Severe, symptomatic hyponatremia is a life threatening emergency! If patients are obtunded, seizing, or at imminent risk of herniating due to increased intracranial pressure you should aim to correct the serum sodium by approximately 5mmol in as little as 30 mins. This is done with intravenous 3% or 5% sodium chloride, and if you are going this route you had better be sure of exactly what you are doing, or consult someone who is! Once this is done, if they are symptomatically improved, you then need to correct more slowly.
Asymptomatic hyponatremia is less life threatening. In fact, the doctor may be the most dangerous thing the patient encounters. If one corrects the sodium too quickly the patient is at risk of central pontine myelinolysis which can lead to severe morbidity. Goal is to correct 6-8mmol/24h.
In general the approach to correcting the sodium is dependent on whether the patient is hypovolemic, euvolemic, or hypervolemic.
- Hypovolemic -- i.e. dehydration repleted with hypotonic fluid, diuretics, GI losses, adrenal insufficiency
Replete volume if hemodynamically unstable. Can use fluid that is isotonic to their serum if there is a concern about changing the sodium with rescucitation. Watch for free-water diuresis when euvolemic as the stimulus for ADH may be the hypovolemia. In cases where the initial sodium is less than 120 consider giving a small dose of DDAVP (2-4mg IV q12h) to prevent this massive free-water diuresis causing rapid over correction. - Euvolemic -- SIADH, hypothryoidism, adrenal insufficiency, psychogenic polydipsia
Try and stop the stimulis for the SIADH. Fluid restriction is usually sufficient to correct the hyponatremia. If not working and patient adhering to fluid restriction, can restrict further or add low dose loop diuretic like furosemide. - Hypervolemic -- Heart failure, nephrotic syndrome, cirrhosis
Fluid restriction plus loop diuretics.
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