Cardiac & Resuscitation, Patient Care, Trauma

Timely Prehospital Management of Stroke Victims Crucial for Patient Outcome

Issue 1 and Volume 40.

Although prevention and early treatment have markedly reduced the morbidity and mortality of stroke, it remains a significant health and social burden. This past decade saw stroke drop from the third to the fourth leading cause of death in the United States, but it remains a leading cause of adult disability.1

The cost of stroke is crippling, both in direct costs and lost opportunity. The global circumstances of stroke are even more dire—in many countries, it’s the second leading cause of death, and the rates of stroke are projected to double by 2030.2 To make an impact on this growing societal epidemic, the healthcare community must continue to improve our prevention and overall management of stroke.3

Fortunately, professionals involved in stroke care can learn from other healthcare successes. For medical conditions where timely identification, transport and intervention may mean the difference between life or death, integrated systems of care, including prehospital care coordinated with regional hospital services, saves lives.4

Outcomes data clearly show the benefits of such systems of care for trauma and ST elevation myocardial infarction (STEMI). More recently, data from similar systems of care for stroke suggest improved outcomes and less morbidity.5,6 

Biology of Stroke

The term “stroke” collectively refers to all acute cerebrovascular disease, including ischemic and hemorrhagic types. Both forms share many risk factors, including diabetes, hypertension, smoking and age, and typically produce focal neurologic symptoms that are important to recognize. Prevention strategies and early management principles are similar between the two forms of stroke, but definitive interventions are specific to each type. Regardless of cause, targeted therapies that improve patient outcomes must be delivered within minutes to hours from symptom onset in order to be maximally effective.

Ischemic strokes occur due to an arterial occlusion, which causes brain tissue to infarct from a lack of oxygen and glucose. (See Figure 1 below). Occlusions can occur from either local vessel narrowing, causing thrombotic strokes, or due to clots originating elsewhere like the heart, which embolize to the vessel and cause embolic strokes. Regardless of cause, brain tissue is extremely sensitive to ischemia and begins to suffer irreversible damage within minutes of onset. To minimize permanent disability, blood flow must be restored quickly and overall brain physiology carefully managed, including in the prehospital setting.

Figure 1: Ischemic vs. hemorrhagic stroke

CanStockPhoto/alila

 

In the U.S., hemorrhagic strokes occur much less frequently than ischemic strokes, accounting for about 20% of acute infarcts. However, in other countries such as China, over half of all strokes are hemorrhagic. Intracerebral hemorrhage (ICH) is a form of stroke that causes bleeding into the brain tissue itself.8

In older patients, ICH typically occurs due to amyloid deposition in smaller arteries, producing typically smaller, less disabling strokes. In younger patients, ICH is associated with hypertension, producing vascular damage in small blood vessels deep within the brain. Due to the hemorrhage size and location, it’s more often disabling and lethal.

Subarachnoid hemorrhage (SAH) typically occurs in younger patients due to a structural weakness in an artery producing an aneurysm in the vessel wall, which suddenly ruptures. Both forms of hemorrhagic stroke tend to be more severe than ischemic stroke.

Goals of Treatment

The goals of emergent stroke treatment are twofold: First, prevent or reverse the source of injury (limit hemorrhage growth in ICH or restore blood flow in ischemic stroke), and second, optimize the patient’s physiology as soon as possible to maximize chances for injured, but not infarcted, tissue to recover.

In ischemic stroke, the area of brain tissue that’s irreversibly injured is referred to as the “infarct” or “core.” The area of brain with decreased blood flow that hasn’t experienced irreversible damage is called the “penumbra.”

The penumbra is the target of directed interventions. Opening obstructed blood vessels with either thrombolytics, such as recombinant tissue plasminogen activator (rt-PA), or direct intra-arterial clot removal, may restore blood flow to the penumbra, limiting damage and reversing some if not all neurologic deficits.

The key to these interventions is time. If blood flow isn’t restored within the first several hours from symptom onset, the tissue will infarct, leaving little chance of improving outcomes.

Physiologic management in ischemic stroke parallels many strategies employed for traumatic brain injury and post-cardiac arrest. Maintaining cerebral blood flow, ensuring appropriate oxygenation and maintaining optimal serum glucose levels are key to maximizing brain tissue function and limiting secondary injury.6

In the prehospital setting, physiologic management is largely based on optimizing the ABCs—airway, breathing and circulation. Currently, specific targeted stroke interventions are typically reserved for the hospital setting once the stroke type is established and the patient’s comorbidities considered. Yet, recognizing the importance of time, ongoing studies may demonstrate that similar strategies can and should be deployed in the prehospital setting to maximize patient outcomes.

