Bispectral index (BIS) monitoring is used to titrate depth of anaesthesia. A BIS value in which range indicates an adequate level of general anaesthesia with minimal risk of awareness?

• A BIS 60–70
• B BIS 20–40
• C BIS 70–80
• D BIS 40–60 ✓

Explanation

BIS is a processed EEG parameter (0–100 scale) derived from frontal cortical activity. A BIS of 100 represents full wakefulness; 0 represents isoelectric EEG. The target range for general anaesthesia is 40–60, corresponding to an adequate hypnotic state with minimal awareness risk. BIS <40 indicates deep anaesthesia (burst suppression begins around 30), increasing risk of intraoperative hypotension and delayed emergence. Values >70 suggest light sedation with residual consciousness; awareness risk increases significantly above 60.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.