Types of temperature curves A number of infectious processes have typical temperature curves characterizing the manifestations of fever. The following forms of fever are distinguished, according to the elevation of the temperature: a) subfebrile (not above 38 C, b) moderate (up to 39 C) , c) high (39-41), and d) excessively high - hyperpyretic (41 C and higher). The body temperature very rarely rises above 41 C. The following main forms of fever are distinguished according to the character of the temperature curves: 1 Continuous fever (febris continua) in which the elevated temperature for some time persists on a high level, the difference between the morning and evening temperature not exceeding 1 C. The fever may end abruptly (crisis) or gradually (lysis) . This form includes typhoid fever early in the course of the disease, the fever in croupous pneumonia, typhus and certain other infectious disease. 2. Remittent fever (febris remittens) in which the difference between the morning and evening temperature exceeds 1 C. It includes the temperature curves observed during the late course to typhoid fever, sepsis and catarrhal pneumonia. 3 Intermittent fever (febris intermittens) which is characterized by regular alternation of brief attacks of fever (paroxysms) with feverless periods (apyrexia). High temperature persists for several hours, drops to normal and then rises again. The length to the feverless periods may vary. This form of temperature curve is characteristic of malaria. Attacks of fever may occur every third day (febris quartana), every second day (febris tertina ) or every day (febris quotidiana) 4 Recurrent fever (febris recurrents) which is characterized by longer periods of pyrexia than in intermittent fever (5-8 days). The duration of these periods corresponds to that of the periods corresponds to that of the periods of normal temperature. Such a curve is characteristic of replasing fever. There are fevers- which at first run the course of febris continua and then change to febris remittens (for example, in typhoid fever). There are also fevers of short duration (ephemeral) with an indefinite or irregular course (considerable diurnal variations in body temperature) and fevers with a perverted course, for example, an elevation of temperature in the morning and a drop in the evening (in some forms of sepsis and tuberculosis) . The aforementioned types of temperature curves dc not exhaust their variety. The type of temperature curve is determined not only by the character of the infection, but also by the reactivity of the characterized by increased heat loss and its predominance over heat production which may relatively even increase. Heat lass increases as a result of excessive perspiration (sometimes very profuse) and considerable dilatation of the peripheral vessels. The ratio of heat production to heat loss is the reverse of that observed during the first stage of fever. Then heat production, heat loss and body temperature return to normal. At this stage the temperature is often unstable. The temperature drops either rapidly (crisis) or slowly, gradually (lysis). A critical drop in temperature, especially in cases of cardiovascular insufficiency, in dangerous because it requires a rapid adjustment of the organism to the new conditions of the internal environment. This may result in a shock reaction (collapse). In all the aforedescribed stages physical and chemical thermoregulation functions concertedly. In man the disturbance in physical thermoregulation is of the utmost importance. The different stages of the febrile reaction may be characterized by noticeable fluctuations in the heat balance due to compensation for the disturbed functions, which is in its turn connected with the physiologic defence role of the central nervous system. Thus the course of the different stages of the febrile process is determined, not only by the etioiogic factor, but also by the general state of the organism, its reactivity, metabolism and intensity of the oxidative processes. Metabolism in Fever Metabolic disturbances in fever are caused by various factors. These factors are: I) etiological peculiarities, most frequently of the infectious agent; 2) elevation of body temperature; 3) starvation which in some measure accompanies fever since, owing to loss of appetite and digestive disturbances, the organism consumes and assimilates less food than usual. Metabolic disturbances vary with the various fevers, but are nevertheless subject to certain regularities characteristic of most fevers. In most cases metabolism is increased, this increase underlying the greater heat production. In moderately severe-fevers metabolism may increase 5—10 per cent and may even remain within normal limits (Du Bois). The oxidative processes are somewhat intensified partly because of increased respiration and cardiac action. For example, in the quinea pig a 1 rise in temperature is accompanied by a 3.3 per cent increase in oxygen consumption. However, there may be a discrepancy between the amount of oxygen consumed by the organism and heat production, with accumulation of underoxidised metabolites and, in connection. with it, a decrease in the respiratory quotient. In fever carbohydrate metabolism is increased; this can be seen from the decrease in glycogen in the liver and the possible development of hyperglycemia. The fat metabolism is appreciably increased mainly in lingering fevers of infectious origin. The increased expenditure of fats is due not only to the fever, but also to the concurrent starvation and, in a certain measure, perhaps to intoxication. Ketonemia and ketonuria are sometimes observed as a result of carbohydrate deficiency and decreased oxidation of fats. Protein metabolism may be disturbed. In fever involving a high temperature the expenditure of protein is increased out of proportion to that of fats and carbohydrates; .elimination of nitrogen in the urine is increased. In cases of moderate fever the share of protein in the total energy balance is often