Stroke Systems of Care

In 1996, the Food and Drug Administration (FDA) approved intravenous rt-PA as the first treatment of acute ischemic stroke. Despite the approval, the healthcare community took a decade to realize that hospitals needed to organize internal and external stroke systems of care to optimally utilize the drug and to maximize the chance for favorable outcomes in all stroke patients, not just those who received rt-PA.9

The development of primary stroke centers (PSCs) was the first and most important step in establishing stroke systems. From the very beginning, prehospital care was a critical stakeholder in the process and an enthusiastic promoter of emergency stroke care. Similar to lessons from the U.S. trauma model, stroke healthcare professionals soon realized that more comprehensive stroke centers (CSCs) were required to diagnose and treat more severe ischemic strokes and all forms of hemorrhagic strokes.10

Services provided by CSCs are highly specialized and require a significant commitment of personnel and resources. (See Table 1 below.) Through various certifying organizations, roughly 1,600 of the 5,000 hospitals in the U.S. are certified as PSCs or CSCs. Recognizing that patients with suspected stroke may not be near a PSC or CSC, acute stroke-ready hospitals (ASRH) were established to provide the minimum service required to diagnose ischemic strokes and consider treatment with rt-PA.11,12

Table 1: stroke hospital capabilities and requirements 

Most ASRHs don’t have onsite neurologic expertise, so telemedicine systems providing real-time video and voice communication and teleradiology allow remote stroke experts to assess the patient and collaborate with onsite physicians to make treatment decisions. This organization makes a difference—certified stroke centers, especially those that treat large numbers of patients, are more likely to administer thrombolytics in a timely fashion to eligible patients.7,13,14 Although ED physicians can safely administer thrombolytics, dedicated stroke teams have better protocol compliance.15

Establishing individual stroke centers is necessary but not sufficient for optimizing stroke care. Again similar to trauma and STEMI care, regional resources must be integrated into a cohesive system that uniquely utilizes all local resources, including hospitals, prehospital care systems, dispatch centers and air medical services.5 (See Figure 2 below.)

Figure 2: Stroke systems of care

Engaging all stakeholders from the onset of stroke system development is essential to overcoming logistical and political barriers. Several states such as Florida, California, New York and South Carolina have used legislation to form task forces to establish stroke systems of care.16,17

Through these stroke systems of care, patient outcomes improve by providing optimal acute treatment and attention to overall stroke management and prevention strategies. Studies show that patients presenting to PSCs have better outcomes in general compared to non-stroke centers, and more severe strokes are better addressed at CSCs.18 As a result, CSCs are increasingly becoming integrated regional centers that provide immediate support to smaller, surrounding hospitals.5

Integrated stroke systems of care are a two-way street: not all patients can go to a CSC or PSC. Therefore, elevating the level of stroke care everywhere is key, and utilizing expertise at CSCs and PSCs can help provide critical feedback to healthcare providers who collaborate on public and healthcare provider education.

Regardless of stroke care capability, all hospitals within a region must have a stroke plan and a protocol for interfacing with other hospitals in the local stroke system.

Prehospital Stroke Management

Prehospital management begins when patients or bystanders recognize stroke signs and symptoms and call 9-1-1, but rapid assessment and transport are of little utility if the patients don’t arrive at the hospital within treatment windows.

The American Heart Association has developed the stroke chain of survival (detection, dispatch, delivery, door, data, decision, drug), where the initial links focus on stroke recognition and EMS engagement. Community education on stroke symptoms and early EMS access are critical.

Most recently, the pneumonic “think FAST”—facial droop, arm weakness, speech slurred and timeliness—is being used to educate the public on strokes. However, although some educational programs have successfully increased awareness of stroke symptoms, the majority of patients still miss the treatment window.19

9-1-1 Activation

Once 9-1-1 is activated, stroke recognition is essential. With the advent of emergency medical dispatch tools and the use of dispatch protocols, patients with stroke-like symptoms are more easily recognized by 9-1-1 operators. However, there’s still variability, with correct identification varying between 30% and 83%.19

Any patient presenting within a 6–8 hour window of symptom onset should still be considered a candidate for acute endovascular intervention and appropriate response configurations utilized. Use of protocols clearly helps determine dispatch prioritization, which is critical to early intervention.

