Heat Illness

The protocol for Heat Illness: 

Heat Illness


Let’s break it down!

Heat illness is a term that describes a range of conditions that can occur when the body becomes overheated.  It can be minor, moderate, or severe. 

Minor heat illness describes hemodynamically stable patients who experience localized heat-related symptoms like heat cramps, heat rashes, heat edema, etc.  Although they can be painful and annoying, it is not life-threatening so the protocol doesn’t focus on this  

Moderate heat illness or “Heat exhaustion” is when the body begins to systemically react to the rigors of the heat with a range of symptoms (nausea, headache, tachycardia, etc.), but is still able to compensate and keep the body at a normal temperature.  In addition, the patient is also still able to maintain a normal mental status, which is key in diagnosing.  

Severe heat illness, also known as “Heat Stroke“, occurs when the body’s cooling mechanisms (sweating, cutaneous vasodilation, etc.) begin to fail.  The patient’s core body temperature gets above 104 degrees and several physiological consequences begin to occur: enzymes denature, blood is shunted away from the vital organs, and eventually, the patient succumbs to multi-system organ failure. Also, the patient’s mental status begins to decline from encephalopathic changes (hence the term heat stroke). Although a patient with a heat stroke is not necessarily having an actual “stroke”, it can be just as life-threatening. The mortality rate is anywhere from 10%-50%.  Elderly patients are especially at risk because their cooling mechanisms do not function as efficiently.   

Heat illness is still a major problem today, especially for athletes and soldiers who exert themselves in hot, humid environments quite frequently.  The military alone had up to 344 cases of heat-related injuries, and those were just the ones reported. Annually in the US, an average of 658 people die from heat illness.

The video below by Dr. ER summarizes the topic very well:

Heat Exhaustion

If you’ve ever been hard at work outside in the summer and you felt like crap, you probably had some degree of heat exhaustion.  Headache, nausea, dizziness, and tachycardia are all pretty typical. It’s also not uncommon for patients to physically collapse or experience a brief, syncopal episode. 

Profuse diaphoresis (sweating) is also a good indicator that the body’s temperature-regulating mechanisms are still functioning, but don’t rely too heavily on this for a diagnosis; heatstroke patients have historically been ignored due to the false security that the patient still had sweat on their skin. 

Health & Exercise For Busy People: Heat Stroke Vs Heat Exhaustion ...







Heat Stroke

Two defining features are required for a heat stroke diagnosis: 

  1. Temperature >104 degrees F.
  2. Altered Mental Status

The temperature needs to be a core temperature taken the rectal route; other forms have taking temperature have proved to be unreliable. Altered mental status can be anything from being unable to answer questions appropriately to delirium or coma. The video below shows a real heat stroke patient.  As you can see, it can get pretty serious:


The best, and only real treatment, for heat illness is rapidly cooling the patient.  This means removing them from their current environment and taking actions to actively bring their core temperature down to a normal level. For patients with just heat exhaustion, letting them relax in a nice air-conditioned area might be enough.  But for heatstroke patients, more aggressive measures need to be taken. The gold standard for rapidly reducing body temperature is to do a full-body immersion in ice water, being sure to keep the head elevated out of the water.  We also need to be careful that we don’t cool the patient for too long and cause hypothermia, which can be just as hemodynamically damaging.

If you don’t have a tub or enough ice to do this, then the next best thing is to use continuous dousing of cold water or ice sheets.  Be prepared to switch out ice sheets frequently, especially if you’re in a hot environment.

NAR Polar Skin Ice Sheet - Large | North American Rescue

If conductive measures aren’t available, then another effective cooling mechanism we can maximize is evaporation. By spraying the patient with light coats of water and encouraging surrounding air movement with a fan, the water will evaporate and take with it the heat from the patient’s body. This is essentially why sweating can cool us in the first place.

Glucose is mentioned as a potential treatment as well.  Not because the glucose does anything to cool the patient, but because there is always a chance that heat illness could be confused with hypoglycemia. Giving an empiric dose of glucose or sugar-rich food source is a good way of ruling this out.  

Glutose 15 Oral Gel – Amada First Aid




3. Treat per Dehydration protocol

Suffering from a heat illness doesn’t necessarily mean that the patient is inherently dehydrated, but usually, they are. A good rule of thumb is to initiate oral rehydration before moving to IV fluids, which is shown to be just as effective. If the patient has an altered mental status, go straight to IV fluids.

4. Treat per Nausea/Vomiting protocol

As we discussed earlier, nausea is a frequent symptom of heat exhaustion/heat stroke. Rehydration itself may help with nausea, but if not, Ondansetron would be a good choice for nausea control.  Promethazine can be considered if active vomiting is occurring, but it’s generally not ideal for heat illness due to its sedative properties and potential side effects. 

5. For cola-colored urine or severe muscle pain, treat per Rhabdomyolysis protocol

Patients with heat illness who just finished with rigorous physical activity are also at risk for a condition called Rhabdomyolysis. In a nutshell, rhabdomyolysis is a condition caused by extensive injury to the skeletal muscles, resulting in a leakage of large quantities of potentially toxic intracellular contents like myoglobin, potassium, etc. The kidney has a difficult time processing these contents, which is why patients may present with cola-colored urine. If the patient has this or excessive muscle pain, then you’ll initiate treatment via the Rhabdomyolysis protocol, which entails aggressive IV fluid hydration and management of hyperkalemia (high potassium)

Rhabdomyolysis - Wikipedia






Most patients with heat exhaustion can be managed by the medic and be observed for a while to ensure that symptoms of heatstroke don’t develop. If the patient has a core temperature greater than 104 degrees F. and altered mental status though, rapidly cool the patient and then get them the hell out of there. These patients will need a hospital team if multi-system organ failure sets in.


Good luck out there!



Brandon Simpson, PA-C
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