Using vital signs to diagnose impaired consciousness: cross sectional observational study

OBJECTIVES: To determine whether any vital signs can be used to quickly identify brain lesions in patients with impaired consciousness. DESIGN: Cross sectional observational study. SETTING: Emergency department of an urban hospital, Japan. PARTICIPANTS: 529 consecutive patients (mean age 65 years) presenting with impaired consciousness (score <15 on the Glasgow coma scale) during 2000. MAIN OUTCOME MEASURES: The receiver operating characteristic curve was used to quantify the relation between the vital signs on arrival and the final diagnosis of a brain lesion. Stratum specific likelihood ratios were calculated to define strata with optimal discriminating power. RESULTS: 312 (59%) had a brain lesion which accounted for the impaired consciousness. The area under the receiver operating curve for systolic blood pressure was 0.90 (SE 0.01), indicating significantly higher accuracy (P<0.01) in the identification of a brain lesion than using diastolic pressure 0.82 (0.02) or pulse rate 0.63 (0.03). Likelihood ratios for systolic blood pressure lower than 90 mm Hg were less than 0.04, and those for systolic pressure higher than 170 mm Hg were greater than 6.09. CONCLUSIONS: Systolic blood pressure is useful for diagnosing brain lesions in patients with impaired consciousness.