Hyperthermia

“ For, although oxidation at any point raises the heat of the blood at the point, this heat is carried by the blood to other parts, to which the surplus is given up, while blood cooled in the skin goes to the hotter inward parts to cool them and be warmed itself. In fact, heat is expended by conduction and radiation, through respiration, perspiration, and heat given to the urine and fæces. It is, therefore, largely, 75 to 80 per cent., carried off through the skin and the lungs; 60 to 70 per cent. is lost by radiation to the air and other bodies with which the body comes in contact ”

“ This is why we are warm. But from some places, as from the skin, the venous blood goes away cooler than the arterial which came, because while journeying through the capillaries of the skin it has given up much of its heat to whatever is touching the skin, and has also lost much heat in turning liquid perspiration into vapour. This is why so long as we are in health we never get hotter than a certain degree of temperature, the so-called blood-heat, 98° Fahr., and why we make warm the clothes which we wear and the bed in which we sleep. ”

“ Indeed, the most effective mechanisms of heat loss involve evaporation of water from the surface of the skin or respiratory pathways (e.g., by sweating, salivation, or polypnea) , which strains the body's precious water resources, whereas heat production (nonshivering or shivering thermogenesis) depletes the body's energy stores. In contrast to autonomic thermoregulation, behavior places no demands on the body's water or energy resources; furthermore, behavioral thermoregulation can compensate for much greater thermal loads. ”

“ When the body is heated to a certain degree, the fluid portions are all directed to the skin, and escape gradually through these pores in the form of perspiration, and the cooling power thus produced is capable of immediately removing the superabundant heat. The moment perspiration broke out on the bodies of the experimenters who ventured into the heated oven, all sense of pain was removed; and in many fatal disorders to which man is subject, the first symptom of returning health is a similar occurrence. ”

“ Heat is lost by the skin, respiration, feces, etc. The great regulator, however, is undoubtedly the skin. The more blood passes through the skin the greater will be the loss of heat by conduction, radiation, and evaporation. The working of this heat-regulating mechanism is well seen in the case of exercise. Since every muscular contraction gives rise to heat, exercise must increase for the time being the production of heat; yet the bodily temperature rarely rises as much as a degree C., if at all. By exercise the respiration is quickened and the loss of heat by the lungs increased. ”

“ While bodily heat is being continually produced, it is also as continually being lost by the lungs, by the skin, and to some extent, by certain excretions. The blood, in its swiftly flowing current, carries warmth from the tissues where heat is being rapidly generated, to the tissues or organs in which it is being lost by radiation, conduction, or evaporation. Were there no arrangement by which heat could be distributed and regulated, the temperature of the body would be very unequal in different parts, and would vary at different times. ”

“ The hand of an invalid, suffering from inflammation of the chest, or from an attack of fever, is burning; that of one affected by serious asthma, or by emphysema, is as cold to the touch as marble. This is because animal heat varies greatly in different pathological states. Sometimes it rises, sometimes it falls; and the morbid influence is scarcely ever compatible with the body's degree of normal temperature. In Hippocrates's time, when examination of the pulse was not yet practised, the increase of temperature was the only element in the commonest of maladies, fever. ”

“ It is only in those parts of the body to which arterial blood, and with it the oxygen absorbed in respiration, is conveyed that heat is produced. Hair, wool, or feathers do not possess an elevated temperature. This high temperature of the animal body, or, as it may be called, disengagement of heat, is uniformly and under all circumstances the result of the combination of combustible substance with oxygen.
"In whatever way carbon may combine with oxygen, the act of combination cannot take place without the disengagement of heat. ”

“ If chemists apply their theories to these morbid changes of heat, instead of considering them as a necessary consequence of the state in which the vital forces are then found, they will necessarily find in them an insurmountable obstacle.
When we run swiftly, when the blood is violently agitated in the paroxysm of fever, more caloric is disengaged than at any other time. Does this prove that it is the general circulation which contributes to the disengagement of caloric, and that it takes place in the great vessels? No more than a copious sweat proves that the heart drives it out. ”

“ Anything which causes an increase in heat radiation, as perspiration, lowers the temperature, and the open pores of the skin [Pg 30] are valuable aids in equalizing the body heat. A person who perspires freely does not suffer with heat, during excessive exercise, as does one whose pores are closed.
One ready means of regulating the body heat is the bath. If one takes a hot bath, the temperature is materially raised by the artificial heat, but there is a recompense in the increase of heat radiation from the skin. ”

“ In contrast, PVH-lesioned rats were allowed to select their preferred Ta and used behavioral thermoregulation (moved to a warmer environment) while responding to LPS administration in the present study. Not only does a supraneutral environment warms the body of a rat exposed to it, but it also allows the animal to mount the fever response by using skin vasoconstriction instead of the energetically expensive thermogenesis [48] , [49] . Hence, the PVH is likely involved in the circuitry of fever when the response is mounted primarily by activation of brown fat thermogenesis. ”

“ No peril need attend a change from a hot to a cold temperature if the power to evolve heat inherent in the system be entire and active and persistent, not lessened by any of those circumstances which have the effect of weakening it, such as local disease, and fatigue. Cold is dangerous, not especially when the body is hot, but when it is cooling after being heated. At such times taking a large draught of cold water, or cooling the body suddenly some other way might cause death immediately; if not, an inflammation of some internal part of the body might arise. ”

