What are the guidelines to correct hyponatremia (low sodium levels)?

Guidelines for Correcting Hyponatremia

Initial Assessment and Classification

Hyponatremia correction must be guided by symptom severity, chronicity, and volume status, with the overriding principle that correction rates should never exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Determine Severity and Symptom Status

• Mild hyponatremia: 130-135 mmol/L 1
• Moderate hyponatremia: 120-125 mmol/L 1
• Severe hyponatremia: <120 mmol/L 1

Severe symptoms (requiring immediate intervention): seizures, coma, altered mental status, cardiorespiratory distress 1, 2

Mild symptoms: nausea, vomiting, headache, weakness 1, 3

Assess Volume Status

Determine if the patient has:

• Hypovolemic hyponatremia: orthostatic hypotension, dry mucous membranes, poor skin turgor, urine sodium typically <30 mmol/L 1
• Euvolemic hyponatremia: no edema, normal blood pressure, urine sodium >20-40 mmol/L (suggests SIADH) 1
• Hypervolemic hyponatremia: edema, ascites, jugular venous distention (heart failure, cirrhosis) 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

Administer 3% hypertonic saline immediately with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve. 1, 4

Specific protocol:

• Give 100-150 mL bolus of 3% hypertonic saline over 10 minutes 1, 5
• Can repeat up to 3 times at 10-minute intervals until symptoms improve 1
• Critical safety limit: Total correction must not exceed 8 mmol/L in 24 hours 1, 4
• After initial 6 mmol/L correction, limit to only 2 mmol/L in the following 18 hours 4

Monitoring during acute correction:

• Check serum sodium every 2 hours during initial correction 1
• Transition to every 4 hours after severe symptoms resolve 1, 4
• Discontinue 3% saline when severe symptoms resolve and switch to mild symptom protocol 4

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment is determined by volume status:

Hypovolemic Hyponatremia

• Discontinue diuretics immediately 1
• Administer isotonic (0.9%) saline for volume repletion 1
• Correction rate should not exceed 8 mmol/L in 24 hours 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is the cornerstone of treatment 1, 6
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• Second-line options: urea (effective and safe), vaptans (tolvaptan 15 mg daily, titrate to 30-60 mg), demeclocycline, or lithium 1, 7

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• For cirrhotic patients: Consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present 1

Critical Correction Rate Guidelines

Standard Patients

Maximum correction: 8 mmol/L in 24 hours 1, 4, 2

High-Risk Patients (Require Slower Correction: 4-6 mmol/L per day)

Patients at higher risk for osmotic demyelination syndrome include those with: 1

• Advanced liver disease
• Alcoholism
• Malnutrition
• Severe hyponatremia
• Prior encephalopathy

The FDA warns that correction >12 mEq/L in 24 hours can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, spastic quadriparesis, seizures, coma, and death. 6

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours: 1

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1, 8
• Target reduction to bring total 24-hour correction to no more than 8 mmol/L from starting point 1

Special Populations and Considerations

Neurosurgical Patients

Distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches differ fundamentally: 1

• CSW requires volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1
• Consider fludrocortisone for hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Cirrhotic Patients

• More cautious correction rates (4-6 mmol/L per day) due to higher risk of osmotic demyelination 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

Use of Vaptans (Tolvaptan)

FDA-approved for euvolemic and hypervolemic hyponatremia: 6

• Must initiate and re-initiate in hospital with close sodium monitoring 6
• Starting dose: 15 mg once daily, titrate to 30-60 mg as needed after at least 24 hours 6
• Do not use for more than 30 days due to hepatotoxicity risk 6
• Avoid fluid restriction during first 24 hours of tolvaptan therapy 6
• Contraindicated in: hypovolemic hyponatremia, patients unable to sense thirst, anuria, concurrent strong CYP3A inhibitors 6

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leading to osmotic demyelination syndrome 1
• Using fluid restriction in cerebral salt wasting, which worsens outcomes 1
• Inadequate monitoring during active correction 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant, as it increases fall risk (21% vs 5%) and mortality 1, 2

Monitoring for Osmotic Demyelination Syndrome

Watch for signs typically occurring 2-7 days after rapid correction: 1

• Dysarthria
• Dysphagia
• Oculomotor dysfunction
• Quadriparesis
• Lethargy
• Affective changes