How should hyponatremia be treated based on its severity, symptoms, and underlying cause?

Treatment of Hyponatremia

Hyponatremia treatment is determined by symptom severity, volume status, and underlying cause, with the overriding principle that sodium correction must never exceed 8 mmol/L in any 24-hour period to prevent osmotic demyelination syndrome. 1

Immediate Assessment and Symptom-Based Treatment

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, 2

• Give 100 mL boluses of 3% NaCl over 10 minutes, repeating up to three times at 10-minute intervals 3
• Check serum sodium every 2 hours during initial correction 1
• Total correction must not exceed 8 mmol/L in 24 hours 1, 2
• ICU admission is required for close monitoring 1

Mild to Moderate Symptoms or Asymptomatic

Treatment depends on volume status (see below) 3, 2

Treatment Based on Volume Status

Hypovolemic Hyponatremia

Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion. 1

• Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 4
• Urine sodium <30 mmol/L predicts good response to saline (positive predictive value 71-100%) 1
• For cirrhotic patients, consider albumin infusion (8 g per liter of ascites removed) alongside isotonic saline 1
• Correction rate: 4-6 mmol/L per day for high-risk patients (cirrhosis, alcoholism, malnutrition), maximum 8 mmol/L in 24 hours 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment. 1, 2

• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For severe symptoms: 3% hypertonic saline with goal of 6 mmol/L correction over 6 hours 1
• Pharmacological options for resistant cases:
  • Vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrate to 30-60 mg) 1, 5
  • Urea 1, 2
  • Demeclocycline 1
  • Loop diuretics 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L. 1, 3

• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• For cirrhosis: consider albumin infusion 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1
• Treat underlying condition (optimize heart failure management, manage cirrhosis) 3, 2

Critical Correction Rate Guidelines

Standard correction rate: 4-8 mmol/L per day, not exceeding 10-12 mmol/L in 24 hours. 1

High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours. 1

• Overly rapid correction causes osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically 2-7 days after correction 1
• Risk of osmotic demyelination syndrome is 0.5-1.5% in liver transplant recipients 1

Special Populations

Neurosurgical Patients: Cerebral Salt Wasting vs. SIADH

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

• CSW: Treat with volume and sodium replacement (isotonic or hypertonic saline), NOT fluid restriction 1
  • For severe symptoms: 3% hypertonic saline plus fludrocortisone 0.1-0.2 mg daily in ICU 1
  • Hydrocortisone may prevent natriuresis in subarachnoid hemorrhage patients 1
• SIADH: Treat with fluid restriction 1
• In subarachnoid hemorrhage patients at risk of vasospasm: never use fluid restriction 1

Cirrhotic Patients

More cautious correction (4-6 mmol/L per day) due to higher risk of osmotic demyelination syndrome. 1

• Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Fluid restriction may prevent further decline but rarely improves sodium significantly 1
• Sodium restriction (not fluid restriction) results in weight loss as fluid follows sodium 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, 6
• Goal: bring total 24-hour correction back to ≤8 mmol/L from baseline 1

Pharmacological Agents

Vasopressin Receptor Antagonists (Vaptans)

Tolvaptan is indicated for euvolemic or hypervolemic hyponatremia resistant to fluid restriction. 1, 5

• Starting dose: 15 mg once daily, titrate to 30-60 mg based on response 1, 5
• Avoid fluid restriction during first 24 hours to prevent overly rapid correction 5
• Monitor sodium every 8 hours initially 5
• Caution in cirrhosis: higher risk of gastrointestinal bleeding (10% vs. 2% placebo) 1
• Use limited to ≤30 days in cirrhotic patients due to hepatotoxicity risk 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leads to osmotic demyelination syndrome 1
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting worsens outcomes 1
• Failing to recognize and treat the underlying cause 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, when it increases fall risk and mortality 1, 2

Monitoring Requirements

• Severe symptoms: serum sodium every 2 hours during initial correction 1
• After symptom resolution: serum sodium every 4 hours 1
• Mild symptoms: serum sodium every 24-48 hours initially 1
• Watch for signs of osmotic demyelination syndrome 2-7 days after correction 1