What is the recommended dosage and administration of hypertonic saline (hypertonic saline solution) bolus for a patient with severe hyponatremia or elevated intracranial pressure?

Hypertonic Saline Bolus Dosing and Administration

For Elevated Intracranial Pressure

Administer 250 mL of 7.5% hypertonic saline as a bolus over 15-20 minutes for acute ICP elevation, or use continuous infusion of 3% hypertonic saline targeting serum sodium of 145-155 mmol/L for sustained control. 1, 2

Bolus Therapy Protocol

• 7.5% hypertonic saline at 250 mL is the recommended bolus dose for acute ICP reduction, infused over 15-20 minutes 1
• Alternative bolus dosing: 5 mL/kg of 3% hypertonic saline (approximately 5.3 mL/kg) over 15-20 minutes 2
• Maximum effect occurs at 10-15 minutes and lasts 2-4 hours 1, 2
• Do not re-administer bolus until serum sodium is <155 mmol/L 1, 2

Continuous Infusion Strategy

• 3% hypertonic saline at 1 mL/kg/hour as continuous infusion for sustained ICP control 1
• Target serum sodium concentration: 145-155 mmol/L 1, 2
• This approach reduces frequency of ICP spikes and avoids repeated sodium fluctuations 1
• Particularly validated in pediatric traumatic brain injury with mean treatment duration of 7.6 days 1, 2

Critical Monitoring Requirements

• Measure serum sodium within 6 hours of any bolus administration 1, 2
• Check serum sodium every 4-6 hours initially, then every 6 hours once stable 1
• Monitor serum osmolality every 6 hours; hold infusion if ≥320 mOsm/kg 1
• Never exceed serum sodium of 155-160 mmol/L to prevent complications 1, 2
• Hold infusion immediately if sodium >155 mmol/L 1

Clinical Indications

• Traumatic brain injury 1, 2
• Subarachnoid hemorrhage 1, 2
• Intracerebral hemorrhage 1, 2
• Malignant MCA infarction with cerebral edema 1
• Acute liver failure 1, 2

Superiority Over Mannitol

• Hypertonic saline produces more rapid ICP reduction and greater increases in cerebral perfusion pressure at equiosmolar doses compared to mannitol 1, 3
• Meta-analysis of 8 prospective RCTs showed higher treatment failure rates with mannitol versus hypertonic saline 3
• Preferred in hypovolemic patients, as mannitol causes osmotic diuresis leading to hypovolemia 1

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For Severe Hyponatremia

For symptomatic severe hyponatremia (serum sodium ≤120 mmol/L), administer 250 mL of 3% hypertonic saline as a rapid bolus to achieve a 4-6 mmol/L increase in serum sodium within the first 4 hours. 4, 5

Acute Symptomatic Hyponatremia (<48 hours)

• 250 mL bolus of 3% hypertonic saline is more effective than 100 mL, achieving ≥5 mmol/L rise in 52% vs 32% of patients within 4 hours 4
• Target initial increase: 4-6 mmol/L to reverse life-threatening symptoms (seizures, respiratory arrest, coma) 5
• This is a true emergency requiring prompt intervention with hypertonic saline 5
• No risk of osmotic demyelination syndrome in acute hyponatremia (<48 hours), so correction can be more aggressive 6

Chronic Hyponatremia (>48 hours)

• Use same bolus approach (250 mL of 3% saline) but with stricter correction limits 4
• Correction limits to prevent osmotic demyelination:
  • ≤10 mmol/L in first 24 hours (or ≤15 mmol/L if no other risk factors present) 6, 5
  • ≤18 mmol/L in 48 hours 5
  • ≤20 mmol/L in 72 hours 5
• If risk factors present (hypokalemia, liver disease, malnutrition, burns), limit correction to ≤10 mmol/L per 24 hours 6

Therapeutic Goals

• First 24 hours: 6-8 mmol/L increase 5
• 48 hours: 12-14 mmol/L increase 5
• 72 hours: 14-16 mmol/L increase 5

Preventing Overcorrection

• Frequent monitoring of serum sodium and urine output is mandatory 5
• Inadvertent overcorrection commonly occurs due to unexpected water diuresis 5, 7
• Administer desmopressin (1-2 µg parenterally every 6-8 hours) concurrently with hypertonic saline to prevent overcorrection by controlling water diuresis 7
• This combined strategy prevents overcorrection >12 mmol/L in 24 hours or >18 mmol/L in 48 hours 7
• If overcorrection occurs (>15 mmol/L in 24 hours), rapidly decrease serum sodium with hypotonic fluids and dDAVP to reduce myelinolysis risk 6

Safety Considerations

• The 250 mL bolus does not increase overcorrection risk compared to 100 mL (21% in both groups), but is more effective 4
• No osmotic demyelination syndrome occurred in the 250 mL bolus study 4
• Overcorrection typically occurs after median of 13 hours (range 9-17 hours) 4

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Critical Limitations

Despite robust evidence for ICP reduction (Grade A) and effective correction of severe hyponatremia, hypertonic saline has NOT been shown to improve neurological outcomes (Grade B) or survival (Grade A) in patients with raised intracranial pressure. 1, 2

Common Pitfalls to Avoid

• Never use hypertonic saline for volume resuscitation in hemorrhagic shock unless combined with severe head trauma and focal neurological signs 1, 2
• Avoid hypotonic solutions (Ringer's lactate, 5% dextrose, 0.45% saline, Hartmann's) as they worsen cerebral edema 1
• Do not use mannitol and hypertonic saline together; use hypertonic saline instead of mannitol 1
• Avoid rapid sodium correction exceeding 10 mmol/L per 24 hours in chronic hyponatremia to prevent osmotic demyelination 1, 6