normal (10-15 per cent), as is, for example, the case in influenza and certain forms of tonsillitis. In fevers with a high temperature the share of protein may reach 30 per cent, in which cases the amount of urea in the urine increases. Disintegration of protein is particularly great in infectious fevers (toxogenic protein disintegration). The loss of valuable proteins by the feverish organism may be in some measure compensated by consumption of carbohydrates, fats and proteins. The loss of valuable proteins by the feverish organism may be in some measure compensated by consumption of carbohydrates, fats and proteins. In severe fevers some investigators have observed an increased specific dynamic effect of protein, which also explains the increased loss of nitrogen with the urine in high fever. The problem of metabolism in fever is very important for the choice of diet for feverish patients. It is difficult completely to eliminate the losses of tissue proteins in fever, especially infectious fever involving high temperature. In severe infections it is necessary to strive for a possible limitation of protein expenditure by a plentiful administration of carbohydrates. For this purpose patients are intravenously administered glucose which is more easily oxidized and is in a certain measure capable of making up for the caloric deficiency and the excessive expenditure of protein, the latter imperilling the feverish organism which is fighting the active, in most cases infectious, agent. In fever the water and salt metabolism is more or less altered. As a result of increased metabolism and accumulation of underoxidized products the tissue retain water. The dysfunction of the renal filter due to intoxication and the rise in organism, the extent of its sensation of foreign proteins, in particular . Stages of Fever Three periods of stages may be distinguished in most fevers. These are; 1) the stage of elevation of the body temperature (stadium incrementi) 2) the stage in which the temperature is at its acme (stadium fastigii) and 3) the stage of decreasing temperature (stadiuim decrementi). These three stages are characterized by a certain disturbance in the interrelation between heat production and heat loss, and disorders of the different forms of metabolism, excretion of urine, etc. The first, usually short stage is characterized by a rapid or gradual elevation of body temperature. The temperature rises because in the beginning of fever, as a result of spasm of the vessels in the skin, less heat is lost, while heat production begins to increase. The ratio of heat production to heat loss increases, the disparity between heat production and heat loss in cases of rapidly rising temperature being accompanied by chills -a sensation of cold and shivering, pallor of the skin and appearance of "goose flesh". At the same time the increase in muscle tone and. the contraction of various groups of muscles lead to still greater heat production. The chills are due to stimulation of the nerve endings in the skin as a result of the drop in its temperature caused by spasm of the superficial vessels. The cooling of the superficial layer of the skin reflexly causes shivering. Heat production increases also in the fever. The faster fever develops, the greater the disparity between physical and chemical thermoregulaton, and the more strongly pronounced the chills. In these cases heat production always exceeds heat loss. The second stage is characterized by establishment of the ratio of heat production to heat loss on a definite level. The heat loss increases mainly by dilation of the vessels in the skin and accelerated respiration. Compared with the first stage heat production may decrease, sometimes even to normal, but the balance between heat production and heat loss is established on a higher level than in healthy people. The organism retains its ability to regulate the newly established temperature. Heat is lost through the same channels as usual and only perspiration plays a less important role. The therapeutic measures employed during this period (cupping, wrapping, rub-downs) are aimed at facilitating physical thermoregulation. The third stage - the stage of falling temperature is temperature is also of same importance. The second stage of fever is accompanied by decreased excretion of urine. The retention of. water is noticeable excretion of water by the kidneys is observed in addition to the sharp increase in heat loss and excessive perspiration. It is not yet entirely clear precisely what tissues retain water in fever. As in inflammation, a very important part is apparently played by connective tissue. As for the salt metabolism, the disturbed water metabolism involves retention of chlorides; during the third period, when the excretion of urine begins to increase, more chlorides are eliminated. More phosphates and potassium salts are excreted as a result of tissue disintegration. Changes in the Functions of the Internal Organs in Fever Disturbances underlying the disorders of thermoregulation arise in the nervous system. Moreover, phenomena due to changes in body temperature and intoxication are observed. Hyperthermia may of itself (in so-called aseptic fevers) , depending on its intensity, stimulate and subsequently inhibit the central nervous system. Infectious fever are not infrequently accompanied by a sensation of heaviness in the head, general indisposition, clouded consciousness, delirium, hallucinations, etc. Children react to pyrexia by greater excitement than do adults. In emaciated patients fever is usually attended with phenomena of depression of the nervous system. As regards the vegetative nervous system, the functions of its sympathetic division predominate. In fever the cardiac rhythm is accelerated as a result of excitation of the sympathetic nervous system. The etiologic factors causing fever — mainly infectious agents and toxins, as well as toxic metabolites - stimulate cardiac activity. Usually a 1 rise in temperature is accompanied by an increase