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Hypothermia & the Trauma Patient
By: Scott Rolfe, RN, BSN

By: Scott Rolfe, RN, BSN; Trauma Research & Education Coordinator

Hypothermia is an increasing clinical problem that requires rapid response with properly trained personnel and techniques. Traumatically injured patients are at greater risk for hypothermia due to blood loss, environmental exposure, and resuscitation efforts. During 2003, 196 patients were transported to UMC's Trauma Center with a temperature below 35° C (95.9 F). So far during 2004, 139 patients have arrived with a temp below 35° C. Thirty-four percent of these hypothermic patients arrived by helicopter with ground transport accounting for the remaining 66 percent.

Infusion of fluids at the scene and in the hospital tends to worsen hypothermia if warmers are not used. Other mechanisms that can lead to hypothermia are improper clothing, wetness, fatigue, dehydration, poor food intake and alcohol intake. Initial recognition and treatment of hypothermia is essential to improving the outcome of the patient.

The human body is equipped with a thermoregulatory system that is controlled by the hypothalamus. The hypothalamus is sensitive to changes as little as 0.5° C. Heat loss occurs from four different methods; radiation, conduction, convection and evaporation.

1. Radiation is the loss of heat due to the difference in the body’s temperature to the environment without actual physical contact.
2. Conduction heat loss occurs when the body comes in physical contact with an object that is colder than the body.
3. Convection is heat loss through movement.
4. Evaporation is heat loss from liquid being converted to gas.

Hypothermia is defined as the drop of the central body core temperature below 35° C or 95.9° F. The core body temperature should be obtained as soon as possible. Hypothermia can be classified as mild, moderate, and severe.

1. Mild hypothermia is noted with core temp of 34-36° C (93.2—96.8° F). Physical symptoms include but are not limited to agitation, lethargy, confusion and shivering. During mild hypothermia the basal metabolic rate and oxygen consumption gradually fall. An increase in the heart rate can be seen. Mild confusion may also be seen though usually the patient remains alert. Vasodilatation occurs to provide warm blood to the extremities. If the patient can voluntarily stop shivering they are still in a state of mild hypothermia.

2. Moderate hypothermia is noted when the body core temp is from 30—34° C (86.0—93.2° F). Physical symptoms include pupil dilation as well as a decrease in cardiovascular activity. Basal metabolic rate and oxygen consumption continue to fall. Shivering normally stops at this stage and confusion, delirium and lethargy begin. Respiratory rate begins to drop leading to hypoxia and hypercarbia. Vasodilatation is replaced by vasoconstriction as the body attempts to keep the core of the body warm. Extremities may feel very cold to touch and pulses may not be palpable. A radial pulse can still be palpated in moderate hypothermia. If a radial pulse is not palpable the patient has progressed to severe hypothermia.

3. Severe hypothermia occurs when the body core temperature is below 30° C (86° F). Due to severe vasoconstriction a patient in severe hypothermia may appear clinically dead. The skin may appear very pale and pupils may remain dilated. Respirations and peripheral pulses may be undetectable. As the core body temp decreases the body attempts to move into a hibernation state. Atrial and ventricular arrhythmias can result from hypothermia. Asystole and ventricular fibrillation can begin spontaneously at core temps below 25° C.

Hypothermia affects virtually all organ systems. The most significant occurs in the cardiovascular and central nervous system (CNS). Hypothermia results in decreased depolarization of cardiac pacemaker cells causing bradycardia. Since this bradycardia is not vagally mediated it can be refractory to Atropine. Hypothermia progressively depresses the CNS. The triad of hypothermia, acidosis and coagulopathy has been recognized as a significant cause of death in trauma patients. Hypothermia is said to be the third most significant complication in the trauma patient with hypovolemia and hypoxia being numbers one and two. As the patient’s hypothermia increases, acidosis and coagulopathy increase.

At core temps less than 33°C, brain electrical activity becomes abnormal. At temps 20°C and below, an EEG may appear consistent with brain death.

Intervention & Treatment

It is essential for the outcome of the patient that early intervention and re-warming is conducted as soon as possible. This means that interventions must start in the field. Core body temp measurement is essential.

Mild Hypothermia Intervention

The first thing that must be done with any hypothermic patient is to reduce further heat loss. Passive re-warming techniques should be initiated. Remove any wet clothing. Minimize contact with surfaces that are colder than the patient. Hypothermic state is very irritating to the body. Minimize movement to the patient. Avoid alcohol, caffeine, tobacco/nicotine as they will lead to further dehydration and vasoconstriction. If fluids are to be given, orally or parenterally, they should be warm. Warm blankets and/or warming lights are essential.

Moderate Hypothermia Intervention

When treating hypothermia don’t forget your ABC’s. With moderately hypothermic patients you must move to active re-warming. A warming blanket should be placed on the patient. This is not a blanket taken out of a warmer but rather a blanket that has continuous circulating warm air or fluid. It is vital to warm the trunk of the patient along with the extremities. Warm humidified oxygen, hot packs to the groin, neck and axilla will help to prevent a phenomenon called afterdrop. Afterdrop occurs when the extremities are warmed causing vasodilatation. The vasodilatation in the extremities then causes cooler blood to be dumped into the bodies core further decreasing the core temp. In addition to these re-warming techniques, radiant warming lights are an excellent method to re-warm and keep your trauma patient warm.

Severe Hypothermia Intervention

Basic life support efforts and aggressive active re-warming techniques are essential in the severely hypothermic patient. Rapid active internal warming, in addition to those used for less severe hypothermia, must be used. This includes warm peritoneal and gastric lavage. Instillation of warm fluid in the bladder should also be considered. All medications should be held until the patient is warmed to 30° C. A new technique called arteriovenous or A-V re-warming has proven very successful. This method involves placing a catheter into a femoral artery and vein. In order for this procedure to work the patient must have a spontaneous pulse with a systolic pressure of at least 80. The artery and vein catheters are connected to a Level I fluid warmer circulating the patient’s own blood and returning it warmed. This method has proven to warm patients five times faster than other methods.

Remember, the hypothermic patient may appear clinically dead. All resuscitation measures should continue until the patient is warmed.

Scott Rolfe, RN, BSN
Trauma Research & Education Coordinator