The nitrogen-containing end products of metabolism as well as the ash of the burned foods, are soluble in water and are eliminated in solution in the urine, and to a minor degree in the perspiration. When an insufficient amount of liquid is taken, the urine may be so concentrated that the adequate elimination of end products is not possible. In experimental work it has been shown that if an apparently normal person is deprived of fluid for four days there is a loss of about 6 per cent of body weight. The urine becomes concentrated, and albumin, pus and blood are likely to appear in it. Giving fluid promptly corrects all of these findings.
If three or four pints of urine are produced daily, the body is being provided with adequate water, for only after the tissues are properly supplied is such a volume of urine excreted. There is no apparent advantage in drinking very large quantities of fluid. It is true that the urine will be more dilute, but the solid residues will be essentially unchanged in amount for the whole day. In addition to the water or fluid that is taken by mouth one of the final products of metabolism is water, so that the quantity available for excretion is actually more than that taken in as such.
A FACTOR IN THE REGULATION OF BODY TEMPERATURE
The role of water in the regulation of the body temperature is one of the problems which has received considerable attention in medical research work. For a long time it was believed that somewhere in the brain there was a heat-regulatory center or thermostat. Although such a center may be present, it has never been located.
There is increasing evidence that the maintenance of a normal body temperature, in health and disease, is largely brought about by an adequate output of water.
Under normal conditions the body maintains a fairly constant temperature so that its heat elimination is equal to its heat production. Heat is lost from the body mainly in two ways: by contact, and by the vaporization of water.
By Contact. Heat is lost from the body when it comes in contact with substances cooler than itself, such as clothing, the surrounding air, and the inspired air. Under the usual conditions of moderate activity, about 75 per cent of the heat is lost from the body in this manner.
By the Vaporization of Water. The body loses heat by the vaporization of water. This is the most flexible manner of losing heat for it requires a large amount of heat to change water into water vapor. While it requires but 100 calories of heat to raise a liter of water from the freezing to the boiling point, it requires 537 calories to change the same unit-volume of water at the boiling point into steam or water vapor. Because steam has the same temperature as boiling water, this heat which seems to disappear in the change is known as “latent” or hidden heat. The principle here involved is used in the heating of houses by steam. The steam generated in the boiler passes with this great load of latent heat to the various radiators in the house where as it cools and changes back to water it gives up this large amount of heat to the rooms. The body changes water to water vapor at body temperature, and in so doing gives up approximately the same large amount of heat. The air which is breathed out is saturated with water vapor, and as activities are increased with a consequent increase in the breathing, still more water vapor with its latent heat is lost from the body.
In the same manner heat is lost from the body by the vaporization of perspiration. At all times, even when none is visible, some perspiration is formed and with its vaporization a considerable amount of heat is given off. When a person perspires profusely, especially when there is a breeze which increases the rapidity of vaporization, there is danger of cooling the body too rapidly. It is to prevent such a rapid loss of heat that the pitcher of a baseball team even on the hottest summer day puts on a heavy woolen sweater at the close of an inning; football players are promptly covered with thick woolen blankets or sweaters between playing periods; and following a horse race the attendants promptly cover the sweating horse with blankets.
By means of a respiratory calorimeter the amount of heat lost from the body in vapor can be accurately measured. Experiments have shown that in heightened metabolism caused by exercise, as high as 47.6 per cent of the total heat dissipated from the body may be lost in this manner. Keeton has shown that if the temperature of the surrounding air is as high as that of the body, and consequently no heat can be lost by contact, then all of the heat lost is by means of the vaporization of water.
The need for copious amounts of water while strenuous work is being done is a matter of common experience. Men who do manual labor, such as the building and maintaining of railroads in our desert sections, are allowed one quart of water each hour.
High Humidity and Heat Prostration. The rate at which heat is lost from the body by vaporization of water depends not only upon the amount of heat produced within the body, but also upon external factors which influence vaporization, among which is the relative humidity of the atmosphere. The expression, relative humidity, is familiar to readers of the weather reports. The warmer the air the more water vapor it can contain. Its relative humidity is the percentage of water vapor it contains at a given temperature compared with its saturation point at that same temperature. Thus, if the relative humidity of the air at a temperature of 130° F. is 10 per cent, this means that it contains 10 per cent as much moisture as it can contain at this temperature. A relative humidity of 96 per cent on a hot, sultry day with a temperature of 100° F. means that the air contains 96 per cent as much moisture as it can contain at this temperature. When the relative humidity is high at ordinary living temperatures, the loss of heat from the body by the vaporization of water is seriously lessened.
