What is the treatment for seizures in severe hyponatremia?

Treatment of Seizures in Severe Hyponatremia

Immediately administer 100 mL of 3% hypertonic saline intravenously over 10 minutes as first-line treatment for hyponatremia-induced seizures, targeting a sodium correction of 6 mmol/L over 6 hours or until seizures resolve, with a strict maximum correction limit of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 2

Immediate Emergency Management

• Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeating every 10 minutes if seizures persist, up to three total boluses 1, 3
• Target an initial sodium increase of 4-6 mEq/L in the first hour to abort cerebral edema and seizure activity 1, 4
• Use anticonvulsants (such as lorazepam or diazepam) as adjunctive therapy only, not as monotherapy—the primary treatment is correcting the sodium 1, 3
• Avoid phenytoin for seizure prophylaxis in this setting, as it is associated with excess morbidity and mortality 2
• Ensure airway patency and have ventilatory support immediately available, as respiratory depression is the most important risk with benzodiazepines and severe hyponatremia 5, 2

Critical Correction Rate Guidelines

The correction rate is the most critical safety consideration to prevent osmotic demyelination syndrome:

• Correct by 6 mmol/L over the first 6 hours or until seizures resolve 1, 2
• Never exceed 8 mmol/L correction in 24 hours for most patients 1, 2, 6
• If 6 mmol/L is achieved in the first 6 hours, limit further correction to only 2 mmol/L in the remaining 18 hours 1
• For high-risk patients (advanced liver disease, alcoholism, malnutrition), use even more cautious rates of 4-6 mmol/L per day 2, 7

ICU Monitoring Protocol

• Check serum sodium every 2 hours during initial correction, then every 4 hours after seizures resolve 1, 2
• Monitor strict intake and output, obtain daily weights 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 2, 1
• Transfer to ICU for close monitoring in all cases of seizures from hyponatremia 7

Determining the Underlying Cause

While treating the seizure emergently, simultaneously evaluate the etiology:

• Assess extracellular fluid volume status (orthostatic hypotension, dry mucous membranes for hypovolemia; edema, ascites, jugular venous distention for hypervolemia) 1, 2
• Obtain serum and urine osmolality, urine sodium concentration, and serum uric acid 1, 2
• Distinguish between SIADH and cerebral salt wasting based on volume status: SIADH presents with euvolemia, while cerebral salt wasting shows true hypovolemia with high urine sodium despite volume depletion 1, 2
• Serum uric acid <4 mg/dL suggests SIADH (positive predictive value 73-100%) 2

Post-Acute Management Based on Etiology

For SIADH (Euvolemic):

• Implement fluid restriction to 1 L/day as cornerstone therapy 7, 2
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 1, 2
• Consider vaptans (tolvaptan 15 mg once daily) for resistant cases 2, 7

For Cerebral Salt Wasting (Hypovolemic):

• Treat with volume and sodium replacement using isotonic or hypertonic saline—never fluid restriction 1, 2
• Consider fludrocortisone for severe symptoms or in subarachnoid hemorrhage patients at risk of vasospasm 1, 2
• Hydrocortisone may prevent natriuresis in subarachnoid hemorrhage patients 1, 2

For Hypervolemic Hyponatremia (Heart Failure, Cirrhosis):

• Implement fluid restriction to 1-1.5 L/day 2
• Consider albumin infusion in cirrhotic patients 2
• Avoid hypertonic saline after initial seizure management unless life-threatening symptoms recur 2

Common Pitfalls to Avoid

• Never use fluid restriction in cerebral salt wasting—this worsens outcomes and can be fatal 1, 2
• Overcorrection exceeding 8 mmol/L in 24 hours risks osmotic demyelination syndrome, which can cause permanent neurological damage or death 1, 6, 8
• Do not delay hypertonic saline while pursuing diagnostic workup—treat the seizure first 4
• Failing to recognize the underlying cause leads to recurrence of hyponatremia and seizures 1, 2
• Inadequate monitoring during active correction can result in inadvertent overcorrection, which occurs in 4.5-28% of cases without proper protocols 6, 9