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A new closed-loop control system for isoflurane using bispectral index outperforms manual control
Stephan Locher1, Konrad S Stadler, Thomas Boehlen
1Department of Anesthesiology, Research Section, University of Berne, Switzerland.
Anesthesiology
|August 27, 2004
Summary
Closed-loop anesthesia control using the Bispectral Index (BIS) with isoflurane via a vaporizer offers superior safety and efficacy compared to manual control. This automated system significantly reduces inadequate sedation events during surgery.
Area of Science:
- Anesthesiology
- Medical Devices
- Control Systems Engineering
Background:
- Automatic control of hypnosis depth using the Bispectral Index (BIS) can minimize inadequate anesthesia control.
- Previous studies demonstrated automated BIS control with propofol or isoflurane infusion systems.
- A comparable study using isoflurane via a vaporizer was lacking.
Purpose of the Study:
- To evaluate the clinical safety and efficacy of a novel closed-loop control system for Bispectral Index (BIS) using isoflurane administered via a vaporizer.
- To compare the performance of this closed-loop system against manual BIS control in maintaining a target BIS range.
- To test the hypothesis that the closed-loop system maintains BIS within a defined target range more effectively than manual control.
Main Methods:
- Twenty-three patients undergoing spinal surgery were randomized to either closed-loop or manual BIS control with isoflurane.
- A target-controlled infusion of alfentanil was administered, and the BIS target was set to 50.
- Key metrics included human intervention, inadequate sedation events (BIS <40 or >60), prolonged inadequate control (BIS ≥65 for >3 min), and performance indicators (mean absolute deviation, median absolute performance error).
Main Results:
- No human intervention was required in the closed-loop control group.
- The closed-loop system demonstrated significantly lower instances of inadequate BIS levels (0.5% vs. 10.3% of anesthesia time) and prolonged inadequate control (one event vs. nine events).
- Performance parameters, including mean absolute deviation and median absolute performance error, were over 30% better with closed-loop control (P < 0.05).
Conclusions:
- Closed-loop BIS control using isoflurane via a vaporizer is safe for clinical application.
- The closed-loop system significantly outperforms manual control in maintaining BIS within the target range.
- This automated approach is effective even during unpredictable stimulation changes during surgery.