EMS Management of Acute Stroke—Out-of-Hospital Treatment andStroke System Development (Resource Document to NAEMSP Position Statement)

Abstract

The American Heart Association estimates an annual incidence of stroke in the United States at 700,000, leading to over 150,000 deaths. Of all strokes, approximately 88% are ischemic and12% are hemorrhagic. Almost half of all stroke deaths occur in the out-of-hospital environment. Within a given region, the emergency medical services (EMS) system has an important role in the management of the acute stroke patient. Decisions made by EMS personnel can affect treatment andcontribute to the immediate, short-term, andlong-term outcomes of the patient. Because the patient may require emergent treatment regardless if the stroke is ischemic or hemorrhagic, EMS personnel should manage all potential stroke patients in a time-dependent nature. Proper treatment anddisposition of the stroke patient begins in the out-of-hospital environment, continues in the emergency department, andthen extends to the inpatient admission. This article reviews the literature on the out-of-hospital treatment of stroke patients andthe role of EMS in the development of stroke systems of care.

Key words:

• stroke
• emergency medical services
• systems of care

Introduction

The American Heart Association estimates an annual incidence of stroke in the United States at 700,000, leading to over 150,000 deaths. Of all strokes, approximately 88% are ischemic and12% are hemorrhagic. Almost half of all stroke deaths occur in the out-of-hospital environment.¹ If recent trends continue, the 30-year projections suggest a 98% absolute increase in stroke deaths from 139,000 in 2002 to 275,000 in 2032 with a corresponding increase in the U.S. population of only 27%.²

Within a given region, the emergency medical services (EMS) system has an important role in the management of acute stroke patients. Decisions made by EMS personnel can affect treatment andcontribute to the immediate, short-term, andlong-term outcomes of the patient.

The first step for EMS is the early identification of patients who may be having a stroke. This begins with entry of the patient into the EMS system via “911” or equivalent emergency call centers. Once potential stroke patients have been entered into the EMS system, it then falls to the responsibility of the on-scene EMS personnel to accurately screen andassess potential stroke patients. Because the patient may require emergent treatment regardless if the stroke is ischemic or hemorrhagic, EMS personnel should manage all potential stroke patients in a time-dependent nature.

In 1995, the National Institute of Neurological Disorders andStroke (NINDS) published a study in which tissue plasminogen activator (t-PA), given within 3 hours of symptom onset, improved outcome for patients with acute ischemic stroke.³ The NINDS study showed that patients given t-PA were more likely to have minimal or no disability at 3 months compared to placebo (favorable outcome by Barthel index of 50% compared to 38%, respectively; relative improvement of 31.6%). At the same time, however, patients given t-PA were at a statistically significant higher risk for intra-cerebral hemorrhage within 36 hours than the placebo group at 6.4% compared to 0.6% respectively (increased relative risk of 9.7%).

Over the past 10 years there has been much controversy over the use of t-PA for acute ischemic stroke. Much of this controversy has revolved around protocol violations andthe exact subset of patients that are appropriate to receive t-PA.⁴, ⁵ Another element of the controversy has been related to the statistical methods used in the NINDS trial. Some authors have argued that the results are not valid due to an imbalance in the study groups.⁶ Because of this concern, a group of independent reviewers recently published results on a reanalysis of the findings from the NINDS trial. Their findings reaffirmed support for the use of t-PA to treat patients with acute ischemic stroke within 3 hours of onset of symptoms, despite an increased incidence of symptomatic intracranial hemorrhage.⁷, ⁸

Regardless of the findings from the independent commission, there continues to be only a small fraction of acute stroke patients who are eligible for thrombolytics due to the restrictive inclusion criteria.⁹ However, beyond the use of intravenous t-PA for the treatment of acute ischemic stroke, there are other treatment modalities that may be beneficial for stroke patients. Many of these additional treatment modalities may be initiated in the out-of-hospital environment andcontinued in the emergency department andfollowing admission. The ideal agent for field use would be a neuroprotective agent that could be administered during transport.¹⁰, ¹¹ However, to date, no neuroprotective agent has been shown to be effective in reducing the morbidity or mortality associated with acute ischemic stroke.

