Hyperthermia/Hypothermia Unit Management

Definition

Hyperthermia/hypothermia unit management is the use of special electronically regulated blankets or pads to adjust body temperature until it returns to normal levels.

Purpose

The human body operates at temperatures within a fairly narrow range. A body temperature of 98.6°F (Fahrenheit), or 37°C (Celsius), is considered to be normal for human beings. In reality, normal body temperature varies not only in different individuals, but also in the same person, depending upon activities engaged in or the time of day. Exercise, eating, and ovulation in women can raise body temperature, while sleeping, drinking fluids, and (for women) menses can lower it. Body temperature is typically at its lowest level at 3 a.m., and at its highest level at 6 p.m. However, all of these variations do not normally extend beyond a range of 97.8°F (36.5°C) and 99°F (37.2°C).

The purpose of hyperthermia and hypothermia units is to correct aberrant temperature and prevent the complications that can occur when this narrow range of human body temperature is not maintained. Sometimes, body temperature is purposefully lowered to aid in certain surgical procedures. The lower body temperature allows vital organs such as the heart to survive with decreased blood supply, thus increasing the available time a surgeon has to operate. But the usual reason hyperthermia or hypothermia equipment is used is because the body has exceeded the extremes in temperature.

Normally, a section of the brain known as the hypothalamus acts to regulate temperature in a manner similar to the workings of a thermostat. Body temperature is constantly monitored by the hypothalamus, and mechanisms to compensate for any abnormality are set in motion. Classic examples of such mechanisms are shivering and perspiring. The hypothalamus reacts to low body temperature by sending neurological impulses that cause shivering. Shivering in turn produces heat from within the body through muscle activity. When the body temperature rises, the hypothalamus causes fluid to be excreted via the skin as perspiration. As the perspiration evaporates, it lowers the body temperature.

Both excessively high and low temperatures can be medical emergencies capable of causing death without immediate, appropriate medical intervention. Among the causes of abnormally elevated or lowered temperature are:

• exposure to extreme heat or cold
• infections
• glandular disorders, especially those that involve the thyroid gland
• certain tumors
• abnormal reaction to anesthesia
• dehydration

Artificially raising a person's body temperature, or inducing hyperthermia, has not been used as a cancer treatment in recent years. Usually, hyperthermia is a pathological condition. Patients whose temperature rises above 105.8°F (41°C) are considered to be at serious risk of brain damage, and those with a temperature above 109.4°F (43°C) will usually not survive. Mental confusion and delirium seizures (especially in young children and infants) are some of the serious problems associated with high fevers.

Hypothermia is medically defined as a drop in body temperature to below 95°F (35°C). Hypothermia can lead to irregular heartbeat and, eventually, cardiac arrest. The elderly and very young children are the most vulnerable to extreme drops in body temperature. The Merck Manual recommends that health care staff consider people with radically low body temperature as viable and treatable until the body has been warmed, and there are still no signs of life such as heartbeat and respirations. Length of exposure to cold and general health are standard predictors of survival, but the National Institute on Aging gives the following guidelines regarding the chances of recovery for hypothermia victims:

• If body temperature has not fallen below 90°F (32.2°C), the likelihood of complete recovery is good.
• When body temperature is between 80°F (26.6°C) and 90°F (32.2°C), the majority of hypothermia victims survive, but are likely to have lasting damage such as brain damage.
• People with temperatures below 80°F (26.6°C) are not likely to live.

Precautions

Hypothermia/hyperthermia units should never be placed in direct contact with the patient's skin due to the risk of burns.

Description

For centuries, wrapping feverish people in cold, wet sheets and immersing them in cool baths helped to lower body temperature. Hot water bottles and blankets were used to warm hypothermia victims. Today, hyperthermia blankets or pads are special medical devices that have a built-in temperature regulator, or thermostat, capable of raising or lowering body temperature. Such blankets or pads circulate solution through them at pre-set temperature levels calculated to raise or lower body temperature. There are various kinds, and manufacturer's instructions for each type must be read and understood. Some utilize dry cold to lower temperature, and are used for just one patient and then discarded. Others have a special adapter to change from heat to cold, and can be used again and again. A K-Pad is one brand of pad used in some health care facilities to raise the temperature in hypothermia victims. K-Pads are composed of tubular forms that are filled with water, which is then heated and monitored by an electronic thermostat to keep it at the correct temperature.

Preparation

Often, the patient with a radical alteration in temperature may be unconscious. But if the person is aware, providing a good explanation of what is being done and why will be very important. Although some brands of hyperthermia/hypothermia blankets are cloth-covered, patients should still always have a bath blanket beneath and over them so that their skin does not come in direct contact with the hyperthermia/hypothermia equipment. This is particularly important when the unit is being used to warm the body, as direct contact can result in burns. K-Pads are filled two-thirds full of water, and superfluous air is removed before use.

Most hyperthermia/hypothermia units have dual temperature monitors for both the temperature of the unit and that of the patient. This temperature probe for the person often involves a rectal probe, as that is the most accurate measure of body temperature. Regardless, it is imperative that the person's temperature be monitored constantly, and if the unit does not measure body temperature, then the temperature must be taken with a regular thermometer. (In the case of hypothermia, a special thermometer that registers below 94°F [34.4°C] will be necessary.)

Aftercare

In the case of hyperthermia, the cooling unit is removed while the body temperature is still slightly above normal, as the body will continue to cool after the unit is removed. The temperature continues to be monitored, and cold packs to axillae (the armpits) and the groin may also be used. Often, fever-reducing medications such as acetaminophen are given once the person is conscious, or may be administered by suppository.

The vital signs (temperature, pulse, respirations, and blood pressure ) continue to be monitored for hypothermia patients. The warming unit is not usually removed until the body temperature rises to normal. Warm liquids may be given once the person is conscious.

Complications

The major complication involved in the use of hypothermia/hyperthermia units is either the occurrence of burns from units used for heating or the discomfort from more direct contact with cooling units. Both can be prevented by following procedures, including the placement of bath blankets between the patient and the unit and reading the manufacturer's instructions.

Results

The optimum outcome from the use of these units is a return to normal bodily temperature without the person sustaining any permanent damage.

Health care team roles

Emergency personnel such as emergency room technicians (EMTs) and physicians are often involved as both hypothermia and hyperthermia are often accidental happenings, occurring due to exposure to heat or cold sustained from immersion in water or being exposed to the elements.

Also, registered nurses (RNs) and licensed practical nurses (LPNs) are responsible for setting up hypothermia/hyperthermia units and caring for the patient undergoing temperature-altering treatment.

KEY TERMS

Axillae— The medical term for the areas under both shoulders commonly called the armpits.

Dehydration— A condition in which a living being's water level within its body has fallen to dangerously low levels.

Hyperthermia— The medical term for abnormally high body temperature.

Hypothalamus— A cherry-sized portion of the brain located behind the eyes that is responsible for the regulation of body temperature, the sympathetic nervous system, and coordination between the nervous and endocrine systems.

Hypothermia— A decrease in body temperature below 95 F(35°C).

Resources

BOOKS

Berkow, Robert, et al., eds. Merck Manual of Diagnosis and Therapy, Home Edition. New York, NY: Pocket Books, 1997.

Kozier, Barbara, Glenora Erb, and Kathleen Blais. Fundamentals of Nursing, Concepts, Process and Practice. Boston, MA: Addison-Wesley Publishing Co. Inc., 1995.