Fever

Introduction An increase in the regulatory body temperature (above 0.5 ° C) caused by the action of the pyrogen causing the body temperature setting point to move up is called fever (also known as fever). Each person's normal body temperature is slightly different and is affected by many factors (time, season, environment, menstruation, etc.). Therefore, it is better to judge whether it is fever or not, and it is better to compare it with the body temperature under the same conditions. If you do not know your original body temperature, the temperature of the armpit (tested for 10 minutes) exceeds 37.4 °C and can be determined to be fever.

Cause

There are many diseases that cause fever, and they can be divided into two categories depending on the cause of the disease.

(1) Infectious diseases

It ranks first in fever, including common infectious diseases caused by various pathogens, systemic or focal infections. Infectious fever caused by bacteria is the most common, followed by viruses.

(2) Non-infectious diseases

1, blood diseases and malignant tumors such as leukemia, malignant histiocytosis, malignant lymphoma, colon cancer, primary hepatocellular carcinoma.

2, allergic diseases such as drug fever, rheumatic fever.

3. Connective tissue diseases such as systemic lupus erythematosus (SIE) dermatomyositis, nodular polyarteritis, mixed connective tissue disease (MCTD), and the like.

4, other

Such as hyperthyroidism, thyroid crisis. Severe water loss or bleeding, heat radiation, heat stroke, fracture, extensive burns, cerebral hemorrhage, visceral vascular infarction, tissue necrosis.

mechanism

Recent studies have shown that fever is caused by exogenous pyrogens, and its mechanism is mainly due to the up-regulation of the body temperature regulation point of the body temperature regulation center. An external pyrogen is an activator (including various pathogens, endotoxins, antigen-antibody complexes, lymphokines, steroid products, and some inflammatory substances) that produces endogenous pyrogen cells in the body. Different pathways activate endogenous and pyrogenic cells to produce and release endogenous pyrogens (interleukin 1, interleukin 2, tumor necrosis factor and interferon, etc.). The mechanism of its fever has not been fully elucidated. It is currently believed that it may be through certain biologically active substances such as prostaglandin E (PGE), monoamine (demethylephrine, serotonin), cyclic adenosine monophosphate (cAMP), calcium/sodium ratio change, endorphin As an intermediary, it acts on the body temperature regulation center and moves the body temperature adjustment point up. The body temperature is readjusted, and the regulating impulse is emitted. The sympathetic nerve causes the skin to contract and the heat dissipation is reduced.

On the other hand, the action of the motor nerve causes periodic contraction of the skeletal muscle to cause chills, which increases the heat production. The skin temperature drops due to skin vasoconstriction, stimulating the cold receptors to send impulses to the lower part of the thalamus, and also participate in the occurrence of chills. Therefore, the result of the adjustment is that the heat production is greater than the heat dissipation, so that the body temperature rises and rises to a new level that is compatible with the body temperature setting point. This is the basic mechanism of elevated body temperature during infectious fever. In recent years, some scholars believe that in the visual crypt of the third ventricle wall, there is a special part of the hypothalamic endplate vascular device, and the endogenous pyrogen acts on the macrophage and is released. The medium acts here to cause fever.

Non-infectious fever such as aseptic tissue injury (myocardial infarction, pulmonary embolism, postoperative fever, chest or abdominal hemorrhage, etc.) allergic reaction, blood group incompatibility, drug fever, drug-induced hemolytic anemia, connective tissue disease, etc. The mechanism of the increase in body temperature is mainly that the antigen-antibody complex has a special activation effect on the production of pyrogenogenic cells, so that endogenous pyrogens are produced and released. Malignant tumors cause fever, some patients have infections, and nearly half of them are caused by simple tumors. Most scholars believe that the inflammatory lesions damaged by malignant tumors and the immune response of fibroids themselves. Common malignant histiocytosis, lymphoma (especially Hodgkin's disease), prostate cancer, kidney cancer, colon cancer, pancreatic cancer, liver cancer, lung cancer, multiple myeloma and the like. Due to fever caused by abnormal heat production, heat production is greater than heat, thyroid crisis, status epilepticus and pheochromocytoma. Atropine poisoning, large amount of water loss, blood loss, etc. due to reduced heat dissipation. The brain has extensive chronic degenerative diseases or cerebral hemorrhage, epidemic encephalitis and other damage to the hypothalamus, which may have super high fever. Sympathetic nerves are inhibited, the skin is dry and sweat-free, and heat dissipation is reduced.