In addition to stroke specific therapies, there are several other treatment measures that should be considered by all EMS personnel when caring for the patient with a potential stroke. These measures include position of patient during transport, use of oxygen therapy andairway management, placement of intravenous lines andadministration of intravenous fluids, electrocardiographic monitoring, blood glucose monitoring andcorrection of hypoglycemia, administration of aspirin, andmonitoring of blood pressure derangements. In the emergency department, acute stroke patients should be assessed for potential candidacy for intravenous or intra-arterial t-PA, or neurosurgical consultation for hemorrhagic stroke. Once the patient has been admitted, acute stroke patients should be managed in consultation with a neurologist andassessed for short-term (e.g., fever, blood glucose derangements, blood pressure derangements, aspiration pneumonia, deep venous thrombosis) andlong-term (i.e., rehabilitation, psychological health) sequela of stroke.

Recently, two independent groups, the Brain Attack Coalition (BAC) andthe American Stroke Association (ASA), a division of the American Heart Association, have developed recommendations for the treatment of stroke patients andthe development of stroke centers.¹², ¹³ The recommendation that all acute stroke patients receive treatment at accredited stroke centers has significant implications because many acute stroke patients are transported to acute care centers through the EMS system. The early identification of the potential stroke patient andsubsequent transport to an appropriate care facility is the responsibility of the EMS system. Therefore, EMS medical directors should develop regional protocols for the identification andtreatment of potential stroke patients andshould be involved in the development of any regional stroke systems of care.

Review of Supporting Literature

Out-of-Hospital Screening for Stroke Patients

Because the outcome of some stroke treatments is time dependent, it is important to rapidly enter a patient who is possibly experiencing a stroke into the EMS system. Entry into the EMS system begins with the “911” or equivalent emergency operator andcontinues with the EMS personnel that provide direct care to the patient.

For EMS personnel to accurately identify a patient who may be having a stroke, it is valuable to have a screening tool that is easy to perform. Two stroke screening assessments have been documented to have a high sensitivity in identifying patients who may be having a stroke in the out-of-hospital setting: the Cincinniti Prehospital Stroke Scale andthe Los Angeles Prehospital Stroke Screen.¹⁴, ¹⁵ It is recommended that all EMS personnel use a screening tool for the assessment of patients who may be having a stroke.

Out-of-Hospital Treatment of Stroke Patients

Transport Position

The primary aim of acute stroke treatment is to restore blood flow to poorly oxygenated brain tissue. Positioning of the head at zero degrees, or supine, during assessment andtransportation may increase arterial blood flow through the effects of gravity. Traditional positioning for most acute neurological conditions has been with 30° of head elevation to decrease intracranial pressure (ICP).¹⁶, ¹⁷, ¹⁸ However, in ischemic stroke patients, ICP does not peak until 48 hours postinfarction, andincreased blood flow may be more beneficial in the acute setting.¹⁹, ²⁰ Schwartz et al. demonstrated an improvement in cerebral perfusion pressure (CPP) from 64.7 ± 1.7 mmHg with a 30° elevation to 77± 1.8 mmHg with a flat position (p < 0.001).²¹ ICP changes were found to be clinically insignificant. Wojner-Alexandrov et al. demonstrated a 20% improvement in middle cerebral artery (MCA) blood flow in a flat position compared to 30° of head elevation with no detrimental effects noted.²²

As of this date, there are no published studies that have examined head positioning of stroke patients in the out-of-hospital setting. Furthermore, proper assessment andmanagement of airway, breathing, andcirculation are of primary importance in acute stroke. Stroke patients may need stabilization of airway andtransportation with aspiration precautions. Therefore, the benefits andrisks of flat head positioning in the prehospital setting are unknown at this time, andfurther studies need to be performed. However, a flat assessment andtransport position for patients with acute stroke that have no clinical evidence of elevated ICP andcan tolerate positional changes may improve blood flow to the brain.

