Impact of Expanding the Prehospital Stroke Bypass Time Window in a Large Geographic Region
Background and Purpose—The Ontario Acute Stroke Medical Redirect Paramedic Protocol (ASMRPP) was revised to allow paramedics to bypass to designated stroke centers if total transport time would be <2 hours and total time from symptom onset <3.5 hours. We sought to evaluate the impact and safety of implementing the Revised ASMRPP.
Methods—We conducted a 12-month implementation study involving prehospital patients presenting with possible stroke symptoms. A total of 1317 basic and advanced life support paramedics, of 9 land services in 10 rural counties and 5 cities, used the Revised ASMRPP to take appropriate patients directly to 6 designated stroke centers.
Results—We enrolled 1277 patients with 98.8% paramedic compliance in form completion. Of these, 755 (61.2%) met the redirect criteria and had these characteristics: mean age 72.1 (range 16–101), male 51.1%, mean time scene to hospital 16.7 minutes (range 0–92). Paramedics demonstrated excellent interobserver agreement (κ, 0.94; 95% confidence interval, 0.91–0.96) and 97.9% accuracy in interpretation of the Revised ASMRPP. Prehospital adverse events occurred in 14.7% of patients, but few were life-threatening. Overall, 71.4% of 755 cases had a stroke code activated at the hospital and 23.2% received thrombolysis. For the 189 potential stroke patients picked up in 1 city, the ASMRPP classified thrombolysis administration with sensitivity 100% and specificity 37.3% and a final diagnosis of stroke, with sensitivity 86.1% and specificity 41.9%.
Conclusions—In a large urban–rural area with 9 paramedic services, we demonstrated accurate, safe, and effective implementation of the Revised ASMRPP. These revisions will allow more patients with stroke to benefit from early treatment.
Stroke is a leading cause of death and morbidity in Canada and elsewhere.1–3 The effectiveness of thrombolysis declines quickly with time, emphasizing the importance of rapid identification and transport of patients by paramedic services to a stroke center.4 The Canadian province of Ontario (population 13.9 million) formalized the Ontario Stroke Strategy in 2001 by designating stroke centers, which are responsible for developing regional stroke plans.5,6 Paramedic services play a pivotal role in ensuring that the patients with stroke have timely access to stroke centers,7 and in 2004, the original Ontario Revised Acute Stroke Medical Redirect Paramedic Protocol (ASMRPP) was implemented. This tool authorized paramedics to bypass local hospitals in favor of stroke centers if the patient fits the criteria outlined on the Paramedic Prompt Card.6 Research in Ontario and elsewhere has shown that paramedics’ diagnostic accuracy for stroke has increased from 61%8 to 79% to 97% using a stroke screening tool,9–12 that the Ontario ASMRPP criteria have a high positive predictive value,13 and that prehospital triage has led to improved access to thrombolysis.14–16
In 2008, the Canadian Best Practice Recommendations for Stroke Care extended the window for thrombolytic treatment from 3 to 4.5 hours.17 In response to these guidelines and other research, Ontario made many revisions to the ASMRPP in 2011: (1) changing the list of symptoms to read unilateral facial droop instead of simply facial droop and (2) the time from a clearly determined time of symptom onset to arrival at a designated stroke center was increased to 3.5 hours from 2 hours. Exclusions for transport under the protocol were also revised: (1) a 2-hour maximum paramedic transport time to reduce the risk of complications or deterioration during transport, (2) the minimum allowable serum glucose level was reduced to 3.0 mmol/L from 4.0 mmol/L, and (3) if stroke symptoms resolve before paramedic arrival or assessment, the patient is not eligible for transport to a stroke center. These changes are summarized in the revised Ontario Paramedic Prompt Card (Figure 1).18
The overall goal of this study was to evaluate the impact and effectiveness of implementing the Revised ASMRPP and Paramedic Prompt Card within a large geographic region and its 9 urban and rural paramedic services. Specifically, we wished to evaluate the accuracy of the Revised ASMRPP criteria for screening of acute stroke patients for medical redirect to a stroke center by paramedics. We also wished to evaluate safety with regards to the frequency and severity of adverse patient outcomes during transport, interrater reliability of paramedic interpretation of the Paramedic Prompt Card criteria, and the impact on patients, paramedic services, hospitals, and emergency departments (EDs).
