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At a glance

SIADH is an acronym that stands for Syndrome of Inappropriate AntiDiuretic Hormone secretion. It is a disorder of impaired water excretion caused by the inability to suppress the secretion of antidiuretic hormone. Water retention leads to the development of hyponatremia if water intake exceeds the reduced urine output.

Synonyms

Schwartz-Bartter Syndrome; Aldosteronism-Normal Blood Pressure Syndrome; Juxtaglomerular Hyperplasia Syndrome.

History

First reported in 1957 by William Benjamin Schwartz, American cardiologist, and Frederic Crosby Bartter, American physician. They described two adult patients with bronchial carcinoma who developed persistent hyponatremia, hypoosmolality, and urinary loss of sodium and chloride.

Pathophysiology

Overproduction of vasopressin from the hypothalamus leads to water retention, urinary sodium loss, and hyponatremia.

Diagnosis

Clinical features and biochemical (low serum sodium levels and low serum osmolality, increased urine sodium content and osmolality, suppression of plasma renin activity, normal/high serum aldosterone level, high plasma antidiuretic hormone and atrial natriuretic hormone levels). Conditions known to be associated with antidiuretic hormone secretion (normal renal, liver, adrenal, thyroid, and cardiac functions) must be excluded. Causes of Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) consist of a long list of medical conditions. (See Table S-1.)

Table S-1Causes of Syndrome of Inappropriate Antiduretic Hormone Secretion (SIADH)

Clinical aspects

Symptoms, when present, are caused by acute loss of sodium and are often masked by or mistaken as manifestations of the primary problem (anorexia, confusion, headache, muscle weakness, vomiting, convulsions, and coma). Chronic hyponatremia, lasting longer than 2 to 5 days, usually has minimal or no symptoms. Vascular volume is normal or mildly increased, and peripheral edema is very rare. Blood pressure is normal, even with postural changes; urine output is usually low.

Anesthetic considerations

Hyponatremia may contribute to delayed awakening ...

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