The syndrome of inappropriate antidiuretic hormone (SIADH) refers to an excessive production of the antidiuretic hormone (ADH) from the pituitary gland even during periods of subnormal serum osmolality. Clients will be unable to excrete dilute urine, fluid is retained, and hyponatremia occurs secondary to dilution (dilutional hyponatremia).
- Often of non-endocrinal origins; may occur in patients with bronchogenic carcinoma, where malignant lung cells are able to synthesize and release ADH.
- Other causes include severe pneumonia, pneumothorax, other disorders of the lungs, and malignant tumors of other organs.
- Disorders of the central nervous system (head injury, brain surgery, tumors, or infection) directly stimulate the pituitary gland, causing SIADH.
- Some medications (vincristine, diuretics, phenothiazines, tricyclic antidepressants) and nicotine may also be implicated in SIADH.
Medical Management
- Resolution of the underlying cause if possible.
- Restriction of fluids and administration of diuretics for resolution of dilutional hyponatremia.
Nursing Management
- Monitor fluid intake and output, daily weight, urine and blood chemistry, and neurologic status.
- Supportive measures with client education regarding procedures and treatment.