What is the treatment for acute hyponatremia?

Treatment of Acute Hyponatremia

The treatment of acute hyponatremia should be guided by symptom severity, with severe symptomatic cases requiring 3% hypertonic saline to correct sodium by 6 mmol/L over 6 hours or until symptoms resolve, while limiting total correction to 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 2

Assessment and Classification

• Evaluate volume status and serum osmolality to determine the underlying cause of hyponatremia (serum sodium <135 mmol/L) 2
• Categorize as hypovolemic, euvolemic, or hypervolemic hyponatremia to guide appropriate treatment 2, 3
• Assess symptom severity: severe symptoms include mental status changes, seizures, or coma; mild symptoms include nausea, vomiting, headache, and general malaise 2, 3
• Determine acuity of onset: acute (<48 hours) versus chronic (>48 hours) 1, 2

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Mental Status Changes, Seizures, Coma)

• Administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2
• Total correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 2, 4
• Monitor serum sodium every 2 hours during initial correction 2
• Consider ICU admission for close monitoring during treatment 1, 2
• Recent evidence suggests that a 250 mL bolus of 3% NaCl is more effective than 100 mL for initial treatment of severe hyponatremia 5

Mild Symptomatic or Asymptomatic Hyponatremia

• For mild symptoms or serum sodium <120-125 mmol/L: implement fluid restriction to 1 L/day 1, 2
• Consider oral sodium supplementation (NaCl 100 mEq orally three times daily) if no response to fluid restriction 2, 4
• Monitor serum sodium every 4-6 hours initially 2
• High protein diet to augment solute intake 4

Treatment Based on Etiology

Syndrome of Inappropriate ADH (SIADH)

• Primary treatment is fluid restriction to 1 L/day 1, 2
• If no response, add oral sodium chloride 100 mEq three times daily 2, 4
• For refractory cases, consider tolvaptan (vasopressin receptor antagonist) starting at 15 mg once daily 2, 6
• Tolvaptan has been shown to effectively increase serum sodium levels in patients with euvolemic or hypervolemic hyponatremia 6

Cerebral Salt Wasting (CSW)

• Volume repletion with normal saline is the primary approach 1, 2
• For severe symptoms, administer 3% hypertonic saline and fludrocortisone 1, 2
• Avoid fluid restriction as it can worsen outcomes 2

Hypervolemic Hyponatremia (Cirrhosis, Heart Failure)

• Fluid restriction to 1000 mL/day for moderate hyponatremia (120-125 mEq/L) 1, 2
• More severe fluid restriction plus albumin infusion for severe hyponatremia (<120 mEq/L) 1, 2
• Discontinue diuretics if they're contributing to hyponatremia 2
• Avoid hypertonic saline unless life-threatening symptoms are present 2

Hypovolemic Hyponatremia

• Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 2
• Once euvolemia is achieved, reassess for persistent hyponatremia 2

Special Considerations and Pitfalls

• Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy are at higher risk for osmotic demyelination syndrome and require more cautious correction (4-6 mmol/L per day) 1, 2
• Avoid using fluid restriction in CSW as it can worsen outcomes 2
• Normal saline may worsen hyponatremia in SIADH but is appropriate for CSW 2
• Risk of overcorrection is higher in severely symptomatic patients; monitor diuresis closely as it correlates with sodium overcorrection 4
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1

Monitoring and Follow-up

• For severe symptoms: monitor serum sodium every 2 hours during initial correction 1, 2
• For mild symptoms: monitor serum sodium every 4-6 hours initially, then daily 2, 4
• Calculate sodium deficit to guide treatment and prevent overcorrection 2, 4
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1