How do we correct symptomatic hyponatremia in a patient with severe symptoms, such as seizures or coma, and serum sodium levels below 125 mmol/L?

Management of Symptomatic Hyponatremia

For severe symptomatic hyponatremia (seizures, coma, altered mental status) with sodium <125 mmol/L, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve, with total correction not exceeding 8 mmol/L in 24 hours. 1

Immediate Emergency Management

Severe symptoms constitute a medical emergency requiring urgent hypertonic saline, not fluid restriction. 1 Severe symptoms include:

• Seizures, coma, or altered mental status 1
• Confusion, delirium, or impaired consciousness 2
• Respiratory arrest or cardiorespiratory distress 3
• Somnolence or obtundation 3

Hypertonic Saline Administration Protocol

Administer 3% hypertonic saline as 100-150 mL intravenous boluses over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve. 1, 4 This rapid intermittent bolus approach is preferred over continuous infusion for symptomatic hyponatremia. 4

The initial infusion rate (mL/kg per hour) can be estimated by: body weight (kg) × desired rate of increase in sodium (mmol/L per hour). 5

Critical Correction Rate Guidelines

The maximum correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 6 This is the single most important safety principle. 1

For the first 6 hours, correct by 6 mmol/L or until severe symptoms resolve. 1 If 6 mmol/L are corrected in the first 6 hours, only 2 mmol/L additional correction is allowed in the remaining 18 hours. 1

High-Risk Populations Requiring Slower Correction

Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require even more cautious correction at 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours. 1, 7 The FDA label for tolvaptan specifically warns that "in susceptible patients, including those with severe malnutrition, alcoholism or advanced liver disease, slower rates of correction may be advisable." 6

Overly rapid correction (>12 mEq/L/24 hours) can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma and death. 6

Intensive Monitoring Protocol

Check serum sodium every 2 hours during the initial correction phase for patients with severe symptoms. 1 After severe symptoms resolve, monitor every 4 hours. 1

ICU admission is recommended for close monitoring during treatment of severe symptomatic hyponatremia. 1

Management Based on Volume Status

Once symptoms are controlled, determine volume status to guide ongoing management:

Hypovolemic Hyponatremia

• Discontinue diuretics immediately and administer isotonic saline (0.9% NaCl) for volume repletion. 1, 2
• Urine sodium <30 mmol/L predicts good response to saline infusion. 1

Euvolemic Hyponatremia (SIADH)

• After symptom resolution, implement fluid restriction to 1 L/day. 1
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily. 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L. 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen fluid overload. 1
• Consider albumin infusion in cirrhotic patients. 1

Special Considerations for Neurosurgical Patients

In neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW), as they require opposite treatments. 1

CSW is characterized by:

• True hypovolemia with low central venous pressure (<6 cm H₂O) 1
• High urine sodium >20 mmol/L despite volume depletion 1
• Clinical signs of volume depletion (hypotension, tachycardia, dry mucous membranes) 1

CSW requires volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction. 1 For severe symptoms, add fludrocortisone 0.1-0.2 mg daily. 1

Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm. 1

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

Recent experimental data suggest that rapidly decreasing serum sodium through hypotonic fluids and dDAVP in overly corrected patients could greatly reduce the risk of myelinolysis. 7

Common Pitfalls to Avoid

• Never use fluid restriction as initial treatment for altered mental status from hyponatremia—this is a medical emergency requiring hypertonic saline. 1
• Never exceed 8 mmol/L correction in 24 hours—overcorrection risks osmotic demyelination syndrome. 1
• Inadequate monitoring during active correction is a common pitfall. 1
• Using fluid restriction in cerebral salt wasting worsens outcomes. 1
• Failing to recognize and treat the underlying cause can lead to poor outcomes. 1

Role of Vaptans

Tolvaptan should be initiated and re-initiated only in a hospital where serum sodium can be monitored closely. 6 The FDA label states that "patients requiring intervention to raise serum sodium urgently to prevent or to treat serious neurological symptoms should not be treated with tolvaptan tablets." 6

Vaptans are not appropriate for emergency management of severe symptomatic hyponatremia. 6 They are reserved for euvolemic or hypervolemic hyponatremia that is refractory to fluid restriction. 1