Altered Mental Status in ICU Patients: Diagnostic Yield of Noncontrast Head CT for Abnormal and Communicable Findings

Objective: To evaluate the diagnostic yield of noncontrast head CT for acute communicable findings in ICU patients specifically scanned for altered mental status. Design: Retrospective observational cohort study. Setting: University Hospital Neuroscience, Medical, and Surgical ICUs. Patients: ICU patients with new-onset altered mental status. Intervention: Noncontrast head CT. Measurements and Main Results: Reports on head CTs from two university hospitals performed for the sole indication of altered mental status in ICU patients between July 2011 and June 2013 were reviewed for 1) acute (new or worsening) hemorrhage, 2) mass effect/herniation, 3) infarction, and 4) hydrocephalus. Subgroup analyses of positive findings were performed by 1) ICU group type, 2) age, and 3) race. A total of 2,486 head CTs were performed in 1,357 patients whose age ranged from 14 to 116 years (median, 59; mean, 57.6 +/- 16). Acute communicable findings in at least one of four categories were present in 22.8% (566/2,486) of examinations, with hydrocephalus being most common (11.5% [286/2,486]). The frequency of any acute communicable findings in neuroscience, medical, and surgical ICUs was 28.6% (471/1,648), 9.8% (43/440), and 13.1% (52/398), respectively. Neuroscience ICU head CTs had significantly higher rates of acute communicable findings in all categories, except for acute infarction, compared with the other two ICUs (p < 0.001). Acute hydrocephalus (13.6% vs 7.4%; p < 0.001) and mass effect (6.7% vs 4.3%; p = 0.01) were more common in patients less than 65 years. For other acute categories, no significant difference was noted by age. There was no significant difference in the likelihood of a positive examination by race. Conclusions: Almost one in four head CTs in a university ICU patient population performed for primary indication of altered mental status yields abnormal communicable findings. In this patient population, utilization management barriers to examination ordering should be minimized.