of 8-10 beats in the heart rate. The extent of the functional changes in the heart muscle and conduction system depends on the character of the infection and intoxication. Elevation of the body temperature in fever is usually accompanied by an acceleration of the pulse, but there are also reverse phenomena which are apparently connected with stimulation of the centre of the vagus nerve in the medulla oblongata. For example, in inflammation of the meninges, tuberculous meningitis in particular, the pulse rate clearly lags behind the rise in temperature. The character of the pulse wave (hard, full, theady, dicrotic, etc.) is, in addition to the pulse rate, also very important for evaluating the state of cardiovascular activity. The changes in the state of the vessels are connected will disturbances in physical heat regulation; for example, chills are accompanied by spasm of the peripheral vessels and a rush of blood to the internal organs; during the second and, especially, the third stages of fever the vessels are dilated. In the beginning of fever the blood pressure is somewhat elevated because of the increased action of the heart and excitation of the vasomotor centers; during the last stage, however, the blood pressure drops as a result of weakened heart action and dilatation of the vessels. The drop in blood pressure may sometimes lead to shock or collapse. In fever the respiration in accelerated simultaneously, with the quickening of the pulse and elevation of the body temperature. Fever also involves a rise in the temperature of the blood and acidosis developed as a result of accumulation of acid metabolites. Respiration participates in the physical regulation of heat along with the vascular system and the sweat glands. A change in respiration is thus one of the mechanisms of physical thermoregulation in fever. The function of the digestive apparatus is altered: the secretion of digestive juices and bile is decreased, the mucous membranes of the mouth and tongue are dry, and intestinal peristalsis is Disturbed. Some cases are accompanied by constipation with increased putrefaction, accumulation of gases and development of meteorism. Digestive insufficiency and diminished absorption lead to a lack of appetite, decreased assimilation of nutritive substances and phenomena of intoxication. The function of the kidneys is also altered. Renal filtration is particularly affecfted by toxins in infectious fevers (for example, scarlet fever, septic diseases). At the height of fever the amount of urine perceptibly diminishes. The water is retained by the tissues. The content of nitrogenous substances in the urine is increased. The amount of urine appreciably increase during the third stage of fever when the body temperature begins to fall. Protein, peptones and albumoses sometimes appear in the urine. The amount of excreted protein in large measure depends on the character and severity of renal affection. Here an important part is played not. so much by hyperthermia, as by the infection and intoxication which have initiated the febrile process. As for pathoanatomical changes, dystrophic phenomena are sometimes observed mainly in the parenchymal organs in fevers with a high temperature. The changes are of the nature of a turbid swelling, sometimes waxy degeneration, and adipose infiltration. Important in these cases is the fever itself and, to an even greater extent, the infection and intoxication which have produced the fever. Phenomena of dystrophy in the internal organs cause disturbances in their functions, which in their turn affect the course of the febrile process. Effects of Fever on the Course of Infectious Processes The question of the effects of fever as a general reaction of the organism mainly to the action of infectious agents is of fundamental importance. It is important to settle this question in order to uncover the adaptive role of fever in the organisms fight against infection and for its therapy. The investigators maintaining that fever harmfully affects the course of infection in the organism point out the concurrent dysfunction of the cardiovascular system, deep metabolic disturbances and dystrophic changes in the organs; however, some infectious diseases run a graver course in the absence of fever or in cases a weak manifestations of fever (for example, croupous pneumonia, influenza, typhus, etc.). A more favourable course of phenomonia and chicken cholera is observed in hyperthermia produced in animals by injury to the corpus striatum. Carefully conducted artificial overheating favours the survival "or prolongs the life of animals infected with anthrax, the Streptococcus pyogenes and the Staphylococcus. There are also some indications that certain adaptive reactions become more intense at a high temperature; these include phagocytosis and production of immune bodies, and such physiologic functions as hematopoisesis, activity of the enzymes, and the barrier and antitoxic functions of the liver. To produce fever for therapeutic purposes, especially in certain chronic infections, pyrogenic therapy is applied in the form of inoculation of malaria (in neurosyphilic) administration of purified pyrogenic substances (pyrexial, pyrogenal, etc. or inductopyrexia, i.e., production of fever by electromagnetic induction. Body temperature is a valuable index of the state of the organism in its struggle against infection since it reflects the reactive ability of the diseased organism. This does not mean that fever must always be considered a positive phenomenon in the development of infectious process. Both an excessive rise in temperature or its sudden drop may prove harmful to the organism. It follows that the course of the fever and its significance to the organism must be given special consideration to each concrete case. As one of the mechanisms formed in the process of evolutionary development fever may, in cases of moderate elevation of body temperature, be useful in the organisms 3 struggle against the infectious agent which has caused it.