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Cerebral perfusion pressure calculation — FRCA Primary MCQ

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EasyPhysiologyCerebral perfusion pressure calculationFRCA Primary

A patient with traumatic brain injury has mean arterial pressure 78 mmHg and intracranial pressure 24 mmHg. Sedation is stable and PaCO2 is 4.6 kPa. What is the cerebral perfusion pressure?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — 54 mmHg

Cerebral perfusion pressure is mean arterial pressure minus intracranial pressure: 78 - 24 = 54 mmHg. The tempting error is to add the two pressures or use systolic pressure. PaCO2 matters because it alters cerebral vascular tone, but it is not part of the CPP equation. This calculation guides resuscitation in raised intracranial pressure.

Reference: RCoA Primary FRCA Syllabus 2026; Ganong's Review of Medical Physiology; West's Respiratory Physiology