Frequency and Accuracy of Prehospital Diagnosis of Acute Stroke
Background and Purpose This pilot study evaluated the frequency and accuracy of diagnosis of stroke made by prehospital care system dispatchers, emergency medical technicians (EMTs), and paramedics in one emergency medical services (EMS) system. In addition, the study determined patient prehospital triage and time intervals in the transport and evaluation of patients given a diagnosis of stroke by this EMS system.
Methods We reviewed records of 4413 consecutive prehospital records of a two-tiered EMS system for patients with potential stroke. Hospital records were obtained for patients given a diagnosis of stroke or transient ischemic attack (TIA) by an EMS dispatcher, EMT, or paramedic. The EMS system studied serves a community of 13 000 within the greater Cincinnati area.
Results Of 4413 EMS on-scene evaluations, the diagnosis of stroke or TIA was made by an EMT or paramedic for 96 patients (2%). Of the study population (n=86), a final hospital discharge diagnosis of stroke or TIA was made for 62 patients (72%). EMS dispatchers correctly identified 52% and paramedics 72% of these 86 patients as having sustained a stroke or TIA. Twenty-two of the 86 patients required paramedic-level interventions, which included three intubations. Of the 24 patients whose symptoms were misdiagnosed as stroke or TIA by the paramedics, 16 (19%) had acute conditions for which effective therapies are available. Prehospital personnel arrived at the scene to examine potential stroke patients in a mean of 3 minutes after the emergency 911 call was received by the dispatcher. Patients transported by basic life support units (EMTs) arrived earlier at the hospital than did those transported by advanced life support units (paramedics) (40±1 versus 45±1 minutes, P=.004). However, patients transported by advanced life support units were seen by a physician sooner after arrival at the emergency department (10±2 versus 20±4 minutes, P=.02) and underwent computed tomography of the brain sooner (47±5 versus 69±10 minutes, P=.04).
Conclusions Prehospital evaluation of potential stroke patients can be accomplished promptly after the EMS system is activated. Urgent evaluation and transport of potential stroke patients is justified because paramedic-level interventions are frequently required and because almost 20% of patients with potential stroke have acute medical conditions for which effective specific therapies are available.
Thrombolytic agents, calcium channel blockers, free radical scavengers, and glutamate antagonists are currently being evaluated for the treatment of acute ischemic stroke.1 2 3 4 5 6 A consistent finding in experimental animal studies is that these agents must be given within a few hours of stroke onset to be effective.7 8 9 Because of the importance of time to treatment and because emergency medical services (EMS) personnel are often the first medical contact for patients presenting with stroke, an investigation of the prehospital and emergency department evaluation of patients with acute stroke is warranted.10 No study to date has investigated the EMS prehospital evaluation of patients with potential stroke.
Reading, Ohio, is a suburb of 13 000 persons within the greater Cincinnati metropolitan area of 1.4 million. The Reading population is similar to the metropolitan area population in age and income.11 The Reading population is served by a two-tiered EMS system, a structure in common use throughout the United States that is organized around basic life support (BLS) and advanced life support (ALS) transport units.12 BLS units are manned by emergency medical technicians (EMTs) who are trained in basic life support techniques. ALS units are manned by paramedics who are trained in advanced life support techniques. The two-tiered EMS system is activated after an emergency 911 telephone contact from the field is received by the EMS telephone dispatchers.
We investigated the Reading EMS system as a model for prehospital stroke patient evaluation by a two-tiered EMS system. By comparing the number of EMS evaluations of potential stroke patients with the total number of EMS evaluations for the same time period, we hoped to approximate the burden placed on the EMS systems by EMS evaluation of stroke patients. By estimating the accuracy of diagnosis, we hoped to determine the possible need for upgrading the education of prehospital-care personnel in cerebrovascular disease. Finally, by identifying EMS features that speed up or slow down identification, transport, and emergency department evaluation of stroke patients, we hoped to guide the planning of future stroke intervention trials.
