Metabolic Augmentation of mREMS: Improved 30-day Mortality Prediction through Lactate and Base Excess Integration in Emergency Patients

Aim: To evaluate whether adding base excess (BE), alone or in combination with lactate, to the modified Rapid Emergency Medicine score (mREMS) improves 30-day mortality prediction in emergency department (ED) red-zone patients. Materials and Methods:This observational cohort study included eligible ED red-zone patients presenting between May 2018 and December 2019 (n=1798).Vital signs, Glasgow Coma scale (GCS) scores, and blood gas parameters were collected.Because the relationship between BE and 30-day mortality was non-linear, BE was categorized using a data-driven, mortality-associated classification approach.The resulting categories were weighted using effect sizes from multivariable logistic regression and converted into an ordinal variable (0-3 points), which was integrated into the mREMS framework.Three models were developed: mREMS-Be, mREMS-L, and mREMS-LBe.Model discrimination was evaluated using the area under the curve (AUC) and comparisons were performed using the DeLong test.Results: Thirty-day mortality was associated with older age, lower systolic blood pressure, lower SpO 2 , and lower GCS (p<0.05).BE was not predictive when modeled as a continuous variable; however, it demonstrated an independent association with mortality when modeled as an ordinal variable (p=0.022).The AUC of the baseline mREMS was 0.753; it increased to 0.767 with the addition of BE and to 0.782 when BE was combined with lactate.Integration of BE into mREMS resulted in a significant improvement in model discrimination in both the overall and the non-traumatic red-zone patient groups. Conclusion:Incorporating BE into mREMS provides complementary prognostic value by improving 30-day mortality discrimination among high-acuity ED patients.