Schwartz-Bartter Syndrome

Synonyms

Syndrome of inadequate ADH secretion (SIADH), ADH excess, ADH overproduction

English: Bartter-Schwarz syndrome

definition

The Schwartz-Bartter Syndrome is a disorder of the regulation of the water and electrolyte balance, in which an inappropriately (inadequate) high secretion of the Antidiuretic hormone (ADH - hormone, also: Vasopressin) leads to a decreased excretion of water (water retention) and a loss of sodium (hyponatremia).

frequency

It is believed that transient inadequate secretion of ADH can occur in almost all patients after surgery.

history

The Schwartz-Bartter Syndrome is named after the American internist William Benjamin Schwartz (* 1922) and Frederic Crosby Bartter (1914-1983).

causes

There are several causes of Schwartz-Bartter syndrome. In 80% of the cases it occurs as paraneoplastic syndrome in small cell lung cancer. A paraneoplastic syndrome describes symptoms accompanying cancer that are not triggered either directly by the tumor or by metastases, but rather through the body's defense reactions against the tumor or through the release of messenger substances such as hormones by the tumor.

Other less common causes can be disorders of the Central nervous system (CNS), such as meningitis (meningitis), Inflammation of the brain (Encephalitis), Tumors, or one traumatic brain injury. Also one lung infection (Pneumonia), tuberculosis and certain drugs (e.g. cytostatics such as vincristine, cyclophosphamide; Indomethacin, Carbamazepine, tricyclic Antidepressants, Morphine, nicotine, barbiturates) can lead to this clinical picture. In addition, it is assumed that almost all patients after surgery can experience a temporary inadequate secretion of ADH.

These processes or substances lead to a decoupling of the control loop and thus to a disinhibition of the ADH secretion from its place of formation, the posterior lobe of the pituitary gland (neurohypophysis). The resulting excess of ADH causes in the kidney the retention (retention) of free water and thus a decrease in urine volume and an increase in body weight. This is often accompanied by an increased feeling of thirst. After distribution in the body, the excess free water first leads to an expansion of the fluid space outside the cells (extracellular), then, as a result of the concentration gradient of the fluids in the body, to an increase in the fluid in the intracellular space. However, this happens without water retention in the tissue (edema). As a counter-regulation to this volume expansion, there is an increase in the excretion of sodium in the urine, which is supposed to pull the excess water with it into the urine. The excretion of sodium (natriuresis) continues until a new equilibrium is reached, the sodium excretion then corresponds to the sodium intake. In the absence of sodium intake, sodium excretion also decreases, which increases water retention and decreases the amount of urine excreted. The regulation of sodium excretion by the kidneys is maintained when the sodium level in the blood serum is low. Although the concentration of ADH in the blood is within its normal range at this point in time, it is increased in relation to the low concentrations of other substances in the blood due to the thinning of the blood (low plasma osmolarity).

The inadequate ADH secretion is biochemically thus i.a. characterized by a thinning of the blood (low plasma osmolarity), a lack of fluid in the urine (high urine molarity) (urine to plasma ratio> 1) and by the low sodium level in the blood (hyponatremia).

Read more about the topic here Hypernatremia

Symptoms

Clinical symptoms of Schwartz-Barrter syndrome may initially include confusion, a headache, Weakness and muscle cramps followed by dizziness, Loss of appetite, nausea, Vomit, Seizures and disorders of consciousness up to coma. These symptoms are caused by excessive water retention (water intoxication) and the resulting hyponatremia. There is also one Weight gain and reduced urine output with highly concentrated urine. The increase in extracellular and intracellular volume increases the risk of fluid accumulation in the brain (Brain edema) which can be fatal without treatment. Other edema on the body is not observed, blood pressure and heart rate are normal.

In general, however, there are no symptoms, i.e. the Schwartz-Bartter syndrome can also be asymptomatic.

diagnosis

The diagnosis of Schwartz-Barrter syndrome is based on detailed questioning of the patient (anamnesis), the symptoms and the results of laboratory tests of the blood and urine. During the survey, it is important to ask about the amount of fluids and urine consumed, and about changes in body weight. A five to ten percent gain in body weight in a very short amount of time for some inexplicable reason without the occurrence of edema is an important indication of that Schwartz-Bartter Syndrome.

Laboratory diagnostics show a low urine volume per unit of time, with the urine being highly concentrated (urine molality:> 300 mosmol / kg, specific gravity increased) and an inappropriately high sodium concentration in the urine (> 20 mmol / liter). The blood shows hyponatremia (serum Na + <135 mmol / l), which is caused by the thinning of the blood (serum osmolality: <300 mosmol / kg).

Determining the ADH concentration in the blood makes little sense because the values ​​can be normal or elevated, but do not have to be elevated. However, the levels are never lowered, as is the case with other forms of hyponatremia.

Differential diagnosis

The hyponatremia of Schwartz-Bartter syndrome must be distinguished from hyponatremia in the case of heart failure, nephrotic syndrome and liver cirrhosis, and hyponatremia in the case of a lack of blood plasma volume, e.g. B. after diarrhea, sweating or taking diuretics, a drug used to flush water out of the body.

You might also be interested in this topic: Conn syndrome

therapy

The focus is on therapy for the underlying disease that triggers it. After successful therapy, the Schwartz-Bartter syndrome usually heals spontaneously (spontaneous remission).

The symptomatic therapy of the Schwartz-Bartter syndrome consists of a restriction on the amount of drinking (water restriction), which alone usually leads to an improvement in the symptoms. In addition, a slow infusion of isotonic (0.9%) or hypertonic (10%) saline (sodium chloride solution) can be given to compensate for the hyponatremia. If the saline solution is infused too quickly, it may lead to impaired consciousness, Seizures or to one central pontine myelinolysis can cause damage to the sheath (myelin sheath) of nerve fibers, especially in the brain stem (Pons) is coming. It should also be noted that hyponatremia is usually accompanied by a Hypokalemia, i.e. a lack of potassium in the blood. For this reason, potassium should also be given, which releases sodium from the cells and thus helps to balance out the hyponatremia in the extracellular space.

In the case of water intoxication, in addition to hypertonic saline solution, furosemide (Lasix®), a loop diuretic, used to flush water out of the body.

The Schwartz-Bartter syndrome can be treated with direct ADH antagonists, so-called vaptans. Vaptans work on the ADH receptors in the kidney, blocking the effects of ADH and thus promote the excretion of electrolyte-free water. Tolvaptan has been available in Germany as the first and so far only oral ADH antagonist since August 2009.

forecast

With successful therapy of the underlying disease, the Schwartz-Bartter syndrome usually heals spontaneously. Thus, the prognosis depends heavily on the cause of the syndrome.

Summary

The Schwartz-Bartter Syndrome is caused by an inappropriately increased ADH secretion with water retention and Hyponatremia. Most often it occurs as paraneoplastic syndrome in small cell Bronchial carcinoma but can also occur with central nervous disorders, infections or as a side effect of certain drugs. Symptoms include reduced urine output, Weight gain, dizziness, Nausea, impaired consciousness and seizures. Laboratory diagnostics show a highly concentrated urine (high urine molality) and an inappropriately high sodium concentration in the urine. In contrast, the blood is diluted (low plasma osmolarity) with hyponatremia. The focus is on the therapy of the underlying disease. Symptomatically, Schwartz-Bartter syndrome is treated with fluid restriction and compensation of hyponatremia with saline solution.