Importance of respiratory rate for the prediction of clinical deterioration after emergency department discharge: a single-center, case-control study

Aim: The purpose of the present study was to investigate the predictors of clinical deterioration soon after emergency department (ED) discharge. Methods: We undertook a case-control study using the ED database of the Nagano Municipal Hospital (Nagano, Japan) from January 2012 to December 2013. We selected adult patients with medical conditions who revisited the ED with deterioration within 2 days of ED discharge (deterioration group). The deterioration group was compared with a control group. Results: During the study period, 15,724 adult medical patients were discharged from the ED. Of these, 170 patients revisited the ED because of clinical deterioration within 2 days. Among the initial vital signs, respiratory rate was less frequently recorded than other vital signs (P < 0.001 versus all other vital signs in each group). The frequency of recording each vital sign did not differ significantly between the groups. Overall, patients in the deterioration group had significantly higher respiratory rates than those in the control group (21 5/min versus 18 +/- 5/min, respectively; P = 0.002). A binary logistic regression analysis revealed that respiratory rate was an independent risk factor for clinical deterioration (unadjusted odds ratio, 1.15; 95% confidence interval, 1.04-1.26; adjusted odds ratio, 1.15; 95% confidence interval, 1.01-1.29). Conclusions: An increased respiratory rate is a predictor of early clinical deterioration after ED discharge. Vital signs, especially respiratory rate, should be carefully evaluated when making decisions about patient disposition in the ED.