Impact of anion gap on in-hospital mortality in trauma-induced coagulopathy patients: a MIMIC-IV study

This study aimed to investigate the association between anion gap (AG) and clinical outcomes in patients with trauma-induced coagulopathy (TIC), and to evaluate the predictive value of dynamic AG trajectories for 28-day mortality. A retrospective cohort study was conducted using the MIMIC-IV database, including 1,358 TIC patients (INR > 1.4 or PTT > 40 s). Demographics, laboratory data (including AG), vital signs, and severity scores within 24 h of ICU admission were collected. Latent class growth modeling was used to identify AG trajectories at 8, 16, and 24 h. The primary outcome was 28-day mortality, analyzed via Cox regression and Kaplan–Meier survival analysis. Among 1,358 patients, the 28-day mortality rate was 19.9%. Non-survivors were older and had worse vital signs, higher AG, and lower platelet and bicarbonate levels (P < 0.05). Elevated AG was independently associated with increased mortality (HR = 2.615, P < 0.001), even after multivariate adjustment. Patients with AG > 14.5 mEq/L had significantly reduced 28-day survival (P < 0.001). Four distinct AG trajectories were identified; Class 4, with persistently rising AG, showed the highest mortality risk (HR = 2.46, P = 0.033). AG is an independent predictor of 28-day mortality in TIC patients. AG > 14.5 mEq/L and persistently elevated trajectories are associated with poor short-term outcomes, especially in those with renal dysfunction or myocardial infarction. Dynamic AG monitoring may help identify high-risk patients early and guide clinical management.