A patient with a traumatic brain injury (GCS 8) has an ICP of 28 mmHg. The CPP (MAP 75 mmHg) is 47 mmHg. Which osmotic agent is preferred for acute ICP reduction and WHY?

• A 20% Mannitol 0.5 g/kg — superior because it reduces blood viscosity and has diuretic effect
• B 20% Mannitol is universally preferred per current TBI guidelines over hypertonic saline
• C Both are equivalent; choice depends solely on serum sodium level
• D 3% Hypertonic saline 250 mL — preferred because it does not cause hypotension, avoids crossing a disrupted BBB, and maintains intravascular volume ✓

Explanation

Current evidence supports hypertonic saline as the preferred osmotic agent when haemodynamic instability coexists with raised ICP, because mannitol causes osmotic diuresis leading to hypotension and further CPP reduction. Hypertonic saline does not cross a disrupted BBB (unlike mannitol after repeated dosing), expands intravascular volume, and directly reduces ICP via osmotic water shift from brain parenchyma. BTF guidelines (4th edition) indicate both agents are effective, but hypertonic saline is preferred when MAP is borderline (CPP <60). Mannitol is contraindicated with serum osmolarity >320 mOsm/kg.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.