DIABETES INSIPIDUS
Definition is a disorder of the posterior lobe of the pituitary gland due to a deficiency of vasopressin, the anti-diuretic hormone (ADH).
Causes
Cause is unknown It may be secondary to head trauma, brain tumor or surgical ablation or irradiation of the pituitary gland
Pathophysiology
Without the action of vasopressin on the distal nephron of the kidney, Ban enormous daily output of very dilute, water-like urine with a specific gravity of 1001-occurs. The urine contains no abnormal substances, such as sugar and albumin Because of the intense thirst, the patient tends to drink 4-40 of fluid daily, with a special gravity for cold water.
The disease cannot be controlled by limiting the intake of fluids since urine loss of high volumes of urine continues even without fluid replacement. Attempts to do this cause the patient to suffer extremely from an insatiable craving for fluid and to develop severe dehydration and hypernatremia]
Clinical Manifestations
1. Marked polyuria-daily output 20 litre of dilute urine
Appearance of Urine - Water. Specific gravity-1.000-1.005
Urine osmolality 50-200 m Osm/kp
2. Polydipsia (intense thirst) drinks 40 litre of fluid/day has craving for cold water.
3. High serum osmolality (above 295m Osm) and high serum sodium level (>145 mEq/L)
Diagnostic Evaluation
The fluid deprivation test)- fluids are withheld for 8-12 hrs. or until 3% of body weight is lost. The patient is weighed frequently during the time fluid is withheld urine osmolality studies are done at the beginning and end of the test. increase specific gravity and osmolality of the urine are characteristic of DI Plasma and Inability to
Serum osmolality-high; urine osmolality - low. Measurements of serum and urine ADH - decreased to absent.
Management
1. Administration of ADH or its derivative.
a. Desmopressin (DDAVP), synthetic vasopressin. It is administered intranasally, with the patient sniffing the solution into his nose through a flexible plastic tube. (Duration of action 12-24 hrs.)
b. Vasopressin (Pitressin) - administered IM
(Vasopressin tannate in oil, which is given at intervals of 36-48 hrs or longer.
The vial should be warmed or shaken vigorously prior to administration [to ensure uniform dispersion, because active component settles at bottom of vial). The injection is given in the evening so flat maximum results are obtained during sleep. [S/E-Abdominal cramps].
c. Lypressin (Diapid nasal spray) absorbed through nasal mucosa Duration of action 4-6 hrs.]. May cause chronic nasal irritation. It is absorbed through the nasal mucosa into the blood.]
d. Clofibrate, a hypolipidemic agent probably acts by augmenting ADH secretion from posterior pituitary
e. Chlorpropamide (Diabinese) and thiazide diuretics potentiate the action of vasopressin.
[The patient receiving chlorpropamide should be warmed of the possibility of hypoglycaemic reactions]
f. Carbamazepine (Tegretol) vasopressin potentiates action of endogenous
Complications
1. If untreated, may result in death,
2. Over treatment of desmopressin (DDAVP) may cause hyponatremia and water intoxication
Nursing Management
1. Measure fluid 1 & O accurately.
2. Monitor daily weights.
3. Monitor hemodynamic status as indicated, via frequent BP, heart rate, CVP and other measurements.
4. Provide patient with ample water to drink and administer IV fluids as indicated.
5. Monitor results of serum and urine osmolality and serum sodium tests.
6. Administer or teach self-administration of medication as prescribed.
7. Advise patient to avoid limiting fluids to decrease urinary output, thirst is a protective function.
8. Teach patient to be alert for signs of dehydration increased thirst, dry skin anti mucous membranes and decreased weight, decreased urine output and over hydration, increased weight and edema and report these to the physician.
9. Tell patient to consider eliminating coffee and tea for diet may have an exaggerated diuretic effect.
10. Give written instruction on vasopressin administration. Have the patient demonstrate intranasal and infection technique.
