What to order for a patient with hyponatremia (sodium level of 124 mEq/L) after a nephrologist (kidney specialist) consultation?

From the Guidelines

For a patient with hyponatremia (Na 124) who already has nephrology consultation, I would implement fluid restriction to 1-1.5 liters per day while awaiting nephrology recommendations. This approach is supported by the most recent guidelines, such as those published in Gut in 2021 1, which suggest that fluid restriction may be helpful in preventing further decrease in serum sodium levels, although it is rarely effective in improving serum sodium concentration. I would closely monitor serum sodium levels every 6 hours, assess volume status, and review all medications that could contribute to hyponatremia (such as diuretics, SSRIs, or antiepileptics). If the patient is symptomatic with confusion, seizures, or altered mental status, I would consider 3% hypertonic saline at 100-150 mL over 1 hour with close monitoring, aiming for sodium correction of no more than 6-8 mEq/L in 24 hours to avoid osmotic demyelination syndrome, as recommended by the 2010 EASL clinical practice guidelines on the management of ascites, spontaneous bacterial peritonitis, and hepatorenal syndrome in cirrhosis 1. I would also check serum and urine osmolality, urine sodium, and thyroid and adrenal function if not already done. While nephrology will provide definitive management, these initial steps help stabilize the patient and provide valuable clinical information. The underlying cause of hyponatremia (SIADH, heart failure, cirrhosis, medications, etc.) will ultimately guide long-term treatment, which may include salt tablets, urea, or vasopressin receptor antagonists depending on the specific etiology.

Some key points to consider in the management of hyponatremia include:

• The importance of distinguishing between hypovolemic and hypervolemic hyponatremia, as the treatment approach differs significantly 1
• The need for careful monitoring of serum sodium levels and adjustment of treatment as needed to avoid overly rapid correction and the risk of osmotic demyelination syndrome 1
• The potential role of vaptans, such as tolvaptan, in the treatment of severe hypervolemic hyponatremia, although their use requires careful consideration of the potential risks and benefits 1
• The importance of addressing the underlying cause of hyponatremia, whether it be SIADH, heart failure, cirrhosis, or another condition, in order to guide long-term treatment and management.

Overall, the management of hyponatremia requires a careful and nuanced approach, taking into account the underlying cause of the condition, the severity of symptoms, and the potential risks and benefits of different treatment options.

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. The primary endpoint for these studies was the average daily AUC for change in serum sodium from baseline to Day 4 and baseline to Day 30 in patients with a serum sodium less than 135 mEq/L. Compared to placebo, tolvaptan caused a statistically greater increase in serum sodium ( p <0. 0001) during both periods in both studies

For a patient with hyponatremia (Na 124 mEq/L), and a nephrologist already consulted, the hospitalist may consider ordering tolvaptan as it has been shown to increase serum sodium levels in patients with euvolemic or hypervolemic hyponatremia.

• The initial dose of tolvaptan is 15 mg once daily, which 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.
• It is essential to monitor serum sodium concentrations and adjust the dose accordingly to avoid overly rapid correction of serum sodium 2.

From the Research

Treatment Options for Hyponatremia

Given the patient's sodium level of 124 and consultation with a nephrologist, the following treatment options can be considered:

• Fluid restriction: This is a common approach for treating euvolemic hyponatremia, as seen in 3 and 4.
• Hypertonic saline: This can be used to treat severe or symptomatic hyponatremia, as mentioned in 3, 4, and 5.
• Vasopressin receptor antagonists (vaptans): These can be used to treat euvolemic and hypervolemic hyponatremia, as discussed in 3, 5, and 6.
• Urea: This can be used to treat euvolemic and hypervolemic hyponatremia, as mentioned in 5 and 6.
• Isotonic saline: This can be used to treat hypovolemic hyponatremia, as seen in 4 and 7.
• Loop diuretics: These can be used to reduce water retention in patients with heart failure, as mentioned in 5 and 7.

Considerations for Treatment

When treating hyponatremia, it is essential to:

• Limit the daily increase of serum sodium to less than 8-10 mmol/liter to avoid osmotic demyelination, as mentioned in 3.
• Monitor serum sodium levels closely, especially during the first 24 hours of treatment, as seen in 3.
• Consider the underlying cause of hyponatremia and address it accordingly, as discussed in 4 and 5.
• Be aware of the potential side effects of treatment, such as thirst, polydipsia, and frequency of urination with vaptans, as mentioned in 3.