Hyponatraemia: new associations and new treatments

Abstract

Hyponatraemia is the commonest electrolyte abnormality in clinical practice, and is the biochemical manifestation of a huge variety of illnesses. It is a common complication of malignancy, neurosurgical conditions, cardiac, liver and renal failure and pulmonary disorders. It is a side effect of many drugs and a frequent finding in the elderly, particularly those in long-stay institutions. Perhaps, because of the fact that hyponatraemia is a complication of so many disparate disorders, it has not traditionally fitted easily into the aegis of a single ‘ology’; endocrinologists, renal physicians, geriatricians and internists may all assume responsibility for the diagnosis and treatment of hyponatraemia, according to the profile of the hospital and the clinical interests of the specialists which they employ. In some hospitals, there is no designated specialist who takes an interest in hyponatraemia. The evidence in the literature suggests that hyponatraemia is not only suboptimally investigated, but also poorly managed. The explanation is probably multifactorial – lack of dedicated specialists with an interest in hyponatraemia, poor awareness of investigative protocols and failure to recognise that hyponatraemia contributes to morbidity and mortality – but also that it is perceived that effective treatment is not available. In this supplement, we have reviewed the evidence which suggests that hyponatraemia is associated with significant morbidity. In addition, new complications of mild hyponatraemia are being recognised which challenge the prevalent opinion that mild to moderate hyponatraemia does not require treatment, other than that directed to the underlying causative illness. We further discuss the potential role for the vaptans, the new aquaretic vasopressin antagonists, in the management of euvolaemic hyponatraemia.