What is the appropriate emergency department management of acute hypernatremia in a patient with a traumatic subdural hematoma?

Emergency Department Management of Acute Hypernatremia in Traumatic Subdural Hematoma

Correct hypernatremia at a rate not exceeding 0.5 mmol/L per hour (or 10 mmol/L per 24 hours) using hypotonic fluids or free water, while monitoring serum sodium every 2-4 hours and avoiding rapid correction that can precipitate cerebral edema and seizures. 1

Immediate Assessment and Risk Stratification

Determine Hypernatremia Severity and Onset

• Acute hypernatremia (developing over <48 hours) carries higher risk of neurological complications including seizures, particularly when sodium >155 mmol/L 1
• In traumatic brain injury patients, hypernatremia is often iatrogenic from hypertonic saline administration for intracranial pressure control or inadequate free water replacement 1
• The combination of subdural hematoma and hypernatremia creates dual risks: the mass effect from the hematoma and osmotic brain cell dehydration from elevated sodium 1

Identify High-Risk Features Requiring Seizure Prophylaxis

• Initiate levetiracetam prophylaxis if the patient has intracranial hemorrhage (including subdural hematoma), age >65 years, or chronic subdural hematoma 2
• Loading dose: 1000-1500 mg IV, followed by maintenance 500-1500 mg IV/PO twice daily for maximum 7 days 2
• Avoid phenytoin due to higher morbidity, mortality, and poorer cognitive outcomes 2

Correction Protocol

Target Correction Rate

• Maximum correction rate: 0.5 mmol/L per hour or 8-10 mmol/L per 24 hours 1
• Slower correction (10-15 mmol/L per 24 hours maximum) prevents cerebral edema, seizures, and neurological injury 1
• Critical pitfall: Rapid correction induces cerebral edema and seizures, particularly dangerous in patients with pre-existing brain injury 1

Fluid Selection and Administration

• Use hypotonic fluids (0.45% saline or 5% dextrose in water) to provide free water 1
• Calculate free water deficit: 0.6 × body weight (kg) × [(current Na - 140)/140] 1
• Replace deficit over 24-48 hours depending on chronicity 1
• Avoid large volumes of hypotonic fluids that could worsen cerebral edema in the setting of subdural hematoma 2

Monitoring Requirements

Frequent Sodium Checks

• Check serum sodium every 2-4 hours during active correction 1
• Monitor other electrolytes (particularly chloride, as hyperchloremia impairs renal function) 1
• Adjust fluid rate based on sodium trend to maintain target correction rate 1

Neurological Surveillance

• Watch for signs of neurological deterioration during correction: altered consciousness, new focal deficits, seizures 1
• Consider continuous EEG monitoring if mental status is disproportionately depressed relative to injury severity, as non-convulsive seizures occur in approximately 19% of patients with intracranial hemorrhage 2
• Perform serial neurological examinations every 1-2 hours during active correction 1

Special Considerations for Traumatic Brain Injury

Avoid Prolonged Induced Hypernatremia

• Do not use prolonged induced hypernatremia for intracranial pressure control in traumatic brain injury patients 1
• Risk of "rebound" intracranial pressure during correction outweighs benefits 1
• If hypernatremia was therapeutically induced, taper slowly while monitoring ICP 1

Renal Replacement Therapy for Severe Cases

• For severe hypernatremia (sodium >160 mmol/L) with mortality risk up to 86.8%, continuous renal replacement therapy (CRRT) allows slow, controlled, continuous sodium reduction 3
• CRRT is particularly useful when conventional treatment fails or correction rate cannot be adequately controlled 3
• If patient requires hemodialysis, supplement levetiracetam with additional 250-500 mg after each dialysis session 2

Critical Pitfalls to Avoid

• Never correct faster than 0.5 mmol/L per hour – this is the single most important safety threshold 1
• Never extend seizure prophylaxis beyond 7 days unless actual seizures occur, as prolonged use worsens neurological outcomes 2
• Never use high-dose glucocorticoids after severe traumatic brain injury, as they increase mortality 2
• Never use valproate for seizure prophylaxis in traumatic brain injury due to increased mortality 2
• Never ignore signs of subdural hematoma progression – 6.5% of conservatively managed subdural hematomas require delayed surgery (median 9.5 days), with risk factors including thicker hematoma, greater midline shift, and convexity location 4

Disposition and Follow-Up

• Admit all patients with acute hypernatremia and traumatic subdural hematoma to intensive care or neurosurgical service 1
• Continue sodium monitoring every 4-6 hours until stable in normal range 1
• Maintain seizure prophylaxis for 7 days total in high-risk patients 2
• Obtain neurosurgical consultation for subdural hematoma management decisions 4