The Systematic Approach for Identification of Cause Among Out-of-hospital Cardiac Arrest Survivors

To identify the classification of OHCA cause, the cause classification of OHCA (CCCA) protocol was established based on previous studies, expert physician's experience and questionnaire of young physicians.

Residents from emergency department of National Taiwan University Hospital participated the program and received the lecture concerning the Utstein's template, the epidemiology of cardiac arrest, interpretation of examinations, and the CCCA protocol. To evaluate the learning effect of the lecture, pre-lecture and post-lecture questionnaire were designed, which included the knowledge for OHCA classification, confidence for correct diagnosis during CPR and after return of spontaneous circulation (ROSC), and the mandatory examinations for cause identification. Confidence level more than 50% was recognized as sufficient to make proper cause identification. The enrolled residents were asked to review the medical records of 3 non-traumatic adult OHCA patients before lecture and identified the OHCA cause by their own without the assist of the CCCA protocol. After lecture, another 3 medical records were reviewed by the participants with the use of the CCAC protocol. The consistency of OHCA cause between young physicians were evaluated before and after lecture, respectively.

To validate the efficiency of the CCCA protocol, these trained residents further identified the arrest cause of 586 non-traumatic adult OHCA patients who survived to ICU admission from January 2015 to July 2021 in NTUH following the established protocol.

The primary outcome was the consistency of OHCA cause between protocolized diagnosis, expert diagnosis and the discharge diagnosis. The diagnosis made by young physicians with protocol defined as protocolized diagnosis. The expert physician is an experienced emergency physicians specialized in both emergency and critical care, who has reviewed the medical records without the assistance of the established CCCA protocol. Expert diagnosis was recognized as diagnosis identified by expert physician. The discharge diagnosis is the major diagnosis related to index cardiac arrest.

Categorical variables are presented as numbers (percentages) and evaluated by the Chi-Squared test. The continuous variables are presented as mean ± standard deviation. The Light's kappa was used to evaluate the consistency of OHCA classification. The value ≤ 0.40 indicates minimal agreement, while value ≥ 0.80 represent strong and almost perfect consistency16-17. The statistical significance was set at p <0.05. All statistical analyses were performed using Statistical Package for Social Sciences Statistics (version 21.0; IBM, Chicago, IL, USA).