Neurogenic hyperthermia (fever)

Physiological circadian regulation of body temperature allows it to normally fluctuate from the minimum value in the early morning (about 36 °) to the maximum in the afternoon (up to 37.5 °). The level of body temperature depends on the balance of the mechanisms regulating the processes of heat production and heat transfer. Some pathological processes can cause an increase in body temperature as a result of insufficiency of thermoregulatory mechanisms, which is commonly called hyperthermia. An increase in body temperature with adequate thermoregulation is called a fever. Hyperthermia develops with excessive metabolic heat production, excessively high ambient temperature, or with defective heat transfer mechanisms. To some extent, it is possible to distinguish three groups of hyperthermia (more often their cause is complex).

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]

The main causes of neurogenic hyperthermia:

I. Hyperthermia caused by excessive heat production.

1. Hyperthermia in Exercise
2. Heat stroke (with physical stress)
3. Malignant hyperthermia for anesthesia
4. Lethal catatonia
5. Thyrotoxicosis
6. Pheochromacytoma
7. Intoxication with salicylates
8. Drug abuse (cocaine, amphetamine)
9. Delirium tremens
10. Epileptic status
11. Tetanus (generalized)

II. Hyperthermia due to a decrease in heat transfer.

1. Thermal shock (classical)
2. Use of heat-resistant clothing
3. Dehydration
4. Autonomic dysfunction of psychogenic origin
5. Introduction of anticholinergic drugs
6. Hyperthermia in anhidrosis.

III. Hyperthermia of complex genesis in disorders of the hypothalamus.

1. Malignant neuroleptic syndrome
2. Cerebrovascular disorders
3. Encephalitis
4. Sarcoidosis and granulomatous infections
5. Craniocerebral injury
6. Other disorders of the hypothalamus

I. Hyperthermia due to excessive heat production

Hyperthermia with exercise. Hyperthermia is the inevitable consequence of prolonged and intense physical stress (especially in hot and humid weather). Its lung forms are well controlled by rehydration.

Thermal shock (with physical stress) refers to the extreme form of hyperthermia of physical effort. There are two types of heat stroke. The first type is a heat stroke with physical stress, which develops with intensive physical work in a damp and hot environment, usually in young and healthy people (athletes, soldiers). Predisposing factors include: insufficient acclimatization, regulatory disorders in the cardiovascular system, dehydration, wearing warm clothing.

The second type of heat stroke (classical) is typical for older people with disturbed heat transfer processes. Anhidrosis often occurs here. Predisposing factors: cardiovascular diseases, obesity, use of cholinergic agents or diuretics, dehydration, old age. Urban living for them is a risk factor.

Clinical manifestations of both forms of heat stroke include acute onset, a rise in body temperature above 40 °, nausea, weakness, krampi, impaired consciousness (delirium, stupor or coma), hypotension, tachycardia, and hyperventilation. Epileptic seizures are often observed; Sometimes focal neurological symptoms, edema on the fundus are revealed. Laboratory studies show hemoconcentration, proteinuria, microhematuria and impaired liver function. The level of muscle enzymes is increased, severe rhabdomyolysis and acute renal failure are possible. Frequently, symptoms of disseminated intravascular coagulation are revealed (especially in the case of heat stroke during physical exertion). In the latter variant, there is often concomitant hypoglycemia. The study of acid-base balance and electrolyte balance, as a rule, reveals respiratory alkalosis and hypokalemia in the early stages and lactate acidosis and hypercapnia - in the later stages.

The death rate for heat shock is very high (up to 10%). The causes of death can be: shock, arrhythmia, myocardial ischemia, renal failure, neurological disorders. The prognosis depends on the severity and duration of hyperthermia.

Malignant hyperthermia in narcosis refers to the rare complications of general anesthesia. The disease is inherited by an autosomal dominant type. The syndrome usually develops shortly after the injection of anesthetic, but can develop later (up to 11 hours after drug administration). Hyperthermia is very pronounced and reaches 41-45 °. Another main symptom is pronounced muscular rigidity. There are also hypotension, hyperpnoea, tachycardia, arrhythmia, hypoxia, hypercapnia, lactate acidosis, hyperkalemia, rhabdomyolysis and DIC syndrome. Characterized by high mortality. The therapeutic effect is intravenous administration of a solution of dantrolene. Urgent withdrawal of anesthesia, correction of hypoxia and metabolic disorders and cardiovascular support are necessary. Physical cooling is also used.

Lethal (malignant) catatonia is described in the pre-lethal era, but it is clinically similar to a malignant neuroleptic syndrome with deafness, severe rigidity, hyperthermia and vegetative disorders leading to death. Some authors even consider that neuroleptic malignant syndrome is a drug-induced lethal catatonia. However, a similar syndrome is described in patients with Parkinson's disease with a sharp abolition of dopa-containing agents. Rigidity, tremor and fever are also observed in serotonin syndrome, which sometimes develops with the introduction of MAO inhibitors and serotonin-raising agents.

