Emergency medical services/original researchEffect of Transport Interval on Out-of-Hospital Cardiac Arrest Survival in the OPALS Study: Implications for Triaging Patients to Specialized Cardiac Arrest Centers
Introduction
Despite more than 4 decades of development of sophisticated emergency medical services (EMS) systems, very little is known about the effect of out-of-hospital care on patient outcomes.1, 2, 3, 4, 5 The most dramatic exception to this is the ability to successfully resuscitate victims of sudden cardiac death with timely provision of resuscitative care in the field.6, 7, 8, 9, 10 In fact, survival from out-of-hospital cardiac arrest is so extremely time-sensitive that, if patients do not achieve return of spontaneous circulation before arrival at the hospital, survival is exceptionally rare.11 Survival from out-of-hospital cardiac arrest is so dependent on timeliness and sequencing of specific interventions that, for decades, events occurring in the field were believed to be the only significant determinants of outcome.11, 12, 13, 14, 15, 16, 17 Perhaps this explains why a widespread sense of futility has been identified in the inhospital approach to patients who have return of spontaneous circulation but do not immediately appear to be neurologically and hemodynamically intact. Many patients with return of spontaneous circulation do not receive aggressive postarrest care after arrival at the hospital unless they are alert and relatively stable.18, 19, 20, 21, 22 However, this approach is highly inappropriate, given the results of several recent investigations. In the setting of aggressive postarrest critical care, the initiation of mild therapeutic hypothermia in patients who remained comatose after return of spontaneous circulation has yielded dramatic improvement in the rates of neurologically intact survival.23, 24, 25, 26, 27 With the appearance of hope that such care may have a major effect on outcome for patients with return of spontaneous circulation, the concept of bypassing closer hospitals en route to regional centers that can provide the entire spectrum of interventions and critical care has been suggested.28, 29 However, the potential benefits of triaging patients to more distant regional centers must be weighed against the risks involved in prolonging the time patients spend in the ambulance before arrival at the hospital.
Despite many years of intense investigation of out-of-hospital cardiac arrest, almost nothing is known about whether the amount of time required to transport the patient from the scene to the hospital affects patient outcomes. Without such information, the advisability of triaging patients to regional centers must be questioned. Thus, the objective of this study was to evaluate any potential effect of out-of-hospital transport interval on outcome, using patient data from a very large out-of-hospital cardiac arrest database.
Section snippets
Setting and Selection of Participants
The Ontario Prehospital ALS (OPALS) Study is a multicenter, multisystem, clinical trial evaluating numerous aspects of the effect of providing basic life support (BLS) and advanced life support (ALS) out-of-hospital care to patients presenting with out-of-hospital cardiac arrest. The methodology of the study has been reported in detail.30 The OPALS study was funded by Ontario Ministry of Health and Canadian Health Services Research Foundation.
Methods of Measurement
The cardiac arrest database developed for the study
Characteristics of Study Subjects
The Figure shows the adult out-of-hospital cardiac arrest cases of presumed cardiac origin that were entered into the OPALS database during the study period. Among the 20,695 cases, 1,708 were excluded because they were witnessed by EMS personnel, leaving 18,987 cases eligible for this analysis. Among these patients, 15,559 (81.9%) had complete data, and this cohort composed the overall study group. Patient outcome (the dependent variable) was missing in only 5 cases (0.024%). In the study
Limitations
This investigation has several limitations. First, this was a secondary review. Thus, unidentified confounders may have “masked” an underlying association between transport interval and survival. Despite this, we believe that the size of the database and the fact that the cases were prospectively entered into the study with the intention of specifically identifying the characteristics that affect survival add credence to the findings. Certainly the opposite finding would have been significant.
Discussion
A long history of intense evaluation has shown dramatic variation in the ability of EMS systems to affect survival from out-of-hospital cardiac arrest. In fact, success rates have varied across more than an order of magnitude: from dismal to impressive.6, 7, 8, 35, 36, 37, 38, 39 Until recently, emphasis on the out-of-hospital aspects of post–cardiac arrest care overshadowed discussions about the interventions and critical care provided after arrival at the hospital. This was partially due to
References (69)
- et al.
The National EMS Research Agenda executive summaryEmergency medical services
Ann Emerg Med
(2002) - et al.
Emergency Medical Services Outcomes Project I (EMSOP I): prioritizing conditions for outcomes research
Ann Emerg Med
(1999) The future of emergency care in the US: the Institute of Medicine Subcommittee on Prehospital Emergency Medical Services
Ann Emerg Med
(2006)- et al.
Cardiac arrest and resuscitation: a tale of 29 cities
Ann Emerg Med
(1990) - et al.
Effectiveness of emergency medical services for victims of out-of-hospital cardiac arrest: a meta-analysis
Ann Emerg Med
(1996) - et al.
Cardiocerebral resuscitation improves survival of patients with out-of-hospital cardiac arrest
Am J Med
(2006) - et al.