There are many barriers to treatment, primarily due to delays in hospital arrival after symptom onset.5 Patients who don’t call 9-1-1, have a stroke history or mild symptoms, or who are ethnic minorities or live in rural communities, all have lower rates of treatment.7

Most importantly for prehospital providers, the early EMS notification of the receiving hospital will make timely treatment more likely. Therefore, barriers should be identified to ensure optimal care.

Prehospital Assessment

As with all initial assessments, the airway should be assessed in standard fashion, but note that stroke patients may have difficulty managing their secretions and could be prone to vomiting.

If possible, the head of the stretcher should be elevated to 30 degrees. If the patient’s symptoms worsen with the head of the bed elevated, place the patient’s head back to flat since the patient may require the higher blood pressure to perfuse the area of stroke.

Typically for most stroke patients, breathing isn’t substantially altered, but if it is, ventilator assistance is warranted. Hyperventilation should be avoided unless the patient’s presentation suggests impending herniation (i.e., hypertension, bradycardia, irregular respiratory pattern) and is approved by medical control.

Circulatory status is assessed with vital signs and ECG monitoring, as stroke patients are at risk for dysrhythmias. Reassessment is required as the patient’s condition may dramatically change en route.

After the primary survey and baseline vitals, performance of a validated stroke assessment tool aids in the recognition of possible stroke. There are a variety of prehospital scales and screens that are widely used, but the most common are the Cincinnati Prehospital Stroke Scale and the Los Angeles Motor Scale.20,21 (See Table 2 below.)

Table 2: Prehospital stroke scales

If any one of these is abnormal then there’s an 88% sensitivity for anterior circulation stroke.

The LAMS socre is closely correlated with the full National Institutes of Health stroke scale. LAMS > 4 carries an over seven-fold increase in risk for large vessel occlusion.

 

 

These screening tools  attempt to balance ease of use with accuracy in order to help identify the presence of neurologic impairment, but they have some limitations.

First, the gross motor exams utilized can miss subtle strokes. Conversely, most prehospital stroke scales fail to grade the severity of the stroke, which may have implications in selecting an appropriate destination facility. Second, these scales may suggest a stroke when another cause of the patient’s symptoms exist, conditions termed “mimics.” (See Table 3 below.)

Table 3: Conditions with stroke-like symptoms (mimics) and unique features

More comprehensive, graded exams may help to identify and quantify specific stroke characteristics that assist in determining triage and treatment options.22 These scales are also available online and as smartphone applications. Unfortunately, these scales are more time consuming and may be more difficult to remember than the earlier stroke assessment tools, but in conjunction with a good patient history, the newer scales can provide a clearer picture of the patient’s condition.

Stroke mimics may account for more than 20% of patients with neurologic symptoms being considered as an acute stroke in the prehospital setting.23

Although it’s impossible to exclude all stroke mimics in the prehospital setting, a basic understanding of mimics should prompt providers to ask pertinent questions of the patient or family, which may lead to more effective patient care. Regardless of the stroke tool used, providers should always consider stroke mimics in their differential but should err on the side of treating the patient as a stroke.

The patient’s medical history is critically important. Particular attention should be paid to potential stroke risk factors, such as atrial fibrillation, hypertension, diabetes, previous strokes, transient ischemic attacks, recent surgeries and smoking.6

One of the most important elements of the patient’s history is the time of symptom onset, which will dictate many treatment options. The time of onset is based on the last time the patient was known to be “normal” or at their baseline, as opposed to when the patient was found with the neurologic deficits.

Current guidelines support the use of rt-PA within 0–4.5 hours in carefully selected patients and endovascular therapies up to 8 hours from symptom onset in patients with more severe strokes.

It’s also important to document the patient’s baseline physical and mental state, especially for patients with previous neurologic, physical or cognitive deficits. To determine last “normal” time, ask the patient, family members, caregivers or bystanders.

If they’re unsure about a specific time, inquire about other time clues such as daily routines, TV shows or recent phone conversations.6

The process of stroke identification in the prehospital setting is constantly evolving as treatments become more advanced. Consider stroke severity and time from symptom onset when triaging a patient; this also helps to provide important prearrival information to the stroke team.