Subjects and Methods
The EMS system of Reading, Ohio, was chosen because detailed, computerized records of all patient evaluation and transport have been kept since 1985. In Reading’s two-tiered EMT/paramedic-driven system, the EMS dispatcher sends a paramedic to all scenes. At the time of dispatch, the EMS dispatcher informs the paramedic of the nature of the call. The paramedic decides at the scene whether the patient requires a BLS or ALS unit transport. A prehospital assessment is then recorded by either the paramedic or the EMT at the scene. No published guidelines for cerebrovascular disease are used by the dispatcher, EMT, or paramedic to determine a prehospital diagnosis.
The records of all EMS runs from January 1986 through October 1990 were reviewed retrospectively. For patients to be considered for analysis as potential stroke patients, the inclusion criteria were (1) a diagnosis of transient ischemic attack (TIA) or stroke made by the EMT or paramedic and (2) the availability of EMS, emergency department, and inpatient hospital records. It should be noted that not all patients diagnosed by the EMS dispatcher as potential TIA or stroke were included because the stroke study population was selected by the diagnosis of potential TIA or stroke as made by the EMT or paramedic, not the EMS dispatcher.
The following data were abstracted from the EMS prehospital record: clinical presentation, diagnosis of the EMS dispatcher, initial prehospital vital signs, time of dispatch, time of arrival of EMS personnel at the scene, prehospital diagnosis made by the EMT or paramedic, paramedic-level interventions, and transport time to the hospital. EMS records of patients with paramedic-level interventions were reviewed to determine whether the interventions were medically indicated and met local paramedic guidelines. Demographic factors, time of symptom onset, vital signs at the emergency department, chief complaint, time to initial physician contact, time to computerized tomography (CT), and final diagnosis made by the emergency department were abstracted from emergency department records. The patient’s mental status, speech, motor function, and ability to walk were determined by the study investigator by reviewing the prehospital and emergency department records. If the patient was admitted, the final discharge diagnosis and ultimate disposition were abstracted from the inpatient chart. The final diagnosis of stroke or TIA was then defined as a final emergency department or inpatient discharge diagnosis of TIA, ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage (International Classification of Diseases, 9th Revision, Clinical Modification, codes 430 through 432 and 434 through 437).
Demographic characteristics and level of transport (ie, BLS versus ALS) for the study population and for nonstudy patients transported by Reading EMS units were compared by χ2 test. Clinical findings were compared for potential stroke patients transported by ALS versus BLS by χ2 and Fisher’s exact test. Mean time intervals (±95% confidence interval) were calculated and compared by two-tailed, unpaired Student’s t test. A value of P<.05 was considered statistically significant for all tests.
For the 58-month study period, evaluation and transport by the Reading EMS were completed for 4413 patients. Ninety-six (2%) patients were given a prehospital diagnosis of stroke or TIA by an EMT or paramedic. The mean age of transported patients with an EMS diagnosis of stroke or TIA was 72 years. The majority were white (94%) and female (62%). Reading BLS units transported 49 of the patients (51%) with potential stroke, and ALS units transported the other 47 patients (49%).
Of the 96 potential stroke patients, 86 met the study inclusion criteria. Ten patients were excluded from the study because their prehospital or hospital records were unavailable. The demographic characteristics of the 86 study patients and their levels of transport were not significantly different from the 10 patients that were excluded (P>.05).
Of the 86 study patients with an EMT or paramedic diagnosis of stroke or TIA, 62 (72%) were subsequently verified as having had a stroke or TIA by either the emergency physician or the admitting physician (Table 1⇓). Thirty-five patients (56%) had a diagnosis of brain infarct; 15 (24%) had a diagnosis of TIA, 10 (16%) had intracerebral hemorrhage, and 2 (3%) had subarachnoid hemorrhage. An incorrect diagnosis of stroke or TIA was made by the EMTs or paramedics for 24 patients (Table 1⇓). In 8 of these 24 patients, an infectious cause of their illness was eventually diagnosed. The infectious causes included sepsis, urinary tract infection, pneumonia, and encephalitis. Another 7 of the 24 patients with misdiagnosis were later determined to have either myocardial ischemia or syncope.
