What is the management of hyponatremia (low sodium levels)?

From the Guidelines

The management of hyponatremia should prioritize the correction of the underlying cause, with treatment tailored to the patient's volume status and symptom severity, as evidenced by the most recent guidelines 1.

Key Considerations

• The approach to hyponatremia management depends on the severity, chronicity, and underlying cause of the condition.
• For hypovolemic hyponatremia, treatment involves discontinuation of diuretics and/or laxatives and providing fluid resuscitation, typically with 5% IV albumin or crystalloid solution 1.
• Euvolemic hyponatremia should be managed based on the specific underlying cause, and treatment may include fluid restriction, reduction or discontinuation of diuretics and laxatives, administration of hyperoncotic albumin, and/or vasopressin receptor antagonists (“vaptans”) 1.
• For severe symptomatic hyponatremia, hypertonic saline may be administered, but the correction rate should not exceed 8-10 mmol/L/day to avoid osmotic demyelination syndrome 1.

Treatment Strategies

• Fluid restriction to 800-1000 mL/day may be sufficient for mild to moderate hyponatremia with minimal symptoms, particularly in SIADH or heart failure.
• For volume-depleted patients, isotonic saline (0.9% NaCl) at 100-150 mL/hr should be given until euvolemia is achieved.
• Specific medications, such as tolvaptan, may be used for euvolemic or hypervolemic hyponatremia, with close monitoring of sodium levels.
• Loop diuretics like furosemide may be needed for hypervolemic states, but should be used with caution to avoid worsening hyponatremia.

Monitoring and Prevention

• Regular monitoring of serum sodium (every 2-4 hours initially in severe cases) is essential to ensure appropriate correction rates.
• Underlying causes must be addressed simultaneously, including discontinuing offending medications, treating infections, or managing endocrine disorders.
• The management of hyponatremia balances the risks of cerebral edema from undercorrection against osmotic demyelination from overcorrection, with treatment tailored to the patient's volume status and symptom severity 1.

From the FDA Drug Label

Removal of excess free body water increases serum osmolality and serum sodium concentrations. All patients treated with tolvaptan, especially those whose serum sodium levels become normal, should continue to be monitored to ensure serum sodium remains within normal limits If hypernatremia is observed, management may include dose decreases or interruption of tolvaptan treatment, combined with modification of free-water intake or infusion.

The management of hyponatremia with tolvaptan involves monitoring serum sodium levels and adjusting the dose as needed to prevent hypernatremia. Key considerations include:

• Monitoring serum sodium levels regularly
• Adjusting the dose of tolvaptan if hypernatremia occurs
• Modifying free-water intake or infusion as needed to prevent hypernatremia
• Being aware of the potential for hypernatremia, especially in patients whose serum sodium levels become normal 2 2 2

From the Research

Diagnosis of Hyponatremia

• Hyponatremia is defined by a serum sodium level of less than 135 mEq/L and most commonly results from water retention 3.
• It can be classified according to the measured plasma osmolality as isotonic, hypertonic or hypotonic 4.
• Hypotonic hyponatremia is further classified according to the volume status of the patient as hypovolaemic, hypervolaemic or euvolaemic 4.

Management of Hyponatremia

• The approach to managing hyponatremia should consist of treating the underlying cause 3.
• For most patients, fluid restriction and close monitoring alone are sufficient, while a slow correction by 0.5 mEq/l/h may be attempted in symptomatic patients 4.
• Urea and vaptans can be effective treatments for the syndrome of inappropriate antidiuresis and hyponatremia in patients with heart failure, but have adverse effects 3.
• Tolvaptan, an oral vasopressin V2-receptor antagonist, can lead to an increase in serum sodium concentration and is the only medication licenced in Europe for the treatment of euvolaemic hyponatraemia 5.
• Hypertonic saline is reserved for patients with severely symptomatic hyponatremia, and the rate of correction is dependent upon the duration, degree of hyponatraemia and the presence or absence of symptoms 3, 4.

Treatment of SIADH

• The syndrome of inappropriate antidiuresis (SIADH) should be suspected in any patient with euvolaemic hyponatraemia with a urine osmolality above 100 mOsm/kg and urine sodium concentration above 40 mEq/l 4.
• Tolvaptan can be used to correct SIADH-related hyponatraemia, but the risk of overly rapid sodium increase should be monitored 5.
• A lower starting tolvaptan dose of 7.5 mg has been evaluated in small cohort studies, demonstrating its efficacy, but it still remains unclear as to whether it can reduce the risk of overcorrection 5.

Complications of Hyponatremia

• Overly rapid correction of chronic hyponatremia may cause osmotic demyelination, a rare but severe neurological condition, which can result in parkinsonism, quadriparesis, or even death 3, 4.
• Excessive rapid correction should be avoided in both acute and chronic hyponatremia, because it can lead to irreversible neurological complications including central osmotic demyelination 4.