What are the guidelines for correcting severe hyponatremia (serum sodium level less than 125 mmol/L) in patients?

Severe Hyponatremia Correction Guidelines

Critical Correction Rate Limits

The maximum correction rate must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome, with high-risk patients requiring even slower correction at 4-6 mmol/L per day. 1

• High-risk populations include patients with advanced liver disease, alcoholism, malnutrition, severe hyponatremia (<120 mmol/L), or prior encephalopathy 1, 2
• The FDA mandates hospital initiation and re-initiation of tolvaptan with close sodium monitoring, as correction >12 mEq/L/24 hours can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, seizures, coma, and death 2
• Slower correction rates (4-6 mmol/L per day) are advisable in susceptible patients 1, 2

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma, Altered Mental Status)

Administer 3% hypertonic saline immediately with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve. 1, 3

• Give 100-150 mL boluses of 3% saline over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms improve 1
• Total 24-hour correction must not exceed 8 mmol/L 1, 3
• Monitor serum sodium every 2 hours during initial correction 1
• This is a medical emergency requiring ICU admission 1, 3

Moderate Symptomatic Hyponatremia (Nausea, Headache, Confusion)

• Use 3% hypertonic saline with slower infusion rates 1
• Target correction of 4-6 mmol/L in first 24 hours 1
• Monitor sodium every 4 hours 1

Asymptomatic Severe Hyponatremia

• Implement fluid restriction to 1-1.5 L/day as first-line therapy 1, 3
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 1, 4
• Reserve hypertonic saline for patients with imminent liver transplantation 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia (Urine Sodium <30 mmol/L)

• Administer isotonic saline (0.9% NaCl) for volume repletion 1, 5
• Initial infusion rate: 15-20 mL/kg/hour, then 4-14 mL/kg/hour based on response 1
• Discontinue diuretics immediately 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is the cornerstone of treatment 1, 3
• Add oral sodium chloride 100 mEq three times daily if fluid restriction fails 1, 4
• Consider vaptans (tolvaptan 15 mg daily, titrate to 30-60 mg) for resistant cases 1, 2
• Alternative options: urea, demeclocycline, or lithium 1, 3

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 5
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens ascites and edema 1

Special Population Considerations

Neurosurgical Patients (Cerebral Salt Wasting vs. SIADH)

Distinguishing between cerebral salt wasting (CSW) and SIADH is critical, as they require opposite treatments. 1

• CSW requires volume and sodium replacement with normal saline or hypertonic saline, NOT fluid restriction 1
• Add fludrocortisone 0.1-0.2 mg daily for severe CSW symptoms 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1
• CSW characteristics: true hypovolemia, CVP <6 cm H₂O, urine sodium >20 mmol/L despite volume depletion 1

Cirrhotic Patients

• Maximum correction: 4-6 mmol/L per day, not exceeding 8 mmol/L in 24 hours 1
• Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Tolvaptan carries higher risk of gastrointestinal bleeding in cirrhosis (10% vs. 2% placebo) 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediately intervene to prevent osmotic demyelination syndrome. 1

• Discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Administer desmopressin to slow or reverse the rapid rise 1
• Target relowering to bring total 24-hour correction to ≤8 mmol/L from starting point 1

Monitoring Protocol

• Severe symptoms: Check sodium every 2 hours during initial correction 1
• Mild symptoms: Check sodium every 4 hours after symptom resolution 1
• Asymptomatic: Check sodium every 24-48 hours initially 1
• Watch for osmotic demyelination syndrome signs (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1, 2

Common Pitfalls to Avoid

• Never exceed 8 mmol/L correction in 24 hours for chronic hyponatremia 1, 3
• Inadequate monitoring during active correction leads to overcorrection 1
• Using fluid restriction in cerebral salt wasting worsens outcomes 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—it increases fall risk and mortality 1, 3