A 55-year-old man on ICU has a traumatic brain injury with diffuse cerebral oedema. His ICP is 28 mmHg and CPP is 55 mmHg. The team has administered I...

Question

A 55-year-old man on ICU has a traumatic brain injury with diffuse cerebral oedema. His ICP is 28 mmHg and CPP is 55 mmHg. The team has administered IV mannitol 20% (0.5 g/kg). After 20 minutes, ICP drops to 18 mmHg. What is the mechanism of action of mannitol for ICP reduction?

Accepted Answer

Mannitol creates an osmotic gradient across the intact blood-brain barrier (BBB), drawing free water from the cerebral parenchyma into the intravascular space; it also has rheological effects (reducing blood viscosity, improving cerebral microcirculation, leading to reflex vasoconstriction and reduced cerebral blood volume)

Answer

Mannitol reduces CSF production

Answer

Mannitol is a direct cerebral vasoconstrictor

Answer

Mannitol reduces cerebral metabolic rate

Answer

Mannitol acts as a diuretic only - the ICP reduction is purely from dehydration

uk-fficm MCQ (SBA): Mannitol Mechanism of Action

A 55-year-old man on ICU has a traumatic brain injury with diffuse cerebral oedema. His ICP is 28 mmHg and CPP is 55 mmHg. The team has administered IV mannitol 20% (0.5 g/kg). After 20 minutes, ICP drops to 18 mmHg. What is the mechanism of action of mannitol for ICP reduction?