Best Practice & Research Clinical Endocrinology & Metabolism
1Diagnosis and treatment of hyponatraemia
Section snippets
Epidemiology
Hyponatraemia is a clinical feature in 15–42% of non-selected emergency admissions to secondary care. Importantly, it is associated with increased length of hospital stay and morbidity in patients presenting with a range of conditions [1]. Moreover, it has prognostic significance. Hyponatraemia is a predictive indicator of outcome in malignancy and an independent predictor of all-cause in-patient mortality [2], [3]. However, the relationship between serum sodium concentration and clinical
Presentation of hyponatraemia: the clinical picture
The symptoms and signs of hyponatraemia cover a broad range from coma and seizures, to normal or near-normal function [10] (Table 1). Of course it is common for hyponatraemia to be only one feature of the overall clinical presentation, which is often dominated by the major underlying precipitant (e.g. sepsis, intra-cranial haemorrhage). Given this context, the symptoms and signs attributable to the electrolyte disturbance may be either not apparent, or non-specific. This has practical
The physiology of body water homeostasis
Serum sodium concentration reflects both sodium and water content of the aqueous phase of the circulation. Sodium balance, water balance and circulating volume are regulated in parallel through integrated neurohumoral processes that have key roles in the development and maintenance of hyponatraemia.
Sodium balance is regulated chiefly though the Renin-Angiotensin-Aldosterone system (RAS), natriuretic peptides and sympathetic nervous system working to modify renal sodium loss. Activation of the
Investigation and differential diagnosis of hyponatraemia
Identifying the mechanism(s) underlying presentation with hyponatraemia can be challenging. Several factors contribute to this challenge. Multiple comorbidities are common in patients presenting with hyponatraemia; and concurrent medication is a common confounder. As a consequence, hyponatraemia is often multifactorial. Moreover the clinical situation may be dynamic; and key supportive information may not be available when it's needed most.
As effective circulating volume status is a key driver
Treatment of hyponatraemia
Hyponatraemia can be life threatening. However, because of the capacity of the CNS to adapt to osmolar stress, long standing hyponatraemia can be tolerated very well, even when it is profound. Indeed correction of hyponatraemia to which the brain has adapted can produce significant changes in volume of neurones and supporting cells, triggering osmotic demyelination syndrome (ODS). This is a rare but life-threatening complication of over-rapid correction of hyponatraemia. The treatment of
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