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be absent. A two-pound weight loss after a dive indicates a loss of one quart of body water. Losses greater than four pounds indicate marked dehydration. Muscle cramps may develop. A rapid increase in pulse rate can indicate severe hyper-thermia. Divers may experience sensation of being hot, fatigued, disoriented, or nauseated before they collapse. Collapse may occur suddenly without prior warning signs.

Divers may appear physically functional in the water, but collapse when they exit the water. Therefore, all divers who have been in the water for more than an hour should be assisted out of the water and monitored carefully. If they feel lightheaded when standing, they should lie down, receive adequate rehydration, and cease diving until the next day.

3-12.3.5 Preventing Hyperthermia. Like hypothermia, hyperthermia can be insidious and cause problems without the diver being aware of it. Acclimatization, adequate hydration, experience, and common sense all play a role in preventing hyper-thermia. Shelter personnel from the sun and keep the amount of clothing worn to a minimum. Adequate predive hydration is essential. Urinating 1-2 times per hour, where urine is pale and clear, usually indicates adequate hydration. Standby divers and support personnel should consume about one quart of fluid per hour in hot environments. Frequent rest periods are advised.

3-12.4 Dehydration. Dehydration is a concern to divers, particularly in tropical zones. It is defined as an excessive loss of water from the body tissues and is accompanied by a disturbance in the balance of essential electrolytes, particularly sodium, potassium, and chloride.

3-12.4.1 Causes of Dehydration. Dehydration can occur through excessive perspiration or long periods of breathing dry gases.

Immersion in water creates a condition resembling a gravity-free state. The weight of the body and the hydrostatic gradient in the circulatory system are almost exactly counterbalanced by the ambient water pressure. This reduces the volume of pooled blood in the leg veins and results in an increase in central blood volume, leading to an increase in urination (immersion diuresis). The increased urine flow leads to increasing loss of water from the body during the dive.

3-12.4.2 Preventing Dehydration. Dehydration is felt to increase the incidence of decompression sickness. Prevention is the best medicine. Divers should increase their fluid intake during diving operations to keep themselves well hydrated.

3-12.5 Hypoglycemia. Hypoglycemia is an abnormally low blood sugar (glucose) level.

It is a condition that is not due to respiratory difficulties, but can complicate or be confused with them. Sugar, derived from food, is the body's main fuel. It is carried to the tissues by the blood and if the blood level falls, tissue function is affected.

3-12.5.1 Symptoms of Hypoglycemia. The brain is especially sensitive to lack of glucose.

The highly variable symptoms can sometimes closely resemble those of other conditions in which brain function is affected, including carbon dioxide intoxication, hypoxia, carbon monoxide poisoning, oxygen toxicity, and arterial gas embolism. Some of the more common symptoms are unusual hunger, excessive sweating, numbness, chills, headache, trembling, dizziness, confusion, incoordination, anxiety, and fainting. In severe cases, loss of consciousness and convulsions may occur.

3-12.5.2 Causes of Hypoglycemia. There are several possible causes of hypoglycemia.

Simply missing a meal tends to reduce the blood sugar level, but the body normally can draw on its stored supplies to keep the level close to normal for a long time. A few individuals who are otherwise in good health will develop some degree of hypoglycemia if they do not eat frequently. Severe exercise on an empty stomach will occasionally bring on the symptoms even in a person who ordinarily has no abnormality in this respect. Normally, the body secretes insulin which promotes the use and storage of glucose. People with diabetes do not secrete enough insulin and have an excess of glucose in their blood. They must take insulin by injection to avoid the symptoms of the disease and to keep their blood sugar at a normal level. If they take too much, or if some factor such as unexpectedly hard work reduces the amount needed, serious hypoglycemia can develop rapidly. For this reason, diabetics are considered bad risks in diving.

3-12.5.3 Preventing Hypoglycemia. The possibility of hypoglycemia increases during long, drawn out diving operations. Personnel have a tendency to skip meals or eat haphazardly during the operation. For this reason, prevention through proper nutrition is the best medicine. Prior to long, cold, arduous dives, divers should be encouraged to load up on carbohydrates. For more information, see Naval Medical Research Institute (NMRI) Report 89-94. A diver who often experiences definite weakness (or other symptoms mentioned) when he misses meals, should have a physical examination to determine whether hypoglycemia is the cause and if he is particularly susceptible to it. If hypoglycemia is present, giving sugar by mouth (or if the victim is unconscious, intravenous glucose) relieves the symptoms promptly and proves the diagnosis.

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