How to manage a patient with severe hyponatremia (low sodium levels)?

From the Guidelines

For a patient with severe hyponatremia (sodium level of 119), the most appropriate initial treatment is to begin with a 100-150 mL bolus of 3% hypertonic saline over 10-20 minutes, which can be repeated up to 2-3 times if severe symptoms persist, as recommended by recent guidelines 1. The goal of this treatment is to raise sodium levels by 4-6 mEq/L in the first 6 hours to address life-threatening symptoms. After initial stabilization, it is crucial to limit sodium correction to no more than 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome, a potentially devastating complication of overly rapid correction of hyponatremia 1. For volume-depleted patients, isotonic saline (0.9% NaCl) may be appropriate, while in SIADH cases, fluid restriction to 800-1000 mL/day is often necessary, and vasopressin receptor antagonists like tolvaptan (starting at 15 mg daily) may be considered for resistant cases 1. Loop diuretics such as furosemide (20-40 mg IV) can help with fluid overload states. Throughout treatment, monitoring serum sodium every 2-4 hours initially, then every 4-6 hours, and adjusting therapy based on sodium levels and clinical response is essential. The underlying cause of hyponatremia (medications, SIADH, adrenal insufficiency, heart failure, etc.) must be identified and addressed simultaneously for effective long-term management. Key considerations include the type of hyponatremia (hypovolemic, euvolemic, or hypervolemic), the presence of symptoms, and the rate of correction to avoid complications. Given the complexity and potential for severe complications, management of severe hyponatremia should be tailored to the individual patient's needs and monitored closely.

From the FDA Drug Label

In two double-blind, placebo-controlled, multi-center studies (SALT-1 and SALT-2), a total of 424 patients with euvolemic or hypervolemic hyponatremia (serum sodium <135 mEq/L) resulting from a variety of underlying causes (heart failure, liver cirrhosis, syndrome of inappropriate antidiuretic hormone [SIADH] and others) were treated for 30 days with tolvaptan or placebo, then followed for an additional 7 days after withdrawal.

Patients were randomized to receive either placebo (N = 220) or tolvaptan (N = 223) at an initial oral dose of 15 mg once daily. The mean serum sodium concentration at study entry was 129 mEq/L

Fluid restriction was to be avoided if possible during the first 24 hours of therapy to avoid overly rapid correction of serum sodium, and during the first 24 hours of therapy 87% of patients had no fluid restriction.

The treatment for severe hyponatremia (low sodium levels) with a serum sodium level of 119 mEq/L may involve the use of tolvaptan, starting with an initial oral dose of 15 mg once daily. It is essential to avoid fluid restriction during the first 24 hours of therapy to prevent overly rapid correction of serum sodium. The dose of tolvaptan can be increased at 24-hour intervals to 30 mg once daily, then to 60 mg once daily, until either the maximum dose of 60 mg or normonatremia (serum sodium >135 mEq/L) is reached. Patients should be monitored to ensure serum sodium remains within normal limits, and management may include dose decreases or interruption of tolvaptan treatment, combined with modification of free-water intake or infusion if hypernatremia is observed 2.

From the Research

Treatment of Hyponatremia

To manage a patient with severe hyponatremia, the following steps can be taken:

• Identify the underlying cause of hyponatremia and treat it accordingly 3, 4
• Categorize patients according to their fluid volume status (hypovolemic, euvolemic, or hypervolemic) to guide treatment 3, 4
• For severely symptomatic hyponatremia, use bolus hypertonic saline to increase serum sodium levels by 4-6 mEq/L within 1-2 hours, but not exceeding 10 mEq/L within the first 24 hours 3, 4
• For hypovolemic hyponatremia, treat with normal saline infusions 4
• For euvolemic hyponatremia, restrict free water consumption or use salt tablets or intravenous vaptans 4, 5
• For hypervolemic hyponatremia, manage the underlying cause and restrict free water intake 4

Medications for Hyponatremia

• 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, 5
• Vasopressin receptor antagonists (vaptans) can be used to treat hyponatremia, but their use should be monitored to prevent overly rapid correction of sodium levels 5, 6
• Vaptans should be discontinued with caution to prevent hyponatremic relapse, and serum sodium levels should be monitored after treatment 5

Important Considerations

• Overly rapid correction of chronic hyponatremia can cause osmotic demyelination, a rare but severe neurological condition 3, 4
• The daily increase of serum sodium should be limited to less than 8-10 mmol/L to prevent osmotic demyelination 5
• Treatment of hyponatremia should not be delayed while pursuing a diagnosis, and calculators can be used to guide fluid replacement and avoid overly rapid correction of sodium concentration 4