Diabetes Insipidus
AVP, Aqueous vasopressin (Pitressin)
1. Route: Parenteral 2. Dose: 5-10 U SC q4h 3. t1/2: 4h 4. Adverse effects: HTN, coronary vasospasm
Nephrogenic diabetes insipidus lab results:
1. Urine osmolality can be <100mmol/L. 2. After water deprivation, urine remains dilute. 3. After exogenous AVP administration, urine osmolality usually does not rise but may rise modestly. 4. Hypercalcemia or hypokalemia may be found to be the cause. 5. In cases of lithium-related diabetes insipidus, lithium levels may well be within therapeutic range, and the effect may persist for weeks after lithium is discontinued.
Central diabetes insipidus lab results:
1. Urine osmolality is typically <200mmol/L 2. Plasma osmolality is >290mOsmol/kg 3. Hypernatremia 4. Random plasma AVP very low or undetectable 5. After water deprivation, urine remains abnormally dilute; urine osmolality does not rise to greater than 6. plasma osmolality. 7. After exogenous AVP administration, urine osmolality increases by >50% in those with 'complete' central diabetes insipidus (unable to concentrate urine at all). 8. In 'partial' cases (can concentrate urine to some degree), increase in urine osmolality is at least 10%.
DI signs
1. dehydration 2. enlarged bladder 3. delirium 4. hypotension 5. tachycardia 6. Dry mucous membranes 7. poor skin turgor 8. sunken eyes or fontanelles (infants)
DI Tx
2. Most patients can drink enough fluid to replace their urine losses. 3. Replace losses with D5W or IV fluid hypo-osmolar to the patient's serum. 4. In case of inadequate thirst, desmopressin is the drug of choice. 5. Avoid hyperglycemia, 6. Avoid volume overload 7. Avoid correction of hypernatremia that is too rapid.
Central diabetes insipidus: Idiopathic (autoimmune process): Malignant or benign tumors of the brain or pituitary; metastases (esp lung and breast): Secondary to head trauma: Iatrogenic:
30-50% 25% 16% following cranial surgery 20%
Frequency DI
is uncommon, 1 case per 25,000 people
Benefit of Antilipemic agents --
may increase the release of ADH in partial DI.
Diabinese (Chlorpropamide) --
not only causes some release of ADH but also potentiates the action of ADH on the kidney.
Atromid-S (Clofibrate) --
recommended for adults only; 500 mg po qidds
ADH's main target is the kidney, where it acts by altering __________
the water permeability of the cortical and medullary collecting tubules
Essentials of Diagnosis DI is a temporary or chronic disorder of the neurohypophyseal system due to deficiency of ___________ and characterized by ___________.
vasopressin (ADH) Lots of clear pee and excessive thirst
Clofibrate (Atromid-S)
1. Antilipemic 2. Adults only 3. 500 mg po qid
Benefits of Hypoglycemics --
1. Help relieve diuresis.
Chlorpropamide (Diabinese)
1. Hypoglycemic 2. Induces ADH release 3. Potentiates kidney's sensitivity to ADH
Antilipemic agents
1. Increase ADH release in partial DI
DI Prevention:
1. Not preventable 2. Good education and regular review prevents recurrence
DI Surgical therapy:
1. Postoperatively: desmopressin 2. Hypotonic IV fluids to match urine output.
DDAVP (Desmopressin)
1. Reduces U/O 2. simplifies fluid therapy 3. Long t½: 12h - be judicious 4. Doses: 1 μg IV/SC x 1 10 μg IN if stable mucosa 100 μg PO
Benefit of Hypoglycemics -
- Help relieve diuresis.
Benefits of Diuretic Tx
- Reduce flow to the ADH-sensitive distal nephron
Benefit of Hormone tx
-- Reduce complications and comorbidity.
Antilipemic agents -
Atromid-S (Clofibrate) --
DI Imaging Studies:
Brain MRI Pituitary MRI: Absence of a posterior pituitary "bright spot" on MRI is suggestive of central DI (primary).
___________ test is the simplest and most reliable method for diagnosing DI but should be performed only while the patient is under constant supervision.
The water deprivation
DI Hormone drugs
Desmopressin (DDVAP) AVP, Arginine vasopressin (Pitressin)
Hypoglycemics drug--
Diabinese (Chlorpropamide) --
DI Diuretics Tx -
HCTZ (Hydrochlorothiazide) Amiloride (Midamor)
DI pharmacology
Hormones -- Prevent complications and reduce morbidity. 1. Hormones 2. Diruetics 3. ADH releasing drugs
Essentials of Diagnosis ___________ occurs if fluid intake is inadequate.
Hypernatremia
DI Tx ADH-releasing drugs
Hypoglycemics - Antilipemic agents
ADH is the primary determinant of __________
free water excretion in the body
A defect in the kidney tubules that interferes with water reabsorption. There is normal secretion of vasopressin. The polyuria is unresponsive to vasopressin.
Nephrogenic DI
DI Sex:
No significant sex differences in central or nephrogenic DI exist - Male = Female Inherited nephrogenic DI is X-linked; only males are clinically affected, whereas females are carriers
Nephrogenic diabetes insipidus:
Nocturia Inherited form presents soon after birth or in early infancy often asymptomatic excessive thirst and polyuria severe dehydration --> Weakness
Central diabetes insipidus symptoms:
Nocturia abrupt onset Preference for cold drinks may be asymptomatic primary lesion tumors may be associated with headaches, visual disturbances, and/or other neurologic manifestations
_______ DI: is due to damage to hypothalamus or pituitary by tumor, anoxia, surgery, trauma, infection. _______ DI: without an identifiable organic lesion noted on MRI of pituitary and hypothalamus. _______ DI is characterized by a decrease in the ability to concentrate urine due to a resistance to ADH action in the kidney:
Secondary central Primary central Nephrogenic
MRI shows a bright mass or thickening in the pituitary stalk.
This is indicative of central secondary DI.
Nephrogenic diabetes insipidus: Inherited: Acquired:
Uncommon Common--commonly Li
Essentials of Diagnosis Antidiuretic hormone (ADH) deficiency causes central _________ with ___________.
diabetes insipidus polyuria and polydipsia
