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Hyponatraemia: Difference between revisions
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Hyponatraemia is most commonly hypotonic. The most common causes overall are heart failure, liver failure, dehydration, and SIADH. | Hyponatraemia is most commonly hypotonic. The most common causes overall are heart failure, liver failure, dehydration, and SIADH. | ||
Depending on whether the cause is acute or chronic, hyponatraemia can be acute or chronic as well. | Depending on whether the cause is acute or chronic, hyponatraemia can be acute or chronic as well. Hyponatraemia is acute if it has developed over 48 hours or less. | ||
== Pathophysiology == | == Pathophysiology == | ||
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=== Determining renal sodium loss === | === Determining renal sodium loss === | ||
Measuring | Measuring the level of sodium in the urine is important in the evaluation of hypovolaemic hypotonic hyponatraemia. High urine sodium (>25-40 mmol/L) points to renal disease, causing the kidney to excrete more sodium than necessary. Other possible causes include glucocorticoid and mineralocorticoid deficiency, diuretics, and cerebra salt wasting syndrome. | ||
Low urine sodium (< 25 mmol/L) points to loss of sodium from places other than the kidney (extrarenal sodium loss), for example diarrhoea, vomiting, or third spacing of fluid. | |||
== Management == | |||
Treatment depends on the underlying cause. Any drugs which can contribute to hyponatraemia should be discontinued if possible. Fluid restriction and increased intake of dietary salt is usually sufficient, but fluid restriction should not be used in those who are hypovolaemic. People who have symptomatic hyponatraemia require hospital admission. | |||
In moderate cases, intravenous infusion of isotonic (0,9%) NaCl can be considered. In severe hyponatraemia, hypertonic (3%) saline can be considered. | |||
=== Rate of correction === | |||