skip to main content

Beach Chair Cerebral Ischaemia — FRCA Final MCQ

Instant feedback + full explanation. One question, done properly.

HardAnaesthetic Equipment & SafetyBeach Chair Cerebral IschaemiaFRCA Final

A 40-year-old man undergoes total shoulder replacement under general anaesthesia in the 60° beach-chair position. The radial arterial-pressure transducer remains level with the right atrium and displays a MAP of 72 mmHg. The external auditory meatus is 30 cm above the transducer. Twenty minutes after positioning, the BIS falls rapidly from 45 to 22. The end-tidal sevoflurane concentration is unchanged, SpO2 is 99%, end-tidal CO2 is 4.7 kPa, and the BIS signal-quality and EMG indicators are satisfactory. What is the immediate concern?

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

Reveal the answer and explanation

Correct answer: D — Cerebral hypoperfusion

The immediate concern is cerebral hypoperfusion. Because the arterial transducer is at heart rather than brain level, the displayed MAP overestimates cerebral-level pressure: the estimated MAP at the external auditory meatus is only about 50 mmHg. The abrupt BIS reduction is not diagnostic of cerebral ischaemia, but with severe brain-level hypotension, unchanged anaesthetic concentration and a satisfactory signal it is an important warning. Cerebral perfusion should be restored promptly while causes are assessed. Excessive hypnotic effect is less likely without a concentration change. Venous air embolism would more typically produce an abrupt fall in end-tidal CO2 and cardiorespiratory disturbance. Brachial plexus injury does not explain the EEG change, and monitor artefact is less likely with satisfactory signal-quality indicators. A universal autoregulatory threshold should not be assumed; safe pressure is patient-specific.

Reference: Murphy GS, Greenberg SB, Szokol JW. Safety of Beach Chair Position Shoulder Surgery: A Review of the Current Literature. Anesthesia & Analgesia. 2019. https://pubmed.ncbi.nlm.nih.gov/20514957/