CLINICIAN'S CAPSULE
What is known about the topic?
Extracorporeal cardiopulmonary resuscitation (ECPR) is an emerging resuscitative modality that could improve survival for ED patients with refractory cardiac arrest.
What did this study ask?
What proportion of refractory cardiac arrests would be eligible for ECPR at our center, based on published inclusion/exclusion criteria?
What did this study find?
This 2-year health records review found that a small but meaningful number of ED patients could be eligible for ECPR.
Why does this study matter to clinicians?
Institutions need a clear picture of the potential impact for ED and hospital operations before initiation of ECPR programs.
INTRODUCTION
Cardiac arrests have historically poor outcomes. For out-of-hospital cardiac arrest, the inevitable delay to appropriate treatment and limitations of conventional treatment results in survival rates of less than 10%.Reference Brooks, Schmicker and Rea1–Reference Bellezzo, Shinar and Davis4 However, a novel resuscitative therapy known as extracorporeal cardiopulmonary resuscitation (ECPR) has recently shown promising results in patients with refractory cardiac arrest.Reference Bellezzo, Shinar and Davis4,Reference Yannopoulos, Bartos and Martin5 ECPR is a form of extracorporeal cardiopulmonary support used to resuscitate the failing circulatory system in cases of refractory cardiac arrest or cardiogenic shock. While still in its infancy, the use of ECPR has been described in numerous centers with impressive results in appropriately selected patients; namely, neurologically intact survival in excess of 30% for refractory out-of-hospital cardiac arrest.Reference Bellezzo, Shinar and Davis4–Reference Stub, Bernard and Pellegrino6 Despite this widespread interest, there exists many barriers to the implementation of what can be considered a low volume and resource-intensive endeavor. Therefore, the aim of this study is to assess the potential impact of an ECPR program in the context of a high-volume, tertiary care, academic emergency department that currently partners with cardiac care services in a regionalized ST-elevation myocardial infarction (STEMI) and post-return of spontaneous circulation (ROSC) care program. Specifically, we sought to retrospectively review the characteristics of cardiac arrest patients who presented to our ED and assess if they would meet criteria for ECPR according to current literature.Reference Yannopoulos, Bartos and Martin5
METHODS
Study design and settings
This is a retrospective health records review of selected patients who presented with out-of-hospital cardiac arrest or ROSC to either campus of our tertiary-care academic hospital during a 2-year period from January 1, 2015, to December 31, 2016. This investigation was approved by the Ottawa Health Science Network Research Ethics Board and conducted at The Ottawa Hospital.
Selection of participants
We abstracted data from the health records of all patients aged 18 to 75 years within the defined 2-year time period who presented to our ED with a chief complaint of cardiac arrest, vital signs absent, or ROSC, or an ED discharge diagnosis of cardiac arrest, ROSC, or death. Based on our review of existing ECPR literature, we created an extensive list of characteristics to extract from charts that could be used to extrapolate relevant prognostic information. Exclusion criteria included: traumatic cardiac arrest etiology, no true arresting rhythm identified at any point, and transfers to our institution from a peripheral ED.
Establishment of ECPR criteria
We performed a scoping review of existing ECPR literature to define a priori two sets of liberal and restrictive criteria to later apply to our cohort for possible initiation of ECPR. These criteria (see Figure 1), were selected based on either their association with survival and good neurological outcome, or their recurring use as inclusion/exclusion criteria in the ECPR literature. Witnessed cardiac arrest, CPR within 10 minutes,Reference Yannopoulos, Bartos and Martin5–Reference Johnson, Acker and Hsu7 immediate bystander CPRReference Bellezzo, Shinar and Davis4 and < 60 minutes prehospital time were shown to be predictors of good outcome (p value ≤ 0.05).
Figure 1. ECPR eligibility criteria. *Favorable pre-morbid status was defined as an absence of significant pre-arrest morbidities, including severe chronic obstructive pulmonary disease (COPD), severe heart disease, dependency, life expectancy < 1 year, and terminal cancer. Note: Reported percentages reference proportion of refractory out-of-hospital cardiac arrest that would have been ECPR-eligible by these criteria. CA, cardiac arrest; VT/VF, ventricular tachycardia/ventricular fibrillation.
A shockable recorded cardiac arrest rhythm was selected based on the findings of Yannopoulos et al.,Reference Yannopoulos, Bartos and Martin5 who used only patients meeting these criteria for their observational study, citing the overwhelming majority (>80%) of cardiac arrest survivors emerging from this group.Reference Yannopoulos, Bartos and Martin5 Nonasystole rhythms have been described in other studiesReference Bellezzo, Shinar and Davis4 and may have a role in more liberal extracorporeal life support programs (i.e., massive pulmonary embolism).
