What is the recommended approach for correcting severe hyponatremia?

Severe Hyponatremia Correction

For severe symptomatic hyponatremia (seizures, coma, altered mental status), immediately administer 3% hypertonic saline with an initial target of 6 mmol/L correction over 6 hours or until severe symptoms resolve, but never exceed 8 mmol/L total correction in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

Before initiating treatment, determine three critical factors:

• Symptom severity: Severe symptoms include seizures, coma, confusion, or cardiorespiratory distress requiring immediate intervention 1, 2
• Acuity: Acute (<48 hours) versus chronic (>48 hours) onset, as chronic cases require more cautious correction 1
• Volume status: Hypovolemic, euvolemic, or hypervolemic, which guides underlying etiology and subsequent management 1

Check serum and urine osmolality, urine sodium, and assess extracellular fluid volume status to determine the underlying cause 1.

Emergency Management for Severe Symptomatic Hyponatremia

Immediate Hypertonic Saline Protocol

Administer 3% hypertonic saline immediately for patients with severe neurological symptoms 1, 2:

• Initial bolus: 100 mL of 3% saline over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve 1
• Target correction: Increase sodium by 6 mmol/L over the first 6 hours or until severe symptoms resolve 1, 3
• Monitoring frequency: Check serum sodium every 2 hours during initial correction 1

Critical Safety Limits

The most important principle is never exceed 8 mmol/L correction in any 24-hour period 1, 3, 4. This limit is absolute and takes precedence over symptom resolution 1.

• After achieving the initial 6 mmol/L correction, limit further correction to only 2 mmol/L in the following 18 hours 3
• For high-risk patients (advanced liver disease, alcoholism, malnutrition, severe hyponatremia), use even more conservative rates of 4-6 mmol/L per day 1, 4

When to Stop 3% Saline

Discontinue 3% hypertonic saline when severe symptoms resolve 3:

• Transition to protocols for mild symptoms or asymptomatic hyponatremia 3
• Switch monitoring from every 2 hours to every 4 hours 3
• Implement fluid restriction to 1 L/day 3
• Continue treatment until sodium reaches 131 mmol/L 3

Management Based on Volume Status

Hypovolemic Hyponatremia

Begin with isotonic (0.9%) saline to restore intravascular volume 1:

• Discontinue diuretics immediately 1
• Urinary sodium <30 mmol/L predicts response to saline with 71-100% positive predictive value 1
• Once euvolemic, reassess and adjust therapy based on sodium response 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment for mild to moderate cases 1, 3:

• For severe symptoms, use 3% hypertonic saline as described above 1
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• Avoid fluid restriction during the first 24 hours of hypertonic saline therapy 4

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1:

• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1
• Temporarily discontinue diuretics if sodium <125 mmol/L 1

Special Populations Requiring Extra Caution

High-Risk Patients for Osmotic Demyelination

Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require correction rates of only 4-6 mmol/L per day 1, 4:

• These patients have a 0.5-1.5% risk of osmotic demyelination syndrome even with appropriate correction 1
• Monitor for signs of osmotic demyelination (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1, 4

Neurosurgical Patients

Distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches differ fundamentally 1:

• CSW requires volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1
• For CSW with severe symptoms, use 3% hypertonic saline plus fludrocortisone 1
• In subarachnoid hemorrhage patients at risk for vasospasm, avoid fluid restriction even for mild hyponatremia 1

Managing Overcorrection

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

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1, 5
• Target relowering to bring total 24-hour correction to no more than 8 mmol/L from baseline 1

Pharmacological Options for Refractory Cases

Vasopressin Receptor Antagonists (Tolvaptan)

Tolvaptan is FDA-approved for euvolemic or hypervolemic hyponatremia but requires hospital initiation 4:

• Starting dose: 15 mg once daily, can titrate to 30-60 mg after at least 24 hours 4
• Must be initiated in hospital with close sodium monitoring due to risk of overly rapid correction 4
• Avoid fluid restriction during first 24 hours of tolvaptan therapy 4
• Do not use for more than 30 days due to hepatotoxicity risk 4
• Contraindicated in hypovolemic hyponatremia and with strong CYP3A inhibitors 4
• In cirrhotic patients, tolvaptan carries higher risk of gastrointestinal bleeding (10% vs 2% placebo) 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leading to osmotic demyelination syndrome 1
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting, which worsens outcomes 1
• Failing to recognize high-risk patients who need slower correction rates 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Ignoring mild hyponatremia (130-135 mmol/L), which increases fall risk and mortality 1

Monitoring Protocol

During Active Correction

• Severe symptoms: Check sodium every 2 hours initially 1
• After symptom resolution: Check every 4 hours 1, 3
• Subsequent days: Daily monitoring until stable 1

Post-Treatment

After discontinuing therapy, patients should resume fluid restriction and be monitored for changes in sodium and volume status 4.