[　Characteristics and Causes of Hyperthermia (The difference between "Heat Stroke" and "Fever")　]

Hyperthermia consists of two onsets, such as "heat stroke" and "fever". The "heat stroke" is not caused by diseases, but caused by extrinsic disorders, such as by a high-temperature environment and by troubles in his/her thermolysis. The heat of an infant is released by four means, such as radiation, convection, conduction, and transpiration in order to keep his/her body temperature constantly. However, under the high- temperature environment and high humidity, the thermolytic function is greatly suppressed in him/her, which brings him/her the hyperthermia ("heat stroke"). Under such conditions, peripheral blood vesseles are dilated, the hands and feet are warm, his/her skin is moist and sweat, because the peripheral deep temperature is elavated. The infant in "heat stroke" must reduces his/her basal metabolism not to elevate his/her core body temperature. In order to decrease his/her thermogenesis, the infant falls in sleep, reduces body movements and relaxes the muscles, in order to decrease his/her thermogenesis. For the treatment, it is important to remove promptly their clothes and to carry him/her to a cool place with wind.

Fever (caused by diseases) Heat Stroke (from extrinsic disorders) Etiology diseases (such as infections) ●　high-temperature environment ●　 over-clothing, ●　prone sleeping, （risk factor of SIDS） Central deep-body temperature ↑ ↑ Peripheral deep-body temperature ↓ ↑ Thermogenesis muscular strain/trembling/shivering ↑ ↓ ●temperatures of 　　　hands and feet ●sweating ●deep sleeping ＜ fever ＞ ⇔ ＜recovering＞ cold warm No Yes No Yes(?) warm Yes Yes Respiratory inhibition No Yes Treatment ●　treatment (with antibiotic therapy) of underlying disease ●　sleeping tablets (vasodilation + decrease of muscular strain) ●　removing clothes, (cap, socks, , and bedclothes,etc.) ●　carry to a cool place with a wind

On the other hand, "fever" is usually accompanied with infections and other diseases. In the case of infection, thermogenesis is remarkably increased and thermolysis is inhibited by peripheral vasoconstriction. In spite of a high-fever, a patient feels "cold" and shivers, because thermoregulation-center is set erroneously at a high level by pyrogens. Thermoregulation of the infected patient is similar to one of the person who regulates body temperature at a low-temperature environment. Therefore, thermogenesis is promoted by enhanced muscle movements as "shivering". At the same time, thermolysis is inhibited by peripheral vasoconstriction and decreased blood flow, therefore hands and feet get cold and do not sweat. For the treatment of "fever", it is important to remove the cause of infection(s) and to take some medicines which reduce muscle strain ( to decrease thermogenesis) and dilate peripheral blood vessels ( to increase thermolysis), such as tranquilizers. In general sweating is observed when peripheral vessels are dilated and the symptoms begin to recover. Although both "fever" and "heat stroke" are classified as hyperthermia, there are fundamental differences in the thermoregulations and treatments between them.