an examination

Related inspection

Body temperature measurement

First, medical history and physical examination

It is important to have a detailed and detailed physical examination of the medical history (including epidemiological data). If the onset is urgent, the height and change of the fever period and body temperature are considered to be mostly chills, but about 2/3 of lymphoma and malignant histiocytoma also have chills, indicating that chills are not unique to infectious diseases. However, there are obvious chills that are common in serious bacterial infections (pneumococcus pneumonia, sepsis, acute pyelonephritis, acute cholecystitis, etc.), malaria transfusion or infusion reactions. Tuberculosis, typhoid rickettsial disease and viral infection are rare. Generally not seen in rheumatic fever. Fever is often accompanied by non-specific symptoms such as dizziness, dizziness, headache, and loss of appetite. There is no differential diagnosis. However, local symptoms of localization have important reference value. Such as fever with neurological symptoms, such as severe headache and vomiting. Consciousness disorder and convulsions, meningeal irritation signs, etc. suggest that the lesions in the central nervous system, should consider encephalitis, meningitis, elderly patients with serious infections, often have a change in consciousness, and body temperature is not necessarily high.

Asking about epidemiological history such as disease area, season, age occupation, living habits, history of travel and close contact with the same disease, history of surgery, blood transfusion and history of blood products, history of cattle and sheep contact, etc., are important in diagnosis Sometimes a little bit of discovery can provide important diagnostic clues.

Second, laboratory and auxiliary inspection

It is necessary to selectively combine clinical performance analysis and judgment according to specific conditions. Such as blood routine, urine routine pathogen examination (direct smear, culture, specific antigen antibody detection molecular biological test, etc.) X-ray, B-mode ultrasound, CTMRI, ECT examination, tissue biopsy (lymph node liver, skin decidua), bone marrow Puncture, etc.

Differential diagnosis

First, several common fevers:

1. Irregular heat means there is no certain law of fever, and the duration is not necessarily. Can be seen in a variety of lung diseases, heart pleurisy.

2, the concept of generalized unexplained fever refers to all unexplained fever. However, in the clinic, the narrow concept of fever is also adopted, that is, fever is unknown. The fever lasted for more than 3 weeks, the body temperature was above 38.5 °C, and the diagnosis was not confirmed by detailed medical history, physical examination and routine laboratory tests.

3. Cancer fever refers to the non-infectious fever directly related to cancer that occurs in cancer patients without the infection and antibiotic treatment, and the fever caused by treatment during the development of the tumor.

4. Q fever is a natural epidemic infection caused by systemic infection caused by coxiella burnetii, also known as cox body disease. Livestock such as cattle, sheep, dogs, horses, donkeys and pigs are the main source of infection. The clinical features are fever, headache, and general muscle pain, but no rash, sometimes with interstitial pneumonia, and a small number of patients with chronic hepatitis or fatal endocarditis.

5, infectious fever: various infectious diseases such as bacteria, viruses, fungi, spirochetes, malaria parasites and other effects on the body temperature regulation center, body temperature central dysfunction or various causes of excessive heat production, heat reduction, resulting in elevated body temperature Exceeding the normal range.

6. Central fever refers to fever caused by abnormalities in the body temperature regulation center caused by central nervous system diseases.

According to the level of fever, it can be divided into the following clinical classifications: low heat 37.4 ° C ~ 38 ° C moderate heat, 38.1 ° C ~ 39 ° C high heat 3, 9.1 ° C ~ 41 ° C, ultra high heat 41 ° C or more, lasting more than 4 weeks, For persistent fever.

Relaxation heat is also called septicemia. It means that the body temperature continues to be above 39 degrees, and the fluctuation range is large. The body temperature fluctuation range exceeds 2 degrees within 24 hours, but both are above the normal level. Common in sepsis, rheumatic fever, severe tuberculosis and suppurative inflammation. Persistent relaxation heat can be seen in malignant granuloma.

