A disorder of the posterior pituitary gland resulting in deficient antidiuretic hormone (ADH, vasopressin) production. This results in large volumes of dilute urine to be excreted, even when dehydrated. Polydipsia follows.
- May occur secondary to head trauma, brain tumors, and surgical ablation or irradiation of the pituitary gland.
- May also follow infection of the central nervous system (meningitis, encephalitis, tuberculosis), or with other tumors (metastatic disease, lymphoma of the breast or lung).
- Failure of the renal tubules to respond to ADH (nephrogenic form of DI) may also cause DI, resulting from hypokalemia, hypercalcemia, and a variety of medications eg. lithium, demeclocycline (Declomycin)
Clinical Manifestations
- Polyuria: excessively dilute urine, reaching a specific gravity of 1.001 to 1.005. Even when dehydrated, the patient will continue to produce excessive urine. This may lead to dehydration and hypernatremia without adequate .
- Polydipsia: intense thirst, especially for cold water, which may reach up to 20 liters of consumption in a single day.
- Onset: may begin at birth if inherited, while onset may either be insidious or abrupt in adults.
Assessment Findings
- Fluid Deprivation Test: fluids are withheld for 8 to 12 hours until 3% to 5% of body weight is lost. Urine specific gravity and osmolality is measured during the duration. In DI, urine concentration does not increase with increasing dehydration.
- Plasma ADH and plasma/urine osmolality
- A trial of desmopressin (synthetic vasopressin) therapy and an intravenous infusion of a hypertonic saline solution may also be performed.
Nursing Management
- Client and family education on follow-up care and emergency measures:
- Provide verbal and written instructions, including the actions and adverse effects of all medications being used.
- Demonstrate correct medication administration and observe return demonstrations.
- Advise the patient to wear a medical identification bracelet and a disorder information card at all times.
Medical Management
- Replace ADH
- Replace fluids
- Correct underlying intracranial pathology (if applicable/possible). Nephrogenic causes require different management approaches.
Pharmacologic Treatment
- Desmopressin (DDAVP) Intranasal od or bid to control symptoms.
- ADH (vasopressin tannate in oil) IM q24hr to q96hr reduces urinary volume
- Should be shook vigorously or warmed, administered in the evening, and rotated between sites to prevent lipodystrophy.
- Clofibrate (Atromid-S): a hypolipidemic agent, but has been found to produce an antidiuretic effect when patients have residual hypothalamic vasopressin.
- Chlorpropamide (Diabinese) and Thiazide Diuretics potentiate the action of vasopressin, and as such is used for milder forms of DI.
- Thiazide Diuretics, Mild Salt Depletion, Prostaglandin Inhibitors (Ibuprofen, Indomethacin, Aspirin) are used for the nephrogenic form of DI.