of embolic strokes is atrial fibrillation, which may lead to embolization of a clot from the heart. Hypertension is a significant risk factor for stroke, with studies showing evidence that blood pressure control to <150/90 mmHg reduces the incidence of stroke and moderate evidence that control to <140/85 mmHg is associated with a more significant decrease in incidence. Diabetes mellitus is a risk factor for stroke in all ages, but most prominently in those less than 65 years old. It is also an independent risk factor for recurrent stroke. Atrial fibrillation is a significant risk factor for stroke, increasing the risk approximately fivefold. Studies regarding the risk of high cholesterol have shown inconsistent associations at best. Smoking is proven to increase the risk of stroke up to fourfold. Genetic components have also been shown to increase risk, as stroke is known to be a hereditable disease [1].
When occlusion of a cerebral vessel occurs, there is a central area or “core” of ischemia in that region of the brain. However, there can also be a surrounding area that has decreased blood supply with the potential to recover without permanent damage. This zone surrounding the central area of ischemia is referred to as the “ischemic penumbra.” Salvage potential for the ischemic penumbra depends on the severity and duration of ischemia. Restoring blood flow to this penumbra will serve to improve neurologic recovery and patient outcomes. In addition to the effects of lack of blood supply, several chemical responses occur on a cellular level and affect brain function. These include the release of excitatory amino acids, alterations in calcium release, and free radical formation. Inflammatory responses and alterations in chemical function also affect the penumbra and its ability to recover [2].
Spontaneous ICH may result from several underlying diseases. Risk factors include hypertension, arteriovenous malformations, brain masses, and current anticoagulation or antiplatelet medication use. Patients with ICH may have more dramatic presentations, accompanied by nausea and vomiting, headache, or a sudden decrease in level of consciousness. These are the result of the nature of the insult, where the hemorrhage acts to abruptly increase intracerebral pressure. Specific neurologic deficits will be dependent on the location and extent of the bleeding. Patients with ICH may deteriorate rapidly and require airway support as the hemorrhage expands. The mass effect of an expanding hematoma may also cause contralateral motor deficits, ECG abnormalities, and dysrhythmias.
When neurologic deficits consistent with a stroke occur, but then resolve spontaneously, this is referred to as a transient ischemic attack (TIA). A TIA, according to the National Institute of Neurological Disorders and Stroke (NINDS), is a focal neurologic deficit lasting only a few minutes [3]. TIAs had been previously defined as a neurologic deficit that resolved within 24 hours. In fact, most TIAs resolve within 60 minutes, and many do so within half an hour. Patients who experience a TIA have a 10% to 20% risk of stroke in the subsequent 90 days, and half will occur within the next 24 to 48 hours [4]. TIAs should be considered very serious events that require prompt diagnostic evaluations.
An estimated 7.2 million Americans over the age of 20 self‐report a personal history of stroke. Studies differ slightly, but the generally accepted prevalence of stroke is 2.7% for both males and females over the age of 18. There are racial and geographical disparities, with African‐Americans and residents of southeastern United States having the highest prevalence. An estimated 4.1% of non‐Hispanic blacks, 1.5% of Asian/Pacific Islanders, 2.3% of Hispanics, 5.2% of American Indian/Alaska Natives, and 4.7% of other races/multiracial people have a history of stroke. Geographically, 1.9% of Minnesota residents and 4.3% of Alabama residents have a history of stroke. These data offer further evidence for the existence of a “stroke belt” in the southeastern United States, which has experienced higher rates of stroke since 1940 [1].
Each year, an estimated 795,000 individuals experience new or recurrent strokes, with a stroke occurring every 40 seconds within the United States. The death rate has decreased significantly due to early identification and intervention. Non‐Hispanic black females and males have higher death rates for stroke. Females account for approximately 58% of all U.S. stroke deaths. Geographical disparities also exist concerning mortality, with a death rate approximately 30% higher in the “stroke belt” than in the rest of the nation [1].
Emergency medical dispatch
As the first point of contact for EMS systems, a telecommunicator at a public safety answering point has the opportunity to influence the expediency of stroke patient care. In one review of recorded calls to 9‐1‐1, telecommunicators were able to identify and correctly categorize calls as strokes only 31%‐52% of the time. The caller using the word stroke was highly predictive of an actual stroke. The study concluded that telecommunicator recognition of stroke could be improved if key words such as stroke, difficulty communicating, weakness or falling, and facial droop were communicated by the caller [5]. Another study found that, even when the caller used the word stroke, the call was dispatched as a stroke only 48% of the time, and only 41% were dispatched as high priority [6]. The most frequently reported symptoms by callers were speech problems (26%), followed by extremity weakness (22%). Interestingly, fall was stated as the primary problem in 21%. Symptoms such as vertigo or sensory impairment were mentioned much less frequently [7].
Use of a modified stroke scale may help telecommunicators identify potential stroke patients and ensure appropriate prioritization of calls. The goal is to facilitate patient arrival to an ED as expeditiously as possible to facilitate imaging studies and treatment within a narrow window of opportunity. After sending appropriate resources, the telecommunicator should also provide prearrival instructions to the caller. In addition to providing dispatch life support, telecommunicators can help expedite the time EMS personnel will spend on the scene by preparing the caller for certain important questions. These include past medical history, current medications, allergies, and, most importantly, when the patient was last known to be at his or her neurologic baseline. This information is crucial for EMS clinicians, as they begin to make transport decisions regarding specific receiving facilities. The use of modified stroke assessment tools and software that meet American Heart Association (AHA) and American Stroke Association (ASA) standards may help to identify stroke patients correctly. All telecommunicators should complete formal emergency medical dispatch courses and be certified [8]. (See Chapter 88.)
Prehospital care
As always, initial attention should be directed to airway, breathing, and circulation issues to ensure a stable patient, notwithstanding the new neurologic deficit. EMS personnel should be intimately familiar with the signs and symptoms of stroke, and with regional therapeutic protocols. Scenario and simulation‐based education leads to significant improvement in EMS clinician knowledge of stroke patient care.
A stroke scale should be completed, as it will help to add a degree of objectivity to the description of exam findings that can be conveyed to medical personnel later in the sequence of care. There are several prehospital stroke assessment tools available to assist with stroke identification. The Cincinnati Prehospital Stroke Scale (CPSS) and the Los Angeles Prehospital Stroke Scale (LAPSS) are both validated instruments that can increase the sensitivity for identification of stroke [9–11]. (See Tables 18.1 and 18.2.)
Prehospital stroke scales are valuable tools. However, EMS clinicians should also consider stroke mimics (Box 18.1). Not all of these conditions will be easily differentiated in the field. However, hypoglycemia is capable of manifesting with focal neurologic findings. Thus, all potential stroke patients should have point‐of‐care glucose testing, and hypoglycemia should be treated. Additional historical features may help to determine the nature of some problems that subsequently appear similar to strokes. For example, preceding seizure activity might indicate Todd’s paralysis or increase the probability of ICH. Accompanying symptoms of migraine might indicate a complex migraine. In any case, expediency is important, but taking the time to obtain an accurate history is of vital importance to an appropriate stroke patient evaluation and potential interventions.