What is the dosing of 3% hypertonic saline solution to increase sodium levels in patients with hyponatremia?

From the Guidelines

The recommended dosing for 3% hypertonic saline to increase serum sodium is typically 1-2 mL/kg given intravenously over 10-20 minutes, which can be repeated if needed, with a goal to raise sodium by up to 5 mmol/L in the first hour and a limit of 8–10 mmol/L every 24 hours thereafter until the serum sodium concentration reaches 130 mmol/L, as suggested by the most recent guidelines 1.

Key Considerations

• The use of 3% hypertonic saline is reserved for patients with severely symptomatic acute hyponatremia, especially if a transplant is imminent, due to the risk of worsening fluid overload 1.
• It is crucial to avoid correcting sodium too rapidly to prevent osmotic demyelination syndrome, a serious neurological complication, with a recommended increase of no more than 8-10 mEq/L in the first 24 hours 1.
• Continuous infusion can be used at rates of 0.5-2 mL/kg/hour, with frequent monitoring of serum sodium levels (every 2-4 hours initially) to ensure safe and effective correction of hyponatremia.
• The treatment should be administered in a monitored setting with regular electrolyte checks and should be slowed or stopped once symptoms improve or target sodium levels are reached.

Mechanism and Monitoring

• The mechanism of action of 3% hypertonic saline involves creating an osmotic gradient that pulls water from intracellular to extracellular spaces, thereby increasing serum sodium concentration and reducing cerebral edema.
• Frequent monitoring of serum sodium levels is essential to avoid overcorrection and to adjust the treatment regimen as needed, with a focus on preventing complications such as osmotic demyelination syndrome 1.

From the Research

Dosing of 3% Hypertonic Saline Solution

• The dosing of 3% hypertonic saline solution to increase sodium levels in patients with hyponatremia is typically administered as a 100- to 150-ml intravenous bolus or continuous infusion 2.
• For symptomatic hyponatremia, rapid correction is usually obtained by hypertonic saline (3%) infusion 3.
• A 4- to 6-mmol/L increase in serum sodium concentration is adequate in the most seriously ill patients and this is best achieved with bolus infusions of 3% saline 4.
• The European guidelines recommend bolus-wise administration of 150 mL of 3% hypertonic saline for the treatment of symptomatic hyponatremia 5.

Correction Rates

• The treatment target is defined as an increase in serum sodium by 5-10 mEq/L within the first 24 h and a maximum of 8 mEq/L during subsequent 24 h 5.
• Appropriate therapy should keep the patient safe from serious complications of hyponatremia while staying well clear of correction rates that risk iatrogenic injury, with suggested therapeutic goals of 6 to 8 mmol/L in 24 hours, 12 to 14 mmol/L in 48 hours, and 14 to 16 mmol/L in 72 hours 4.
• Overcorrection of hyponatremia (defined as 10 mmol/L in 24 hours, 18 mmol/L in 48 hours, and 20 mmol/L in 72 hours) risks iatrogenic brain damage 4.

Administration and Monitoring

• Frequent monitoring of the serum sodium concentration and urine output are mandatory 4.
• Administration of desmopressin to terminate an unwanted water diuresis is an effective strategy to avoid or reverse overcorrection 4.
• Reducing bolus-volume and reevaluation before repeating bolus infusion might prevent overcorrection, especially in severely symptomatic patients 5.