“ The actual deficiency of heat may exist in one part of the body, and the pain of cold be felt most vividly in some other part associated with it by sensitive sympathy. So a chillness down the back is first attended to in ague-fits, though the disease perhaps commences with the torpor and consequent coldness of some internal viscus. But in whatever part of the system the defect of heat exists, or the sensation of it, the convulsions of the subcutaneous muscles exerted to relieve it are very general ”

“ A person in a condition of fever, suffering from intense heat arising from a diseased state of the blood, could not be said to be absorbing heat. Nor could such a description apply to a person who, by a very rapid walk, has raised the temperature of his body considerably above its natural state, by the internal combustion which has already been described. A person feeling hot in bed, from excessive clothes, feels hot from the development of heat internally, which is not conducted away with sufficient rapidity to maintain the natural temperature of the body. ”

“ It is in consequence of this peculiarity of heat in each system, that each gives a different sensation in inflammation. Compare the sharp and biting heat of erysipelas with that of phlegmon; certain dull, obscure heats, the forerunners of organic affections, with the acute heats of different inflammations; apply the hand to the skin in different fevers, you will see that each is almost marked by a particular kind of heat. Animal bodies alone exhibit these varieties of nature in heat; minerals have only varieties in degree. ”

“ If we know anything of the laws of electricity, we must know velocity modulates its temperature. Thus heat and cold are the effect.
If we understand anatomy as we should, we know man is the greatest engine ever produced, complete in form, an electro-magnet, a motor, and would be incomplete if it could not burn its own gases.
When man, is said to have fever, he is only on "fire," to burn out the deadly gases, which a perverted, dirty, abnormal, laboratory, has allowed to accumulate by friction of the journals of his body, or in the supply of vital fluids. ”

“ The blood has a tendency to absorb heat, and if it does so it must of course become thinner, for this is the nature of all fluids, and indeed it is abundantly manifest that fluidity in all cases is an effect of the absorption of heat.153 In consequence of this absorption, the body towards the latter end feels cold, the heat seems to retire from the extremities towards the vital parts, and the vessels contracting and losing their power by reason of the abstraction of sensible heat, the pulse ceases entirely some time before death. ”

“ The body, even when exposed stark naked to the air, is not wholly without defense against heat and cold. It can, up to a certain point, itself regulate the expenditure of caloric by the intervention of the vaso-motor nerves that go to the capillaries of the skin. Cold provokes a shrinking of the little vessels, and, restraining the peripheric circulation, diminishes the radiation and the transpiration to such a degree as to protect the internal organs for a considerable time. ”

“ It allows the heart to pump large amounts of blood out to the surface to be purified by the sweat glands, and to breathe out a little of its carbon dioxid and other gas-poisons.
The Skin as a Heat Regulator. Heat, as well as waste, is given off by the blood when it is poured out to the surface; so another most important use of the skin is as a heat regulator. As we have already seen, every movement which we make with our muscles, whether of arms and limbs, heart, or food tube, causes heat to be given off. We very well know, when we work hard at anything, we are likely to "get warmed up." ”

“ There has been a good deal of discussion as to whether fevers are caused by an increase of heat production or by an impairment of the machinery for getting rid of heat. There is no doubt that in fevers the resting metabolism is much greater than in health; it is not by any means always the case, however, that the total metabolism of an individual lying quietly in bed with a fever is greater than that of a healthy individual doing heavy manual labor. We must therefore look to an interference with the process of losing heat to account for the rise in temperature. ”

“ He found, moreover, that if the heat were withdrawn before it has produced permanent injury to the nervous system, blood or other tissues, the convulsions and unconsciousness are immediately relieved and the animal recovers.
Other conditions may be adduced as predisposing or concurrent causes of thermic fever. Whatever impairs the animal vigor has this effect. Fatigue, as already noticed, is a potent factor, in man a drinking habit; in all animals a long persistence of the heat during the night as well as the day ”

“ But here, too, treatment may be successful if it is promptly applied. Besides these, other varieties depending on the prominence of certain symptoms are occasionally met with. The chief changes in the body after death from heatstroke are those of anaemia of the brain and congestion of the lungs, together with softness of the heart and of the muscular tissues generally. The blood is dark, and fluid and the blood corpuscles are somewhat altered in shapes. Attacks of sunstroke are apt to leave traces of their effects upon the constitution, especially upon the nervous system. ”

“ A heat, however great, shut up in a well-closed vessel, will not produce inflammation unless touched with an inflamed matter; so, likewise, to whatsoever degree a fluid is cooled, it will not freeze unless it touch something already frozen, and this is what happens when the tube is shaken or uncorked; the particles of water, which are frozen in the external air, or in the air contained in the tube, strike the surface of the water, and communicate their ice to it. In inflammation, the air, at first very much rarefied by heat, loses its volume, and fixes itself suddenly. ”

“ The cause of heat-stroke with its high fever is unknown, but probably it is due to some effect on the heat center in the brain. Heat prostration is also due to prolonged exposure to heat, but is generally accompanied by a subnormal temperature. The effect of cold, as in freezing, is to diminish all the metabolic activities of the body. The temperature can be artificially regulated more or less by variations of food, varying amounts of exercise, by drugs, etc. ”

“ H. soon learnt to differentiate this pain, due to a hot object, from a true sensation of heat; he frequently said, "Any ordinary patient would have called such stimuli hot, because the pain produced is of a kind associated in daily life with the action of hot bodies only. Further, a patient is told to say if he feels heat, cold, or a touch. Given, then, that he knows his thermal sensibility is being tested, he would certainly call the sensation I experience 'hot.'"
Occasionally, contact with a neutral tube would cause an indeterminate and somewhat tingling sensation over the affected area ”