75 mmol/L (OR = 2.772, 95%CI was 1.754-4.380, P < 0.001). When the Lac ≥ 5.95 mmol/L, the patients with sepsis-associated AKI had a 2.511 times higher risk of in-hospital death than those with Lac < 5.95 mmol/L (OR = 2.511, 95%CI was 1.378-4.574, P = 0.003).Elevated Lac level is an independent risk factor for the incidence and mortality of sepsis-associated AKI. When Lac ≥ 2.75 mmol/L, the risk of AKI in patients with sepsis increased by 1.772 times; when Lac ≥ 5.95 mmol/L, the risk of in-hospital death in patients with sepsis related AKI increased by 1.511 times.