The presence of a major pre-existing medical co-morbidity was an almost universally used exclusion criteria in the ECPR literature.Reference Stub, Bernard and Pellegrino6,Reference Sakamoto, Morimura and Nagao9,Reference Grunau, Scheuermeyer and Stub10 As such, the absence of such pre-existing co-morbidities, including severe COPD, severe heart disease, functional dependency, life expectancy < 1 year, and terminal cancer, was selected as both a liberal and restrictive criteria under “favorable premorbid status.”
The categorization of these criteria as either “liberal” or “restrictive,” was done by determining which criteria corresponded to higher or lower numbers of cardiac arrest cases, based on the results of the scoping review.Reference Yannopoulos, Bartos and Martin5–Reference Johnson, Acker and Hsu7
Data collection and quality control
Charts were manually reviewed using our hospital electronic medical record which archives lab data, diagnostic imaging, scans of handwritten paper charts and dictated notes. The chart review was conducted by one of the principal investigators (L.M.), with 20% of charts randomly reviewed by a second investigator (G.M.) to ensure calibration. Any discrepancies or ambiguities found in the review were resolved by consensus between both investigators.
Analysis
Data were deidentified and entered into a spreadsheet (Microsoft Excel, 2013). Simple descriptive statistics were performed to identify eligible candidates.
RESULTS
During the study period, 220 patients with out-of-hospital cardiac arrest in the selected age group were brought to our EDs (Supplemental Online Appendix B). A total of 33 patients were excluded from the study based on criteria identified above: 32 for traumatic cardiac arrest, and 1 patient who was determined to have never suffered an arresting rhythm. A further 105 patients achieved ROSC. Characteristics of all out-of-hospital cardiac arrest patients included in the analysis are described in the Supplemental Online Appendix A.
We determined that of the remaining 82 patients with refractory out-of-hospital cardiac arrest, all of whom died, two-thirds (65.9%) had favorable premorbid status. Applying the liberal and restrictive eligibility criteria to our study population, 33 and 5 patients, respectively, would have been candidates for ECPR (Supplemental Online Appendix C). This translates to an estimated 0.2–1.4 patients per month that would have potentially qualified for ECPR at our institution.
DISCUSSION
This study was designed to evaluate the feasibility of ECPR at our institution by first assessing the existing volume of out-of-hospital cardiac arrest patients. In our center, 3 to 18% of out-of-hospital cardiac arrest patients brought to our ED per year appear to meet criteria for ECPR, depending on the strictness of inclusion criteria that our center may choose to implement. Our findings suggest that a target population for this novel therapy does exist in our region, although it remains small. These data may help illustrate an anticipated volume for similar medium-sized academic centers.
Limited comparative data exist for these rates, although our estimated numbers (5–33 patients out of an out-of-hospital cardiac arrest pool of 187 patients) are aligned with the registry study by Grunau et al.,Reference Grunau, Scheuermeyer and Stub10 which found that approximately 10% of prehospital out-of-hospital cardiac arrest patients would be eligible for ECPR based on their selection criteria. In planning implementation at our center, we expect that it will be prudent to adopt somewhat more restrictive inclusion criteria (Figure 1) initially, to optimize systems and processes, and foster institutional buy-in.
The main limitation to our study was the quality of records used. As the study was retrospective, the largely handwritten records reviewed had, at times, missing or incongruous variables that were of interest to our study. As such, the true number of eligible ECPR candidates might be underestimated. Furthermore, as a single-institution study, our data do not include potential candidates within a reasonable geographic radius who were brought to community hospitals. The sample population may also be biased by prehospital termination-of-resuscitation (TOR) criteria used in conjunction with on-line medical control: either biasing toward patients with a higher potential survivability (those not terminated in the field), or by increasing “low-flow” times for patients who may have otherwise been good ECPR candidates. This highlights a need for system-level protocols to be developed, such as the load-and-go criteria. Finally, our study is limited by the retrospective application of criteria, which may prove more difficult to ascertain prospectively for an unknown patient coming into the ED in arrest.
CONCLUSION
We found that 6–40% of refractory out-of-hospital cardiac arrest patients presenting to a tertiary care ED would have been potential ECPR candidates, translating to 0.2–1.4 patients per month. A majority of patients brought to our EDs in cardiac arrest had at least some favourable characteristics. These findings suggest that there appears to a distinct, although small, population of cardiac arrest patients that would be eligible for an ED ECPR program at our institution.
Supplemental material
The supplemental material for this article can be found at https://doi.org/10.1017/cem.2019.472.
Competing interests
None declared.
