SYNDROME OF INAPPROPRIATE ANTIDURETIC HORMONE SECRETION
SIADH refers to excessive ADH secretion from the pituitary gland even in the face of subnormal serum osmolarity. Patients cannot excrete a dilute urine. They retain fluids and develop a sodium deficiency. It is of nonendocrine origin. That is the syndrome may occur in patients with bronchogenic carcinoma in which malignant lung cells synthesize and release ADH. SIADH has also occurred with severe pneumonia, pneumothorax and other disorders of the lungs in addition to malignant tumors that affect other organs.
Causes
Disorders of CNS head injury, brain surgery or tumor or meningitis produce SIADH by direct stimulation of pituitary gland.
Medical Management
- Vincristine; pheno thiazines, tricyclic antidepressants others either directly stimulate the pituitary gland, or increase the sensitivity of renal tubules to circulating ADH
- It is managed by eliminating the cause and by restricting the patient's fluid intake.
- [Since retained water is slowly excreted through the kidneys the extra cellular fluid volume contracts and the serum Na concentration gradually increases towards normal).
- Diuretics with fluid restriction - if severe hyponatremia is present.
Nursing Management
- Monitor signs of hyponatremia, weight change, fluid imbalance.
- Restrict water intake.
- Observe closely - restlessness, CHF - convulsions.