In-hospital resuscitation following unsuccessful prehospital advanced cardiac life support: “heroic efforts” or an exercise in futility?
Ann Emerg Med
(1988) - et al.
Clinical, electrophysiologic and hemodynamic profile of patients resuscitated from prehospital cardiac arrest
Am J Med
(1980) - et al.
Prognostic indicators of ultimate long-term survival following advanced life support
Ann Emerg Med
(1981) - et al.
Continuation of CPR on admission to emergency department after out-of-hospital cardiac arrest: occurrence, characteristics and outcome
Resuscitation
(1997)
Cardiopulmonary resuscitation: historical perspective to recent investigations
Am Heart J
Post-resuscitation care: is it the missing link in the chain of survival?
Resuscitation
Cardiopulmonary resuscitation of adults in the hospital: a report of 14720 cardiac arrests from the National Registry of Cardiopulmonary Resuscitation
Resuscitation
Assessment of neurological prognosis in comatose survivors of cardiac arrest
Lancet
Post resuscitation care: what are the therapeutic alternatives and what do we know?
Resuscitation
In-hospital factors associated with improved outcome after out-of-hospital cardiac arrest: a comparison between four regions in Norway
Resuscitation
Is hospital care of major importance for outcome after out-of-hospital cardiac arrest?experience acquired from patients with out-of-hospital cardiac arrest resuscitated by the same emergency medical service and admitted to one of two hospitals over a 16-year period in the municipality of Goteborg
Resuscitation
The feasibility of a regional cardiac arrest receiving system
Resuscitation
The Ontario Prehospital Advance Life Support (OPALS) Study: rationale and methodology for cardiac arrest patients
Ann Emerg Med
Prospective validation of a new model for evaluating EMS systems by in-field observation of specific time intervals in prehospital care
Ann Emerg Med
Cardiac Arrest Resuscitation Evaluation in Los Angeles: CARE-LA
Ann Emerg Med
Outcome of CPR in a large metropolitan area—where are the survivors?
Ann Emerg Med
An outcome study of out-of-hospital cardiac arrest using the Utstein template—a Japanese experience
Resuscitation
Major differences in 1-month survival between hospitals in Sweden among initial survivors of out-of-hospital cardiac arrest
Resuscitation
Systematic review of early prediction of poor outcome in anoxic-ischaemic coma
Lancet
Efficacy of therapeutic hypothermia after out-of-hospital cardiac arrest due to ventricular fibrillation
Resuscitation
Induced hypothermia is underused after resuscitation from cardiac arrest: a current practice survey
Resuscitation
Impact of percutaneous coronary intervention or coronary artery bypass grafting on outcome after nonfatal cardiac arrest outside the hospital
Am J Cardiol
Implementation of a standardized treatment protocol for post resuscitation care after out-of-hospital cardiac arrest
Resuscitation
Reversible myocardial dysfunction after cardiopulmonary resuscitation
Resuscitation
Improved survival after cardiac arrest using emergent autopriming percutaneous cardiopulmonary support
Ann Thorac Surg
Systematic review of percutaneous cardiopulmonary bypass for cardiac arrest or cardiogenic shock states
Resuscitation
Cardiopulmonary cerebral resuscitation using emergency cardiopulmonary bypass, coronary reperfusion therapy and mild hypothermia in patients with cardiac arrest outside the hospital
J Am Coll Cardiol
Regional trauma system design: critical concepts
Am J Surg
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Association between coronary angiography with or without percutaneous coronary intervention and outcomes after out-of-hospital cardiac arrest
2018, ResuscitationCitation Excerpt :About 100 EMS agencies and 40 Cardiac Receiving Centers (CRCs) responding to approximately 80% of the Arizona’s population voluntarily participated in the state-sponsored Save Hearts in Arizona Registry and Education (SHARE) Program during the study period. SHARE has been described previously [10–14]. In order to be recognized as a CRC, a hospital must have: 1) primary 24/7 PCI capability with a protocol including calling cardiology for OHCA, 2) a dedicated TTM protocol for OHCAs that remain comatose, 3) an evidence-based termination of resuscitation protocol which includes a 72-h moratorium on termination of care for patients receiving TTM, and 4) commitment to on-going data submission for all OHCA patients (www.azshare.gov).
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Supervising editor: Donald M. Yealy, MD.
Author contributions: DWS, IGS, JM, JD, and GAW conceived the OPALS study, designed the original trial, obtained research funding, and supervised the conduct of the trial and data collection. All authors made substantial contributions to the conception and design of this secondary analysis and analyzed the meaning, conclusions, and limitations of the results. MDB and GAW provided statistical advice, and MDB analyzed the data and served as the statistical consultant. DWS drafted the article, and all authors contributed substantially to its revision. DWS takes responsibility for the paper as a whole.
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement. Funded by Ontario Ministry of Health and Canadian Health Services Research Foundation.
Publication date: Available online January 23, 2009.
Reprints not available from the authors.