What is the recommended infusion rate for hypertonic saline (3% sodium chloride) to safely correct symptomatic hyponatremia in an adult?

Hypertonic Saline (3% NaCl) Infusion Rate for Symptomatic Hyponatremia

For severe symptomatic hyponatremia, administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeating up to three times at 10-minute intervals until symptoms resolve or a 5 mEq/L rise is achieved, then transition to continuous infusion or maintenance therapy based on symptom resolution. 1, 2, 3

Initial Bolus Protocol for Severe Symptoms

Severe symptoms include altered mental status, seizures, coma, or signs of cerebral edema (nausea, vomiting, headache progressing to obtundation). 1, 2, 4

• Administer 100 mL of 3% NaCl IV over 10 minutes as the first bolus 1, 2, 3
• Repeat the 100 mL bolus every 10 minutes up to three total doses if severe neurologic symptoms persist 1, 2, 3
• Target an initial rise of 4–6 mEq/L within the first 1–2 hours or until severe symptoms resolve 1, 2, 4
• Check serum sodium 4–6 hours after the initial bolus to guide further therapy 1, 5

The 100 mL bolus regimen is safer than larger volumes (e.g., 250 mL) for controlled correction, though 250 mL boluses are more effective at achieving a ≥5 mEq/L rise within 4 hours (52% vs 32% success rate) without increasing overcorrection risk. 6 However, the 100 mL protocol remains the guideline-recommended approach for emergency treatment. 1, 3

Continuous Infusion Protocol

After initial bolus therapy or for patients with moderate symptoms:

• Administer 500 mL of 3% NaCl at 100 mL/hour (over 5–6 hours) as a continuous infusion 2, 7
• This approach has been demonstrated safe and effective in prospective studies, achieving mean sodium increases of 3.8 mEq/L at 3 hours and 7.1 mEq/L at 12 hours 7
• Monitor serum sodium every 2 hours during active correction of severe symptoms 1, 5

Critical Safety Limits

Never exceed 8 mmol/L correction in any 24-hour period to prevent osmotic demyelination syndrome. 1, 5, 4

• Initial target: 5–6 mEq/L rise in the first 1–2 hours for severe symptoms 2, 4
• Maximum 24-hour correction: 8–10 mEq/L (some sources allow up to 10 mEq/L in the first 24 hours, but 8 mEq/L is the safer ceiling) 1, 2, 4
• If 6 mEq/L is corrected in the first 6 hours, only 2 mEq/L additional correction is permitted in the next 18 hours 1, 5

For high-risk patients (cirrhosis, alcoholism, malnutrition, advanced liver disease), limit correction to 4–6 mEq/L per day with an absolute maximum of 8 mEq/L in 24 hours. 1

Transition and Discontinuation Criteria

Discontinue 3% saline when severe symptoms resolve, typically after achieving a 4–6 mEq/L rise. 1, 5, 3

• Switch to isotonic maintenance fluids (0.9% NaCl) after symptom resolution 1, 5
• Implement fluid restriction to 1 L/day for euvolemic hyponatremia (SIADH) after acute phase 1, 5
• Reduce monitoring frequency to every 4 hours (from every 2 hours) once severe symptoms resolve 1, 5
• Continue treatment until sodium reaches 125–130 mEq/L, not necessarily normal range 1, 4

Administration Route

3% saline can be safely administered through a peripheral IV line—central access is not required. 3 Peripheral administration has low complication rates (infiltration 3.3%, phlebitis 6.2%) and avoids the risks of central line placement. 1

Common Pitfalls

• Waiting for severe symptoms to develop before treating early signs (nausea, vomiting, headache) increases morbidity and mortality 2, 3
• Overcorrecting beyond 8 mEq/L in 24 hours risks osmotic demyelination syndrome, which manifests 2–7 days post-correction with dysarthria, dysphagia, quadriparesis 1, 2
• Delaying treatment due to concerns about demyelination risk—the risk of untreated hyponatremic encephalopathy (death from herniation) far exceeds the risk of demyelination with appropriate correction rates 2, 3
• Using continuous infusion alone without initial bolus therapy in severely symptomatic patients delays symptom resolution 2, 3