How to manage a patient with severe hyponatremia?

Management of Severe Hyponatremia (Sodium 125 mmol/L)

For a patient with severe hyponatremia (sodium 125 mmol/L), immediately assess symptom severity and volume status to determine treatment urgency—if severely symptomatic (seizures, altered mental status, coma), administer 3% hypertonic saline targeting 6 mmol/L correction over 6 hours; if asymptomatic or mildly symptomatic, implement fluid restriction to 1-1.5 L/day for hypervolemic states or isotonic saline for hypovolemic states, never exceeding 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome. 1

Immediate Assessment Required

Symptom Severity Classification

• Severe symptoms (medical emergency): Seizures, coma, altered mental status, obtundation, cardiorespiratory distress 1, 2
• Moderate symptoms: Nausea, vomiting, confusion, headache, weakness 2, 3
• Mild/asymptomatic: Minimal or no symptoms despite low sodium 1

Volume Status Determination

• Hypovolemic signs: Orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Euvolemic signs: Normal volume status, no edema, normal blood pressure 1
• Hypervolemic signs: Peripheral edema, ascites, jugular venous distention, pulmonary congestion 1

Treatment Algorithm Based on Symptom Severity

For Severe Symptomatic Hyponatremia (Emergency)

• Administer 3% hypertonic saline immediately with target correction of 6 mmol/L over first 6 hours or until symptoms resolve 1, 2, 3
• Bolus dosing: 100 mL of 3% saline over 10 minutes, can repeat up to 3 times at 10-minute intervals 1
• Maximum correction limit: Never exceed 8 mmol/L in 24 hours 1, 2, 4
• Monitor sodium every 2 hours during initial correction phase 1
• ICU admission required for close monitoring 1

For Asymptomatic or Mildly Symptomatic Hyponatremia

If Hypovolemic (Urine Sodium <30 mmol/L)

• Discontinue diuretics immediately 1
• Administer isotonic (0.9%) saline for volume repletion 1, 3
• Correction rate: 4-8 mmol/L per day, maximum 8 mmol/L in 24 hours 1

If Euvolemic (SIADH suspected)

• Fluid restriction to 1 L/day as cornerstone of treatment 1, 3
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 1
• Consider vaptans (tolvaptan 15 mg daily, titrate to 30-60 mg) for resistant cases 1, 5
• Avoid hypertonic saline unless severely symptomatic 1

If Hypervolemic (Heart Failure, Cirrhosis)

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 3
• Discontinue diuretics temporarily until sodium improves 1
• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms present 1

Critical Correction Rate Guidelines

Standard Patients

• Target rate: 4-8 mmol/L per day 1
• Absolute maximum: 8 mmol/L in 24 hours 1, 2, 4
• Never exceed 10-12 mmol/L in 24 hours even in standard risk patients 1

High-Risk Patients (Requires Slower Correction)

High-risk populations include those with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy 1, 2

• Target rate: 4-6 mmol/L per day 1
• Absolute maximum: 6-8 mmol/L in 24 hours 1

Essential Diagnostic Workup

Initial Laboratory Tests

• Serum osmolality to exclude pseudohyponatremia 1, 4
• Urine osmolality and urine sodium to determine etiology 1, 3
• Serum uric acid (<4 mg/dL suggests SIADH with 73-100% positive predictive value) 1
• TSH and cortisol to rule out endocrine causes 1

Urine Studies Interpretation

• Urine sodium <30 mmol/L: Suggests hypovolemic hyponatremia, predicts 71-100% response to saline 1
• Urine sodium >20-40 mmol/L with urine osmolality >300 mOsm/kg: Suggests SIADH 1

Pharmacological Options

Tolvaptan (Vasopressin Receptor Antagonist)

• Starting dose: 15 mg once daily, titrate to 30-60 mg as needed 5
• Indication: Euvolemic or hypervolemic hyponatremia resistant to fluid restriction 1, 5
• Hospital initiation required to monitor correction rate 5
• Maximum duration: 30 days to minimize liver injury risk 5
• Avoid fluid restriction during first 24 hours of tolvaptan therapy 5
• Contraindicated with strong CYP3A inhibitors (ketoconazole increases tolvaptan exposure 5.4-fold) 5

Special Cautions with Tolvaptan

• Cirrhotic patients: Higher gastrointestinal bleeding risk (10% vs 2% placebo) 1, 5
• Monitor for hypernatremia: Occurs in 1.7% of patients 5
• Risk of osmotic demyelination if correction too rapid 5

Critical Safety Considerations

Preventing Osmotic Demyelination Syndrome

• Never exceed 8 mmol/L correction in 24 hours for chronic hyponatremia 1, 2, 4
• Monitor sodium every 2 hours during active correction 1
• Watch for ODS symptoms 2-7 days post-correction: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1

If Overcorrection Occurs

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider desmopressin to slow or reverse rapid sodium rise 1
• Goal: Bring total 24-hour correction to ≤8 mmol/L from starting point 1

Common Pitfalls to Avoid

• Ignoring mild hyponatremia (130-135 mmol/L)—even mild levels increase fall risk 21% vs 5% and mortality 60-fold 1, 2
• Using fluid restriction in cerebral salt wasting—worsens outcomes, requires volume replacement instead 1
• Inadequate monitoring during correction—check sodium every 2-4 hours initially 1
• Using hypertonic saline in hypervolemic states without life-threatening symptoms—worsens edema 1
• Failing to identify underlying cause—treat etiology alongside sodium correction 1
• Overly rapid correction exceeding 8 mmol/L/24 hours—causes osmotic demyelination syndrome 1, 2, 6

Monitoring Protocol

During Active Correction

• Severe symptoms: Check sodium every 2 hours 1
• Mild symptoms: Check sodium every 4 hours 1
• After symptom resolution: Check sodium every 4-6 hours until stable 1

Long-Term Management

• Daily weights to track fluid balance 1
• Monitor for underlying cause resolution 1
• Resume fluid restriction after discontinuing tolvaptan 5