Among the patients whose illness was correctly diagnosed by the EMTs or paramedics as stroke or TIA, 32 of 62 (52%) were correctly diagnosed by the EMS dispatchers. Eight patients who were identified as having a possible stroke by the EMS dispatcher were later found to have a diagnosis other than stroke (Tables 2⇓ and 3⇓).
Prehospital personnel arrived on-site to evaluate the potential stroke patients in a mean of 3 minutes after the emergency 911 call was received (range, 1 to 10 minutes). Those patients transported by BLS units had significantly shorter on-scene evaluation times than patients transported by ALS units (19±1 versus 24±1 minutes, P=.0005) (Figure⇓). Consequently, BLS transports required less time for arrival at the hospital than ALS transports (40±1 versus 45±1 minutes, P=.006). However, once stroke patients arrived at the hospital, those transported by ALS units were seen by a physician twice as fast (10±2 versus 20±4 minutes, P=.02) and had CTs performed almost 30 minutes sooner (46±5 versus 69±10 minutes, P=.04) than patients transported by BLS units. There was no difference in the overall time from EMS dispatch to physician evaluation between stroke patients transported by ALS versus BLS units (55±2 versus 57±5 minutes, P=.55). Compared with patients transported by BLS, patients transported by ALS units were more likely to be mute (29% versus 7%, P=.03), have a flaccid extremity (24% versus 7%, P=.07), and be unable to walk (52% versus 29%, P=.07) on arrival at the emergency department. Overall hospital mortality was not significantly different between BLS- and ALS-transported patients (10% versus 14%, P=.80).
Of the 86 potential stroke patients transported, 22 patients had a total of 44 paramedic-level interventions in accordance with local paramedic guidelines (Table 4⇓). On review, all interventions were determined to be medically indicated. Seven patients required advanced airway management (3 required intubation, and 4 required nasopharyngeal airways). Eighteen patients were given 50% dextrose for possible hypoglycemia (including 11 with a final physician diagnosis of stroke or TIA), 13 naloxone, and 2 diazepam (for seizures). All patients who received paramedic-level interventions were noted to be confused or unable to communicate by the paramedics before treatment. Cardiac arrhythmias noted by paramedics included multifocal premature ventricular complexes, atrial fibrillation, bradycardia, and a four-beat run of ventricular tachycardia. However, none of these patients required treatment.
Our results provide the first published data regarding the role of EMS in treating patients with ischemic and hemorrhagic stroke. For the Reading, Ohio, EMS system, patients with a possible stroke constituted 2% of all on-scene evaluations. This figure may approximate the case load in many US metropolitan areas.
Our data also indicate that the urgent evaluation and transport of these patients is medically important and should not be delayed. Twenty-two of the 86 (26%) patients in our potential stroke population necessitated paramedic-level interventions while en route to the hospital. Seven patients required advanced airway management, including three intubations, and 2 patients required intravenous anticonvulsant therapy. Only half of the patients (32 of 62) who sustained a stroke or TIA were correctly identified by EMS dispatchers; 3 of the 8 patients whose symptoms were incorrectly diagnosed as stroke had treatable medical illnesses (Table 3⇑). Similarly, of the 24 patients incorrectly diagnosed as having stroke by EMTs or paramedics, 16 patients had treatable medical illnesses.
