Clinical paperEpidemiology and outcome of emergency medical service witnessed out-of-hospital-cardiac arrest by prodromal symptom: Nationwide observational study
Introduction
Out-of-hospital cardiac arrest (OHCA) is a major public health burden around the world.1 Although the concept of chain of survival was introduced to improve the outcome of OHCA, the survival rate still remains low.2 One of the reasons for low survival is that cardiac arrest occurs suddenly and little is known about an individual’s specific condition before it occurs; thus, it cannot be prepared for.3
A victim of emergency medical service– (EMS-) witnessed OHCA is not in cardiac arrest when an emergency medical technician (EMT) arrives, but progresses to cardiac arrest during transportation to the hospital.4, 5 EMS-witnessed OHCA makes up about 7–14% of total OHCA, and it has a higher survival rate than other OHCA5, 6, 7, 8 because EMT can immediately treat the patient and the time interval from collapse to the start of cardiopulmonary resuscitation (CPR) and defibrillation is short.6, 9 This characteristic makes EMS-witnessed OHCA a valuable opportunity to gain information about the pre-arrest situation of OHCA.3, 10 Therefore, studies on EMS-witnessed OHCA were conducted to learn of its characteristics and the prodromal symptoms of cardiac arrest.10, 11
The prevalence of prodromal symptoms in cardiac arrest has been reported differently in studies.5, 10, 11 Although about 50% of OHCA with cardiac etiology had symptoms of acute myocardial infarction (AMI), EMS-witnessed OHCA had 80–90% of prodromal symptoms.5, 11, 12 There are also variations of prognosis according to the prodromal symptom of OHCA. A Japanese study reported that patients with prodromal symptoms had better outcomes than those without prodromal symptoms.10 In a North American study, patients with chest pain had a higher survival rate, but patients with dyspnea or unconsciousness had a poorer prognosis.5 The typical symptoms of AMI, such as chest pain, are relatively well known to the public; however, unusual symptoms such as dyspnea and vomiting are less familiar and it can be reasons to delay activating EMS.12 Despite the importance of early EMS activation, there are still few studies on prodromal symptoms of OHCA, especially for non-cardiac etiology.13 It is still unclear what prodromal symptoms appear before cardiac arrest and whether these warning symptoms have prognostic value according to the etiology of OHCA. Cardiac arrest worsen rapidly once it occurs.14, 15 If a patient or bystander knows of the prodromal symptoms and activates EMS earlier, EMT might be able to avoid OHCA or EMT earns time for treatment and the proportion of EMS-witnessed OHCA, which has a higher survival rate, can be increased.9, 10 EMT also can prepare for high-risk patients based on knowledge of prodromal symptoms.
The aim of this study was to investigate the epidemiologic characteristics and outcomes of EMS-witnessed OHCA, focusing on its prodromal symptoms. We also examined the time from EMS scene arrival to occurrence of cardiac arrest according to the symptoms to investigate the time window of EMT to avoid OHCA or to prepare for OHCA.
Section snippets
Study setting
In Korea, the National Fire Agency (NFA) operates EMS exclusively. There are four level of EMS personnel in Korean NFA: level 1 EMT, level 2 EMT, basic level EMT, and nurse. The level 1 EMT are graduates of emergency rescue department in the university and functioned as US EMT-intermediate level (EMT-I). They can provide IV fluid administration and apply advance airway (supraglottic airway and endotracheal intubation) to the OHCA patients, following the EMS CPR protocol.2 However, drug
Study population
Of the 171,534 EMS-assessed OHCAs during the study period (The incidence of OHCA per 100,000 population per year was 56.2), a total of 12,969 patients were included in the study population: 9361 cases of cardiac etiology and 3424 cases of non-cardiac etiology (Fig. 1).
Demographic findings
Among 12,969 EMS-witnessed OHCAs, 7723 cases (59.5%) had no prodromal symptoms, 1987 cases (15.3%) had neurologic symptoms, 1410 cases (10.9%) had respiratory symptoms, 505 cases (3.9%) had cardiac symptoms, and 541 cases (4.2%)
Discussion
This study investigated the characteristics of EMS-witnessed OHCA according to its prodromal symptoms using the national OHCA database. The numbers showed that 37.6% of OHCA with cardiac etiology had prodromal symptoms and 48.2% of non-cardiac etiology had prodromal symptoms. In cardiac etiology, patients with cardiac symptoms had the best survival outcome, while in non-cardiac etiology, patients with respiratory symptoms had the best survival outcome. In EMS-witnessed OHCA, most cardiac
Conclusion
Forty percent of the EMS-witnessed OHCA patients had prodromal symptoms before cardiac arrest. Of the cardiac etiology patients, the patients with cardiac symptoms had the best rate of survival to discharge and good neurological outcome compared with other symptom groups. Of the non-cardiac etiology patients, those with respiratory symptoms had the best survival outcome. Since most EMS-witnessed OHCA occurred in 5–9 min from EMS arrival, promoting awareness of prodromal symptoms is needed to
Funding acknowledgement
This study was supported by the National Fire Agency of Korea and the Korea Centers for Disease Control and Prevention (KCDC).
Conflict of interest
All authors have no other relationships/conditions/circumstances that present potential conflict of interest.
CRediT authorship contribution statement
Sun Young Lee: Data curation, Formal analysis, Writing - original draft. Kyoung Jun Song: Conceptualization, Investigation, Writing - review & editing, Supervision. Sang Do Shin: Project administration, Conceptualization, Supervision. Ki Jeong Hong: Data curation, Writing - review & editing.
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