Neurogenic hyperthermia (increased body temperature)

Physiological circadian regulation of body temperature allows it to fluctuate normally from a minimum value in the early morning (around 36°) to a maximum in the afternoon (up to 37.5°). The level of body temperature depends on the balance of 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 usually called hyperthermia. An increase in body temperature with adequate thermoregulation is called fever. Hyperthermia develops with excessive metabolic heat production, excessively high ambient temperatures, or defective heat transfer mechanisms. To some extent, three groups of hyperthermia can be conditionally distinguished (usually their cause is complex).

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The main causes of neurogenic hyperthermia are:

I. Hyperthermia caused by excessive heat production.

1. Hyperthermia during physical exertion
2. Heat stroke (due to physical exertion)
3. Malignant hyperthermia during anesthesia
4. Lethal catatonia
5. Thyrotoxicosis
6. Pheochromocytoma
7. Salicylate intoxication
8. Drug abuse (cocaine, amphetamine)
9. Delirium tremens
10. Status epilepticus
11. Tetanus (generalized)

II. Hyperthermia caused by decreased heat transfer.

1. Heat stroke (classic)
2. Use of heat-resistant clothing
3. Dehydration
4. Vegetative dysfunction of psychogenic origin
5. Administration of anticholinergic drugs
6. Hyperthermia in anhidrosis.

III. Hyperthermia of complex genesis in case of dysfunction of the hypothalamus.

1. Neuroleptic malignant syndrome
2. Cerebrovascular disorders
3. Encephalitis
4. Sarcoidosis and granulomatous infections
5. Traumatic brain injury
6. Other hypothalamic lesions

I. Hyperthermia caused by excessive heat production

Hyperthermia during physical exertion. Hyperthermia is an inevitable consequence of prolonged and intense physical exertion (especially in hot and humid weather). Its mild forms are well controlled by rehydration.

Heat stroke (during physical exertion) refers to an extreme form of hyperthermia of physical effort. There are two types of heat stroke. The first type is heat stroke during physical exertion, which develops during intense physical work in humid and hot external conditions, 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 (classic) is typical for elderly people with impaired heat transfer processes. Anhidrosis often occurs here. Predisposing factors: cardiovascular diseases, obesity, use of anticholinergics or diuretics, dehydration, old age. Urban living is a risk factor for them.

Clinical manifestations of both forms of heatstroke include acute onset, a rise in body temperature above 40°, nausea, weakness, cramps, impaired consciousness (delirium, stupor, or coma), hypotension, tachycardia, and hyperventilation. Epileptic seizures are common; focal neurologic symptoms and fundus edema are sometimes present. Laboratory studies reveal hemoconcentration, proteinuria, microhematuria, and liver dysfunction. Muscle enzyme levels are elevated, severe rhabdomyolysis and acute renal failure are possible. Symptoms of disseminated intravascular coagulation are common (especially in cases of exertional heatstroke). In the latter variant, concomitant hypoglycemia is often present. Acid-base and electrolyte balance studies usually reveal respiratory alkalosis and hypokalemia in the early stages and lactic acidosis and hypercapnia in the late stages.

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

Malignant hyperthermia during anesthesia is a rare complication of general anesthesia. The disease is inherited in an autosomal dominant manner. The syndrome usually develops soon after the anesthetic is administered, but may also develop later (up to 11 hours after the drug is administered). Hyperthermia is very pronounced and reaches 41-45°. Another main symptom is pronounced muscle rigidity. Hypotension, hyperpnea, tachycardia, arrhythmia, hypoxia, hypercapnia, lactic acidosis, hyperkalemia, rhabdomyolysis, and DIC syndrome are also observed. High mortality is typical. Intravenous administration of dantrolene solution has a therapeutic effect. Urgent withdrawal of anesthesia, correction of hypoxia and metabolic disorders, and cardiovascular support are necessary. Physical cooling is also used.

