Endocrine Abstracts

Introduction

Hyponatraemia is the most common electrolyte abnormality encountered within the inpatient setting and is associated with increased morbidity, mortality and length of hospital stay. It compromises a spectrum of symptoms, from being asymptomatic to varying degrees of neurological disturbances including gait abnormalities with increased risk of falls, confusion and rarely seizures. This is of particular relevance in the midst of an aging population worldwide and in the context of the current COVID pandemic, where measures are required to avoid lengthy hospitalisation. Syndrome of inappropriate diuresis (SIAD) remains the most common underlying cause. In addition to treating the aetiology, non-pharmacological treatment of SIAD include fluid restriction which is poorly effective. Medical treatment with demeclocycline and vaptans (vasopressin receptor antagonists) may offer reliable alternatives. However, these agents are not without risk, particularly where significant shifts in sodium levels are observed over a short time period. We propose the temporary use of sodium chloride (NaCl) tablets together with fluid restriction as an effective and safe way to treat refractory SIAD in hospitalised elderly patients, facilitating prompt discharge and reducing further risk of hospital-acquired morbidity.

Illustrative cases

We present two cases: 74-year-old and 82-year-old female patients who were admitted to the Cambridge University Hospitals NHS Foundation Trust between September and December 2020 and were found to be symptomatic with acute on chronic hyponatraemia. Clinical and biochemical assessment was consistent with SIAD, with chest and brain imaging excluding additional pathology. First line management involved commencement of an observed fluid restriction with a slow and limited improvement in the degree of hyponatraemia. Modified release NaCl tablets at a dose of 2.4 g twice daily were subsequently introduced whilst both patients remained on fluid restriction. Within 72 h of commencement of NaCl tablets, both patients improved clinically, with serum sodium correction to a level that was deemed safe for discharge (≥130 mmol/l). Their serum sodium did not increase more than 10 mmol/l in a 24-h period. A short course of oral NaCl tablets was recommended following discharge with follow up in the outpatient Endocrinology clinic.

Conclusion

The temporary use of oral NaCl tablets, in addition to fluid restriction, is a well-tolerated, safe and effective way to treat refractory SIAD in hospitalised elderly patients, thus facilitating early discharge and reducing the morbidity and mortality associated with prolonged hospital admissions.