From the Guidelines
Sodium replacement should be guided by the severity and rate of sodium depletion, with a goal correction rate not exceeding 8-10 mEq/L in the first 24 hours to prevent osmotic demyelination syndrome, as recommended by the most recent guidelines 1.
Severity-Based Approach
The approach to sodium replacement varies based on the severity of hyponatremia:
- For mild hyponatremia (sodium 130-135 mEq/L), oral sodium chloride tablets (1-2 g three times daily) or increased dietary salt intake may be sufficient.
- For moderate hyponatremia (125-130 mEq/L), intravenous normal saline (0.9% NaCl) at 50-100 mL/hour is typically appropriate.
- In severe cases (<125 mEq/L) with neurological symptoms, 3% hypertonic saline may be administered at 1-2 mL/kg/hour, with careful monitoring to prevent over-correction 1.
Key Considerations
- The underlying cause of hyponatremia must be addressed simultaneously.
- Fluid restriction is necessary for euvolemic or hypervolemic hyponatremia, while volume repletion is needed for hypovolemic states.
- Careful monitoring is essential as both under-correction (risking cerebral edema) and over-correction (risking osmotic demyelination) can have serious neurological consequences.
- Patients with chronic hyponatremia require more gradual correction than those with acute onset, with a goal rate of increase of serum sodium of 4-6 mEq/L per 24-hour period, not to exceed 8 mEq/L per 24-hour period 1.
Monitoring and Adjustment
- Sodium levels should be checked every 2-4 hours during rapid correction.
- The use of vasopressin receptor antagonists can raise serum sodium during treatment, but should be used with caution only for a short term (≤30 days) 1.
- Hypertonic saline administration should be reserved for those who are severely symptomatic with acute hyponatraemia, with serum sodium slowly corrected to prevent central pontine myelinolysis 1.
From the Research
Sodium Replacement Guidelines
- The approach to managing hyponatremia should consist of treating the underlying cause, and sodium replacement guidelines vary depending on the severity of symptoms and the patient's fluid volume status 2, 3.
- For severely symptomatic hyponatremia, US and European guidelines recommend treating with bolus hypertonic saline to increase the serum sodium level by 4 mEq/L to 6 mEq/L within 1 to 2 hours, but by no more than 10 mEq/L within the first 24 hours 2, 4.
- The treatment target for symptomatic hyponatremia is an increase in serum sodium by 5-10 mEq/L within the first 24 hours and a maximum of 8 mEq/L during subsequent 24 hours 5.
- Hypertonic saline should be used in patients with hyponatremia associated with moderate or severe symptoms to prevent neurological complications, and the dose and administration modality should be carefully considered to avoid overcorrection 6.
- Overly rapid correction of hyponatremia can cause osmotic demyelination, a rare but severe neurological condition, and frequent monitoring of the serum sodium concentration and urine output are mandatory to avoid this complication 4, 5.
Treatment Approaches
- Hypovolemic hyponatremia is treated with normal saline infusions 3.
- Euvolemic hyponatremia is treated by restricting free water consumption or using salt tablets or intravenous vaptans 2, 3.
- Hypervolemic hyponatremia is treated primarily by managing the underlying cause and free water restriction 3.
- Desmopressin can be used to terminate an unwanted water diuresis and avoid overcorrection of hyponatremia 4.
Considerations
- Symptoms caused by hypovolemia can be misinterpreted as severely symptomatic hyponatremia, and diuresis should be monitored to avoid overcorrection 5.
- Reducing bolus-volume and reevaluating before repeating bolus infusion might prevent overcorrection 5.
- The use of hypertonic saline should be carefully considered, and the dose and administration modality should be individualized to avoid overcorrection and ensure safe and effective treatment 6.