Altered Level of Consciousness in a Tertiary Emergency Department: Etiologies, Mortality, and Outcomes

<b>Background/Objectives</b>: Altered level of consciousness (ALC) is a common emergency department (ED) presentation with high mortality. We evaluated etiologies and early ED-course prognostic markers for mortality. <b>Methods</b>: We retrospectively identified adult ED visits with ALC (September 2023-August 2025) and classified etiologies using the ALC-10 framework. Patients transferred directly to other hospitals were excluded because post-transfer outcomes were unavailable; sensitivity analyses were performed. Overall mortality was ED death or in-hospital death, and ED mortality was death during the ED stay. Nested logistic models were prespecified: overall-mortality Model A included age, initial Glasgow Coma Scale (GCS), etiologic category, and ICU admission, and Model B added vasopressor use and mechanical ventilation within 1 h; ED-mortality Model A included age and initial GCS, and Model B added vasopressor use and mechanical ventilation. <b>Results</b>: ALC accounted for 2.85% (2194/76,957) of adult ED visits; 1932 patients were analyzed after excluding 262 transfer-outs. Systemic infection (25.8%) and metabolic causes (23.7%) were most frequent. Observed overall mortality was 23.6% (455/1932), including ED mortality of 6.4% (124/1932); model-based sensitivity analysis estimated adjusted overall mortality to be 23.2% (95% uncertainty interval, 22.9-23.7) among all ALC visits. In adjusted models, older age, lower initial GCS, and vasopressor use were associated with higher odds of both outcomes, while ICU admission and mechanical ventilation were associated with overall mortality. Model B showed improved discrimination (AUC 0.795 overall; 0.869 ED). <b>Conclusions</b>: These findings highlight the prognostic significance of age, initial neurologic status, and etiology. This study may assist in risk stratification and early resource allocation.