Question

Which of the following is the most common method used to know the depth of anaesthesia?

• A. BIS (Bispectral index)
• B. Oesophageal contractility
• C. Depressed responses
• D. Hypotension

Hint:

A processed-EEG number where 45 to 60 is the surgical plane and 100 is awake.

Answer 1

The Correct Option is A

Step 1: Monitoring depth of anaesthesia aims to avoid awareness and excessive depth.
Step 2: The bispectral index (BIS) was the first scientifically validated and commercially available monitor of anaesthetic depth. It processes EEG signals (and related parameters such as eye blinks) into a single dimensionless score.
Step 3: The BIS score runs from 100 (fully awake) down to 0 (isoelectric, completely silent brain). Adequate surgical anaesthesia corresponds to a score of about 45 to 60.
Step 4: Oesophageal contractility, clinically depressed responses and hypotension are non-specific or older indicators, so BIS is the most common method and is the correct answer.