What is the recommended acute management for a symptomatic patient with severe hyponatraemia (serum sodium <120 mmol/L) presenting with confusion, seizures, severe headache, vomiting, or coma?

Severe Hyponatremia Management

For a symptomatic patient with severe hyponatremia (serum sodium <120 mmol/L) presenting with confusion, seizures, severe headache, vomiting, or coma, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over the first 6 hours or until severe symptoms resolve, while ensuring total correction does not exceed 8 mmol/L in any 24-hour period. 1

Immediate Emergency Management

Initial Bolus Administration

• Administer 100 mL boluses of 3% hypertonic saline intravenously over 10 minutes, which can be repeated up to three times at 10-minute intervals until severe neurological symptoms improve 1
• This approach is specifically indicated for patients presenting with confusion, seizures, coma, severe headache, vomiting, or respiratory distress 1, 2
• The goal is to raise serum sodium by approximately 1-2 mmol/L per hour during the initial emergency phase 3

ICU Admission and Monitoring

• Admit to intensive care unit for close monitoring during active correction 1
• Check serum sodium every 2 hours during the initial correction phase for patients with severe symptoms 1
• After severe symptoms resolve, continue monitoring every 4 hours 1

Critical Correction Rate Guidelines

Standard Correction Limits

• Maximum correction of 8 mmol/L in any 24-hour period to prevent osmotic demyelination syndrome 1, 4
• Target correction of 6 mmol/L over the first 6 hours, which means only 2 mmol/L additional correction is permitted in the remaining 18 hours 1
• Do not aim for normonatremia acutely—the therapeutic goal is 125-130 mmol/L, not the normal range 1

High-Risk Populations Requiring Slower Correction

• Patients with advanced liver disease, chronic alcoholism, malnutrition, severe hyponatremia, or prior hepatic encephalopathy require even more cautious correction at 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1, 4
• These patients have a 0.5-1.5% risk of osmotic demyelination syndrome even with careful correction 1

Treatment Based on Volume Status

After Initial Stabilization

Once severe symptoms are controlled, determine the underlying etiology based on volume status:

For Hypovolemic Hyponatremia:

• 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
• Urine sodium <30 mmol/L predicts good response to saline infusion 1

For 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
• Consider vasopressin receptor antagonists (tolvaptan 15 mg once daily) for resistant cases 1

For Hypervolemic Hyponatremia (cirrhosis, heart failure):

• 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 ascites and edema 1

Special Considerations for Neurosurgical Patients

Distinguishing Cerebral Salt Wasting from SIADH

• In neurosurgical patients, cerebral salt wasting (CSW) is more common than SIADH and requires opposite treatment 1
• CSW is characterized by true hypovolemia with CVP <6 cm H₂O, high urine sodium >20 mmol/L despite volume depletion, and evidence of extracellular volume depletion 1
• Never use fluid restriction in CSW—this worsens outcomes and can precipitate cerebral ischemia 1

Treatment of CSW

• Aggressive volume and sodium replacement with isotonic or hypertonic saline (50-100 mL/kg/day) 1
• For severe symptoms, add fludrocortisone 0.1-0.2 mg daily 1
• In subarachnoid hemorrhage patients at risk of vasospasm, never use fluid restriction—consider hydrocortisone to prevent natriuresis 1

Management of Overcorrection

If Sodium Rises Too Rapidly

• If correction exceeds 8 mmol/L in 24 hours, immediately discontinue hypertonic saline 1
• Switch to D5W (5% dextrose in water) to relower sodium levels 1
• Consider administering desmopressin to slow or reverse the rapid rise 1
• Target is to bring the total 24-hour correction back to ≤8 mmol/L from baseline 1

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—this causes osmotic demyelination syndrome with dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis typically 2-7 days after rapid correction 1, 4
• Do not delay treatment while pursuing diagnostic workup—treat severe symptoms immediately 5
• Inadequate monitoring during active correction can lead to overcorrection 1
• Using fluid restriction as initial treatment for altered mental status from hyponatremia is dangerous—this is a medical emergency requiring hypertonic saline 1
• Failing to distinguish between SIADH and CSW in neurosurgical patients leads to opposite and potentially harmful treatments 1
• Mortality in severe hyponatremia remains high at approximately 20%, with sepsis, respiratory failure, and presence of neurologic symptoms predicting poor outcome 6