Management of Hyponatremia
The management of hyponatremia should be based on the severity of symptoms, volume status, and underlying cause, with correction rates not exceeding 10 mmol/L per day to prevent osmotic demyelination syndrome. 1
Classification and Initial Assessment
Hyponatremia is classified based on serum sodium levels:
- Mild: 126-135 mEq/L
- Moderate: 120-125 mEq/L
- Severe: <120 mEq/L 2
Volume status assessment is critical for determining the underlying cause:
| Volume Status | Clinical Signs | Urine Sodium | Likely Causes |
|---|---|---|---|
| Hypovolemic | Orthostatic hypotension, dry mucous membranes, tachycardia | <20 mEq/L | GI losses, diuretics, cerebral salt wasting |
| Euvolemic | No edema, normal vital signs | >20-40 mEq/L | SIADH, hypothyroidism, adrenal insufficiency |
| Hypervolemic | Edema, ascites, elevated JVP | <20 mEq/L | Heart failure, cirrhosis, renal failure |
Treatment Algorithm Based on Symptom Severity
Severe Symptomatic Hyponatremia (Seizures, Coma, Respiratory Distress)
- Emergency treatment: Administer 3% hypertonic saline to increase serum sodium by 4-6 mEq/L within 1-2 hours 3
- Initial infusion rate (ml/kg per hour) = body weight (kg) × desired rate of increase in sodium (mmol/L per hour) 4
- Monitor serum sodium every 2 hours initially, then every 4 hours 2
- Critical safety limit: Do not exceed correction of 10 mmol/L in 24 hours 1
Moderate to Mild Symptomatic Hyponatremia
- Treat according to volume status:
Hypovolemic Hyponatremia
- Administer isotonic (0.9%) saline to restore volume 2
- Avoid hypotonic fluids as they can worsen hyponatremia 2
- Address underlying cause (stop diuretics, replace GI losses)
Euvolemic Hyponatremia (SIADH)
- Fluid restriction to 1,000-1,500 mL/day for mild hyponatremia 2
- For moderate to severe cases, consider:
Hypervolemic Hyponatremia
- Fluid restriction 2
- Judicious use of loop diuretics if signs of congestion are present 2
- For liver cirrhosis patients: albumin infusion may be beneficial, especially with hypoalbuminemia 2
- Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1
Special Considerations
Neurosurgical Patients
- Fludrocortisone may be considered in subarachnoid hemorrhage patients at risk of vasospasm 1
- Hydrocortisone may be used to prevent natriuresis in subarachnoid hemorrhage patients 1
- Cerebral salt wasting should be treated with sodium replacement and IV fluids 1
Rate of Correction
- For chronic hyponatremia: 4-6 mEq/L per 24-hour period, not exceeding 8 mEq/L per 24 hours 2
- Caution: Overly rapid correction can cause osmotic demyelination syndrome, which can result in parkinsonism, quadriparesis, or death 3
- High-risk patients (alcoholics, malnourished, liver disease): limit correction to 4-6 mEq/L per day 6
Prevention of Overcorrection
- Consider using desmopressin to prevent unwanted water losses that could lead to overcorrection 6
- If correction is proceeding too rapidly, administer hypotonic fluids and desmopressin to re-lower sodium 7
Complications of Untreated Hyponatremia
Even mild chronic hyponatremia is associated with:
Severe hyponatremia (<120 mEq/L) has a mortality rate of 25% compared to 9.3% in patients with sodium >120 mEq/L 2
Hyponatremia management requires careful monitoring and a balanced approach to correction. The key is to treat the underlying cause while ensuring safe correction rates to prevent neurological complications.