We conducted a 12-month multicentre, prospective cohort study involving all prehospital patients presenting <6 hours with possible stroke symptoms. Paramedics evaluated and collected the Revised ASMRPP criteria on the Paramedic Prompt Card.
The study setting included 1015 basic and 302 advanced life support paramedics from 9 land paramedic services, operating in a catchment area of 10 rural counties and 5 cities, with 22 acute care hospitals and 2 university hospital regional stroke centers. Southeastern and eastern Ontario comprised 39 500 km2 and has a population of 1.7 million (Figure I in the online-only Data Supplement). Two academic hospital stroke centers are affiliated with the University of Ottawa and Queens University medical schools (Ottawa and Kingston). At the onset of the study, there was 1 additional district stroke hospital (Pembroke), and the longest typical land transport time within the study region was ≈2 hours. During the study period, 1 additional district stroke center (Belleville) and 2 telestroke centers (Cornwall and Hawkesbury) were designated.
Data were collected on all patients evaluated by paramedics for a possible acute stroke, not just those requiring direct transport to a stroke center according to the Revised ASMRPP criteria. We included a consecutive cohort of all adult patients, aged 16 years and older, who were evaluated for possible acute stroke by paramedics from 1 of the 9 participating paramedic services during the 12-month study period. Specifically, patients who presented with sudden onset of at least one of the following signs suggestive of an acute stroke were included: (1) unilateral arm/leg weakness or drift, (2) slurred or inappropriate words or mute, or (3) facial droop. New onset was liberally defined as any new stroke symptoms within the past 6 hours, in order that we could evaluate paramedic accuracy in applying the new time criteria. Similarly, we wished to include in the study patients who would be ineligible for bypass based on the 7 contraindications listed on the Paramedic Prompt Card (Figure 1), to further evaluate paramedic accuracy.
We did, however, exclude patients from study data collection if (1) they had suffered acute trauma (we did not exclude those with head injury from a fall if the paramedics believed that limb paresis or dysphasia may be because of a stroke that preceded the fall), (2) their only neurological symptom was numbness, (3) they were under the age of 16 years, or (4) the time of symptom onset was unknown, such as a patient awakening in the morning with new neurological deficit. We did not exclude eligible patients who were intoxicated with drugs or alcohol because these patients may have a treatable stroke.
As all patients were treated by the same provincial protocol, local research ethics boards waived the need for informed consent.
Before the 2004 implementation of the original ASMRPP, paramedics from the 9 study paramedic services had undergone a 60- to 90-minute training session. To train paramedics for the Revised ASMRPP and this study, many modes were used, including direct presentations, an online training module, and certification once objectives were met. Paramedics completed a Paramedic Prompt Card data form for every eligible study patient, either on paper or on the electronic patient care record. For the first month of the study period, 2 paramedics independently completed the data form for each patient. For cases requiring bypass, Paramedic crews radioed ahead to the nearest stroke center. At most centers, a stroke code was initiated by the attending ED physician after arrival, whereas for Kingston General Hospital and Quinte Health Care, Belleville, emergency medical services initiated the code before arrival. Patients not eligible for bypass were taken to the nearest hospital as per normal dispatch policies.
Compliance with the data form and appropriate use of the ASMRPP criteria was monitored by review of all ambulance call reports with a final prehospital diagnosis of stroke or transient ischemic attack. Quality assurance staff at the Regional Paramedic Program of Eastern Ontario provided prompt feedback if patients were inappropriately taken to local hospitals rather than the stroke centers or if the data form was not correctly completed.
Outcome Measures and Data Collection
Data were collected for the following 3 categories of study patient from paramedic, ED, and hospital records: (1) the main prospective cohort of patients redirected to a stroke center, (2) the prospective cohort of patients not redirected but taken to local hospital, and (3) the subset of (1) and (2), that is, all patients picked up in a predetermined area where the closest hospital was the Kingston General Hospital, either on redirect or as closest hospital. Kingston General Hospital is the only site in Kingston that receives ambulances and therefore gave us an opportunity to evaluate both the sensitivity and the specificity of the Revised ASMRPP. We had originally planned to collect similar data for the previous 12-month period from the Canadian Stroke Registry, but such data were not available at study completion.
