How should I safely correct hyponatremia, specifying the recommended rate of sodium rise and treatment steps for chronic asymptomatic hyponatremia versus acute or symptomatic hyponatremia?

Correction of Hyponatremia

The rate and method of sodium correction must be determined by symptom severity and chronicity: severely symptomatic hyponatremia requires immediate 3% hypertonic saline targeting 6 mmol/L correction over 6 hours, while chronic asymptomatic hyponatremia should be corrected at 4-6 mmol/L per day, never exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Acute Symptomatic vs. Chronic Asymptomatic: The Critical Distinction

Severely Symptomatic Hyponatremia (Medical Emergency)

For patients with seizures, coma, altered mental status, or respiratory distress, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over the first 6 hours or until severe symptoms resolve. 1, 2

• Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeating up to three times at 10-minute intervals until symptoms improve 1
• Monitor serum sodium every 2 hours during initial correction 1
• The total correction must not exceed 8 mmol/L in any 24-hour period 1, 2
• If 6 mmol/L is corrected in the first 6 hours, only 2 mmol/L additional correction is permitted in the remaining 18 hours 1
• Discontinue 3% saline once severe symptoms resolve and transition to protocols for mild symptoms 2

Chronic Asymptomatic Hyponatremia

For chronic hyponatremia (>48-72 hours) without severe symptoms, correction should be limited to 4-6 mmol/L per day, with an absolute maximum of 8 mmol/L in 24 hours. 1, 3

• Implement fluid restriction to 1 L/day for euvolemic hyponatremia (SIADH) 1
• For hypovolemic hyponatremia, administer isotonic saline (0.9% NaCl) for volume repletion 1
• For hypervolemic hyponatremia (cirrhosis, heart failure), implement fluid restriction to 1-1.5 L/day 1
• Monitor serum sodium every 4-6 hours initially, then daily once stable 1

Treatment Algorithm Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1
• Urine sodium <30 mmol/L predicts good response to saline (71-100% positive predictive value) 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is first-line treatment 1
• If no response, add oral sodium chloride 100 mEq three times daily 1
• Consider vasopressin receptor antagonists (tolvaptan 15 mg daily) for resistant cases 1

Hypervolemic Hyponatremia (Cirrhosis, Heart Failure)

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms present 1

High-Risk Populations Requiring Slower Correction

Patients with advanced liver disease, chronic alcoholism, malnutrition, or prior encephalopathy require even more cautious correction at 4-6 mmol/L per day, with an absolute maximum of 8 mmol/L in 24 hours. 1, 4

• These patients have a 0.5-1.5% risk of osmotic demyelination syndrome even with careful correction 1
• For severe hyponatremia with initial sodium <115 mmol/L, limit correction to <8 mmol/L in 24 hours 4
• Thiamine supplementation (500 mg IV three times daily) should be administered before any glucose-containing fluids in chronic alcoholics 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediately discontinue current fluids and switch to D5W (5% dextrose in water). 1

• Consider administering desmopressin to slow or reverse the rapid rise 1, 5
• The goal is to bring the total 24-hour correction back to ≤8 mmol/L from baseline 1
• Overcorrection occurs in 4.5-28% of patients treated with hypertonic saline 6, 7

Special Considerations for Neurosurgical Patients

In neurosurgical patients, distinguishing cerebral salt wasting (CSW) from SIADH is critical because they require opposite treatments. 1

• CSW requires volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1
• SIADH requires fluid restriction to 1 L/day 1
• For subarachnoid hemorrhage patients at risk of vasospasm, never use fluid restriction 1
• Consider fludrocortisone (0.1-0.2 mg daily) for CSW in severe cases 1

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—this causes osmotic demyelination syndrome 1, 5
• Inadequate monitoring during active correction increases risk of overcorrection 1
• Using fluid restriction in cerebral salt wasting worsens outcomes 1
• Failing to recognize and treat the underlying cause leads to treatment failure 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms worsens fluid overload 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—even mild hyponatremia increases fall risk and mortality 1, 8

Monitoring Requirements

• Severe symptoms: Check serum sodium every 2 hours during initial correction 1
• Mild symptoms: Check serum sodium every 4 hours after symptom resolution 1, 2
• Chronic correction: Monitor daily initially, then adjust frequency based on response 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1