How is hyponatremia corrected?

Hyponatremia Correction

The treatment of hyponatremia should be based on symptom severity, onset timing, and underlying cause, with a maximum correction rate of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

• Hyponatremia (serum sodium <135 mmol/L) should be classified by severity, volume status, and symptom severity 1
• Evaluate the patient's volume status to determine if they have hypovolemic, euvolemic, or hypervolemic hyponatremia, as this will guide appropriate treatment 1
• Check urine sodium and osmolality to help distinguish between SIADH and Cerebral Salt Wasting (CSW), as treatment approaches differ significantly 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (seizures, coma)

• Administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1
• For severe symptoms, rapid intermittent administration of hypertonic saline is preferred over continuous infusion 2
• Do not exceed total correction of 8 mmol/L over 24 hours to prevent osmotic demyelination syndrome 1

Moderate to Mild Hyponatremia

• For asymptomatic mild hyponatremia, implement fluid restriction to 1-1.5 L/day with adequate solute intake (salt and protein) 1, 2
• For chronic hyponatremia, avoid rapid correction exceeding 1 mmol/L/hour 1
• Patients with advanced liver disease require even more cautious correction (4-6 mmol/L per day) due to higher risk of osmotic demyelination 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1
• For severe dehydration with neurological symptoms, consider hypertonic saline with careful monitoring 1

Euvolemic Hyponatremia (SIADH)

• Implement fluid restriction to 1L/day for mild/asymptomatic cases 1
• For severe symptomatic cases, use 3% hypertonic saline with careful monitoring 1
• Consider vasopressin receptor antagonists (tolvaptan) for resistant cases, starting with 15 mg once daily 1, 3
• Oral urea is considered to be an effective and safe treatment alternative 2

Hypervolemic Hyponatremia (cirrhosis, heart failure)

• Implement fluid restriction to 1000 mL/day for moderate hyponatremia (120-125 mmol/L) 1
• For severe hyponatremia (<120 mmol/L), more severe fluid restriction plus albumin infusion may be necessary 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1

Pharmacological Interventions

Vasopressin Receptor Antagonists (Vaptans)

• Tolvaptan is FDA-approved for euvolemic or hypervolemic hyponatremia 3
• Initial dose is 15 mg once daily, which can be increased to 30 mg and then 60 mg once daily if needed 3
• In clinical trials, tolvaptan significantly increased serum sodium levels compared to placebo 3
• Patients on tolvaptan required less fluid restriction (14% vs 25% for placebo) 3
• Caution is advised in patients with cirrhosis due to increased risk of gastrointestinal bleeding 3

Monitoring and Safety Considerations

• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
• Monitor serum sodium levels every 2-4 hours during active correction 1
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1, 4
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Common Pitfalls to Avoid

• Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1
• Inadequate monitoring during active correction 1
• Using fluid restriction in CSW, which can worsen outcomes 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Attempting to fully normalize sodium levels too quickly rather than aiming for gradual correction 2

Special Considerations

• Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy are at higher risk for osmotic demyelination syndrome and require more cautious correction rates (4-6 mmol/L per day) 1
• Even mild and apparently asymptomatic hyponatremia may lead to falls because of impaired gait and increased likelihood of fracture due to hyponatremia-induced osteoporosis 5
• In neurosurgical patients, cerebral salt wasting (CSW) is more common than SIADH, and treatment focuses on volume and sodium replacement rather than fluid restriction 1