The primary stroke outcomes were (1) thrombolysis given, (2) final hospital diagnosis of stroke, and (3) admitted to the stroke center. Additional treatment, disposition, and diagnosis data were also collected from the stroke centers. To evaluate patient safety, adverse outcomes that occurred during transport and within 1 hour of ED arrival were collected from paramedic patient care reports and hospital records: (1) death, (2) airway obstruction or respiratory failure requiring airway management or ventilatory assistance, (3) cardiac arrest, (4) hemodynamic instability, defined as systolic blood pressure <100 mm Hg or heart rates <50 or >120 per minute, (5) deterioration in Glasgow Coma Scale score during transport compared with initial Glasgow Coma Scale score, (6) vomiting leading to aspiration, (7) acute coronary syndrome, and (8) diversion to nearest hospital because of patient instability. We evaluated patient impact by (1) number of patients who did and did not receive thrombolysis, (2) Glasgow Coma Scale score on ED arrival, (3) survival to hospital discharge, and (4) modified Rankin Scale score at hospital discharge.
For this observational study, most measures were tabulated in a descriptive manner as proportions, means, or medians. For the secondary cohort of patients transported to a single city, we calculated sensitivity and specificity of the ASMRPP with 95% confidence intervals. As secondary analyses, we reported absolute counts of hospital outcomes during the study period and the previous 12 months, using prehospital and hospital data provided by the regional base hospital (RPPEO). We lacked ASRMPP data for the baseline period. We measured interobserver agreement for the independent interpretation of 12 Paramedic Prompt Card criteria by 2 paramedics using the κ statistic with 95% confidence intervals.
Paramedics from the 9 services enrolled patients for a 12-month period between March 2011 and July 2012 and completed the data forms for 1277 of 1293 (98.8%) potential stroke cases (Figure 2). Of 780 patients meeting the criteria for bypass, one was diverted to a nonstroke center, and 24 were lost to follow-up, leaving 755 cases with hospital data. Figure 2 also shows the subset of all possible stroke patients taken to the Kingston General Hospital (n=189).
The 755 redirected patients ranged in age from 16 to 101 years, with 78.4% exhibiting speech difficulties, 64.4% having limb weakness, and 48.5% showing facial weakness (Table 1). Transport times exceeded 30 minutes for 15.1% of cases but exceeded 60 minutes for only 1.4%. Prehospital adverse events occurred in 14.7% of patients, but few were life-threatening, and there were no deaths. Prehospital characteristics of 497 patients not redirected are shown in Table I in the online-only Data Supplement.
The interobserver agreement between paramedics for 275 patients was excellent for the individual redirect criteria and contraindications, as well as overall redirect status (0.94; 95% confidence interval, 0.91–0.96; Table 2). The overall accuracy of the paramedic interpretation (n=1277) was judged by the investigators to be 97.9%. The most common errors were not transporting patients whose symptoms had resolved en route and transporting those with Glasgow Coma Scale <10.
The redirected patients were taken to 2 regional stroke centers, 2 district stroke centers, and 2 telestroke centers (Table 3). The introduction of the 1 new District Center and the 2 Telestroke Centres during the study likely reduced the number of cases with extended transport times. Overall, 71.4% of cases had a stroke code activated at the hospital, 23.2% received thrombolysis, and 69.3% were admitted to hospital. Relatively few patients suffered adverse events in the first hour, and no patient died in the ED. Adverse event rates did not differ among those transported in <30 minutes (6.4%), 30 to 60 minutes (4.1%), and >60 minutes (0%). The final diagnoses were stroke for 52.2% and transient ischemic attack for 18.4% of cases. Of those admitted, survival to discharge was 87.3% with a median modified Rankin Scale score of 2.0.