Oxygen

Supplemental oxygen therapy is frequently a routine intervention in the prehospital patient with acute stroke. Decreases in oxygen saturation can lead to worsening of cerebral ischemia.²³ Furthermore, administration of supplemental oxygen to those that are not hypoxic may improve oxygen supply to ischemic tissue andthereby minimize the ischemic penumbra.

Animal studies have suggested that there may be some benefit to administering 100% supplemental oxygen to nonhypoxic ischemic stroke victims.²⁴, ²⁵ However, human studies that have compared the use of supplemental oxygen to no oxygen therapy for stroke patients have shown no additional improvement of outcomes with oxygen administration.²⁶, ²⁷ The use of hyperbaric oxygen therapy has also been shown to have no benefit in the treatment of stroke.²⁸ Furthermore, there is some evidence that suggests that hyperoxia may be harmful.²⁹, ³⁰ Currently, the best evidence with regards to the use of oxygen is in the maintenance of homeostasis.³¹ Stroke units that have tried to maintain normal oxygen saturation in addition to euglycemia andnormothermia have demonstrated the best stroke outcomes.³¹, ³², ³³

Current recommendations based on available literature are to monitor oxygen saturation continuously with a pulse oximeter andtreat hypoxia with supplemental oxygen. Because there is no conclusive evidence that supplemental oxygen for those that are not hypoxic causes harm, clinicians may consider the use of oxygen in stroke for patients who are not hypoxic.³⁴ However, because the goal of treatment should be to maintain normoxia, supplemental oxygen for those who are not hypoxic should be given at low flow rates. Additional research is needed to determine if there are any benefits or harm from the use of supplemental oxygen in nonhypoxic acute stroke patients.

IV Access

Since acute stroke should be treated as a time-dependent emergency, rapid transport to a definitive care facility is of utmost importance. Delays in the prehospital setting need to be avoided. One potential time delay relates to the establishment of intravenous (IV) access. A field line may be appropriate for cases when acute resuscitation medications are needed. Otherwise, transportation should be started immediately andIV access secured en route. Although paramedics have demonstrated proficiency at prehospital line placement, attempts prior to transport can lead to increased scene time.³⁵, ³⁶, ³⁷

In the hospital, intravenous lines are useful for obtaining blood for laboratory tests andfor administering medications including contrast agents during imaging. The current imaging gold standard for acute stroke is computed tomography (CT) without contrast to separate hemorrhagic from ischemic stroke.³⁸, ³⁹ Other imaging modalities that are being used with increased frequency include magnetic resonance imaging (MRI) with or without contrast, diffusion weighted imaging with MRI, CT angiography, andCT perfusion imaging. MRI contrast is administered manually such that the size of the line is not crucial. However, contrast CTs are performed with power injectors that often require IV lines to be large bore andno more distal than the antecubital fossa.

The current recommendations for patients not requiring acute resuscitation are to minimize scene time andto establish IV access en route. Medical directors should know the diagnostic capabilities of area hospitals andencourage EMS units to establish IV access to meet these needs. Assuming that establishing an IV does not increase the EMS transport time, placing a line that meets therapeutic anddiagnostic requirements may save critical time by eliminating the need to establish an IV as a first priority when the patient arrives at the hospital.¹⁰, ¹¹

IV Fluid Administration

Once vascular access has been established, there is a tendency for EMS providers to administer intravenous fluids. However, it remains unclear what type of fluid to administer andhow much to give. In theory, hemodilution will decrease viscosity, improve cerebral blood flow, andsubsequently decrease infarct size. A Cochrane review on hemodilution for acute stroke using plasma volume expanders concluded that this therapy has not been proven to improve survival or functional outcome.⁴⁰ The administration of hypertonic saline has also been recommended to decrease ICP in the setting of acute stroke.⁴¹ However, correcting ICP in the prehospital setting where it cannot be measured or monitored is potentially dangerous. In an animal study using hypertonic saline acutely for stroke without regard to monitoring ICP, hypertonic saline was shown to worsen the infarct size of cortical infarcts.⁴² Glucose-containing solutions must be avoided because hyperglycemia has been shown to be detrimental in the acute setting.⁴³, ⁴⁴

IV fluids should be used cautiously in stroke patients with other underlying medical conditions such as heart failure or renal failure in which volume overload could be detrimental. Conversely, patients who are dehydrated or poorly perfusing, should receive boluses of balanced salt solutions to improve circulation andpotentially cerebral blood flow.⁴⁵, ⁴⁶ No benefit from routine hemodilution has yet been demonstrated for use in the acute setting. In patients who are hemodynamically stable, the current recommendation is to saline lock the line or run a balanced salt solution at a minimal rate to keep the line open (TKO).

