What is the best way to treat hyponatremia?

Treatment of Hyponatremia

The best approach to treating hyponatremia depends on symptom severity, volume status, and chronicity, 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 plus treatment of underlying condition), always limiting total correction to 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Before initiating treatment, rapidly determine three critical factors:

• Symptom severity: Assess for severe symptoms including seizures, coma, altered mental status, confusion, or cardiorespiratory distress versus mild symptoms (nausea, headache, weakness) versus asymptomatic 1, 2
• Volume status: Evaluate for hypovolemia (orthostatic hypotension, dry mucous membranes, decreased skin turgor), euvolemia (normal examination), or hypervolemia (edema, ascites, jugular venous distention) 1, 3
• Chronicity: Determine if onset is acute (<48 hours) or chronic (>48 hours), as this affects correction rate safety 1

Obtain serum and urine osmolality, urine sodium, and urine electrolytes to determine the underlying cause, though treatment should not be delayed while pursuing diagnosis 1, 2

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with seizures, coma, altered mental status, or severe neurological symptoms:

• Immediately administer 3% hypertonic saline as 100-150 mL IV bolus over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve 1, 4
• Target correction: Increase sodium by 6 mmol/L over the first 6 hours or until severe symptoms resolve 1, 2
• Maximum correction limit: Do not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 3
• 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: Urine sodium <30 mmol/L, signs of volume depletion 1, 5

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1
• Urinary sodium <30 mmol/L predicts 71-100% positive response to saline infusion 1
• Once euvolemic, reassess and adjust management based on sodium levels 1

Euvolemic Hyponatremia (SIADH)

Characterized by: Urine sodium >20-40 mmol/L, urine osmolality >300 mOsm/kg, normal volume status 1, 5

First-line treatment:

• Fluid restriction to 1 L/day is the cornerstone of therapy 1, 3
• Approximately 50% of SIADH patients do not respond to fluid restriction alone 4

Second-line options if fluid restriction fails:

• Add oral sodium chloride 100 mEq three times daily 1
• Urea (very effective and safe second-line option) 4
• Tolvaptan 15 mg once daily, titrated to 30-60 mg based on response 6, 3
• Alternative agents: demeclocycline, lithium, or loop diuretics (less commonly used due to side effects) 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Characterized by: Edema, ascites, elevated jugular venous pressure 1, 3

Management approach:

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 2
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• For cirrhotic patients: Consider albumin infusion alongside fluid restriction 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) 2, 3
• Tolvaptan may be considered for persistent severe hyponatremia despite fluid restriction and optimization of guideline-directed therapy, but use with extreme caution in cirrhosis due to increased gastrointestinal bleeding risk (10% vs 2% placebo) 6, 3

Critical Correction Rate Guidelines

Standard correction rates (to prevent osmotic demyelination syndrome):

• Maximum correction: 8 mmol/L in 24 hours for all patients 1, 2, 3
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): Limit to 4-6 mmol/L per day 1, 4
• For severe symptoms: 6 mmol/L over first 6 hours, then slow to achieve no more than 8 mmol/L total in 24 hours 1, 2

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 in serum sodium 1, 7
• Therapeutic relowering with electrolyte-free water or desmopressin is supported by animal data and small clinical trials 7
• Monitor closely for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Special Populations

Neurosurgical Patients (Cerebral Salt Wasting vs SIADH)

Critical distinction: Cerebral salt wasting (CSW) requires opposite treatment from SIADH 1, 3

CSW characteristics:

• True hypovolemia with low central venous pressure (<6 cm H₂O) 1
• Urine sodium >20 mmol/L despite volume depletion 1
• More common in poor clinical grade, ruptured anterior communicating artery aneurysms 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
• Hydrocortisone may prevent natriuresis in subarachnoid hemorrhage patients 1
• Never use fluid restriction in CSW or subarachnoid hemorrhage patients at risk of vasospasm 1

Cirrhotic Patients

• Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Require more cautious correction (4-6 mmol/L per day) due to higher osmotic demyelination risk 1
• Sodium restriction (not fluid restriction) results in weight loss as fluid follows sodium 1
• Reserve hypertonic saline only for life-threatening symptoms 1

Monitoring Requirements

• Severe symptoms: Check serum sodium every 2 hours during initial correction 1
• After symptom resolution: Check every 4 hours 1
• Asymptomatic patients: Daily monitoring until stable 1
• Track daily weights, fluid balance, and clinical status 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leads to osmotic demyelination syndrome 1, 3
• Using fluid restriction in CSW worsens outcomes 1
• Inadequate monitoring during active correction 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—even mild hyponatremia increases fall risk (21% vs 5%), fracture risk, and mortality 1, 3