What is the treatment for hyponatremia (low sodium levels)?

Treatment of Hyponatremia

For hyponatremia treatment, the approach 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 or mild cases are managed with fluid restriction (1 L/day for euvolemic) or isotonic saline (for hypovolemic), always limiting total correction to 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Determine symptom severity immediately - this dictates urgency of treatment:

• Severe symptoms (seizures, coma, altered mental status, cardiorespiratory distress) require emergency intervention 1, 2
• Mild symptoms (nausea, vomiting, headache, weakness) allow for more measured approach 3
• Asymptomatic hyponatremia permits diagnostic workup before treatment 1

Assess volume status through physical examination:

• Hypovolemic: orthostatic hypotension, dry mucous membranes, decreased skin turgor 1
• Euvolemic: no edema, normal blood pressure, normal skin turgor 1
• Hypervolemic: peripheral edema, ascites, jugular venous distention 1

Obtain essential labs: serum and urine osmolality, urine sodium, urine electrolytes, serum creatinine 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

Administer 3% hypertonic saline immediately 1, 2, 3:

• Give as 100-150 mL IV bolus over 10 minutes 1
• Can repeat up to 3 times at 10-minute intervals 1
• Target: increase sodium by 6 mmol/L over first 6 hours OR until symptoms resolve 1
• Critical limit: do not exceed 8 mmol/L correction in 24 hours 1, 4

Monitor serum sodium every 2 hours during initial correction phase 1

The FDA label for tolvaptan explicitly warns that correction >12 mEq/L per 24 hours can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, seizures, coma and death 4. The guideline consensus is more conservative at 8 mmol/L per 24 hours 1.

Mild Symptomatic or Asymptomatic Hyponatremia

Treatment depends on volume status:

For Hypovolemic Hyponatremia:

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion 1
• Urine sodium <30 mmol/L predicts response to saline with 71-100% positive predictive value 1

For Euvolemic Hyponatremia (SIADH):

• First-line: Fluid restriction to 1 L/day 1, 2
• If no response after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1
• Second-line options for resistant cases: urea or vaptans (tolvaptan) 1, 2, 5
• Urea is considered very effective and safe, though has poor palatability 2, 5
• Tolvaptan 15 mg once daily, can titrate to 30-60 mg 4

For Hypervolemic Hyponatremia (heart failure, cirrhosis):

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms present - it worsens edema and ascites 1

Critical Correction Rate Guidelines

Standard correction rates 1:

• Maximum 8 mmol/L in 24 hours for most patients
• For severe symptoms: 6 mmol/L over first 6 hours, then slow to reach 8 mmol/L total at 24 hours

High-risk patients require slower correction (4-6 mmol/L per day) 1:

• Advanced liver disease
• Alcoholism
• Malnutrition
• Prior encephalopathy
• Severe hyponatremia (<120 mmol/L)

These patients have 0.5-1.5% risk of osmotic demyelination syndrome even with appropriate correction 1.

Special Populations

Neurosurgical patients require distinction between SIADH and cerebral salt wasting (CSW) 1:

• CSW: Treat with volume and sodium replacement (isotonic or hypertonic saline), NOT fluid restriction 1
• Add fludrocortisone for severe symptoms 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Cirrhotic patients 1:

• Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36)
• Tolvaptan carries higher risk of GI bleeding (10% vs 2% placebo) 1
• More cautious correction rates essential

Management of Overcorrection

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

• Immediately discontinue current fluids
• Switch to D5W (5% dextrose in water)
• Consider administering desmopressin to slow or reverse the rapid rise
• This prevents osmotic demyelination syndrome

Common Pitfalls to Avoid

• Never use fluid restriction in cerebral salt wasting - worsens outcomes 1
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Never correct chronic hyponatremia faster than 8 mmol/L per 24 hours 1, 4
• Never ignore mild hyponatremia (130-135 mmol/L) - increases fall risk and mortality 1
• Never fail to monitor sodium levels frequently during active correction 1

Pharmacological Options

Tolvaptan (vasopressin receptor antagonist) 4:

• FDA-approved for euvolemic and hypervolemic hyponatremia
• Starting dose: 15 mg once daily, can increase to 30-60 mg
• Must initiate in hospital with close sodium monitoring 4
• Avoid fluid restriction during first 24 hours of tolvaptan therapy 4
• Do not use for >30 days due to liver injury risk 4
• Contraindicated in hypovolemic hyponatremia 4
• In clinical trials, increased sodium by 4.0 mmol/L at Day 4 vs 0.4 mmol/L with placebo 4