Electrocardiographic (ECG) Monitoring

Stroke patients are at risk for adverse cardiac outcomes as mediated through an increase in sympathetic tone andthe release of catecholamines causing a proarrhythmic state.⁴⁷, ⁴⁸, ⁴⁹, ⁵⁰ The increase in tone can also cause heart strain andmyocardial infarction.⁵¹ Potential ECG changes include QT prolongation, T-wave flattening or inversion, ST segment alteration, andsupraventricular dysrhythmias.⁵², ⁵³ Moreover, stroke itself can be caused by the release of blood clots associated with underlying atrial fibrillation or prior myocardial infarction. Given the wide range of cardiac risk factors andcomplications, continuous three-lead ECG monitoring, when available, is recommended for all cases.

Blood Glucose Monitoring

In the setting of acute stroke symptoms, capillary blood glucose (CBG) measurement should be obtained as soon as possible. Early hypoglycemic patients can present with focal neurological findings that mimic a stroke.⁵⁴ In addition, severe andprolonged hypoglycemia can lead to brain injury such that prompt identification andcorrection of hypoglycemia is imperative.

The identification of hyperglycemic patients is also important. Hyperglycemia is recognized as an independent risk factor for increased morbidity andmortality following stroke.⁴³, ⁴⁴, ⁵⁵ Hyperglycemia worsens cerebral edema, enhances hemorrhagic transformation of the stroke, andexacerbates the postischemic injury.⁵⁶, ⁵⁷ The underlying mechanisms include increased anaerobic glycolysis leading to tissue acidosis as well as increased permeability of the blood brain barrier. Recent studies have identified the importance of starting early insulin therapy to achieve euglycemia.⁵⁸, ⁵⁹ Ongoing prospective trials to evaluate early glucose regulation will hopefully show the ideal interventions to improve long-term outcomes.⁶⁰, ⁶¹ In the future, early management of hyperglycemia may be warranted in the prehospital setting. However, at present, no data exist to support this treatment.

In summary, it is important to check a CBG early to identify andtreat hypoglycemic patients as well as identify hyperglycemic patients so that early in-hospital intervention can be started to establish euglycemia.

Aspirin

The goal of early intervention in acute ischemic stroke is to restore blood flow to brain tissue by physically disrupting the clot andpreventing further clot formation. Platelets are believed to play an important role in the pathogenesis of acute ischemic stroke andthe antiplatelet drug aspirin has been demonstrated to have beneficial effects in the treatment of acute stroke.⁶², ⁶³ The International Stroke Trial (IST) andthe Chinese Acute Stroke Trial (CAST) evaluated the effects of early aspirin therapy (within 48 hours) on acute stroke andshowed a reduction in the immediate risk of further stroke or death in the hospital setting andin the overall risk of death or dependency.⁶⁴, ⁶⁵

In theory, giving aspirin to a person with a hemorrhagic stroke could worsen the bleeding. However, a subgroup analysis of the IST andCAST studies showed a net benefit with no unusual risk of hemorrhagic stroke in the use of early aspirin therapy.⁶⁶ Other studies have also failed to show an increased risk in the development or worsening of hemorrhagic stroke with the use of aspirin.⁶⁷, ⁶⁸, ⁶⁹

There is no literature that has examined the benefits andrisks of aspirin therapy for suspected stroke in the prehospital environment. Because the available literature does not show an increased risk of hemorrhage, aspirin could theoretically be given to patients with suspected stroke in the prehospital environment. However, as the literature demonstrates a benefit to aspirin therapy when given in the first 48 hours after onset of symptoms andthere is a theoretical risk of hemorrhage, it is acceptable to delay aspirin therapy until after the patient has arrived at the emergency department. Further research is needed to delineate the benefits andrisks of aspirin administration for suspected stroke patients in the prehospital environment.

