Associations Between Crowding and Ten-Day Mortality Among Patients Allocated Lower Triage Acuity Levels Without Need of Acute Hospital Care on Departure From the Emergency Department

Study objective: We describe the association between emergency department (ED) crowding and 10-day mortality for patients triaged to lower acuity levels at ED arrival and without need of acute hospital care on ED departure. Methods: This was a registry study based on ED visits with all patients aged 18 years or older, with triage acuity levels 3 to 5, and without need of acute hospital care on ED departure during 2009 to 2016 (n=705,699). The sample was divided into patients surviving (n=705,076) or dying (n=623) within 10 days. Variables concerning patient characteristics and measures of ED crowding (mean length of stay and ED occupancy ratio) were extracted from the hospital's electronic health records. ED length of stay per ED visit was estimated by the average length of stay for all patients who presented to the ED during the same day and shift and with the same acuity level. The 10-day mortality after ED discharge was used as the outcome measure. Multivariable logistic regression analyses were conducted. Results: The 10-day mortality rate was 0.09% (n=623). The event group had larger proportions of patients aged 80 years or older (51.4% versus 7.7%) and triaged with acuity level 3 (63.3% versus 35.6%), and greater comorbidity (age-combined Charlson comorbidity index median interquartile range 6 versus 0). We observed an increased 10-day mortality for patients with a mean ED length of stay greater than or equal to 8 hours versus less than 2 hours (adjusted odds ratio 5.86; 95% confidence interval [CI] 2.15 to 15.94) and for elevated ED occupancy ratio. Adjusted odds ratios for ED occupancy ratio quartiles 2, 3, and 4 versus quartile 1 were 1.48 (95% CI 1.14 to 1.92), 1.63 (95% CI 1.24 to 2.14), and 1.53 (95% CI 1.15 to 2.03), respectively. Conclusion: Patients assigned to lower triage acuity levels when arriving to the ED and without need of acute hospital care on departure from the ED had higher 10-day mortality when the mean ED length of stay exceeded 8 hours and when ED occupancy ratio increased.