Fever is rarely a single pathological process. Tumors and connective tissue diseases can be mixed with infectious factors during the fever process, resulting in complex clinical manifestations, but most of them can be diagnosed based on clinical features and comprehensive examination. Understanding the frequency of unexplained fever causes can help provide a logical thinking of clinical diagnosis. According to the heat history, heat type and clinical characteristics, it can be divided into acute fever (thermal path less than 2 weeks), long-term fever (heat cycle more than 2 weeks, and multiple body temperature above 38 °C), and repeated fever (periodic fever). It is generally believed that the infection is the first cause of acute fever, followed by tumor and vascular-connective tissue disease. These three causes summarize the etiological diagnosis of 90% of unexplained fever. Infectious diseases account for the majority of unexplained fever. Systemic infections caused by bacteria, localized abscesses, urinary tract infections, and biliary tract infections are common. Tuberculosis ranks second, with extrapulmonary tuberculosis far more than tuberculosis. Malignant tumors are mainly manifested by fever, followed by lymphoma, malignant histiocytoma and various solid tumors, and the proportion of unexplained fever is higher than before.

The diagnosis principle of unexplained fever is to comprehensively analyze and judge the clinical data, and the length of the heat cycle has a great reference value for diagnosis. The heat history of infectious diseases is relatively short. If the heat stroke is short and the progressive consumption is exhausted, the tumor is more common. Long heat history, no symptoms of poisoning, alternating episodes and remissions, is conducive to the diagnosis of vascular-connective tissue disease. In the process of diagnosis and treatment of unexplained fever, it is necessary to closely observe the condition, pay attention to the newly emerged symptoms and signs, and conduct further examination according to this, which is meaningful for a clear diagnosis.

Second, analyze the heat type

Clinically, various infectious diseases have different heat types, and the heat type also changes during the course of the disease. Therefore, understanding the heat type has certain reference significance for diagnosis, judgment of the disease, evaluation of efficacy and prognosis.

(1) According to the temperature (the armpit temperature)

It is divided into low heat type (<38 °C) medium heat type (38-39), high heat type (39-40 °C), and ultra high heat type (>40 °C).

(2) Classification according to body temperature curve

Such as heat retention, relaxation heat, intermittent heat, wavy heat, irregular heat. The formation mechanism of the heat type has not been fully elucidated. Most of them are considered to be related to the nature of the lesion. The factors that determine the nature of the lesion are the rate and amount of endogenous pyrogen production and the rate at which human blood is released, all of which affect the height and velocity of the temperature-adjusted point.

(1) Surgery fever: The body temperature is maintained at 39 to 40 ° C or even higher for several days or weeks, and the fluctuation within 24 hours does not exceed l ° C, such as lobar pneumonia, typhoid and the like.

(2) Intermittent heat: The body temperature suddenly rises to above 39 °C, and falls to normal for several hours, and rises again for one day or several days, such as malaria and acute pyelonephritis.

(3) Relaxation heat: The body temperature is often above 39 °C, and the fluctuation range exceeds 2 °C within 24 hours, but both are above normal level, such as sepsis, rheumatic fever and the like.

(4) Cycle heat: Also known as wavy heat, body temperature rises above 39 °C, and gradually decreases to normal after a few days, and then gradually increases after several days, such as brucellosis, regression heat.

(5) Irregular heat: There is no regularity in the body temperature curve of fever, such as tuberculosis and kala-azar.

Third, the difference between infectious fever and non-infectious fever

(1) Infectious fever

Infectious fever has the following characteristics:

1. Onset of illness with or without chills.

2, systemic and localized symptoms and signs.

3. Blood: The white blood cell count is higher than 1.2x109/L or lower than 0.5109/L.

4, tetrazolium blue test (NBT): such as neutrophil reduction NBT more than 20%, suggesting bacterial infection, help with the identification of viral infections and non-infectious fever. (Normal value <10%) can be false negative after application of hormones.

5, C-reactive protein determination (CRP): positive suggestive of bacterial infections and rheumatic fever, negative mostly viral infection.

6, neutrophil alkaline phosphatase score increased: normal value is 0 ~ 37, the higher the higher the higher the more favorable for the diagnosis of bacterial infection, when the exclusion of pregnancy, cancer, malignant lymphoma is more meaningful. It can be raised or false positive after application of hormones.

(two) non-infectious fever

Non-infectious fever has the following characteristics:

1. The heat course is longer than 2 months, and the longer the heat stroke, the greater the possibility.

2, long-term fever is generally good, no obvious symptoms of poisoning.

3, anemia, painless multi-site lymphadenopathy, hepatosplenomegaly.

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