What if I use 0.9% (normal) sodium chloride for severe hyponatremia?

From the Guidelines

Using 0.9% sodium chloride (normal saline) for severe hyponatremia is generally not recommended as first-line therapy. Instead, 3% hypertonic saline should be used for severe symptomatic hyponatremia, especially when serum sodium is below 120 mEq/L or neurological symptoms are present, as recommended by recent guidelines 1. For 3% saline, an initial bolus of 100-150 mL over 10-20 minutes can be given, which may be repeated if symptoms persist. The correction rate should not exceed 8-10 mEq/L in the first 24 hours and 18 mEq/L in 48 hours to avoid osmotic demyelination syndrome, as cautioned in the literature 1.

Some key points to consider when managing hyponatremia include:

• Hypovolemic hyponatremia requires plasma volume expansion with saline solution and correction of the causative factor 1.
• Hypervolemic hyponatremia requires attainment of a negative water balance, and non-osmotic fluid restriction may be helpful in preventing a further decrease in serum sodium levels 1.
• Normal saline (0.9%) can actually worsen hyponatremia in some cases, particularly in patients with SIADH or heart failure, as it may increase total body water more than sodium 1.
• If 3% saline is unavailable, 0.9% saline could be used temporarily for hypovolemic hyponatremia patients, but close monitoring of serum sodium levels is essential, as emphasized in the guidelines 1.

The key physiological principle is that effective treatment must increase serum sodium concentration by providing relatively more sodium than free water to the patient. Therefore, the use of 3% hypertonic saline is preferred over 0.9% sodium chloride for severe symptomatic hyponatremia, especially in patients with severe symptoms or neurological manifestations, as supported by the most recent and highest quality study 1.

From the Research

Severe Hyponatremia Treatment

• The use of 0.9% (normal) sodium chloride for severe hyponatremia is not typically recommended as a first-line treatment, as it may not be sufficient to rapidly correct the serum sodium level 2, 3.
• For severely symptomatic hyponatremia, 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.
• Hypertonic NaCl is first-line therapy for acute, severe, and symptomatic hyponatremia; however, its use is often restricted to the intensive care unit (ICU) 4.
• In some cases, hourly oral sodium chloride may provide an attractive alternative to intravenous 3% NaCl for selected patients with severe hyponatremia, but this approach requires careful monitoring of the serum sodium concentration 4.

Correction Rate

• The rate of correction of severe hyponatremia should be no more than 0.5 mM per liter per hour for chronic symptomatic hyponatremia, and the initial treatment should be halted once a mildly hyponatremic range of the serum sodium concentration has been reached (approximately 125 to 130 mM/liter) 5.
• For acute hyponatremia, treatment should be rapid, using hypertonic saline, to initially reach a mildly hyponatremic level 5, 6.
• The use of furosemide and isotonic or hypertonic saline may allow for rapid correction of severe chronic hyponatremia without severe neurologic complications 6.

Fluid Management

• Hypovolemic hyponatremia is treated with normal saline infusions 3.
• Euvolemic hyponatremia includes restricting free water consumption or using salt tablets or intravenous vaptans 3.
• Hypervolemic hyponatremia is treated primarily by managing the underlying cause (e.g., heart failure, cirrhosis) and free water restriction 3.