The potential for EMS providers to influence treatment in patients with stroke is promising. Barsan et al13 found that as many as 47% of patients in three metropolitan communities presenting with stroke used the emergency 911 telephone service as their first medical contact. This number increased to 65% for those patients presenting within 90 minutes of symptom onset. Our study found that the Reading EMS system allowed a healthcare provider to be at the scene within 5 minutes of telephone contact by the patient or a bystander. Paramedics were with the patient almost an hour before a physician saw the patient. Anecdotal experience at the University of Cincinnati indicates that early notification by paramedics via telemetry to the receiving hospital may reduce time to treatment by allowing early mobilization of appropriate personnel (ie, physicians, CT technologists, pharmacists, laboratory technologists, etc).14 In patients with acute myocardial infarction, prehospital identification and early hospital notification reduced time to thrombolytic treatment by 20 to 75 minutes.15 16 17 18 19 20 Our results suggest that a similar approach for stroke could provide up to 60 minutes of lead time to mobilize hospital personnel and resources for stroke patients.
However, before EMS personnel can have a significant impact on the management of patients with stroke, they must be able to accurately identify these patients. Almost half of all stroke patients in this study were dispatched as having something other than stroke. A quarter of all patients identified as having a stroke by paramedics were later discovered to have another cause for their illness. This inaccuracy may be due to the brief interactions that the EMS personnel have with the patients or to a lack of knowledge regarding the signs and symptoms of stroke. Currently, there are no national requirements for dispatcher certification. The National Standard Curriculum recommends only 15 to 21 hours of dispatcher training with no specified training in neurological diseases.21 While paramedic training guidelines (300 hours of classroom training) are much more extensive than dispatcher guidelines, less than 1% of that time is dedicated to “nervous system” diseases.22 Identifying key questions or physical findings that may distinguish stroke from nonstroke patients may improve the ability of EMS personnel to accurately identify patients with stroke.
The most appropriate and expedient mode of EMS transport of patients with stroke is unclear. In the Reading EMS system, patients transported by a BLS unit arrived at the hospital faster than those transported by an ALS unit. However, it took longer for patients transported by BLS units to be seen by a physician and have a head CT once they arrived. The prolonged scene time with ALS transports may reflect the fact that these patients were more disabled (as assessed by speech and motor function) and required intravenous lines and heart monitors in the field. An increased severity of illness could also explain why these patients were given physician evaluations and CT scans more quickly than those transported by a BLS unit.
In addition, over 25% of patients transported by the Reading EMS received treatment that could be provided by paramedics but not by basic EMTs. All patients receiving treatment were noted to be either confused or unable to communicate. Other larger studies are needed to identify other patient findings that may allow prehospital personnel to distinguish between patients requiring ALS transport and those who do not.
This retrospective study was undertaken to obtain preliminary information regarding the prehospital assessment and management of patients with stroke. As such, it has limitations. First, this study evaluated only patients who were identified as potential stroke patients by paramedics or EMTs. It did not address the issue of how frequently prehospital personnel misdiagnose symptoms in patients with stroke. If this number is significant, further education of prehospital personnel could increase the number of patients eligible for future stroke trials. Second, this is a small study evaluating a single EMS system that uses both BLS and ALS units. Other communities use different EMS systems. Some use only BLS or ALS units, and others incorporate fire and law enforcement personnel into their system. Accuracy and time intervals may vary with these different types of EMS systems. Finally, Reading EMS personnel may not be representative of other communities in the United States. Hospitals in the Cincinnati area have been involved with acute therapeutic stroke trials for over 10 years. Although direct educational efforts have not been aimed at the Reading Life Squad, dispersal of information regarding stroke from participating hospitals and general public information may have affected their stroke awareness and transport times.
A prospective community-wide study evaluating the prehospital management of stroke in the entire Cincinnati metropolitan area is currently under way. This larger study evaluates not only patients transported as potential stroke cases but also those patients whose stroke was initially misdiagnosed by prehospital personnel. It involves over 35 community EMS systems and all 19 area hospitals. Further studies evaluating different communities (both urban and rural) with various EMS systems are needed to determine whether our findings can be generalized to other communities.
Reprint requests to Rashmi Kothari, MD, Department of Emergency Medicine, University of Cincinnati College of Medicine, PO Box 670769, Cincinnati, OH 45267.
- Received December 23, 1994.
- Revision received February 22, 1995.
- Accepted February 22, 1995.
- Copyright © 1995 by American Heart Association
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