Blood Pressure Management

Blood pressure management in acute stroke has been a controversial topic.⁷⁰ In theory, a reduction in blood pressure should prevent additional strokes, reduce further vascular damage, decrease cerebral edema, andlessen the chance for hemorrhagic transformation of an ischemic area.⁷¹ However, reducing blood pressure could also reduce cerebral perfusion andlead to enlargement of the area at risk for ischemic injury. Cerebral autoregulation is often disrupted in the setting of ischemia, andcerebral perfusion depends almost entirely on systemic arterial blood pressure. In studies that focused on the first 24 hours after an acute ischemic stroke, it has been noted that although initial hypertension is common, blood pressure often declines without intervention in the first 90 minutes.⁷², ⁷³ Other studies have found that the initial hypertension associated with an acute ischemic stroke was protective andthat interventions to lower it in the first 24 hours worsened outcome.⁷⁴, ⁷⁵, ⁷⁶

For ischemic stroke, a range of systolic blood pressure (SBP) from 140 to 180 mmHg appears to be optimal andreducing SBP below 140 mmHg or by more than 20 mmHg is detrimental.⁷⁶ In fact, evidence is emerging for the use of vasopressors to increase SBP in the management of acute ischemic stroke.⁷⁷, ⁷⁸ Current recommendations for blood pressure management in ischemic stroke are to avoid anti-hypertensives in the acute setting unless SBP is > 220 mmHg or if medically necessary for treating accompanying conditions such as acute myocardial infarction, decompensated heart failure, aortic dissection, acute renal failure, or hypertensive encephalopathy.⁷⁹ In hemorrhagic stroke, the goal of blood pressure management is to maintain mean arterial blood pressure < 130 mmHg andCPP > 70 mmHg.⁸⁰

Because of the importance of not overaggressively treating hypertension in acute stroke, blood pressure management in acute stroke should be done in a controlled manner with continuous assessment andclose titration of medications used. Because it is very difficult to closely monitor blood pressures andtitrate medications in the prehospital environment, current recommendations for the management of blood pressure in the prehospital environment for potential stroke patients are to not intervene andto let the body autoregulate.

Level of Prehospital Care

The availability of advanced life support (ALS) level prehospital care varies from community to community. In communities where ALS care is not immediately available, basic life support (BLS) services can provide prompt andcoordinated care of patients with suspected acute stroke, andtransport should not be delayed when ALS care is not immediately available. Unless resuscitation is required, the BLS skills of early recognition of patients with suspected acute stroke, prompt transport, andcoordination of care with the receiving facility are of more importance than the ALS skills listed above.

Stroke Centers

As recently as 2000, Alberts et al. published recommendations from the BAC for the establishment of primary stroke centers.⁸¹ These recommendations have since been adopted by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) for the accreditation of primary stroke centers.⁸² The recommendations from the BAC focus on two main objectives: patient care areas andsupport services.

Since the publication of the original recommendations by the BAC, this organization, composed of a multidisciplinary group representing a variety of professional organizations andmedical specialties, has subsequently published further recommendations for the development of comprehensive stroke centers.¹² It is the belief of the BAC that there should be two levels of stroke centers: (1) primary centers that are able to provide care for most acute stroke patients and(2) comprehensive stroke centers that act as a referral center for complex cases as well as provide a base for stroke education. In addition to these recommendations, the ASA has also published recommendations for the establishment of stroke systems.¹³

Both the BAC andthe ASA recommendations include sections on EMS andthe management of stroke patients. These recommendations highlight the importance of early identification andnotification to receiving hospitals of potential stroke patients, appropriate treatment of these patients, andtransport and/or transfer to area stroke centers. Recommendations from the BAC stress the importance of continuing education programs on stroke for EMS personnel andthe integration of the EMS system with the greater medical community in the development of stroke systems. The recommendations from the ASA focus on the appropriate identification of stroke patients, dispatch of appropriate level of service to these patients, andtimely transport to stroke centers.¹³

To this date, there have been no studies published that have compared outcomes in patients who are primarily transported to a stroke center to patients primarily transported to a non-stroke center. However, there have been a number of studies published that have demonstrated improved outcomes when patients are either admitted to a stroke unit or receive specialized stroke care.⁸³, ⁸⁴, ⁸⁵, ⁸⁶, ⁸⁷, ⁸⁸ There are many possible reasons for improved outcomes when a patient is admitted to a stroke center.

