Primary prevention
Hyponatraemia is associated with multiple disorders; primary prevention is limited to management of associated illness and avoidance of excessive fluid intake. Patients with congestive heart failure, chronic kidney disease, malignancy (especially of pulmonary origin), cirrhosis, and nephrotic syndrome should have their serum sodium concentration tested regularly. In addition, serum sodium concentration should be tested regularly in patients with balance abnormalities (mild hyponatraemia has been shown to have effects on gait stability and cognitive function, which could result in falls) and those with osteoporosis (which may be associated with long-term, chronic hyponatraemia).[3][23][35][36]
Hospital-acquired hyponatraemia is largely preventable with careful monitoring of serum sodium levels.[24] Levels should be assessed on hospital admission.
Mild hyponatraemia is a physiological finding in pregnancy, but hyponatraemia may complicate pre-eclampsia and worsening hyponatraemia in pregnancy may indicate other conditions. Maternal dilutional hyponatraemia can be prevented by maintaining a neutral fluid balance; there is a 1% incidence of hyponatraemia at delivery with fluid intake of up to 1 L during labour, increasing to 26% at >2.5 L fluid intake.[13] Therefore, fluid balance charts have a key role in any labour management strategy (low or high risk) to help prevent hyponatraemia and any associated adverse effects on maternal or fetal outcomes.[37]
Patients receiving intravenous fluids, particularly fluids that are hypotonic to plasma, should have their serum electrolytes checked on a daily basis, and urgently if signs of cerebral oedema occur. This applies particularly to the administration of hypotonic intravenous fluids in the setting of pain and opioid analgesic use, or the post-operative state. There is evidence to suggest that in hospitalised children (surgical and medical), isotonic saline reduces the risk of hyponatraemia compared with hypotonic saline, without a concomitant increase in the risk of hypernatraemia.[38][39]
Serum sodium levels should be assessed regularly in patients that are taking medications known to cause hyponatraemia (e.g., selective serotonin-reuptake inhibitors, thiazide diuretics).
Avoiding large amounts of fluid intake during physical exercise may prevent exercise-induced hyponatraemia.[40]
Secondary prevention
Once hyponatraemia has been diagnosed, avoiding excessive water intake may prevent further episodes. Medications that are known to cause hyponatraemia should also be avoided.
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