Comparison of closed-loop controlled administration of propofol using bispectral index as the controlled variable versus "standard practice" controlled administration

Background This report describes a new closed-loop control system for propo fol that uses the Bispectral Index (BIS) as the controlled variable in a pa tient-individualized, adaptive, model-based control system, and compares th is system with manually controlled administration of propofol using hemodyn amic and somatic changes to guide anesthesia. Methods: Twenty female patients, American Society of Anesthesiologists phys ical status I or II, who were scheduled for gynecologic laparotomy were inc luded to receive propofolremifentanil anesthesia. In group I, propofol was titrated using a BIS-guided, model-based, closed-loop system. The BIS targe t was set at 50, In group II, propofol was titrated using classical hemodyn amic signs of(in)adequate anesthesia. Performance of control during inducti on and maintenance of anesthesia were compared between both groups using BI S as the controlled variable in group I and the reference variable in group II, and conversely, the systolic blood pressure as the controlled variable in group II and the reference variable in group I. At the end of anesthesi a, recovery profiles between groups were compared. Results: Although patients undergoing manual induction of anesthesia in gro up II at 300 ml/h reached a BIS level of 50 faster than patients undergoing open-loop, computer-controlled induction In group I, manual induction caus ed a more pronounced Initial overshoot of the BIS target. This resulted in a more pronounced decrease in blood pressure in group II. During the mainte nance phase, better control of BIS and systolic blood pressure was found in group I compared with group II. Recovery was faster in group I. Conclusion: A closed-loop system for propofol administration using the BIS as a controlled variable together with a model-based controller is clinical ly acceptable during general anesthesia.