The Outcomes of the Initial Misclassification of Undifferentiated Hypotension in the Emergency Department: A Prospective Observational Study

<b>Background:</b> Managing shock, a life-threatening emergency, is challenging. The influence of the initial misclassification of undifferentiated hypotension (UH) in the emergency department (ED) on patients' outcomes remains uninvestigated. The aim of this study was to investigate whether the initial misclassification of UH in the ED affects patients' clinical outcomes. <b>Materials and Methods:</b> This prospective observational study enrolled 270 non-traumatic adult patients with UH who had visited the ED of National Taiwan University Hospital between July 2020 and January 2022. The patients were divided into same-diagnosis and different-diagnosis groups, depending on the consistency between the initial and final classifications of shock. The outcome was survival to discharge. The clinical variables, management, and outcomes were compared between the groups. <b>Results:</b> A total of 39 of 270 patients (14.4%) were in the different-diagnosis group. Most misclassified patients were initially diagnosed as having hypovolemic shock (HS, <i>n</i> = 29) but finally diagnosed as having distributive shock (DS, <i>n</i> = 28) or cardiogenic shock (<i>n</i> = 1). When compared with the same-diagnosis group, the different-diagnosis group had higher hospitalization (94.9% vs. 81.4%, <i>p</i> = 0.023) but lower ED discharge (5.1% vs. 16.5%, <i>p</i> = 0.046) rates. Logistic regression analysis showed that the HS initially diagnosed was associated with an increased risk of misclassification (odds ratio [OR] = 14.731, 95% confidence interval [CI] = 3.572-60.749, <i>p</i> < 0.001). However, the survival to discharge did not differ between the two groups. DS, when finally diagnosed instead of the initial misclassification, was associated with in-hospital mortality (OR = 0.317, 95%CI = 0.124-0.810, <i>p</i> = 0.016). <b>Conclusions:</b> The misclassification of UH in the ED is not rare, particularly in patients with DS, who are likely to be initially misdiagnosed with HS. Although misclassification may increase hospitalization and decrease ED discharge, it does not affect survival to discharge.