In a prospective study of patients admitted to nine VA hospitals with acute ischemic stroke, Goldstein et al. demonstrated that patients cared for by neurologists have improved outcomes.⁸⁹ Mitchell et al. published similar findings in their study in which stroke patients treated by a neurologist had a 22% less mortality rate than similar patients treated by an internist.⁹⁰ A few of the possible explanations for improved outcomes when stroke patients are managed by a neurologist might be: focused diagnostics, appropriate treatment, prevention of complications, andrehabilitation.

On the basis of the available literature demonstrating improved outcomes when stroke patients receive specific treatment plans, JCAHO has published a list of 10 measures that should be considered in the certification of stroke centers.⁹¹, ⁹² While many of these measures can be accomplished at a typical community hospital, the coordination of all of these measures by a neurologist at an accredited stroke center has the potential to lead to improved outcomes in the care of stroke patients.

Implications for EMS Systems

Emergency medical services systems are a vital component to the management of stroke patients. There continue to be emerging treatment modalities for stroke patients that are applicable to the out-of-hospital environment. Therefore, EMS medical directors should develop protocols that address a multitude of issues related to the care of stroke patients. These protocols may include appropriate identification andtreatment of stroke patients as well as the integration of the EMS system into regional stroke systems.

For the identification of potential stroke patients, EMS medical directors should include training in stroke screening as a part of the formal curriculum within the EMS system. EMS providers working in emergency dispatch centers as well as in the field should use a standardized method to identify andassess patients who may be having a stroke. Standardized screening is an important tool in early identification of potential stroke patients.

For the treatment of stroke patients, protocols should address position of patient during transport, use of oxygen therapy andairway management, placement of intravenous lines andadministration of intravenous fluids, electrocardiographic monitoring, blood glucose monitoring andcorrection of hypoglycemia, administration of aspirin, andmonitoring of blood pressure derangements. These protocols should be continuously reviewed to reflect current evidence-based treatment practices. EMS providers should also have regular continuing education in the evaluation andtreatment of potential stroke patients.

Regarding stroke centers, there may be times when primary transportation to a stroke center is not feasible within an EMS system. There may be some EMS systems that will not have a stroke center in the geographic region. Some EMS systems may be in areas where primary transportation will require excessively long transports taking an EMS unit out of its primary coverage area. There may also be times when primary transportation to a stroke center may be contraindicated such as if the primary hospital is not the closest hospital andthe patient is in need of emergent treatment for situations such as a compromised airway. However, in these situations when primary transportation to a stroke center is not feasible, secondary transfer of these patients to a hospital with specialized stroke services may be necessary.

Regarding the development of stroke systems of care, EMS medical directors andadministrators should be active participants, if not leaders, in the development of regional stroke systems. It is important to note that there is controversy in the concept of developing stroke systems of care. There are no data that demonstrate improved outcomes when patients are primarily transported to stroke centers. However, there are data that show improved outcomes when patients are ultimately cared for at a hospital with the capacity to deliver specialized stroke care, even if this means secondary transfer from the facility where the initial therapy, including the decision to administer or not administer thrombolytics, is made. Therefore, EMS systems andmedical directors should take a leadership role in developing local andregional strategies for the transportation of patients with acute stroke symptoms. These strategies should include the indentification of (1) centers that are capable of providing acute stroke treatment (e.g., thrombolysis) andthe criteria for identifying the patients who should be transported from the scene to these centers and(2) centers that have the capacity to deliver postacute stroke care, andEMS systems should anticipate andbe able to accommodate potential secondary transfers of patients if they are initially taken to a center that doesn't offer these services.