What is the treatment for hyponatremia?

Treatment of Hyponatremia

The treatment of hyponatremia depends critically on symptom severity and volume status, with severe symptomatic cases requiring immediate 3% hypertonic saline to correct sodium by 6 mmol/L over 6 hours, while asymptomatic cases are managed based on whether the patient is hypovolemic (isotonic saline), euvolemic (fluid restriction), or hypervolemic (fluid restriction with underlying disease management). 1

Initial Assessment

Before initiating treatment, rapidly determine three key factors:

• Symptom severity: Severe symptoms include seizures, coma, altered mental status, or cardiorespiratory distress; mild symptoms include nausea, vomiting, headache, or weakness 1, 2
• Volume status: Assess for orthostatic hypotension, dry mucous membranes, skin turgor (hypovolemic); peripheral edema, ascites, jugular venous distention (hypervolemic); or absence of these findings (euvolemic) 1
• Chronicity: Acute (<48 hours) versus chronic (>48 hours) onset, as this determines safe correction rates 1

Obtain serum and urine osmolality, urine sodium, and uric acid to determine the underlying cause, but do not delay treatment while pursuing diagnosis 1, 3

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with seizures, coma, confusion, or severe neurological symptoms:

• Administer 3% hypertonic saline immediately as 100-150 mL IV bolus over 10 minutes, repeatable up to three times at 10-minute intervals 1, 4
• Target correction: 6 mmol/L over the first 6 hours or until severe symptoms resolve 1
• Maximum correction limit: 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
• Monitor serum sodium every 2 hours during initial correction 1
• Consider ICU admission for close monitoring 1

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment is determined by volume status:

Treatment Based on Volume Status

Hypovolemic Hyponatremia

Characterized by: Orthostatic hypotension, dry mucous membranes, decreased skin turgor, urine sodium <30 mmol/L 1

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion 1, 3
• Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1
• Once euvolemic, reassess and adjust therapy based on sodium levels 1

Euvolemic Hyponatremia (SIADH)

Characterized by: Normal volume status, urine sodium >20-40 mmol/L, urine osmolality >300 mOsm/kg 1

First-line treatment:

• Fluid restriction to 1 L/day (or 500 mL/day initially, adjusted based on response) 1, 4
• Adequate solute intake (salt and protein) 4

Second-line options if fluid restriction fails (occurs in ~50% of patients) 4:

• Oral urea: Very effective and safe, though palatability is poor 2
• Oral sodium chloride tablets: 100 mEq three times daily 1
• Tolvaptan (vasopressin V2 receptor antagonist): Start 15 mg once daily, titrate to 30-60 mg based on response 1, 5
  • Increases serum sodium significantly more than placebo, with effects seen within 8 hours 5
  • Monitor closely to avoid overly rapid correction 1
  • Side effects include thirst, dry mouth, polyuria 6

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Characterized by: Peripheral edema, ascites, jugular venous distention 1

• 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
• Treat underlying condition (optimize heart failure management, manage cirrhosis) 3
• For cirrhotic patients: Consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens edema and ascites 1
• Tolvaptan may be considered for persistent severe hyponatremia despite fluid restriction and guideline-directed medical therapy 1, 5

Critical Correction Rate Guidelines

Standard correction rates (to prevent osmotic demyelination syndrome):

• Maximum correction: 8 mmol/L in 24 hours for most patients 1, 2
• Target rate: 4-8 mmol/L per day, not exceeding 10-12 mmol/L in 24 hours 1

High-risk patients require slower correction (4-6 mmol/L per day, maximum 8 mmol/L in 24 hours) 1, 7:

• Advanced liver disease
• Alcoholism
• Malnutrition
• Severe hyponatremia (<120 mmol/L)
• Prior encephalopathy
• Hypophosphatemia, hypokalemia, hypoglycemia 7

Special Considerations

Neurosurgical Patients (Cerebral Salt Wasting vs. SIADH)

Cerebral salt wasting is more common than SIADH in neurosurgical patients and requires fundamentally different treatment 1:

• CSW treatment: Volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1
• For severe symptoms: 3% hypertonic saline plus fludrocortisone 1
• Never use fluid restriction in CSW, as this worsens outcomes 1
• In subarachnoid hemorrhage patients at risk of vasospasm, avoid fluid restriction and consider fludrocortisone or hydrocortisone 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours 1, 7:

• Immediately discontinue current fluids
• Switch to D5W (5% dextrose in water) to relower sodium levels
• Consider administering desmopressin to slow or reverse the rapid rise
• Target reduction to bring total 24-hour correction to ≤8 mmol/L from baseline

Monitoring Requirements

• Severe symptoms: Check serum sodium every 2 hours during initial correction 1
• After symptom resolution: Every 4 hours 1
• Asymptomatic patients: Daily initially, then adjust frequency based on response 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1, 7

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leads to osmotic demyelination syndrome 1, 7
• Using fluid restriction in cerebral salt wasting worsens outcomes 1
• Inadequate monitoring during active correction 1
• Ignoring mild hyponatremia (130-135 mmol/L), which increases fall risk and mortality 2
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Failing to identify and treat the underlying cause 1