In a patient with subdural hematoma requiring rapid intracranial pressure reduction or treatment of symptomatic hyponatremia, how should 3% hypertonic saline be administered?

3% Hypertonic Saline Administration in Subdural Hematoma

In patients with subdural hematoma requiring intracranial pressure reduction, administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals, with a target sodium correction not exceeding 8 mmol/L in any 24-hour period. 1

Indications for 3% Hypertonic Saline in SDH

Use 3% hypertonic saline for:

• Elevated intracranial pressure (ICP) – Hypertonic saline effectively reduces ICP in traumatic brain injury including subdural hematoma, with evidence showing improved cerebral perfusion pressure and reduced duration of intracranial hypertension 1, 2
• Severe symptomatic hyponatremia (sodium <120 mmol/L with neurological symptoms such as altered mental status, seizures, or coma) – This requires immediate intervention regardless of the presence of SDH 1, 3, 4
• Impending herniation – Patients with signs of transtentorial herniation benefit from urgent hyperosmolar therapy 1, 5

Dosing Protocol

Bolus administration:

• Give 100 mL of 3% NaCl intravenously over 10 minutes 1, 3
• May repeat up to three times at 10-minute intervals for severe symptoms or refractory ICP elevation 1, 3
• For ICP management specifically, bolus doses of 250 mL have been used in studies, though 100 mL boluses provide more controlled correction 1

Continuous infusion (alternative approach):

• 3% hypertonic saline continuous infusion may be used for sustained ICP control, particularly in pediatric TBI or when prolonged management is anticipated 1
• Target serum sodium of 145-155 mmol/L has been used safely in some head injury protocols, though this represents controlled hypernatremia requiring careful monitoring 1, 3

Critical Correction Rate Limits

Never exceed 8 mmol/L sodium increase in any 24-hour period to prevent osmotic demyelination syndrome, even in acute settings 1, 3, 6, 7

For severe symptomatic hyponatremia concurrent with SDH:

• Initial target: 6 mmol/L increase over 6 hours or until severe symptoms resolve 3, 6, 4
• After initial 6 mmol/L correction, only 2 mmol/L additional correction is permitted in the remaining 18 hours to stay within the 8 mmol/L/24-hour limit 3, 6

High-risk patients require even slower correction (4-6 mmol/L per day maximum):

• Advanced liver disease 1, 3, 6, 7
• Chronic alcoholism 3, 6, 7
• Malnutrition 3, 6, 7
• Chronic hyponatremia (>48 hours duration) 3, 6, 7

Monitoring Requirements

Serum sodium monitoring:

• Every 2 hours during initial correction phase for severe symptomatic hyponatremia 3, 6, 4
• Every 4-6 hours after symptom resolution or for ongoing ICP management 1, 3, 6
• Re-check within 6 hours after each bolus to guide further therapy 1, 3

Clinical monitoring:

• Neurological examination – Glasgow Coma Scale, pupillary response, motor function 2, 4, 5
• ICP monitoring (if device in place) – Target ICP <20 mmHg 1, 2
• Cerebral perfusion pressure – Maintain CPP >60 mmHg 1, 8

Special Considerations in SDH

Surgical decompression patients:

• Higher doses of hypertonic saline (>8.0 mEq/kg sodium over 5 days) are associated with improved survival in surgically decompressed SDH patients (7.5% mortality vs 38.9% with lower doses) 2
• ≥1400 mEq total sodium administration correlates with better neurological outcomes at 3 months (76.9% following commands vs 50.0% with lower doses) 2
• Continue 3% saline infusion perioperatively when initiated prehospital or in emergency department 5

Combination with surgical evacuation:

• Hypertonic saline as bridge to surgery – Early preoperative administration improves cerebral perfusion pressure and may optimize conditions for surgical intervention 8
• Combined treatment (HTS + surgical evacuation) shows slightly better outcomes than surgery alone in animal models, though both are effective 8

Transition and Maintenance

After initial stabilization:

• Switch to isotonic maintenance fluids (0.9% NaCl) once severe symptoms resolve and sodium reaches 120-125 mmol/L 3, 4
• Avoid hypotonic solutions (0.45% saline, lactated Ringer's, D5W) as they can worsen cerebral edema 3, 4
• For sustained ICP control, may continue 3% infusion for 24-48 hours with intensive monitoring 2, 5

Management of Overcorrection

If sodium rises >8 mmol/L in 24 hours:

• Immediately discontinue hypertonic saline 3, 6, 7
• Administer D5W (5% dextrose in water) to lower sodium 3, 6, 7
• Consider desmopressin to slow or reverse rapid sodium rise 3, 6, 7
• Target: bring total 24-hour correction back to ≤8 mmol/L from baseline 3, 6

Hypernatremia Correction After Prolonged HTS Use

If iatrogenic hypernatremia develops from prolonged 3% saline therapy:

• Do not leave hypernatremia uncorrected – The brain adapts to elevated sodium within 48-72 hours, and failure to correct creates risk of rebound ICP elevation when therapy is discontinued 9
• Maximum correction rate: 10-15 mmol/L per 24 hours using hypotonic fluids (D5W or 0.45% NaCl) 9
• Target rate: 0.4 mmol/L/hour to prevent osmotic demyelination during correction 9
• Monitor sodium every 4-6 hours during correction phase 9

Common Pitfalls to Avoid

• Never use fluid restriction in SDH patients with hyponatremia – This can worsen cerebral perfusion and is contraindicated in neurosurgical patients at risk for vasospasm 1, 3, 4
• Never exceed 8 mmol/L correction in 24 hours – Osmotic demyelination syndrome can occur 2-7 days after rapid correction with devastating neurological consequences 3, 6, 7
• Never continue uncorrected hypernatremia after prolonged HTS therapy – Brain adaptation means rebound ICP elevation risk regardless of iatrogenic cause 9
• Never use lactated Ringer's or other hypotonic solutions in acute SDH management – These worsen cerebral edema 3, 4
• Never delay treatment while awaiting ADH or natriuretic peptide levels – These tests do not alter acute management and cause harmful delays 3, 4

Integration Across Care Continuum

Prehospital to hospital transition:

• Continue prehospital-initiated 3% saline upon trauma center arrival – Integrated protocols improve outcomes 5
• Communicate total sodium administered to receiving team for accurate 24-hour correction tracking 2, 5
• Maintain consistent monitoring intervals across care transitions 5