Brett Patterson

Brett Patterson

Ask Doc

By Brett Patterson

Dr. Clawson:

I am an EMD-Q for my agency and we have a few people who will try to use the stroke card for a heat stroke rather than heat exposure. I wanted to know if we could get the International Academy’s explanation regarding which card to use. I’ve tried explaining the reason for using the heat exposure card; however, I would like to have something in print from the Academy, which would help all of us make the better choice in these situations.

Ashley Partridge


Macoupin County ETSB

Carlinville, Illinois, USA


I forwarded your question to Brett Patterson, chair of the Medical Council of Standards for the Academy. I also added my comments to his response.

Dr. Clawson


Your question is interesting as I have not heard it before. I will try to explain the difference between the two clinical terms you are referring to and describe when to use each associated protocol.

“Stroke” is a term used to describe disruption of blood flow to part of the brain. There are two primary stroke types, the most common of which occurs when a clot lodges in a blood vessel in the brain and cuts off blood supply to the part of the brain fed by the affected artery. Left untreated, this leads to part of the brain dying and the patient experiences symptoms related to that area of the brain’s function, i.e., loss of motor function, paralysis, weakness, speech or sight deficit, and even death. This type of stroke is called a thrombolytic stroke, or a “clot” stroke. It is most common in elderly patients and can now be treated with clot-busting drugs, provided the patient is diagnosed and treated promptly.

The other type of stroke is called a hemorrhagic stroke, or brain “bleed.” In this case, a blood vessel in the brain bursts, often because the vessel is malformed and weak (often called a brain aneurysm). The condition is usually present from birth but the patient is unaware of the problem until the vessel breaks and bleeds into the brain. This condition happens in younger patients far more frequently than clot strokes, and it is often fatal. It is also increased in people with cardiovascular disease and high blood pressure. The symptoms of a hemorrhagic stroke may be the same as a thrombolytic stroke, but often the patient either experiences a sudden onset of a severe headache, or sudden coma, or death.

Fortunately, the EMD does not need to differentiate between a thrombolytic stroke and a hemorrhagic stroke, but rather be familiar with the signs and symptoms, which are usually easy to recognize. In fact, the lay public often recognizes the symptoms of stroke and reports the Chief Complaint as a stroke. Caller accuracy regarding this diagnosis is why Protocol 28 is titled “Stroke,” rather than some symptom of stroke. However, the EMD must also be familiar with the signs and symptoms of stroke, which are listed on Protocol 28 in the STROKE Symptoms definition section. The EMD should select this protocol when the caller either reports a stroke, or when the Chief Complaint is consistent with the signs and symptoms listed in the STROKE Symptoms definition section of Protocol 28. The symptoms include a sudden onset of weakness, numbness, or paralysis on one side of the body; sudden trouble seeing, speaking, or understanding; or sudden loss of coordination or balance. Notice the common theme here? Sudden onset is a hallmark of stroke.

“Heat Stroke” is a diagnosis used to describe the very serious, latter stages of heat exposure when the internal body temperature exceeds 104 degrees (this definition varies by a degree or so, depending on the reference). The word “stroke” is probably used in this diagnosis because severe hyperthermia (high body temperature) affects the brain, and can even destroy brain cells. Heat stroke occurs when a patient is exposed to abnormally high temperatures for an extended period of time or when a patient exercises/works excessively in a warm environment. Various factors that inhibit the body’s ability to cool itself can predispose patients to heat stroke, such as a lack of fluid intake, alcohol/caffeine/stimulant intake, or very young or old age.

The signs and symptoms of heat stroke are different than the more common vascular stroke in several ways. First, the complaint of heat stroke is almost always associated with heat exposure and is preceded by the more common signs and symptoms of heat exhaustion (sometimes referred to as heat prostration). When a patient is exposed to heat, the body naturally cools itself through sweating and exhaling warm air. When the external heat and/or exercise exceeds the body’s ability to cool itself, the patient’s internal temperature rises and the patient becomes fatigued, often nauseated, and may develop cramps. These patients are generally sweaty and pale in color. Eventually, if the patient is not removed from the heat source and cooled down, the patient’s internal temperature rises to a point where the body can no longer maintain a safe temperature, and the brain, being very sensitive to extreme temperatures, becomes affected. This is the point where heat exhaustion becomes heat stroke—the patient’s skin becomes dry and red and her/his level of consciousness deteriorates. S/he may become confused to the point of not recognizing the danger of the heat and, eventually, the patient will become unconscious and may suffer brain damage or even die if not treated promptly. The highest reported human temperature in which the patient survived was 115.70 F (46.50C) in 1980.

Note that a primary difference between these two conditions is the patient’s recent history. A typical stroke has a very sudden onset when blood flow to the brain is suddenly slowed or stopped completely. This is emphasized in the STROKE Symptoms definition section of Protocol 28 by the repeated term “sudden,” i.e., the patient suddenly has trouble speaking or suddenly cannot move the left side of her/his body. Additionally, a typical stroke is most often unilateral. In other words, it generally affects one side of the body only. With heat stoke, the signs and symptoms are associated with heat exposure and a slower development of symptoms, i.e., clammy, nauseated, and cramping, followed by changes in level of consciousness.

Ultimately, correct Chief Complaint Protocol is achieved by listening carefully to the caller’s response to “Tell me exactly what happened?” and repeating/clarifying this when a clear answer is not obtained. A Chief Complaint involving heat exposure drives the selection of Protocol 20, while a complaint of stroke or sudden onset of stroke symptoms should prompt the EMD to select Protocol 28. Familiarity with the signs and symptoms of these two very different conditions will also help the EMD differentiate the two. Fortunately, heat stroke is relatively uncommon, and the likelihood of a caller confusing the two is also low because heat stroke is recognized by callers as being associated with heat exposure and stroke is recognized as a sudden onset of one or more physical deficits, such as the sudden inability to speak, see, or move one side of the body.

I hope this explanation will help clarify for your EMDs which protocol to use for these very different conditions.

Thank you,

Brett Patterson

IAED Academics & Standards Associate

Medical Council of Standards Chair