Altered mental status is a commonly evaluated problem in the ED. Ethanol intoxication is common, and prehospital history may bias emergency physicians to suspect this as the cause of altered mental status. Quantitative ethanol measurement can rapidly confirm the diagnosis, or if negative, prompt further evaluation. Our objective was to identify the etiologies of altered mental status in ED patients initially presumed to be intoxicated with ethanol but found to have negative quantitative ethanol levels.

This was a 5-year (2012–2016) electronic medical record review of ED patients presenting with altered mental status. Patients were included if they presented with presumed ethanol intoxication and had an initial ethanol concentration of zero. Etiologies of altered mental status were categorized into medical, traumatic, psychiatric, and drug-related causes.

29,322 patients presented during the study period with presumed alcohol intoxication, 1875 patients had negative ethanol levels. The etiology of altered mental status was due to illicit substances in 1337 patients (71%), psychiatric causes in 354 patients (19%), medical causes in 166 patients (9%) and trauma in 18 patients (1%). A total of 179 patients (10%) were admitted to the hospital; 19 patients (1%) to the ICU.

The presumptive diagnosis of ethanol intoxication in patients presenting to the ED with altered mental status was inaccurate in 5% of patients. The etiology of altered mental status was serious and required hospitalization in 10% of the cohort. Rapid assessment of quantitative ethanol levels should be performed, breathalyzers may be preferred over serum testing.