The BIS monitor is manufactured by Aspect Medical Systems and the company claims that it is a depth of consciousness monitor. Specifically, the company claims that keeping the monitor reading below a certain value by administering anesthetic agents helps to prevent awareness. On the flip side, by not forcing the monitor reading too low, the company claims that less anesthetic can be utilized safely and allow quicker wake-ups and recovery from anesthesia.

Almost from the moment that the BIS monitor was introduced, those following the issue of "depth of consciousness" monitoring have talked about using the data from the BIS to feedback and control an infusion pump. This would allow an automatic control of the infusion rate in order to keep the BIS monitor reading at a pre-determined number. Theroretically, a system that did this efficiently could be used to maintain unconsciousness while using the minimum amount of anesthetic necessary. A feedback loop such as this has always been something that the company has talked about only as a general idea.

Now, a group of researchers in Japan has taken the theory and changed it into a practical application. In essence they have "closed the loop" and developed computer algorithms that make automatic control of drug infusions possible. The system has already been used safely on over 100 patients with good results. The researchers claim reduced usage of medication with patients waking up faster. This moment by moment titration of drug infusion is likely to be more and more prevalent in anesthesia practice in the future.

The drug used in the study was propofol. In addition, patients also had continuous intravenous infusions of vecuronium and fentanyl. The fentanyl infusion was controlled by a separately controlled software algorithm which is similar in concept to the one controlling the propofol infusion. Of additional interest, the algorithm developed by the researchers includes the ability to control the propofol infusion pump during induction as well, not just during maintenance of anesthesia.

The researchers are still perfecting their software to allow for more precise control of the infusion rates. However, this is proof that the feedback loop can indeed be closed and that infusions can indeed be automated. This has some interesting implications for future research and the way that anesthesia will be delivered in the future.

The researchers intend to develop this into a commercial product. It will be interesting to see how it is received in the anesthesia community. Many still do not utilize the BIS monitor or trust the data that is being derived from it. In addition, there are those that worry that automation of anesthetic delivery may pose risks to patient safety. Lastly, the question is sure to arise as to whether sedation can be given by a computer rather than a trained human being. Clearly. the future of anesthesia is just beginning to be defined.