Thyrotoxicosis in a number of other manifestations (tachycardia, extrasystole, atrial fibrillation, arterial hypertension, hyperhidrosis, diarrhea, weight loss, tremor, etc.) is characterized by an increase in body temperature. Subfebrile temperature is found in more than one third of patients (hyperthermia is well compensated by hyperhidrosis). However, before taking the subfebrile condition due to thyrotoxicosis, it is necessary to exclude other causes that can lead to an increase in temperature (chronic tonsillitis, sinusitis, diseases of the teeth, gall bladder, inflammatory diseases of the pelvic organs, etc.). Patients do not tolerate hot spaces, sunny heat; and insolation often provokes the first signs of thyrotoxicosis. Hyperthermia often becomes noticeable during a thyrotoxic crisis (it is better to measure rectal temperature).

Pheochromacitoma results in a periodic release into the blood of a large amount of adrenaline and norepinephrine, which determines the typical clinical picture of the disease. Attacks of sudden blanching of the skin, especially the face, trembling of the whole body, tachycardia, pain in the heart, headaches, fear, arterial hypertension. The attack lasts a few minutes or several tens of minutes. Between the attacks, the state of health remains normal. During an attack, sometimes there may be hyperthermia of one degree or another.

The use of drugs such as anticholinergics and salicylates (with severe intoxication especially in children) can lead to such an unusual manifestation as hyperthermia.

The abuse of certain drugs, especially cocaine and amphetamine, is another possible cause of hyperthermia.

Alcohol increases the risk of heat stroke, and alcohol can be triggered by delirium (white fever) with hyperthermia.

Epileptic status can be accompanied by hyperthermia, apparently in the picture of central hypothalamic thermoregulatory disorders. The cause of hyperthermia in such cases does not cause diagnostic doubt.

Tetanus (generalized) is manifested by such a typical clinical picture, which also does not give rise to diagnostic difficulties in the evaluation of hyperthermia.

II. Hyperthermia due to decreased heat loss

To this group of disorders, in addition to the classical heat stroke mentioned above, it is possible to include overheating when wearing heat-tight clothing, dehydration (decreased sweating), psychogenic hyperthermia, hyperthermia with anticholinergics (eg Parkinsonism) and anhidrosis.

Pronounced hypohydrosis or anhidrosis (congenital absence or underdevelopment of sweat glands, peripheral vegetative insufficiency) can be accompanied by hyperthermia if the patient is in a high temperature environment.

Psychogenic (or neurogenic) hyperthermia is characterized by a prolonged and monotonously flowing hyperthermia. Often there is an inversion of the circadian rhythm (in the morning the body temperature is higher than in the evening). This hyperthermia is relatively well tolerated by the patient. Antipyretics in typical cases do not reduce the temperature. The heart rate does not change at the same time as the body temperature. Neurogenic hyperthermia is usually observed in the context of other psycho-vegetative disorders (autonomic dystonia syndrome, HDN, etc.); it is especially characteristic for school (especially pubertal) age. Often it is accompanied by an allergy or other signs of immunodeficiency. In children, hyperthermia often stops outside the school season. The diagnosis of neurogenic hyperthermia always requires careful elimination of somatic causes of fever (including HIV infection).

III. Hyperthermia of complex genesis in disorders of the hypothalamus

Malignant neuroleptic syndrome develops, according to some authors, in 0.2% of patients receiving antipsychotics during the first 30 days of treatment. It is characterized by generalized muscle stiffness, hyperthermia (usually above 41 °), vegetative disorders, impaired consciousness. There is rhabdomyolysis, impaired kidney and liver function. Leukocytosis, hypernatremia, acidosis and electrolyte disturbances are characteristic.

Strokes (and subarachnoid hemorrhages, including) in the most acute phase are often accompanied by hyperthermia in the background of severe cerebral disorders and the corresponding neurological manifestations facilitating diagnosis.

Hyperthermia is described in the picture of encephalitis of different nature, as well as sarcoidosis and other granulomatous infections.

Craniocerebral trauma of the middle and, especially, severe degree can be accompanied by pronounced hyperthermia in the acute stage. Here, hyperthermia is often observed in the picture of other hypothalamic and stem disorders (hyperosmolarity, hypernatremia, muscle tone disorders, acute adrenal insufficiency, etc.).

Other damage to the hypothalamus of organic nature (a very rare cause) can also manifest hyperthermia among other hypothalamic syndromes.

Diagnostic studies of neurogenic hyperthermia

• a detailed general-purpose physical examination,
• general blood analysis,
• blood chemistry,
• chest x-ray,
• ECG,
• general urine analysis,
• consultation of the therapist.

You may need: ultrasound examination of the abdominal organs, consultation of the endocrinologist, otolaryngologist, dentist, urologist, proctologist, blood and urine culture, serological diagnosis of HIV infection.

It is necessary to exclude the possibility of iatrogenic hyperthermia (allergy to certain medicines) and, occasionally, an artificially induced fever.

[13], [14], [15], [16]