Lethal (malignant) catatonia was described in the pre-neuroleptic era, but is clinically similar to neuroleptic malignant syndrome with confusion, severe rigidity, hyperthermia, and autonomic dysfunction leading to death. Some authors even believe that neuroleptic malignant syndrome is drug-induced lethal catatonia. However, a similar syndrome has been described in patients with Parkinson's disease with abrupt withdrawal of dopa-containing drugs. Rigidity, tremors, and fever are also observed in serotonin syndrome, which sometimes develops with the introduction of MAO inhibitors and drugs that increase serotonin levels.

Thyrotoxicosis, along with its other manifestations (tachycardia, extrasystole, atrial fibrillation, arterial hypertension, hyperhidrosis, diarrhea, weight loss, tremor, etc.), is also characterized by a rise in body temperature. Subfebrile temperature is found in more than one third of patients (hyperthermia is well compensated by hyperhidrosis). However, before attributing subfebrile temperature to thyrotoxicosis, it is necessary to exclude other causes that can lead to an increase in temperature (chronic tonsillitis, sinusitis, dental disease, gall bladder, inflammatory diseases of the pelvic organs, etc.). Patients do not tolerate hot rooms, sun 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).

Pheochromocytoma causes a periodic release of large amounts of adrenaline and noradrenaline into the blood, which determines the typical clinical picture of the disease. There are attacks of sudden paleness of the skin, especially the face, trembling of the whole body, tachycardia, pain in the heart, headaches, a feeling of fear, arterial hypertension. An attack lasts several minutes or several tens of minutes. Between attacks, the state of health remains normal. During an attack, hyperthermia of varying degrees of severity can sometimes be observed.

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

Abuse of certain drugs, especially cocaine and amphetamines, is another possible cause of hyperthermia.

Alcohol increases the risk of heatstroke, and alcohol withdrawal can trigger delirium (delirium tremens) with hyperthermia.

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

Tetanus (generalized) manifests itself with such a typical clinical picture that it also does not give rise to diagnostic difficulties in assessing hyperthermia.

II. Hyperthermia due to decreased heat transfer

In addition to the classic heat stroke mentioned above, this group of disorders includes overheating when wearing heat-impermeable clothing, dehydration (decreased sweating), psychogenic hyperthermia, hyperthermia when using anticholinergics (for example, in Parkinsonism) and anhidrosis.

Severe hypohidrosis or anhidrosis (congenital absence or underdevelopment of sweat glands, peripheral autonomic failure) may be accompanied by hyperthermia if the patient is in an environment with a high temperature.

Psychogenic (or neurogenic) hyperthermia is characterized by prolonged and monotonous hyperthermia. Inversion of the circadian rhythm is often observed (in the morning, the body temperature is higher than in the evening). This hyperthermia is relatively well tolerated by the patient. Antipyretic drugs in typical cases do not reduce the temperature. The heart rate does not change in parallel with the body temperature. Neurogenic hyperthermia is usually observed in the context of other psychovegetative disorders (vegetative dystonia syndrome, HDN, etc.); it is especially characteristic of school age (especially puberty). It is often accompanied by allergies or other signs of immunodeficiency. In children, hyperthermia often stops outside the school season. The diagnosis of neurogenic hyperthermia always requires careful exclusion of somatic causes of increased temperature (including HIV infection).

III. Hyperthermia of complex genesis in hypothalamic dysfunction

Malignant neuroleptic syndrome develops, according to some authors, in 0.2% of patients receiving neuroleptics during the first 30 days of treatment. It is characterized by generalized muscle rigidity, hyperthermia (usually above 41°), autonomic disorders, and impaired consciousness. Rhabdomylisis, renal and hepatic dysfunction are observed. Leukocytosis, hypernatremia, acidosis, and electrolyte disturbances are characteristic.

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

Hyperthermia has been described in the picture of encephalitis of various origins, as well as sarcoidosis and other granulomatous infections.

