Things to know about Heat Stroke (Sun Stroke or Heat Hyperpyrexia)

Heat stroke, also known as sun stroke or heat hyperpyrexia.is a serious medical emergency, caused by the excessive accumulation of heat in the body when heat dissipation is limited by environ­mental temperature and humidity.

Classically, three criteria are given for the diagnosis of heat stroke:

1. exposure to heat
2. elevated body temperature-generally rectal temperatures of 105 F to 106 F
3. hot, dry skin

The above criteria should be qualified rather extensively, 'especially since we are considering heat stroke primarily in young, healthy, active individuals.

Humidity is of great importance in addition to simple air temperature. Fatal heat stroke has occurred in a football player at an air temperature of 640P with a relative humidity of 100 percent.

While an elevated body temperature is a key part of the heat stroke syndrome, strict adherence to a certain temperature requirement in the diagnosis of the disease can be misleading. Since an accurate rectal temperature is usually not recorded at the time of collapse, some cooling may take place before the core temperature is obtained. Moreover, some individuals may tolerate extremely high rectal temperatures with seeming impunity ­temperatures that would produce coma and even death in many individuals. Top marathon runners have been observed to com­plete races without difficulty with rectal temperatures of 105 F

The third criterion-that of hot, dry skin-may also be mis­leading. Many authors have stated that this is found in the vast majority of cases of heat stroke. In contrast, in one review of thirty-six cases of heat stroke in the Israeli army, all but one were sweating freely just before the onset of heat stroke as well as after the initial loss of consciousness.

The reason for this seeming paradox is that heat stroke in unhealthy or elderly persons contrasts sharply with heat stroke that occurs in young, healthy individuals who become ill while exercising in the heat. In the United States, most cases of heat stroke in this latter situation occur in football players, military recruits, or long distance runners. The common factor is sustained extraordinary physical exertion in a severe environment. Sweating persists in the majority of these cases.

This was the case in the above heat stroke victims. They were young, healthy, Israeli soldiers. Many of them lacked physical conditioning or acclimatization. All had been involved in strenuous physical activity in extremes of heat. Several had had mild illnesses several days prior to the heat stroke, often with vomiting and diarrhea.

One factor that is often present is a determined, enthusiastic or relentless attitude, such as seen in young football players or distance runners. Serious heat illness is virtually unknown in professional football players probably because of experience, in part. Heat stroke may be especially virulent in. healthy, un­acclimatized individuals who undergo strenuous exertion in extremes of heat.

Many writers have stated that the cessation of sweating plays a pivotal role in the development of heat stroke. More recent studies have led to the suggestion that the cessation of sweating is a secondary phenomenon. At any rate, in the appropriate setting, hot, dry skin would strongly support the diagnosis of heat stroke, while continued active sweating by no means rules out heat stroke. Sweating is especially likely to persist in young, previously healthy individuals who collapse after strenuous exer­tion in the heat.

In most cases of heat stroke, there is the abrupt onset of delirium or coma. Sudden loss of consciousness without warning occurs in about two-thirds of the cases. Various symptoms may precede these alterations in consciousness by a few minutes or as long as one to two hours. Occasionally, there may be insidious symptoms for two to three days or more prior to collapse.

Some of these are probably symptoms of dehydration or water-depletion heat exhaustion. Before the onset of heat stroke, victims may experience headache, dizziness, numbness, drowsi­ness, and/or extreme thirst. Their companions may observe restlessness, purposeless and uncoordinated movements, aggressive or bizarre behavior and confusion.

Disturbances of the nervous system are the characteristic initial features of heat stroke. These signs may include disorientation, extreme irritability, manic or very aggressive behavior, confusion, vivid hallucinations, delirium, involuntary movements, and convulsions and coma. Muscles may be flaccid or rigid. Loss of balance and difficulty with speech can occur. Most victims are soon in a coma. The rectal temperature is often over 42.2 C (l08 F) when convulsions or coma develop.

The skin color of heat stroke victims varies from pink to ashen. Cyanosis (a purple discoloration due to oxygen deficiency) of the lips and face is common. On the other hand, the face may be red, blotchy and congested. (It has been noted that heat stroke victims often look like they have been strangled.) These variations in skin color depend at least in part on the state of the circulatory system. The activity of the heart and its output of blood may be greatly increased or decreased. The latter situation is quite grave.

The heart or pulse rate of heat stroke victims is rapid and usually full, often in the 140 to 150 per minute range. In severe cases, heart rates of 170 per minute may be present. The respira­tory rate is rapid, usually over thirty-five per minute, and may be as high as sixty per minute in severe cases. The blood pressure is variable. Shock, with low blood pressure is present in about 1/6 of cases.

A rectal temperature of over 42.2 C suggests a poor outlook. Ashen-gray cyanosis with a rapid, weak pulse and a low blood pressure are ominous signs of shock. They mean that the heart and circulatory system are unable to maintain an adequate volume of blood flow.

Damage to the heart, brain, liver, kidneys, and muscles are frequent complications of heat stroke.