In the ICU, diabetes insipidus (DI) develops in patients with pituitary surgery, brain trauma, intracranial hypertension and brain death. Criteria include the following:
urine output >200 ml/hr or 3 ml/kg/hr
urine osmolality <150 mOsm/kg
serum sodium>145 mEq/L
urine specific gravity<1.005
In the ICU, patients are typically unable to consume free water to compensate for urinary losses, and dehydration, hypotension and hypernatremia occur. Clinical signs may not appear until sodium levels surpass 155-160 mEq/L or serum osmolality surpsses 330 mOsm/kg.
Symptoms include confusion, lethargy, coma, seizures and cerebral shrinkage associated with subdural or intraparenchymal hemorrhage.
Treatment includes
controlling polyuria with vasopressin (antidiuretic, vasoconstrictive effects) and desmopressin (DDAVP - antidiuretic effect)
calculate and replace free water loss
TBW deficit (L) = body weight (kg) x 0.6 x (Na-140)/Na
monitor and replace urine losses hourly (using gastric access if possible)
monitor serum sodium and adjust therapy every 4 hours closely monitor for hyperglycemia and treat to prevent osmotic diuresis due to glucosuria
References
Fink MP, Abraham E, Vincent JL, Kochanek PM, eds. Textbook of Critical Care. 5th ed. Philadelphia, PA: Elsevier/Saunders; 2005.