Moderate and especially severe craniocerebral trauma may be accompanied by pronounced hyperthermia in the acute stage. Here, hyperthermia is often observed in the picture of other hypothalamic and brainstem disorders (hyperosmolarity, hypernatremia, muscle tone disorders, acute adrenal insufficiency, etc.).

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

Diagnostic studies of neurogenic hyperthermia

• detailed general physical examination,
• complete blood count,
• biochemical blood test,
• chest x-ray,
• ECG,
• general urine analysis,
• consultation with a therapist.

The following may be required: ultrasound examination of abdominal organs, consultation with an endocrinologist, otolaryngologist, dentist, urologist, proctologist, blood and urine culture, serological diagnostics of HIV infection.

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

Treatment of neurogenic hyperthermia

Treatment requires immediate medical attention and may include the following steps:

1. Stopping anesthetics: If neurogenic hyperthermia occurs during surgery or a procedure, stop the anesthetic immediately. This will stop any further increase in temperature.
2. Medication: The patient may require treatment with specific medications such as dantrolene or bromocriptine, which can help control hyperthermia and prevent further calcium release into the muscles.
3. Active Cooling: Cooling the patient to reduce body temperature is an important part of treatment. This may include the use of cool compresses, cooling fans, and other active cooling methods.
4. Life support: Patients with neurogenic hyperthermia may require support for vital functions such as breathing and circulation. This may include mechanical ventilation and intensive care.

Treatment of neurogenic hyperthermia requires highly skilled medical care and is carried out in specialized intensive care units. It is important to seek immediate medical attention if this condition is suspected, as it can be fatal if not treated properly.

Prevention

Prevention of neurogenic hyperthermia includes the following measures:

1. Informing Healthcare Professionals: If you or your child has a history of neurogenic hyperthermia or other reactions to anesthetics, be sure to tell your doctor and anesthesiologist before the surgery or procedure. Healthcare professionals should be aware of your medical history so that appropriate precautions can be taken.
2. Avoid triggers: If you or your child have known triggers for neurogenic hyperthermia, such as certain anesthetics or medications, make sure they are not used during the surgery or procedure. Doctors may choose alternative anesthetics and medications.
3. Genetic testing: If you have a family history of neurogenic hyperthermia or have had a case of the condition in your family, genetic testing may be helpful in identifying genetic mutations associated with the condition. This can help doctors provide the most appropriate medical care and avoid triggers.
4. Following Medical Advice: If you have already been diagnosed with neurogenic hyperthermia, it is important to follow medical advice and take precautions as suggested by your doctor.
5. Family Education: If you have relatives with neurogenic hyperthermia, provide them with information about the symptoms, risks, and the need to tell health care providers about the history before surgeries or procedures.

Prevention mainly involves preventing the occurrence of its symptoms by avoiding known triggers and ensuring timely medical advice when risk factors are present.

Forecast

The prognosis for neurogenic hyperthermia (neuroleptic malignant syndrome) can be serious and depends on a number of factors, including:

1. Timing of treatment: Speed of diagnosis and initiation of treatment play a critical role in prognosis. The sooner treatment begins, the better the chances of successful recovery.
2. Severity of the condition: The condition can have varying severity, and the prognosis will depend on the degree of complications and symptoms. Mild cases of neurogenic hyperthermia can be successfully treated, while more severe cases may require intensive care and have a less favorable prognosis.
3. Treatment effectiveness: The effectiveness of the treatment used also plays a decisive role. Successful management of symptoms and complications can significantly improve the prognosis.
4. Complications: Neurogenic hyperthermia can cause serious complications such as organ failure and muscle damage. The prognosis will depend on the presence and severity of these complications.
5. Individual factors: The prognosis may also depend on individual patient factors such as age, overall health, and the presence of other medical problems.

It is important to emphasize that neurogenic hyperthermia is a condition that requires immediate medical attention. The lack of timely and adequate treatment can lead to fatal consequences.