Endocrine Abstracts

Background: Hyponatraemia is the most common electrolyte disorder seen in clinical practice. Even mild hyponatraemia can lead to gait disturbances and cognitive dysfunction in the elderly.

Case history: A 83-year-old lady presented to acute admission unit with worsening of confusion. Her background medical history includes chronic obstructive pulmonary disease for which she is on inhalers. She was also having hyponatraemia for the last 3 years manifesting with recurrent falls and confusion resulting in recurrent prolonged hospital admissions.

Her blood and urine investigations were consistent with syndrome of inappropriate ADH secretion (SIADH). She was thoroughly investigated for any underlying cause for her SIADH and was negative. During her previous admissions she was tried on fluid restriction, demeclocycline, hypertonic saline, and diuretics resulting in variable temporary response. She was also tried on short term tolvaptan on two previous occasions resulting in temporary improvement of her serum sodium and symptoms but relapsed.

During her current hospital admission she was confused with mini mental state examination (MMSE) of 16/30. She was commenced on tolvaptan (vasopressin receptor antagonist) and her sodium normalised. Her confusion improved with MMSE of 26/30 at discharge. Her serum sodium levels remained in normal range 12 months after discharge on tolvaptan. She has not had any further falls and her cognitive function remains good including her quality of life.

Conclusion: Hyponatraemia due to SIADH is common in elderly patients. The most effective treatment for chronic hyponatraemia due to SIADH is the use of vasopressin receptor antagonists which selectively increase solute free water excretion by kidneys. This case highlights that careful selection of patient for treating with tolvaptan will be cost effective in treating SIADH on long-term basis preventing prolonged hospital stays and regaining their independence.