What is the recommended approach for correcting sodium levels in patients with severe, symptomatic hyponatremia?

Management of Severe, Symptomatic Hyponatremia

For severe, symptomatic hyponatremia, administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve, with a maximum increase of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

• Evaluate symptom severity (severe symptoms include seizures and coma) and onset timing (acute <48 hours vs. chronic >48 hours) to determine appropriate correction rate 1
• Assess volume status (hypovolemic, euvolemic, or hypervolemic) and measure serum and urine osmolality and electrolytes to determine the underlying cause 1
• Calculate corrected sodium in hyperglycemic patients by adding 1.6 mEq/L to measured sodium for every 100 mg/dL glucose above 100 mg/dL 2

Treatment Algorithm Based on Symptom Severity

For Severe Symptoms (seizures, coma)

• Administer 3% hypertonic saline with initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1, 3
• Monitor serum sodium every 2 hours during initial correction 1
• Discontinue 3% saline once severe symptoms resolve and transition to protocols for mild symptoms 3
• Do not exceed total correction of 8 mmol/L in 24 hours (after initial 6 mmol/L correction, limit to only 2 mmol/L in the following 18 hours) 1, 3

For Mild/Moderate Symptoms or Asymptomatic

• For euvolemic hyponatremia (SIADH): Implement fluid restriction to 1 L/day 1, 3
• For hypovolemic hyponatremia: Discontinue diuretics and 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 for sodium <125 mmol/L 1

Special Considerations

• Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require more cautious correction (4-6 mmol/L per day) due to higher risk of osmotic demyelination syndrome 1, 4
• In neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW), as CSW requires volume and sodium replacement, not fluid restriction 1
• Tolvaptan should be initiated only in a hospital setting where serum sodium can be closely monitored, with maximum correction not exceeding 12 mEq/L/24 hours 5
• For patients with subarachnoid hemorrhage at risk of vasospasm, avoid fluid restriction 1

Monitoring and Prevention of Complications

• For severe symptoms: Monitor serum sodium every 2 hours during initial correction, then every 4 hours after resolution of severe symptoms 1
• If overcorrection occurs (>8 mmol/L/24 hours), consider relowering with electrolyte-free water or desmopressin 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1, 4

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours can lead to osmotic demyelination syndrome 1, 6
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting can worsen outcomes 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1

Pharmacological Options

• For SIADH resistant to fluid restriction, consider oral sodium chloride tablets, urea, or vasopressin receptor antagonists (tolvaptan) 1, 5
• For CSW, consider fludrocortisone in addition to sodium and volume replacement 1
• Vasopressin receptor antagonists should not be used for hypovolemic hyponatremia 5

Remember that the rate of correction should be guided by symptom severity, with slower correction for chronic hyponatremia after initial symptom control to prevent osmotic demyelination syndrome 1, 7.