Selected Topics: Prehospital Care
Mandated 30-minute Scene Time Interval Correlates With Improved Return of Spontaneous Circulation at Emergency Department Arrival: A Before and After Study

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Abstract

Background

Conflicting ideas exist about whether or not Emergency Medical Service (EMS) personnel should treat a cardiac arrest on scene or transport immediately.

Objective

Our aim was to examine patient outcomes before and after an urban EMS system implemented a protocol change mandating a 30-min scene time interval (STI) for out-of-hospital cardiac arrest (OHCA).

Methods

This was a retrospective, single-center, observational study of OHCA patients before and after an EMS protocol change mandating resuscitation on scene. Data were retrieved from an EMS cardiac arrest database for all adults with non-traumatic OHCA between January 2015 and August 2016. Descriptive statistics were used to summarize the study population, and a regression model was used to determine the associations of the protocol with the return of spontaneous circulation (ROSC).

Results

A total of 633 patients were included in the study population, which was primarily male (61.3%) with a mean age of 65 years. After the 30-min STI was implemented, ROSC from OHCA increased to 40.1% of cases compared to 27.3% before the protocol change (p = 0.001; 95% confidence interval [CI] 0.053–0.203). The STI increased from 19 min 23 s to 29 min 40 s in the pre and post periods, respectively (p < 0.001). Regression indicated that the protocol change was independently associated with an improved chance of ROSC (OR 1.81; 95% CI 1.23–2.64).

Conclusions

A protocol change mandating a 30-min STI in OHCA correlated with increased STI and increased ROSC. While increased ROSC may not always equate with positive neurologic outcome, logistic regression indicated that the protocol change was independently associated with improved ROSC at emergency department arrival.

Introduction

Out-of-hospital cardiac arrest (OHCA) is the most common form of cardiac arrest, with more than 325,000 cases treated by emergency medical services (EMS) in the United States annually. Despite a steady increase in survival over the last 10 years, the chance of survival to hospital discharge after OHCA is still low, at approximately 10% 1, 2. Recent efforts have focused on strategies to improve not only overall survival but also good neurologic function. Several factors that influence outcomes in OHCA and consistently show improved return of spontaneous circulation (ROSC) and good neurologic outcome include non-traumatic etiology, witnessed arrest, delivery of high-quality cardiopulmonary resuscitation (CPR), short time to bystander or EMS response, or presence of a shockable rhythm 1, 2, 3, 4, 5, 6, 7. It is not clear, however, to what extent the time on scene with EMS can affect survival.

Conflicting ideas and data exist on the “scoop and go” vs. “stay and play” methods. Advocates for longer scene time interval (STI) state that crews should stay on scene to provide high-quality CPR until either ROSC occurs or they terminate the resuscitation. Simulated models have shown that the quality of CPR decreases during transport compared to on scene, which could potentially negatively affect ROSC 8, 9, 10, 11. In analyses of real resuscitations, only small variability or no difference was found in CPR quality based on location, however, these studies included continuous CPR feedback, which is not available in many EMS systems 12, 13, 14. Additionally, while it consistently shows a decrease in transport times, emergent transport (i.e., lights and sirens) has been regarded as dangerous and can increase the risk of ambulance crashes (15).

On the other hand, advocates for shorter STI state that crews should transport immediately to the emergency department, as data show potential harm for patients who have aggressive advanced prehospital maneuvers, for example, airway placement (16). To date, the best available evidence supports an intermediate STI (8–16 min), however, these data are primarily from areas where advanced life support (ALS) teams may not necessarily be readily or consistently available and overall survival rates are very low (17).

There is a paucity of evidence suggesting an appropriate STI length in urban environments where EMS can provide advanced care in the field. Therefore, the purpose of this observational study was to examine patient outcomes before and after an urban EMS system implemented a protocol change to increase the STI for OHCA.

Section snippets

Materials and Methods

This study was approved by the University of Arkansas for Medical Sciences (UAMS) Institutional Review Board.

This was a pre–post, retrospective, single-service, observational study of cardiac arrest patients. Metropolitan Emergency Medical Services (MEMS) is the only public ambulance service that serves the Little Rock, AR area. For OHCA, an ALS team consisting of at least one paramedic is dispatched to every scene. As part of routine quality improvement (QI), electronic run sheets on all

Characteristics of Study Subjects

A total of 977 OHCAs were recorded during the study period. Three hundred and forty-four patients were excluded due to age < 18 years, traumatic arrest, or missing data. The remaining sample consisted of 633 patients. Figure 1 presents inclusion and exclusion flow chart for the study population.

Table 1 presents the descriptive statistics for the sample overall and dichotomized by the pre- and post-study period. The study sample consists of 61.3% male and a mean age of 64.6 years (standard

Discussion

This goal of this study was to determine if there was a benefit to spending more time on scene during OHCA vs. using crew discretion on the decision of when to transport to the ED. We used data from a metropolitan EMS database to investigate and compare ROSC in cardiac arrest patients before and after a protocol change mandating a 30-min STI. Our results demonstrated that not only was there an associated increase in scene time with the protocol change, but there was also an independent positive

Conclusions

Our study found that with a protocol change mandating a 30-min STI in OHCA, our scene times increased as well as the rate of ROSC on arrival to the ED. Also, the protocol change was independently associated with improved ROSC in our patient population. Without neurologic outcomes data it is difficult to make recommendations on the most effective STI for OHCA. More studies are needed assessing the functional status of patients who have longer scene times after cardiac arrest.

Article Summary

1.Why is this topic important?

  1. Rates of return of

References (21)

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Cited by (3)

  • Evaluation of optimal scene time interval for out-of-hospital cardiac arrest using a deep neural network

    2023, American Journal of Emergency Medicine
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    The scene time interval (STI) is defined as the time elapsed from the ambulance's arrival at the scene to its departure to the emergency department. Recent studies have reported that an increase in STI was associated with patient outcomes [2,12,13]. Deep learning approaches have recently shown advanced performance in critical care such as hospital cardiac arrest prediction, assessment of severity, and OHCA outcome prediction [14-18] A deep-learning-based early warning system to identify patients at risk of in-hospital cardiac arrest was implemented in a multicenter study, achieving high sensitivity and a low false-alarm rate [18].

  • Outcome in refractory out-of-hospital cardiac arrest before and after implementation of an ECPR protocol

    2021, Resuscitation
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    The change was not statistically significant, but it is worrying if a reduction in number is due to a shift in focus towards early evacuation to arrive at hospital in time for ECPR. Eastin and colleagues demonstrated that changing focus from early transport and mandating EMS personnel to perform longer on-scene ALS, from 19 to 30 minutes, increased the rate of ROSC from 27% to 40%.28 Another study found that intra-arrest transport was found to be associated with a lower probability of survival and a worse neurologic outcome.29

Meetings: Lightening Oral Abstract, Society of Academic Emergency Medicine, 2017.

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