03.05 Hyperthermia (Thermoregulation)

Hyperthermia is where the body temperature is too high, and the regulatory responses fail. Homeostasis is not maintained in the body and cell destruction occurs. Let’s explore why this happens.

So normally the body is able to maintain thermoregulation where the body temperature is kept around 98.9 degrees. When the temperature rises above normal for too long, such as in excessive heat or exerting yourself too much, the thermoregulation of the body is not maintained. For example, a person working in a really hot warehouse all day may overheat. If they’re not drinking enough fluids then they are especially at risk for hyperthermia. Think about when the body is super hot the vessels will dilate to cool itself, and that dilation makes it harder to perfuse organs without enough fluid. On top of that, those that are overheating are sweating profusely which takes away more fluid volume from the body. Certain drugs we will discuss in a bit also can cause hyperthermia.

Next let’s talk about the different types of hyperthermia.

Heat exhaustion occurs from excessive heat exposure. This person will be sweating profusely as the body is attempting to cool itself. The heart rate will increase as the body attempts to continue perfusing the organs. The pulse weakens as the blood pressure drop from the blood volume depletion in the vessels. Next let’s look at heat stroke.

Heat stroke is worse than heat exhaustion and is where the body temperature goes above 104 degrees. At this point, the person is no longer sweating and instead has hot, dry skin because of dehydration. The heart rate continues to go up in attempt to perfuse the organs. The vessels will vasodilate in attempt to cool itself resulting in a drop of blood pressure. The loss of volume from sweating and the vasodilation from overheating will make it very hard to perfuse the organs in the body, leading to hypovolemic shock. Eventually the body goes into multisystem failure. Check out the lesson on SIRS and MODS for more details.

Another form of Hyperthermia is malignant hyperthermia. This  occurs after the patient has an anesthetic drug that creates a reaction where calcium ions are released from the muscle cells sending the body into a hypermetabolic state. This causes the muscle fibers to contract and increase the heat in the body. Some people are genetically susceptible to this and others are not.

Another cause here is neuroleptic malignant syndrome. It is where the body reacts to neuroleptic or antipsychotic drugs disrupting the hypothalamus.  Remember, the hypothalamus is the body’s temperature control center, so in this case the body temperature rises excessively. Next let’s talk about the complications of hyperthermia.

So when the temperature reaches 104 degrees or higher, the patient’s life is at risk as the body cannot maintain homeostasis and is unable to bring the temperature down. The attempts to bring the temp down like vasodilation and sweating end up sending the patient into septic shock.  This patient may have permanent neurological damage from the lack of perfusion to the brain. They might go into multisystem organ failure and then die. Now let’s talk about what the patient will present with.

So this patient is super hot, so they will have a fever. At first the patient will be super sweaty as the body tries to cool itself, but eventually the body has used all efforts and fluid that it can spare, so the patient will then be super hot and dry. Their blood pressure will eventually drop due to the vasodilation that occurs to cool the body and the lack of fluids from all the sweating. And with the vasodilation, lack of fluid volume, and low blood pressure, the organs will not be perfused properly. When there isn’t enough blood bringing oxygen to the brain, damage occurs leading to confusion and even seizures. This can cause permanent neurological damage to the patient.  Now, how are we going to treat this patient?

So the patient with hyperthermia should be drinking water if they are conscious and able. They may be placed in a cool room for passive cooling. A cool wet towel may be applied or ice packs for active cooling. Some facilities have cooling blankets as well. The doctor will order IV fluids to hydrate the patient and help perfuse the organs. Iced saline gastric lavages may be ordered in severe cases to quickly cool the body from the inside by pumping cold water in and pulling it back out. Now we will touch on patient education.

Our patients should be educated to stay hydrated and cool. Dressing for the heat and resting as needed helps to avoid hyperthermia in hot weather.

The priority nursing concepts for the patient with hyperthermia include thermoregulation, fluid and electrolyte balance, and intracranial regulation.