Closed-Loop Control of Anesthesia - A Review

In many fields of human endeavour, ranging from the mundane such as DVD players to the technologically advanced such as space flight, control systems have become ubiquitous, to the point that control technology has been termed by Karl Aström the “hidden technology”. However, in the field of anesthesia, despite efforts going back to 1950, closed-loop control is rarely used to automate the delivery of drugs to safely achieve and maintain a desired clinical effect. This might be because of the complexity of physiological systems, the poor understanding of anesthetic drug mechanisms, the large inter-patient variability, and the difficulty in sensing. Following a brief introduction to general anesthesia, those challenges will be reviewed from a control engineering perspective. Recent developments in sensing and monitoring have resulted in renewed interest in automatic control of anesthesia. These developments will be discussed, and then recent research in control of depth of anesthesia, as well as in analgesia, neuromuscular blockade will be reviewed. The appropriateness of various control methodologies for this problem will also be discussed.