Introduction

The concepts of “time is muscle” for myocardial infarction (MI) patients and “the golden hour” for trauma patients are familiar. Until the mid-1990s, the treatment of stroke was focused on rehabilitation, because there were limited treatment options available. There was no urgency. Thankfully, that is no longer the case. With timely treatment, many stroke patients can return to baseline neurological functioning.

The EMS system plays a vital role in the sequence of events that gets eligible stroke patients to available interventions that will change their outcomes. In addition to EMS providers’ knowledge and skills at identifying strokes and facilitating patients’ access to timely care, they can participate with other health care colleagues to help improve general public awareness of stroke, its symptoms, and the importance of seeking help early. Early diagnosis, within a narrow window of opportunity, helps to keep treatment options available, including possible administration of fibrinolytics or mechanical clot retrieval. Thus, appropriate triage to a facility that can provide these treatments is essential.

Overview of stroke

Stroke is now the fourth leading cause of death in the United States, and it remains the leading cause of adult disability. According to the American Heart Association (AHA), approximately 795,000 people in the United States will suffer strokes each year, with 610,000 being first attacks [1].

In broad terms, strokes are classified as either hemorrhagic or ischemic. Greater than 80% percent of strokes are ischemic, but it is difficult to differentiate between these two subtypes in the prehospital setting. Radiographic imaging in a hospital setting is required. An ischemic stroke is caused by either in situ thrombus formation from atherosclerosis or an embolic event (usually from the heart or large vessels) that leads to occlusion of a cerebral blood vessel and subsequent interruption of blood flow and oxygen supply to an area of the brain. For example, one of the contributing causes of embolic strokes is atrial fibrillation, leading to embolization of a clot from the heart.

Spontaneous intracranial hemorrhage (ICH) may result from several underlying diseases. Hypertension and arteriovenous malformations are two such predisposing conditions. Patients taking warfarin or with brain tumors are also at risk. Patients with ICH sometimes 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 increase intracerebral pressure. Pupillary changes and motor deficits will be dependent on the location and extent of the bleeding. For example, bleeding into the pontine area of the brainstem will result in pinpoint pupils due to the interruption of sympathetic tracts [2].

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 incidental dysrhythmias.

When occlusion of a 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 area surrounding the central area of ischemia is referred to as the “ischemic penumbra.” Whether or not the ischemic penumbra can be salvaged depends on the severity and duration of ischemia. If possible, it is important to restore blood flow to this penumbra to decrease the morbidity and mortality of a stroke. In addition to the aspects of stroke related to blood supply, there are several chemical responses that occur on a cellular level that 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 affect the penumbra and its ability to recover [3].

When neurological deficits consistent with a stroke occur but 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 neurological deficit lasting only a few minutes [4]. TIAs had been previously defined as a neurological deficit that resolved within 24 hours. In fact, most TIAs resolve within 60 minutes and many do so within half an hour. People who experience TIAs have a 10–20% risk of stroke in the subsequent 90 days, and half will occur within the next 24–48 hours [5]. TIAs should be considered very serious events that require prompt diagnostic evaluations.