Musculoskeletal, Neurological, Behavioral/PsychosocialDifficulty 3/5
A patient with a traumatic brain injury has an intracranial pressure of 25 mmHg and a mean arterial pressure of 70 mmHg. What is the cerebral perfusion pressure, and why does it matter?
- A70 mmHg, which reflects systemic pressure and is sufficient
- B95 mmHg, which is adequate and requires no further intervention
- C45 mmHg, which is below target and threatens cerebral ischaemia
- D25 mmHg, which reflects the intracranial pressure alone
Show answer and rationale
Correct: C. CPP = MAP − ICP = 70 − 25 = 45 mmHg, below the usual target range and associated with secondary ischaemic injury. Management addresses both sides of the equation: lower ICP and support MAP.
- B — 95 would be the sum rather than the difference.
- D — ICP alone is not perfusion pressure.
- A — MAP alone ignores the opposing intracranial pressure.