How is hyponatremia (low sodium levels) treated?

Treatment of Hyponatremia

The treatment of hyponatremia should be based on volume status assessment, symptom severity, and underlying cause, with correction rates carefully controlled to prevent osmotic demyelination syndrome. 1

Initial Assessment

• Hyponatremia is defined as serum sodium <135 mmol/L and should be evaluated based on volume status and serum osmolality 1
• Initial workup should include serum and urine osmolarity, urine electrolytes, uric acid, and assessment of extracellular fluid volume status 1
• Categorize patients according to their fluid volume status: hypovolemic, euvolemic, or hypervolemic hyponatremia 2

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (seizures, coma, severe neurological symptoms)

• Administer 3% hypertonic saline with a goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1
• Maximum correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 3
• For patients with advanced liver disease, alcoholism, or malnutrition, use more cautious correction rates (4-6 mmol/L per day) due to higher risk of osmotic demyelination 1
• ICU admission with close monitoring is recommended during treatment 1

Mild to Moderate Symptomatic Hyponatremia

• For hypovolemic hyponatremia: discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1, 4
• For euvolemic hyponatremia (SIADH): implement fluid restriction to 1L/day as first-line treatment 1, 2
• For hypervolemic hyponatremia (cirrhosis, heart failure): fluid restriction to 1000-1500 mL/day for moderate hyponatremia and more severe fluid restriction plus albumin infusion for severe hyponatremia 1, 4

Treatment Based on Specific Causes

Syndrome of Inappropriate ADH (SIADH)

• Primary treatment is fluid restriction to 1 L/day for mild/asymptomatic cases 1
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For resistant cases, consider pharmacological options including vasopressin receptor antagonists (tolvaptan), urea, demeclocycline, or lithium 1, 5
• Tolvaptan has been shown to effectively increase serum sodium levels in patients with euvolemic or hypervolemic hyponatremia 5

Cerebral Salt Wasting (CSW)

• Treatment focuses on volume and sodium replacement, not fluid restriction 1
• For severe symptoms, administer 3% hypertonic saline and consider fludrocortisone 1
• Distinguish from SIADH as treatment approaches differ significantly 1

Hypervolemic Hyponatremia (Cirrhosis, Heart Failure)

• Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L 1
• Consider albumin infusion for patients with cirrhosis 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1

Correction Rate Guidelines

• Maximum increase of 8 mmol/L in 24 hours for most patients 1, 3
• For severe symptoms (seizures, coma), correction by 6 mmol/L over 6 hours or until symptoms improve 1
• For chronic hyponatremia, avoid rapid correction exceeding 1 mmol/L/hour 1
• Patients with advanced liver disease require more cautious correction (4-6 mmol/L per day) 1

Monitoring During Treatment

• For severe symptoms: monitor serum sodium every 2 hours during initial correction 1
• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Pharmacological Options

• Vasopressin receptor antagonists (vaptans) may be considered for euvolemic or hypervolemic hyponatremia resistant to fluid restriction 1, 5
• Tolvaptan starting dose is 15 mg once daily, which can be increased to 30 mg and then 60 mg if needed 5
• Urea can be effective for SIADH but may have poor palatability and gastric intolerance 2

Common Pitfalls to Avoid

• Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1, 3
• 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

Clinical Significance

• Even mild hyponatremia is associated with increased hospital stay, mortality, cognitive impairment, gait disturbances, and increased rates of falls and fractures 2, 3
• Hyponatremia increases fall risk - 21% of hyponatremic patients present with falls compared to 5% of normonatremic patients 1
• In cirrhotic patients, sodium ≤130 mEq/L increases risk for hepatic encephalopathy, hepatorenal syndrome, and spontaneous bacterial peritonitis 1