Resident medical Officer at the Cairns Base Hospital
A Novel Therapy For Hyponatremia: Urea
Case 1: An 88 year old female with moderate euvolemic hyponatremia in the setting of a neck of femur fracture. Her biochemistry was consistent with SIADH with serum sodium was 125 mmol/L, serum osmolality 262 mmol/L; her paired urine sodium was 156 mmol/L and osmolality was 653 mmol/L. Despite a fluid restriction and her regular angiotensin receptor antagonist been withheld, her hyponatremia persisted. Her sodium decreased to 117 mmol/L; subsequently 15 to 30g of oral urea was prescribed and it increased her sodium to 130 mmol/L
Case 2: A 65 year old euvolemic female whom was an inpatient under the care of the psychiatrist for management of bipolar affective disorder. A diagnosis of carbamazepine induced SIADH was confirmed on biochemical analysis with serum sodium was 123 mmol/L and osmolality was 256 mmol/L, and her paired urine osmolality was 530 mmol/L and sodium was 74 mmol/L. Given that there were difficulties with the adherence of a fluid restriction, 30 grams of oral urea was prescribed. This increased her serum sodium from 124 mmol/L to 132 mmol/L, however given the adverse taste that was associated with the use of urea it was discontinued.
Case 3 : A 90 year old male with acute on chronic severe euvolemic hyponatremia, secondary to hospital acquired pneumonia, associated with significant delirium. His bloods were consistent with SIADH with sodium of 113 mmol/L, osmolality of 248mmol/L, and a paired urine osmolality of 248mmol/L and sodium 24mmol/L. A dose of 30g twice daily was commenced. On day 5 of therapy the sodium level was 138mmol/L and urea was discontinued.
Evaluation/Implication for Practice:
Urea was shown in this case series to be effective in the management of hyponatremia by inducing osmostic diuresis. Urea is recommended for treatment of SIADH in patients where fluid restriction is unsuccessful. Therapy with oral urea is advantageous as it safe and an inexpensive