How do I prepare 3% hypertonic saline in a resource-limited setting as an alternative to mannitol for an adult with raised intracranial pressure?

Preparing 3% Hypertonic Saline in Resource-Limited Settings

Direct Preparation Method

To prepare 1 liter of 3% hypertonic saline, add 30 grams of table salt (sodium chloride) to 1 liter of sterile water or normal saline, which equals approximately 5 teaspoons of table salt per liter. 1

Step-by-Step Preparation

• 3% saline contains 30 grams of NaCl per liter (3 grams per 100 mL) 1
• One teaspoon of table salt weighs approximately 5.85 grams 1
• Therefore, 5 teaspoons of table salt dissolved in 1 liter of sterile water produces 3% hypertonic saline 1
• The resulting solution has an osmolarity of 1026 mOsmol/L and contains 513 mmol/L of sodium 1

Critical Safety Requirements for Preparation

• Use only pharmaceutical-grade or food-grade table salt without additives (iodine is acceptable, but avoid anti-caking agents)
• Ensure sterile water or sterile normal saline as the base solution
• Mix thoroughly until all salt is completely dissolved
• Filter the solution if possible to remove any particulate matter
• Label clearly with concentration, date, and time of preparation
• Use within 24 hours of preparation if sterility cannot be guaranteed

Clinical Administration Protocol

Dosing Strategy

For raised intracranial pressure, administer 3% hypertonic saline as a continuous infusion at 1 mL/kg/hour, targeting serum sodium of 145-155 mmol/L. 2

• Bolus dosing: 5 mL/kg administered over 15 minutes for acute ICP elevation 2
• Maintenance infusion: 0.5-1 mL/kg/hour continuous infusion 3
• Maximum effect occurs at 10-15 minutes and lasts 2-4 hours 2, 4

Mandatory Monitoring Requirements

Measure serum sodium within 6 hours of initiating therapy and every 6 hours thereafter. 2, 4

• Do not re-administer bolus until serum sodium is confirmed <155 mmol/L 2, 4
• Check electrolyte panel every 6 hours to monitor for hyperchloremia 2
• Monitor serum osmolality every 6 hours, holding infusion if ≥320 mOsm/kg 2
• Assess renal function daily 2
• Monitor fluid balance to avoid hypovolemia 2

Critical Safety Thresholds

Never exceed serum sodium of 155-160 mmol/L to prevent osmotic demyelination syndrome, seizures, and hemorrhagic encephalopathy. 2, 4

• Sustained sodium >170 mEq/L for >72 hours significantly increases risk of thrombocytopenia, renal failure, neutropenia, and acute respiratory distress syndrome 2
• Avoid sodium correction exceeding 10 mmol/L per 24 hours 2
• Hold infusion immediately if sodium >155 mmol/L 2

Superiority Over Mannitol

Hypertonic saline should be used instead of mannitol for raised intracranial pressure, as it produces more rapid ICP reduction, greater increases in cerebral perfusion pressure, and longer duration of effect. 2, 3

Evidence Supporting Hypertonic Saline

• In pediatric CNS infections, 3% hypertonic saline achieved target ICP <20 mmHg in 79.3% versus 53.6% with mannitol (adjusted HR 2.63,95% CI: 1.23-5.61) 3
• Mean ICP reduction was significantly greater with hypertonic saline (-14.3 mm Hg vs -5.4 mm Hg, p<0.001) 3
• Hypertonic saline produced shorter mechanical ventilation duration (5 vs 15 days, p=0.002), shorter PICU stay (11 vs 19 days, p=0.016), and less severe neurodisability at discharge (31% vs 61%, p=0.049) 3
• In rodent models, hypertonic saline produced 53.9% ICP reduction versus 35.0% with mannitol (p<0.01), with more durable effect lasting up to 500 minutes 5
• Meta-analysis showed ICP was significantly lower at 90-120 minutes with hypertonic saline (MD: -2.33 mm Hg, p<0.00001) 6

Advantages in Resource-Limited Settings

• Hypertonic saline is preferred in hypovolemic patients, as mannitol causes osmotic diuresis leading to hypovolemia 2
• Hypertonic saline is preferred in patients with renal impairment, as mannitol can precipitate acute renal failure when serum osmolarity exceeds 320 mOsm/kg 2
• Longer duration of effect reduces frequency of administration 7

Critical Limitation

Despite robust Grade A evidence for reducing intracranial pressure, hypertonic saline does NOT improve neurological outcomes (Grade B) or survival (Grade A) in patients with raised intracranial pressure. 8, 2, 4

This means hypertonic saline effectively lowers ICP as a temporizing measure but should be part of comprehensive management addressing the underlying cause of elevated ICP.

Common Pitfalls to Avoid

• Never use hypotonic solutions (Hartmann's, Ringer's lactate, 5% dextrose, 0.45% saline) as they worsen cerebral edema 2
• Do not use non-sterile water or contaminated salt for preparation
• Avoid rapid bolus administration faster than 15 minutes 2
• Do not continue therapy without sodium monitoring—this is non-negotiable even in resource-limited settings
• Avoid concomitant nephrotoxic drugs 2