Endocrine Abstracts

An 82-year-old lady, who was fit and well, presented with 4 days history of confusion, vomiting and slurred speech.

She had recurrent cystitis, hypertension and nocturnal enuresis. She was on Adalat LA 20 mg, dosulepin 50 mg, co-amilozide 5/50 mg alternate mornings. She was started on desmopressin 0.2 mg nocte, for nocturia ten days prior to her admission.

Examination showed AMTS 4/10, pulse 65/ min, blood pressure 136/66 mmHg, with no postural drop. Examination did not suggest an infective process. Neurological examination was normal except for extensor plantars. Bloods showed severe hyponatraemia with a Na⁺102 mmol/l, K⁺3.7 mmol/l, urea 5.3 mmol/l, creatinine 80 umol/l, WCC 9.7×10⁹, CRP77 mg/l, urine osmolality 479 mosml/kg, serum osmolality 225 mosmol/kg and urinary sodium <10 mmol/l. Short synacthen test showed good cortisol levels, at baseline 923 nmol/l, 30 min 1547 nmol/l and 60 min 1771 nmol/l. Thyroid function tests showed TSH 0.59 m/l and freeT₄ 21.9 pmol/l. Chest X-ray and urine culture were unremarkable. CT scan brain showed age related changes. CT scan chest, abdomen and pelvis, showed a minimal right pleural effusion, which on aspiration was a transudate.

Her diuretics and desmopressin were stopped and was treated with fluid restriction. Her serum sodium increased to 130 mmol/l on discharge. Her serum sodium ten months prior to admission was 134 mmol/l while on diuretic and antidepressant. The diagnosis of severe hyponatraemia secondary to desmopressin was made.

This case highlights the significant risk of hyponatraemia with the use of desmopressin. Desmopressin is commonly used in the treatment of nocturnal enuresis in children and adults, however it is contra-indicated for treatment of nocturnal enuresis and nocturia in patients more than 65-years-old.

This patient was on a tricyclic antidepressant dosulepin and diuretic co-amilozide. The risk of hyponatraemia could be minimised by avoiding the concomitant use of drugs like tricyclic antidepressants, which increase vasopressin level, and diuretics which produce renal sodium loss.