Rapid Initiation of Treatment & Transport

Once the assessment and history are complete, prehospital focus should be on rapid initiation of treatment and transport. On-scene time should be less than 15 minutes whenever possible and the patient should be treated with the same urgency as major trauma or STEMI.6

The management plan should include frequent reassessment and management of the ABCs, as well as vital signs and cardiac and pulse oximetry monitoring. (See Table 4 below.) If necessary, oxygen therapy should be applied to maintain an SpO2 above 94%, though supplemental oxygen isn’t recommended in nonhypoxic patients with acute ischemic stroke.6

Table 4: American Heart Association recommendations for prehospital management of potential stroke6

Finger-stick blood glucose testing should be performed in all patients with stroke-like symptoms, and hyper- or hypoglycemia should be corrected accordingly.

Other interventions are rarely required in the prehospital setting, unless the patient begins to decompensate with airway or ventilatory compromise, cardiac dysrhythmias or hemodynamic instability. Currently, there’s no evidence to support prehospital lowering of blood pressure in hypertensive patients with possible stroke, and in some cases lowering blood pressures to normal levels could exacerbate the patient’s symptoms. Prehospital administration of aspirin or other antithrombotic agents to these patients is also not supported by published studies at this time.

Transport and destination facilities are critical decisions in effective stroke treatment. As previously mentioned, patient outcomes are better if they’re treated at a stroke center, though in most cases bypassing the closest facility for a higher level of care shouldn’t extend transport time more than 20 minutes.

Use of helicopter EMS (HEMS) increases access to thrombolytics for patients residing in communities that lack specialty facilities and should be utilized when necessary.24–26

If the patient is too unstable for a prolonged transport and HEMS isn’t possible, transport to the closest facility for rapid assessment, stabilization and preparation for transfer to a stroke center.

Early EMS notification of the receiving hospital is critical and has been clearly shown to reduce ED times to definitive treatment.19 Reports should include last known normal time, stroke screen results, vital signs, blood glucose, current medications and any acute interventions.

ED Management

With prehospital notification, all the necessary components of the hospital-based stroke team can be at bedside prior to patient arrival. A rapid assessment of the ABCs on arrival allows for most patients to be taken directly to the CT scanner by EMS, significantly reducing imaging delays. Concurrent physical evaluation, diagnostic testing and medical history review substantially reduce door-to-needle time to less than the currently recommended 60 minutes.

A recent study of 58,353 patients treated with IV rt-PA clearly demonstrated the importance of time to treatment, finding that “among 1,000 treated patients, every 15-minute-faster acceleration of treatment was associated with 18 more patients having improved ambulation at discharge … and 13 more patients being discharged to a more independent environment.”27

Interhospital Transfers

The “drip and ship” practice—assessing a patient and initiating thrombolytics before transfer to a higher level of care—may be an appropriate treatment choice for patients presenting within the therapeutic window.5

EMS providers involved in such patient transfers should carefully monitor vital signs and neurologic exams. Maintaining blood pressure at least below 180/105 mmHg is required after thrombolytics. Clinical deterioration may indicate an intracranial hemorrhage.

Air medical transport has been shown to be safe and effective, including for those patients who’ve received thrombolytics. As with field transport of stroke patients, early hospital notification is critical. Preplanning of the transfer process is key to minimizing delays once a stroke patient requires transfer to a higher level of care.

The Future of Prehospital Stroke Care

Recognizing the need for timely interventions, more and more hospital-based strategies are being deployed in the prehospital setting, including diagnostic tools, directed therapies and physiologic management.

To further minimize delays to treatment, some centers are equipping ambulances with mobile CT scanners, video telemetry and, in some cases, neurologists. This model employed in a study by Audebert and colleagues in Berlin led to a reduction in call-to-needle time of 36 minutes.28

Similar models are being studied in Houston and Cleveland. This high-tech, high-resource approach may not be broadly applicable in more rural areas, but demonstrates the growing appreciation for incorporating the prehospital setting in acute treatment paradigms.

No drug or therapy administered in the prehospital setting has been shown to improve patient outcomes, but recent studies show early treatment is feasible.29

Summary

Stroke is a time-dependent emergency and prehospital involvement is crucial for maximizing patient outcomes. System development of regional resources into a cohesive system is the cornerstone of stroke care.

Early EMS activation, identification, management, and rapid transport and triage to the most appropriate stroke center will give the patient the best chance to make a full recovery. 

References
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