Table II in the online-only Data Supplement displays the prehospital and in-hospital data for all 189 potential stroke patients transported to the Regional Stroke Centre in Kingston, regardless of their ASMRPP status (redirect 130 and no redirect 59). Using the ASMRPP, paramedics classified the 189 patients for the need for thrombolysis with sensitivity 100% and specificity 37.3% (Table 4). For a final diagnosis of stroke, the classification performance was sensitivity 86.1% and specificity 41.9% (Table 4).
Although a lack of complete baseline data precludes a statistical comparison of proportions between the 12 months before and after the introduction of the Revised ASMRPP, we can present absolute numbers of outcomes (Table III in the online-only Data Supplement). Comparing paramedic-transported potential stroke patients between 2010 to 2011 and 2011 to 2012, we see increases in the number of redirects (539–779), admissions to a stroke center (414–523), final diagnosis of stroke (493–533), and thrombolysis (143–175).
This large prospective cohort study evaluated the Revised ASMRPP and involved 1277 potential stroke patients, 1317 paramedics, and 9 land services, in an extensive urban/rural area. Overall, the 755 patients taken to a stroke center on bypass had few adverse events either in the ambulance or after arrival in the ED. The paramedics showed excellent compliance in using the Revised ASMRPP Card to screen potential stroke patients for direct transport to a stroke center. In addition, the paramedics demonstrated good interobserver agreement in completing the Paramedic Prompt Card and 98% accuracy in interpretation. By reviewing all patients taken to the only stroke center in a single city, this study was the first to estimate the classification performance of the ASMRPP. We found the tool to be 100% sensitive in identifying need for thrombolysis and 86.1% sensitive for a final diagnosis of completed stroke with acceptable specificity. The Revised ASMRPP, with its extended time window for bypass, was associated with more direct transports to a stroke center and more patients receiving thrombolysis. There was no evidence of increased burden on the individual hospitals or paramedic services.
Many studies looked at the use of stroke screening tools by paramedics in large urban areas. One of the earliest stroke screening tools described was the Cincinnati Prehospital Stroke Scale, used in 191 patients by paramedics.9 The Los Angeles Prehospital Stroke Screen was originally validated on 206 patients and subsequently shown to significantly increase transports to local stroke centers in Los Angeles County.10,19 The shortened version of the National Institutes of Health Stroke Scale (sNIHSS)-5 scale consists of 5 items and a scale of 0 to 16.20 The Face Arm Speech Test was developed in the United Kingdom in an effort to simplify screening to include only 3 elements.11 Fothergill et al21 found that the Recognition of Stroke in the Emergency Room Tool was not better than Face Arm Speech Test.
Gladstone et al14 and Chenkin et al13 described a significant increase in patients available for thrombolysis after the introduction of the original ASMRPP in Toronto. Verma et al22 found that online physician control reduced the number of false positives with this protocol. We think that our study is the first to evaluate a stroke screening tool by multiple basic and advanced level paramedics in a large mixed rural and urban region. We confirmed both the validity and the effectiveness of the Revised ASMRPP when fully implemented in the field.
Strengths and Limitations
This study had several limitations. We were unable to do a complete comparison with potential stroke patients seen during the year before the implementation of the Revised ASMRPP because the required Canadian Stroke Registry data were not yet available at the time of final data analysis. Nevertheless, we were able to show benefit by an increase in the absolute number of patients transported to a stroke center and receiving thrombolytics. We did not have the resources to follow patients who were not transported to a stroke center but are confident that most missed stroke cases would have been subsequently referred to a stroke center. It is also possible that paramedics may have failed to consider a diagnosis of stroke in some patients and did not complete the study form. Our evaluation of the impact of the Revised ASMRPP was somewhat confounded by the concurrent introduction of 3 additional district stroke centers, thereby reducing the need for prolonged transports. Although paramedics were asked to complete their interobserver forms independently, we suspect there was collaboration in some cases, and paramedic agreement could be explored in future studies.
The study strengths included a large number of patients managed by more than a thousand paramedics from 9 paramedic services in a large geographic area. We had precise data from the paramedic assessments and the in-hospital findings. This was the first study to evaluate the specificity of a stroke screening tool.
