Abstract
Ambulance response time is a prognostic factor for out-of-hospital cardiac arrest (OHCA), but the impact of ambulance response time under different situations remains unclear. We evaluated the threshold of ambulance response time for predicting survival to hospital discharge for patients with OHCA. A retrospective observational analysis was conducted using the emergency medical service (EMS) database (January 2015 to December 2019). Prehospital factors, underlying diseases, and OHCA outcomes were assessed. Receiver operating characteristic (ROC) curve analysis with Youden Index was performed to calculate optimal cut-off values for ambulance response time that predicted survival to hospital discharge. In all, 6742 cases of adult OHCA were analyzed. After adjustment for confounding factors, age (odds ratio [OR] = 0.983, 95% confidence interval [CI]: 0.975–0.992, p < 0.001), witness (OR = 3.022, 95% CI: 2.014–4.534, p < 0.001), public location (OR = 2.797, 95% CI: 2.062–3.793, p < 0.001), bystander cardiopulmonary resuscitation (CPR, OR = 1.363, 95% CI: 1.009–1.841, p=0.044), EMT-paramedic response (EMT-P, OR = 1.713, 95% CI: 1.282–2.290, p < 0.001), and prehospital defibrillation using an automated external defibrillator ([AED] OR = 3.984, 95% CI: 2.920–5.435, p < 0.001) were statistically and significantly associated with survival to hospital discharge. The cut-off value was 6.2 min. If the location of OHCA was a public place or bystander CPR was provided, the threshold was prolonged to 7.2 min and 6.3 min, respectively. In the absence of a witness, EMT-P, or AED, the threshold was reduced to 4.2, 5, and 5 min, respectively. The adjusted OR of EMS response time for survival to hospital discharge was 1.217 (per minute shorter, CI: 1.140–1299, p < 0.001) and 1.992 (<6.2 min, 95% CI: 1.496–2.653, p < 0.001). The optimal response time threshold for survival to hospital discharge was 6.2 min. In the case of OHCA in public areas or with bystander CPR, the threshold was prolonged, and without witness, the optimal response time threshold was shortened.
Highlights
Out-of-hospital cardiac arrest (OHCA) is defined as the termination of cardiac mechanical activity and subsequent cessation of blood circulation in a patient outside of a hospital [1]
Lai et al found that cardiac comorbidities might be predictors of improved survival [11]. ese results suggest that cardiopulmonary resuscitation (CPR)/automated external defibrillators (AEDs) might be more effective for cardiogenic OHCA than for non-cardiogenic OHCA
After adjusting for confounding factors, age (1 additional year, odds ratio (OR) 0.983, 95% confidence interval (CI): 0.975–0.992, p < 0.001), emergency medical service (EMS) response time (1 minute shorter, OR 1.217, 95% CI: 1.140–1.299, p < 0.001), witness, public location, bystander CPR, emergency medical technicians (EMTs)-P, and prehospital defibrillation by AED were statistically and significantly associated with survival to hospital discharge
Summary
Out-of-hospital cardiac arrest (OHCA) is defined as the termination of cardiac mechanical activity and subsequent cessation of blood circulation in a patient outside of a hospital [1]. Despite improvements in prehospital management and the use of automated external defibrillators (AEDs), only 10%–20% of the patients who experience OHCA survive to hospital discharge [2, 3]. Many prehospital factors might influence the outcomes of OHCA, such as location of OHCA, witnessed arrest, bystander cardiopulmonary resuscitation (CPR), initial cardiac rhythm, and level of post-resuscitation care [3,4,5,6]. EMS response time is a key prognostic factor for OHCA, and many studies have shown that short EMS response time is associated with a high probability of survival to hospital discharge and favorable neurologic outcomes [2, 7, 8]. The threshold of EMS response time for survival to hospital discharge after OHCA remains unclear. Patient-level differences and conditions of OHCA might influence the response time threshold. Ono et al found that bystander cardiopulmonary resuscitation (CPR) might prolong the response time threshold from 6.5 min to 7.5 min [7]
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