We vividly recall the occurrence of a 96 per cent relative humidity at a temperature of 100° F. in one of our large inland cities. Beads of perspiration stood out on all the exposed surfaces of the body, the clothing became wet, starched collars wilted quickly, laborers were unable to continue work, and many people died from heat stroke. One may be much more uncomfortable at a temperature of 100° F. with a relative humidity of 96 per cent than at a temperature of 130° F. with a relative humidity of 10 per cent. In the light of what has been said concerning the loss of heat from the body, such discomfort and heat strokes will be readily understood. With the temperature of the air equal to that of the body, practically no heat can be lost by contact, while a relative humidity of 96 per cent permits of very little being lost by the vaporization of water. Under such circumstances, those who cannot reach a cooler or less humid environment find it necessary, in order to avoid serious consequences, to refrain from all unnecessary exertion, and to limit heat production by eating sparingly. Ice cream, which is used in large amounts during hot weather, is an unusually poor hot weather food, because of its high caloric content. Sherbets and iced fruit drinks are much more efficacious in reducing body temperature.
Low Humidity and Heat Prostration. Some very interesting and instructive work was done by Dill, Bok, and Edwards during the construction of Boulder Dam. In this desert region, while the temperature of air often reached a maximum of 130° F. during the summer time, the relative humidity of the air was always low. From the be-ginning of the work on this dam, a generous amount of excellent cooled water was made available to all workers. In spite of this, during the first two years many men had a serious form of heat prostration accompanied by unconsciousness, paralysis, cyanosis, and heavy breathing. This ‘was shown to be due to the loss of salt in the sweat which caused a decrease in body weight associated with an increase in serum protein concentration when water was consumed as desired. Eventually these patients were treated by the intravenous injection of salt solution. The use of an ample amount of salt eliminated practically all forms of heat prostration during the latter years of the construction work.
There is evidence to show that in those diseases characterized by elevation of body temperature, the toxins produced cause the cells of the body to bind water so firmly that the loss of heat by the vaporization of water is interfered with. As a result the heat loss becomes less than the heat produced, and the elevation of temperature follows. The cause of this abnormal binding of water in febrile diseases is not clearly understood, but that it does occur is apparent. In the early stages of a typical case of pneumonia, for example, the patient complains of thirst, the urine is scanty and of high specific gravity, there is little or no visible perspiration, and there is a rapid gain in weight. When the crisis comes, the thirst disappears, many quarts of straw-colored urine are passed, the patient perspires profusely, the weight falls rapidly, and the fever subsides.
Extra Fluids for Febrile Conditions. As every one now knows, it is logical to supply febrile patients with copious amounts of fluid. Most physicians prescribed large amounts of fluid during the two major influenza epidemics of 1918-19. Sufficient fluid in the form of fruit juice mixtures was given to keep the urine straw-colored and of low specific gravity. To accomplish this often required that as much as eight quarts or more of fluid per day be taken. In the beginning of such an acute febrile condition, patients often can absorb one glass of fluid every fifteen minutes.
It is a matter of general observation that patients afflicted with tuberculosis are better in the higher, drier altitudes, and upon the principles stated it is reasonable to assume that this is due in part at least, to the lower relative humidity prevalent in such localities. Patients with chronic diseases, like tuberculosis in the active state, usually have a higher fever during the day time when, because of their waking activities, they elaborate toxins faster than they are burned by the body. At night when the body activities are quieted by sleep toxins form more slowly allowing the accumulated toxins of the day to be destroyed. This liberates the water bound during the day and the patient has a night sweat. Even though the night sweat is one of the characteristics of a febrile disease, it is a good sign for it probably means that the amount of toxins in the body is being rapidly decreased. These observations emphasize the need of rest in the treatment of all patients with febrile conditions.
As stated before, the basal metabolic rate increases approximately 7 per cent with each degree (Fahrenheit) above normal temperature, and thus another of the vicious circles so common in disease is established. With the increased basal rate there is an accumulation of the waste products of metabolism. The higher the temperature the greater the need for losing or dissipating the heat, but with the greater toxemia there is less water available to cool the body by vaporization.
Discussions often arise concerning the value of alcohol in the treatment of febrile diseases. Many maintain that copious amounts of dilute alcohol, popularly known as “whiskey slings” have a beneficial effect in lowering temperature. However, alcohol certainly binds water in the body as evidenced by the thirst which develops, especially when the concentrated liquors are used. This deleterious effect may be counteracted largely by the water when liquors are well diluted. It frequently hap-pens that patients who have a craving for alcohol will drink large amounts of water if it is flavored with this popular drug when they will otherwise fail to do so. The oxidation of the alcohol in the tissues results in increased heat production. In our experience the fruit juices well diluted with water have no deleterious effects and have proved more efficacious in the dissipation of temperature.
A simple method of determining whether or not sufficient water is being taken to carry on the body functions, is the measuring of a twenty-four hour specimen of urine, which should be in the neighborhood of three or four pints.