What is the recommended dose of hypertonic 3% saline (hypertonic saline solution) for an adult patient with a subdural hematoma (SDH)?

Hypertonic Saline Dosing for Subdural Hematoma

For adult patients with subdural hematoma and elevated intracranial pressure, administer 3% hypertonic saline as a continuous infusion at 1 mL/kg/hour, targeting a serum sodium concentration of 145-155 mEq/L, with bolus doses of 5 mL/kg (approximately 250-350 mL for most adults) administered over 15 minutes for acute ICP elevation or signs of herniation. 1, 2

Bolus Dosing for Acute ICP Crisis

• Administer 5 mL/kg of 3% hypertonic saline IV over 15 minutes for acute intracranial hypertension or threatened herniation, which equates to approximately 250 mL for a 50 kg patient or 350 mL for a 70 kg patient 1, 2

• Alternative bolus formulations include 250 mL of 7.5% hypertonic saline administered over 15-20 minutes, which delivers approximately 250 mOsm 1

• Do not re-administer bolus doses until serum sodium is confirmed <155 mEq/L, as exceeding this threshold increases risk of complications 1, 2

• The maximum ICP-lowering effect occurs at 10-15 minutes and lasts 2-4 hours, necessitating repeat dosing if ICP remains elevated 1

• In research settings, larger cumulative doses (≥1400 mEq total sodium over 5 days) were associated with improved neurologic outcomes in surgically decompressed patients with subdural hematoma, with 76.9% following commands at 3 months versus 50.0% with lower doses 3

Continuous Infusion Protocol

• Start continuous infusion at 1 mL/kg/hour of 3% hypertonic saline to maintain sustained ICP control over days rather than hours 1, 2

• Target serum sodium concentration of 145-155 mEq/L throughout therapy 1, 2

• Hold the infusion immediately if serum sodium exceeds 155 mEq/L and recheck labs before resuming 1, 2

• Continuous infusion reduces the frequency of ICP spikes at 6,12,24,48, and 72 hours compared to bolus-only strategies 1

Critical Monitoring Requirements

• Check serum sodium, chloride, and osmolality every 6 hours initially, then continue every 6 hours throughout active therapy 1, 2

• Measure baseline serum sodium and renal function before initiating therapy to ensure sodium is <155 mmol/L 1

• Monitor serum osmolality and hold infusion if osmolality reaches ≥320 mOsm/kg, as this threshold is associated with increased risk of renal failure, thrombocytopenia, and acute respiratory distress syndrome 1, 2

• Sustained sodium >170 mEq/L for >72 hours significantly increases complications 1

• Monitor fluid balance and avoid hypovolemia, as hypertonic saline has minimal diuretic effect compared to mannitol 1, 2

Administration Considerations

• Peripheral IV administration is safe at rates up to 999 mL/hour for 3% hypertonic saline boluses, with no documented episodes of extravasation or phlebitis in emergency settings 4

• An 18-gauge IV in the antecubital fossa is the most common and safe access site for rapid peripheral administration 4

• For patients requiring both volume resuscitation and ICP management, hypertonic saline offers hemodynamic advantages over mannitol by increasing blood pressure without causing osmotic diuresis 1, 2

Comparison with Mannitol

• Hypertonic saline should be used instead of mannitol for ICP management in subdural hematoma, as it produces more rapid ICP reduction and greater increases in cerebral perfusion pressure at equiosmolar doses 1, 2

• Hypertonic saline is particularly preferred in hypovolemic or hypotensive patients, as mannitol causes osmotic diuresis that can worsen hemodynamic instability 1, 2

• At equiosmotic doses (approximately 250 mOsm), both agents have comparable efficacy, but hypertonic saline avoids the risk of renal failure when osmolarity exceeds 320 mOsm/kg 2

Evidence for Subdural Hematoma Specifically

• In a retrospective study of 112 patients with complex traumatic brain injury (71.4% with subdural hematoma), trauma center mortality in surgically decompressed patients was significantly lower with >8.0 mEq/kg sodium (7.5%) compared to ≤8.0 mEq/kg (38.9%) 3

• For patients with subdural hematoma or cerebral contusion, 84.2% followed commands at 3 months with ≥1400 mEq total sodium versus 61.8% with lower doses 3

• Patients with ICP >20 mmHg for ≤10 hours received more sodium (16.5 ± 11.5 mEq/kg) compared to those with prolonged elevation ≥11 hours (9.4 ± 6.3 mEq/kg), suggesting early aggressive dosing may mitigate intracranial hypertension 3

Adjunctive Measures

• Elevate head of bed to 30 degrees to assist venous drainage while administering hypertonic saline 1

• Provide adequate analgesia and sedation to manage pain and agitation 1

• Maintain cerebral perfusion pressure >70 mmHg throughout therapy 1

• Avoid hypotonic solutions including Ringer's lactate, 5% dextrose, 0.45% saline, or Hartmann's solution, as these worsen cerebral edema 1

• Use 0.9% normal saline for maintenance fluids, reserving hypertonic saline specifically for ICP management 1

Critical Limitation

Despite robust Grade A evidence for ICP reduction, hypertonic saline has NOT been shown to improve neurological outcomes (Grade B evidence) or survival (Grade A evidence) in randomized controlled trials of patients with raised intracranial pressure. 5, 1 This means while hypertonic saline effectively lowers ICP, its use should be part of a comprehensive management strategy that includes surgical intervention when indicated, as decompressive surgery has proven mortality benefit in appropriate populations 1

Common Pitfalls to Avoid

• Do not stop monitoring electrolytes after the first 24 hours; continue every 4-6 hours throughout therapy 2

• Do not exceed sodium correction of 10 mmol/L per 24 hours to prevent osmotic demyelination syndrome 1

• Do not use hypertonic saline as a volume resuscitation fluid in hemorrhagic shock; it is specifically for ICP management 1

• Do not administer concomitant nephrotoxic drugs and monitor renal function daily 1