Raised ICP – IV Mannitol — SCE Neurology MCQ

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EasyNeuro-oncologyRaised ICP – IV MannitolSCE Neurology

A 60-year-old man with raised intracranial pressure from a brain tumour is being managed medically while awaiting surgery. His ICP is 30 mmHg (target <20). What is the first-line osmotic agent for acute ICP reduction?

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Correct answer: D — IV mannitol 20% (0.25–1 g/kg over 20 minutes) — draws water osmotically from brain parenchyma into the intravascular space, reducing brain volume and ICP

IV mannitol 20% is the traditional first-line osmotic agent for acute ICP reduction. It works by creating an osmotic gradient across the intact blood-brain barrier, drawing water from brain parenchyma into the intravascular space. Important considerations: (1) requires intact BBB for maximum effect, (2) can cause rebound ICP elevation with prolonged use, (3) monitor serum osmolality (<320 mOsm/kg to avoid renal toxicity), (4) ensure euvolaemia. Hypertonic saline (3% or 23.4%) is an alternative osmotic agent increasingly used, particularly in hyponatraemic or hypovolaemic patients. A: Oral glycerol is less effective. C: Dextrose would worsen cerebral oedema. D: Normal saline alone does not reduce ICP. E: Acetazolamide acts on CSF production, not acute oedema.

Reference: NICE NG128; Neurocritical Care Society ICP Guidelines