A patient following head injury was admitted in intensive care ward with signs of raised intracranial pressure. He was put on ventilator and ataed on intravenous fluids and diuretics. Twenty four hours later his urine output was 3.5 litres, serum sodium 156 mEq/l and urine osmolality of 316 mOsm/kg. The most likely diagnosis based on these parameters is
Answer is A (High output due to diuretics): Presence of high urine osmolality >300 (316 mosmol/Kg) along with increased serum Na suggest a diagnosis of solute diuresis. The patient inquestion has sustained head injury and mannitol is often used insuch cases to reduce the intracranial pressure. Solute diuresis secondary to use of mannitol (diuretic) explains the parameters of the patient in question.
High output due to diuretics
Diabetes insipidus
Too much infusion of normal saline
Cerebral salt retaining syndrome