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Cerebral autoregulation — FRCA Primary MCQ

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HardPhysiologyCerebral autoregulationFRCA Primary

A patient with long-standing hypertension is anaesthetised for carotid endarterectomy. Mean arterial pressure falls to 55 mmHg and processed EEG slows. What is the most likely explanation?

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Correct answer: A — Right-shifted cerebral autoregulation curve

Chronic hypertension shifts the cerebral autoregulation curve to the right, so pressures tolerated by healthy patients may cause cerebral hypoperfusion. Reduced cerebral metabolic rate is an effect of anaesthesia, not hypertension itself. Low PaCO2 causes cerebral vasoconstriction rather than vasodilatation. Cerebral perfusion targets should be individualised in patients with chronic hypertension or cerebrovascular disease.

Reference: Ganong Review of Medical Physiology; Primary FRCA physiology texts