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What is a stroke?


A stroke is different from other conditions, as it's essentially a term for the symptoms and not the cause


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What is a stroke?


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By Stephen Norcup

When we think of a stroke, we think of patients who are suffering some sort of acute neurological issue that manifests itself with a variety of symptoms. These can range from numbness and weakness on one side of the body (hemiparesis), a change in mental status or even in more subtle ways, such as someone who simply feels forgetful or is unable to verbalize complete thoughts.

A stroke is different from many conditions as it essentially a term for the symptoms and not the cause. There are two distinct causes of stroke symptoms, and this is the primary way we begin to stratify stroke. The first is an occlusive stroke, while the second is a hemorrhagic stroke.  Think of an occlusive stroke as something similar to the heart attack that we’re familiar with: a blockage of one of the blood vessels that supplies oxygen-rich blood to the brain deprives a portion of the brain with the oxygen and nutrients needed to function.

Stroke is the number one cause of disability in the United States. (Photo/Pixabay)
Stroke is the number one cause of disability in the United States. (Photo/Pixabay)

A hemorrhagic stroke, on the other hand, is a rupture of one of these blood vessels in the head. These ruptures can be large and develop quickly, or small and subtle and become worse over time. Either way, as free blood leaves the circulatory system, it causes elevated pressure in the patient's brain which increases intracranial pressure (ICP). This increased ICP then prevents blood from perfusing healthy brain tissue, leading to similar symptoms as on occlusive stroke. One interesting note is that a hemorrhagic stroke can have pain associated with it while an ischemic stroke does not.

Generally speaking, the literature shows that occlusive strokes make up 80 percent of all strokes, while hemorrhagic strokes make up the remaining 20 percent. There is also the subject of a Transient Ischemic Attacks (TIA), which are considered by most to be occlusive in nature but resolve on their own without intervention. When speaking in broad terms, TIAs are normally considered non-LVO occlusive strokes and, depending on the context, may not be considered a stroke.

  1. Occlusive Stroke:
    • Large vessel occlusion.
    • Non large vessel occlusion.
  2. Hemorrhagic Stroke
    • Intracerebral hemorrhage.
    • Subarachnoid hemorrhage.

How do we treat a stroke?

Looking back in history to the Dark Ages, we can see evidence of practices such as trepanning, or drilling a hole in someone's head. The logic was similar to that of bloodletting, which has also gone by the wayside, but ironically was most likely effective at reducing ICP, and may have actually done some good if we don’t consider the rate of infection before antibiotics. There was also a long period of time where “supportive care” was considered good clinical practice. This translates into putting the stroke patient into a bed and observing them while trying to keep them comfortable and treating any complications that arose along the way.

In 1996, a medication called tissue plasminogen activator (tPA) was approved for use in the treatment of stroke. Normally, our bodies create blood clots through a mechanism referred to as the clotting cascade, and this enables our bodies to stop leaks in the circulatory system and begin the healing process. After administration, tPA not only prevents the formation of new clots, but can actually break down existing clots into smaller pieces.

After the approval, treatment protocols were developed by physicians to determine when to administer tPA. The problem with interfering with the clotting cascade is that it comes with a significant risk. Uncontrolled bleeding leads to systemic hypovolemic shock, and if the patient has an underlying condition, such as a minor GI bleed or an already leaking aneurysm, tPA can have devastating, if not fatal, side effects. Ultimately, in most healthcare settings, the decision to administer tPA is left to a neurologist. Initial protocols emphasized a three-hour treatment window for administering tPA, as the conclusion seemed to be that brain tissue which had gone more than three hours was most likely not salvageable, thus the risks outweighed the benefits. However, many organizations have pushed this window to four and a half hours.

At the same time, the practice of vascular surgery was busy developing new techniques. Neurologists began snaking catheters from the groin past the chest into the head and physically removing blood clots in patients suffering from LVO stroke. This procedure is referred to as mechanical thrombectomy. While it is still early to consider mechanical thrombectomy the gold standard in occlusive stroke care, that does seem to be the direction we are headed. The most recent American Heart Association guidelines published in 2018 officially recommend considering a hospital bypass in situations where mechanical thrombectomy may be the best course of treatment for the patient.

Hospital Type

Capabilities

Primary Stroke Center

Access to neurology for consult and ability to administer tPA (note: telestroke or remote consults are permissible).

Thrombectomy Capable Stroke Center

Ability to perform mechanical thrombectomy with staff on call.

Comprehensive Stroke Center

Able to perform 2 simultaneous mechanical thrombectomies with staff in house.

There is also the idea that treating hemorrhagic stroke requires surgical intervention to address both the increased ICP, as well as addressing the issue with the circulatory system that caused the issue to begin with. This often involves removing the blood through a surgically placed drain, and often a vascular procedure to clip or repair the leaking blood vessel.

I have heard the question asked many times: “Why don’t we give stroke patients aspirin the same way we do for heart attacks?” While an occlusive stroke patient would most likely benefit from the anticoagulation properties of aspirin, it would do significant harm to the 20 percent  suffering a hemorrhagic event.

The stroke scales in use

Now that we understand the different kinds of stroke, and the treatment options available, let's talk about getting the patients to where they need to go. This article will not cover performing these scales, but talk about the differences between them.

The NIHSS stroke scale is the most comprehensive clinical stroke scale available today. It is, however, a highly involved scale that, generally speaking, is not taught to prehospital providers or used in the field. Initially, EMS began using scales designed to determine if the patient was having a stroke. The two most popular stroke scales in use seem to be the Cincinnati Prehospital Stroke Scale (CPSS), and the LA Prehospital Stroke Screen (LAPSS).

While these scales can be described as effective, many systems (my own included) have begun incorporating additional scales designed to screen specifically for LVO strokes. Specifically, the Rapid Arterial Occlusion Evaluation (RACE) scale, as well as the Los Angeles Motor Scale (LAMS).

EMS ability to treat stroke

We were born as an industry to reduce death and disability on the highways, and we did that by building infrastructure to both respond to and then transport critically ill patients to a network of trauma centers within the golden hour. When we found that we could perform aggressive interventions on heart attack patients if we got them to a cath lab quickly, we applied the same model and it worked.

With the innovation in stroke care over the past decade, we are seeing another opportunity where EMS can have a profound impact on a patient’s outcome if we can accurately identify a disease early and leverage the appropriate resources effectively. Stroke is the number one cause of disability in the United States. Taking the right patient to the right hospital means the difference between walking out of the hospital as opposed to requiring personal care.
 

About the author

Stephen Norcup is a paramedic with Munhall (Pa.) Area Pre-Hospital Services; and director, clinical operations, Forest Devices, Pittsburgh, Pa.

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