Evaluation of Mortality and Prognostic Factors in Patients Presenting to the Emergency Department with Extreme Acidemia: A Retrospective Cohort Study

Objectives: Extreme acidemia is associated with high mortality, but prognosis may depend more on the clinical context than on pH alone. This study evaluated 24-h and 30-day mortality and associated prognostic factors in adults presenting to the emergency department (ED) with extreme acidemia. Materials and Methods: This single-center retrospective cohort study included adults with an initial ED blood gas pH < 6.90. Demographic, clinical, etiological, and laboratory variables were recorded. Separate multivariable logistic regression models were constructed for 24-h and 30-day all-cause mortality. Results: A total of 413 patients were included. Median age was 60 years, 60.8% were male, and 50.4% presented with ongoing CPR. Mortality was 49.2% at 24 h and 75.5% at 30 days. Older age was independently associated with 24-h (aOR 1.35 per 10-year increase; 95% CI 1.14–1.60) and 30-day mortality (aOR 1.47; 95% CI 1.21–1.79). Ongoing CPR at ED arrival showed the strongest association with mortality at 24 h (aOR 16.25; 95% CI 8.71–30.30) and 30 days (aOR 15.22; 95% CI 5.94–38.98). Higher potassium was also independently associated with both outcomes. Admission pH was not independently associated with mortality after adjustment. Model AUCs were 0.896 and 0.904 for 24-h and 30-day mortality, respectively. Conclusions: Mortality is high among patients presenting with extreme acidemia. Within this cohort restricted to pH < 6.90, admission pH was not independently associated with mortality after adjustment, whereas older age, ongoing CPR at ED arrival, and elevated serum potassium were independently associated with both outcomes. The absence of an independent association between admission pH and mortality should be interpreted cautiously, because the restricted pH range and residual confounding may have attenuated its observed prognostic contribution within this cohort.