Correspondence |
Management of hyponatraemia: are we doing enough?
Sir,Hyponatraemia is the commonest biochemical abnormality in hospital patients,1,2 and is often associated with severe illness and poor outcome. We audited the management and outcomes of hyponatraemia in a large district general hospital. For a period of 3 months starting from January 2004, in-patients with hyponatraemia of <126 mmol/l (sodium reference range 132–146) at any time of their hospital stay were identified retrospectively from the laboratory database. A team, including an endocrinologist, a chemical pathologist and a clinical epidemiologist, reviewed the notes and data. All cases were discussed to reach a consensus on the diagnosis. We also looked at mortality rate over the following 6 months.
We identified 91 cases, and reviewed the medical records of 70. Mean age was 74.3 ± 13.4 years; 15 (21%) were aged <65 years and 55 (79%) 
65 years. Twenty-five (35.7%) were male and 45 (64.3%) female. All patients had glucose, creatinine, urea and electrolytes measured. Other investigations included fT4 and TSH (44.3%), urine osmolality (22.8%), plasma osmolality (22.8%), urine sodium (18.6%) and short synacthen test (11.4%). In 46 patients (65.7%), there was no clear diagnosis made on the ward. Twenty-one (30%) died in hospital, and another 11 (16%) died within 6 months of discharge. Only 38 (54%) were still alive 6 months after discharge. Six-month mortality was higher in patients aged 75 years (55%) and in patients with initial sodium level <115 mmol/l (53.8%). Hepatic disease (53%) was the commonest cause in patients aged <65 years; iatrogenic causes (33%) were most commonly seen in patients aged 65 years, with thiazide diuretics the most frequently implicated drugs.
Hyponatraemia is a serious biochemical abnormality associated with high morbidity and mortality (Figure 1), especially in older people and in patients with very low initial sodium level. In keeping with previous reports,1–3 hyponatraemia was more common in the elderly, under-investigated and arbitrarily managed. A correct diagnosis was often not made. A robust management plan and correct diagnosis is important in the medical care of these patients, and expert advice should be obtained if necessary. Therapy should always be targeted at the underlying disease process.
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Stockport NHS Foundation Trust Stockport email: hsoran{at}hotmail.com
References
1. Baron D, Hutchinson TA. The outcome of hyponatraemia in a general hospital population. Clin Nephrol 1984; 22:72–6.[Web of Science][Medline]
2. Gill G, Leese G. Hyponatraemia: biochemical and clinical perspectives. Postgrad Med J 1998; 74:516–23.
3. Crook MA, Velauthar U, Moran L, et al. Review of investigation and management of severe hyponatraemia in a hospital population. Ann Clin Biochem 1999; 36:158–62.
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