The Revised ASMRPP has been shown to be both a sensitive and reliable stroke screening tool that paramedic services can use to redirect potential stroke patients to hospitals with the ability to administer thrombolysis. The specificity of this tool is sufficiently high that its use will not overburden paramedic services with large numbers of prolonged transports nor overwhelm stroke centers with unnecessary transports. The tool is easy to learn and to apply by paramedics.
The Ontario Stroke Network provides provincial leadership and planning for Ontario 11 Regional Stroke Networks supporting the 14 Local Health Integration Networks through measuring and reporting on performance, partnering to achieve best practices, and supporting innovations for stroke prevention, care, recovery and reintegration. The 11 Regional Stroke Networks provide a multifacetted approach to management of acute stroke to a population of 13.9 million people and an area exceeding 1 million square kilometers. All paramedic services in Ontario use the Revised ASMRPP to redirect patients to designated stroke centers if the transport time will be <2 hours, and the patient can arrive within 3.5 hours of symptom onset.7,23 District Stroke Centres (n=17) have written stroke protocols for paramedic, ED, and acute care; ability to offer thrombolytic therapy; timely computed tomographic scanning and interpretation; clinicians with stroke expertise; and linkages to rehabilitation and secondary prevention.24 Regional Stroke Centres (n=11) also have neurosurgical facilities and interventional radiology and provide expertise to other hospitals. The Ontario Telestroke Program is an emergency telemedicine application that provides emergency physicians immediate access to neurologists with expertise in stroke care who can support both the assessment and treatment of patients experiencing acute ischemic stroke symptoms. This program provides stroke patients in remote hospitals (n=22) with access to thrombolysis and uses eHealth Ontario Emergency Neuro Image Transfer System, a centralized web-based picture archiving and communication system for head scans.
Paramedics accurately, safely, and effectively implemented the Revised ASMRPP to redirect potential stroke patients in a large urban–rural area with 9 paramedic services. The criteria were highly sensitive for need for thrombolysis and sufficiently specific to avoid a large number of unnecessary transports to stroke centers. There was an increase in the number of transported patients receiving thrombolysis for acute stroke. The Ontario Stroke Network process of paramedic bypass to Telestroke, District and Regional Stroke Centres is a role model for effective and efficient stroke management.
We gratefully acknowledge the invaluable assistance of the following individuals: Dr Christian Vaillancourt, My-Linh Tran, and Angela Marcantonio (Ottawa Hospital Research Institute); Dr Chris Fabian, Susan Duncan, Jason Rouleau, and Rosie Hawkins (Regional Paramedic Program for Eastern Ontario); Tammy Gray and Jane Reid (Kingston General Hospital); and Linda Kelloway and Chris O’Callaghan (Ontario Stroke Network). We are also grateful to the hundreds of paramedics and the participating paramedic services whose efforts made this project successful. The local site paramedic champions were Cornwall Stormont Dundas and Glengarry Emergency Medical Services (Andre Turbide), County of Renfrew Paramedic Service (Michel Ruest), Frontenac Paramedic Service (Richard Russell), Hastings-Quinte Paramedic Service (Brad Hopper), Lanark County Paramedic Service (Ed McPherson), Leeds Grenville Paramedic Service (JoAnn Hendry), Lennox and Addington County Emergency Medical Services (Jeff Robbins), Ottawa Paramedic Service (Suzanne Noel), and Prescott and Russell Paramedic Service (Louis Rathier).
Sources of Funding
This project has been generously funded, by a grant from the Ontario Ministry of Health and Long-Term Care, administered, and supported by the Ontario Stroke Network. The views expressed do not necessarily reflect those of the ministry or the Ontario Stroke Network. The author contributions were as follows: Dr Stiell secured research funding in response to a request for proposals from the Ontario Stroke Network on behalf of the Ontario Ministry of Health and Long-Term Care and oversaw data management and prepared the article. All authors supervised in the conduct of the trial and data collection, drafted the article, and contributed to its revision, and approved the final version. Dr Stiell is guarantor.
The online-only Data Supplement is available with this article at http://stroke.ahajournals.org/lookup/suppl/doi:10.1161/STROKEAHA.116.014868/-/DC1.
- Received July 28, 2016.
- Revision received December 19, 2016.
- Accepted December 28, 2016.
- © 2017 American Heart Association, Inc.
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