Diabetes Insipidus (DI)
Background
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Central DI:
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↓ secretion ADH
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Most often idiopathic or induced by trauma, pituitary surgery, or hypoxic or ischemic encephalopathy
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Nephrogenic DI:
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Normal ADH secretion but kidneys are resistant to its water-retaining effect
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Diagnosis:
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Dilute urine (<150 mOsm/L)
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Hypernatremia (Na>150)
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Hyper-osmolality (>290)
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Considerations
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Hypernatremia:
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Altered level of consciousness, seizures, coma, hyperreflexia
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Risk of intracranial hemorrhage with acute, severe hypernatremia
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↑ MAC requirements
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Volume depletion:
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Resuscitate with normal saline initially
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Associated conditions:
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Neurogenic (pituitary surgery, traumatic brain injury, tumor, idiopathic)
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Nephrogenic (chronic renal failure, lithium toxicity, hypercalcemia, hypokalemia, congenital, fluoride toxicity)
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Treatment
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Consultation with nephrology may be valuable
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Treat hypernatremia by estimating water deficit & replacing with free water:
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Water deficit = total body water x (Serum Na [ ]/140-1)
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Central DI: desmopressin 1-2 mcg IV BID
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Nephrogenic DI: hydrochlorothiazide/amiloride
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Complications of treatment:
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Avoid rapid overcorrection if chronic hypernatremia (goal = <10 mEq/day)
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Cerebral edema, water intoxication, volume overload
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Potential conflicts
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Emergency surgery vs. need for optimization of electrolytes/volume status