The Relationship Between Lactate Levels and Acute Kidney Injury Risk in Patients with Hemorrhagic Shock and Septic Shock: An Analysis Based on the MIMIC-IV Database

ObjectivesThis study endeavors to examine the relationship between lactate (LA) levels and the risk of acute kidney injury (AKI) in patients with hemorrhagic shock (HS) and septic shock (SS).Methods983 HS and 4086 SS patients from the MIMIC-IV database were included and analyzed using restricted cubic spline (RCS), Cox model, Kaplan-Meier (KM), and receiver operating characteristic (ROC) curve analysis.ResultsMultivariate Cox regression analysis revealed that elevated LA was significantly associated with higher risks of AKI and in-hospital mortality rate (IMR) (all P < .001). After adjusting for confounders, LA had a greater effect on AKI risk in SS patients (hazard ratio (HR) = 1.056 versus 1.05 in HS), whereas LA more strongly influenced IMR in HS patients (HR = 1.115 vs 1.08 in SS). The safe LA thresholds, where HR = 1, were 2.083 mmol/L for SS and 2.31 mmol/L for HS. KM analysis demonstrated significant differences in cumulative AKI incidence and IMR among different LA levels (Log-rank P < .001). In HS patients, AKI risk increased linearly with rising LA, reflecting cumulative hypoperfusion. In SS patients, AKI risk rose sharply at lower LA levels, likely due to the inflammatory cytokine storm. ROC analysis showed that LA improved the predictive performance of the Acute Physiology Score III (APSIII) and the Simplified Acute Physiology Score II (SAPSII), particularly in HS patients. The change in area under the curve (ΔAUC) of SAPSII for predicting IMR was +0.042 in HS and +0.013 in SS.ConclusionsLA is a key predictor of AKI risk and prognosis in HS or SS patients, and its impact is heterogeneous among different populations, suggesting that individualized monitoring thresholds are needed.