Diabetes Insipidus

 

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Diabetes insipidus is a disorder of the posterior lobe of the pituitary gland due to a deficiency of vasopressin, the antidiuretic hormone (ADH). it is characterized by polydipsia and polyuria. Diabetes insipidus may be (1) secondary, related to head trauma, brain tumor, or surgical ablation or irradiation of the pituitary gland or infection of the central nervous system or metastatic tumors (lung or breast); (2) nephrogenic (faliure of the renal tubules to respond to ADH), possibly related to hypokalemia, hypercalcemia, and a variety of medications (eg, lithium, demeclocycline); (3) primary (hereditary), with symptoms possibly beginning t birth (defect in pituitary gland).

The disease cannot be controlled by limiting the intake of fluids because loss of high volumes of urine continues even without fluid replacement. Attempts to restrict fluids cause the patient to experience an insatiable carving for fluid and to develop hypernatremia and severe dehydration.

Clinical Manifestations

  • Polyuria: enormous daily output of very dilute urine (specific gravity 1.001 to 1.005). Primary diabetes insipidus may have ab abrupt onset or an insidious onset in adults.
  • Polydipsia: patient experiences intense thirst, drinking 2 to 20 liters of fluid daily, with a special craving for cold water.
  • Polyuria continues even without fluid replacement.

Assessment and Diagnostic Findings

  • Fluid deprivation test: fluids are withheld for 8 to 12 hours until 3% to 5% of the body weight is lost. Inability to increase specific gravity and osmolality of the urine during test is characteristic of diabetes insipidus.
  • Urine specific gravity, serum osmolality, and serum sodium levels may be obtained.

Medical Management

Objectives of the therapy are to ensure adequate fluid replacement, to replace vasopressin, and to search for and correct the underlying intracranial pathology. Treatment for diabetes insipidus of nephrogenic origin involves using thiazide diuretics, mild salt depletion, and prostaglandin inhibitors (eg. ibuprofen, indomethacin, and aspirin).

Vasopressin Replacement

  • Desmopressin (DDAVP), administered intranasally, 1 or 2 administrations daily to control symptoms.
  • Lypressin (Diapid), absorbed through nasal mucosa into blood; duration may be short for patients with severe disease.
  • Intramuscular administration of ADH (vasopressin tannate in oil) every 24 to 96 hours to reduce urinary volume (shake vigorously or warm; administer in the evening, rotate injection sites to prevent lipodystrophy)

Fluid Conservation

  • Clofibrate, a hypolipidemic agent, has an antidiuretic effect on patients who have some residual hypothalamic vasopressin.
  • Chlorpropramide (Diabinese) and thiazide diuretics are used in mild forms to potentiate the aciton of vasopressin; may cause hypoglycemic reactions.

Nursing Management

  • Encourage and support patient undergoing studies for possible cranial lesion.
  • Instruct patient and family members about follow-up care and emergency measures.
  • Advise patient to wear a medical identification bracelet and to carry medication information about the disorder at all times.
  • Use caution with administration of vasopressin if coronary artery disease is present because of vasoconstrictive action of this drug.

 

Reference:

Joyce Young Johnson et. al Handbook for Brunner & Suddarth’s Textbook of Medical-Surgical Nursing 11th edition

Lippincott Williams & Wilkins pp.297-299

 

 

 

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