Fever is a common pathophysiological phenomenon in daily life, which is a regulated increase in body temperature (more than 0.5℃) caused by the upward shift of the thermoregulatory point due to the action of pyrogen. The normal human body temperature axillary measurement is 36~37°C. Since the normal body temperature of each person is slightly different and influenced by many factors (age, gender, time of day, season, environment, menstruation, etc.), the body temperature usually fluctuates, but the fluctuation range is no more than 1°C. Although fever is a danger sign of disease, but the appearance of fever, but also should not blindly reduce fever, which will not only cover up the disease, but also aggravate the disease. There are many causes of fever, which can be clinically divided into two categories: infectious and non-infectious, with the former being the most common. 1, infectious fever various pathogens such as viruses, bacteria, mycoplasma, rickettsia, spirochetes, fungi, parasites and other infections, whether acute, subacute or chronic, localized or systemic, can appear fever. 2. Non-infectious fever mainly has the following types of causes: (1)
Absorption of aseptic necrotic material: aseptic inflammation due to tissue cell necrosis, tissue proteolysis and absorption of tissue necrosis products can often cause fever, also known as absorption fever. It is common in: (1) mechanical, physical or chemical damage, such as tissue injury after major surgery, internal bleeding, large hematoma, large burns, etc.; (2) internal infarction or limb necrosis of the heart muscle, lung, spleen, etc. caused by vascular embolism or thrombosis; (3) tissue necrosis and cell destruction, such as cancer, leukemia, lymphoma, hemolytic reaction, etc. (2) Antigen-antibody reactions: such as rheumatic fever, serum sickness, drug fever, connective tissue disease, etc. (3) Endocrine and metabolic diseases: such as hyperthyroidism, severe dehydration, etc. (4) Reduced skin heat dissipation: such as extensive dermatitis, ichthyosis and chronic heart failure, etc. resulting in fever, which is usually low. (5)
Some thermogenic factors directly damage the thermoregulatory center without endogenous thermogenic sources, causing the thermoregulatory impulse to be issued after the thermoregulatory point is shifted upward, resulting in a higher heat production than heat dissipation and a higher body temperature, which is called central fever. It is common in: (1) physical: such as heat stroke; (2) chemical: such as heavy sleeping drug poisoning; (3) mechanical: such as cerebral hemorrhage, concussion, skull fracture, etc. The above-mentioned causes can directly damage the thermoregulatory center, resulting in its malfunction and causing fever, and high fever without sweating is the characteristic of this kind of fever. (6)
Autonomic dysfunction: Due to autonomic dysfunction, the normal thermoregulation process is affected, so that heat production is greater than heat dissipation, and the body temperature rises, mostly to hypothermia, often accompanied by other manifestations of autonomic dysfunction, which belongs to the category of functional fever. Common functional hypothermia are: ① primary hypothermia: due to autonomic dysfunction caused by thermoregulation disorders or abnormal body mass, hypothermia can last for months or even years, the heat pattern is more regular, the temperature fluctuation range is small, mostly within 0.5 ℃. ② Post-infection hypothermia: After the fever is caused by virus, bacteria, protozoa and other infections, the hypothermia does not subside, and the original infection has been healed. This is because the thermoregulatory function has not yet returned to normal, but it must be distinguished from fever caused by a potential lesion (such as tuberculosis) activity or other new infections due to a decrease in body resistance. (③) Summer hypothermia: Hypothermia occurs only in the summer and recedes on its own after the autumn cools down, recurring so every year and mostly healing on its own after several consecutive years. It is mostly seen in young children because of the imperfect function of the thermoregulatory center, weakness in summer, and mostly occurs in those with malnutrition or brain underdevelopment. ④Physiological hypothermia: Hypothermia can occur after mental stress or strenuous exercise. Premenstruation and early pregnancy can also have hypothermia. Therefore, once a fever occurs, you cannot blindly take antipyretic drugs, simply bringing down the body temperature can only treat the symptoms but not the root cause, the fundamental problem is to treat the primary disease causing the fever, clinically for patients with body temperature below 38.5 ℃ advocate physical therapy, such as ice or alcohol wipe the whole body, more than 38.5 ℃ before using drug therapy. For people older than 40 years old, the fever caused by infection may be just the tip of the iceberg of other underlying diseases, therefore, it is important to actively search for the cause so as to clarify the diagnosis and avoid delaying the condition and treatment.