Study objective: Out-of-hospital hypotension may signify need for intensive resuscitation and rapid diagnosis on emergency department (ED) arrival. We hypothesized that nontraumatic out-of-hospital hypotension confers risk of inhospital mortality.
Methods: This was a multicenter study of ambulance-transported, nontrauma, non-cardiopulmonary resuscitation patients conducted at 2 venues: (1) a cross-sectional risk assessment study of high-priority medical transports at a US metropolitan county; and (2) a Canadian prospective multicenter cohort study of patients with respiratory distress. Data at both venues were extracted from prospectively recorded, standardized run sheets by either a physician or a paramedic. Data extraction and analysis at each venue were conducted independently. Exposures to hypotension were defined as age older than 17 years old, systolic blood pressure less than 100 mm Hg during transport, and 1 or more of 10 predefined symptoms of circulatory insufficiency. Nonexposures to hypotension had the same definition as exposures, except the systolic blood pressure had to be more than 100 mm Hg during the entire out-of-hospital transport. The main outcome variable was inhospital mortality.
Results: At venue 1, of 3,128 transports, 395 (13%) exposures and 395 nonexposures were identified. Inhospital mortality of exposures was 26% versus 8% for nonexposures (adjusted odds ratio [OR] 4.6; 95% confidence interval [CI] 2.0 to 5.9). At venue 2, of 7,679 transports, 532 exposures (7%) and 7,147 nonexposures were identified. Out-of-hospital exposure to hypotension conferred a mortality rate of 32% versus 11% for nonexposures (OR 3.0; 95% CI 2.4 to 3.7), representing a sensitivity of 18% and a specificity of 95%.
Conclusion: The inhospital mortality rate after out-of-hospital, nontraumatic hypotension is high and reproducible. Future research should focus on ED clinical protocols to ensure appropriate resuscitation and investigation of etiology of out-of-hospital hypotension.