Additional clinical observations utilizing bispectral analysis

Area of Science:

• Anesthesiology
• Neuroscience
• Medical Devices

Background:

• The bispectral (BIS) index is a tool used to monitor anesthetic depth.
• Ketamine and midazolam are commonly used anesthetic agents.
• General anesthesia in nonintubated patients presents unique monitoring challenges.

Purpose of the Study:

• To evaluate the bispectral (BIS) index in nonintubated patients undergoing procedures with ketamine and midazolam.
• To assess the utility of bispectral analysis in maintaining general anesthesia without local anesthesia.
• To compare BIS index values across different anesthetic agents.

Main Methods:

• Bispectral analysis was performed on 25 subjects undergoing extraction procedures with ketamine and midazolam.
• BIS index values were recorded during general anesthesia with propofol.
• Observations were made on BIS index behavior when local anesthesia was omitted.

Main Results:

• BIS index values remained high (in the 80s, low of 77) with ketamine and midazolam, unlike typical sedative ranges (50-70).
• BIS index readings in the 30s were common with propofol, with a lowest observed value of 18.
• Bispectral analysis effectively trended anesthetic states and guided propofol dosage adjustments.
• No laryngospasm or total airway obstruction occurred; one instance of partial obstruction was resolved by repositioning.

Conclusions:

• Bispectral analysis is valuable for monitoring anesthetic depth in nonintubated patients, particularly during general anesthesia without local anesthetic infiltration.
• BIS index values are consistently higher with ketamine compared to other hypnotics.
• A limitation exists in titrating midazolam-induced sedation when ketamine is co-administered, as BIS levels may not decrease as expected.