Pre-Admission Characteristics Predicting an Adverse Outcome in Asthma Exacerbation

Abstract

Background: Pre-admission clinical parameters predicting an adverse outcome in subjects presenting to the emergency department (ED) with acute asthma exacerbation, as well as their cutoff levels, are not well defined. This study aims to identify these parameters. In asthma patients, clinical parameters associated with adverse events are well known. However when these patients present with an acute asthma attack, the pre-admission clinical findings associated with an impending inhospital respiratory failure, as well as their cutoff levels, are still lacking. Our study suggests that O2 saturation of 94 percent and lower, PaCO2 levels above 51.5 mmHg and a history of previous hospitalizations due to asthma exacerbations are independent predictors of in-hospital adverse outcome of the index event. Methods: Records of subjects with an ED diagnosis code for asthma were retrospectively reviewed for 32 clinical parameters, including: demographics, symptoms, asthma-related history, current treatment, risk factors, clinical, laboratory and radiographic findings. These parameters were analyzed for their association with an adverse outcome defined as intensive care unit admission, intubation or death. Results: Files of 266 subjects presented to the Rambam ED with acute asthma attack between 01/01/2012 and 12/31/2015 were analyzed. Adverse outcome was recorded in 22. Parameters associated with adverse outcome in a univariate analysis included: routine use of short-acting beta agonists, recent corticosteroids prescription, and prior asthma related admissions, previous mechanical ventilation, low O2 saturation, leukocytosis, respiratory acidosis and abnormal chest X-ray. In a multivariate analysis, the significant independent predictors for in-hospital adverse outcome were: elevated PaCO2 (95% CI 1.002-1.075; p=0.038), low O2 saturation (95% CI 0.662-0.845; p=0.034) and previous hospital admissions (95% CI 1.108-13.440; p <0.001). Cutoff values were 94% for O2 saturation and 51.5 mmHg for PaCO2 levels. Conclusions: The current study suggests that O2 saturation below 94 percent, PaCO2 levels above 51.5 mmHg and prior asthma related admissions are independent predictors of in-hospital adverse outcome. These subjects should be managed in a more intensive manner in the ED.