Hyponatremia Diagnosis and Management

Hyponatraemia, defined by a serum sodium concentration below 135 mmol/L, is the most common electrolyte disturbance in clinical practice. It arises when water intake or retention exceeds sodium handling, presenting in hypovolaemic, euvolaemic or hypervolaemic states. Clinical features vary from subtle cognitive impairment, gait instability and falls in chronic cases to headache, seizures, coma and risk of cerebral herniation in acute or severe presentations. Diagnosis entails confirmation of hypotonic hyponatraemia through plasma osmolality measurement, followed by assessment of volume status, urinary sodium and urine osmolality to classify the underlying aetiology. Management is guided by acuity and symptom severity. Acute symptomatic cases demand cautious administration of hypertonic saline to alleviate cerebral oedema, whereas chronic or mild cases often respond to fluid restriction, loop diuretics or vasopressin receptor antagonists. Strict monitoring of serum sodium correction—typically limiting increases to 8–10 mmol/L per 24 hours—is essential to prevent osmotic demyelination syndrome. Emerging strategies focus on personalised monitoring protocols, biomarker-guided therapy and integration of point-of-care testing to optimise safety and outcomes on a global scale.

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Hyponatremia Diagnosis and Management publication trend

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Technical terms

Hyponatraemia: A condition in which serum sodium concentration falls below the normal lower limit, indicating excess body water relative to sodium.

Plasma osmolality: A measure of the concentration of solutes in the blood, used to distinguish true hyponatraemia from pseudohyponatraemia.

Euvolaemia: A state of normal body fluid volume, often seen in the syndrome of inappropriate antidiuretic hormone secretion.

Hypertonic saline: A solution containing higher concentrations of sodium than plasma, employed to raise serum sodium rapidly in acute symptomatic cases.

Osmotic demyelination syndrome: A serious neurological complication resulting from overly rapid correction of hyponatraemia, characterised by loss of myelin in brain regions.

References

1. Moderate Hyponatremia Is Associated with Increased Risk of Mortality: Evidence from a Meta-Analysis. PLOS ONE (2013).
2. Current treatment practice and outcomes. Report of the hyponatremia registry. Kidney International (2015).
3. Diagnosis and treatment of hyponatremia: a systematic review of clinical practice guidelines and consensus statements. BMC Medicine (2014).