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BIS Deep Anaesthesia — FRCA Final MCQ

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ModerateGeneral AnaesthesiaBIS Deep AnaesthesiaFRCA Final

A 45-year-old woman (ASA I) is having a laparoscopic hysterectomy under TIVA. The BIS reading is 28. The surgery is proceeding normally with stable haemodynamics. What does a BIS of 28 indicate?

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Correct answer: A — Electrode malfunction

BIS (Bispectral Index) target range for general anaesthesia is 40-60. A value of 28 indicates excessively deep anaesthesia. Deep anaesthesia (BIS <40) is associated with: increased hypotension, increased vasopressor requirements, possible association with increased postoperative mortality (BAG-RECALL trial and BALANCED trial data), delayed emergence, and increased PONV. The propofol/remifentanil infusion rates should be reduced to bring BIS into the 40-60 range. A BIS <20 may indicate burst suppression or equipment malfunction.

Reference: RCOA – 2023 – Depth of anaesthesia monitoring; Sessler DI et al – 2012 – BAG-RECALL trial