Regulating Anaesthesia via Computer

Photo: A person lying on OP table with computers around

Computer instead of anaesthesist -
this might be the operation theatre
of the future; © A. Méndez et al.

"This is an efficient control technique which regulates anaesthesia in operating theatres by computer, with the aim of adapting the dose of the drug administered according to the individual characteristics of each patient", the lead author of the study Juan Albino Méndez says.

The new IT system keeps the patient in the desired hypnotic state throughout the operation. It uses sensors and a monitor to record the patient's encephalogram (EEG) and bispectral index (BIS), a parameter without units that measures hypnotic state and relates this to the patient's level of consciousness.

The BIS value fluctuates between 100 - maximum possible state of alertness - and 0 - lack of cortical electrical activity, the state of deepest unconsciousness. This research focuses on the BIS region involved in general anaesthesia, between 40 and 60.

The data are processed by a computer with specific control software, which can control the pump that injects the anaesthetic in order to regulate the amount given. The IT application is based on adaptive Proportional Integral Derivative (PID) algorithms, a control-loop feedback mechanism that automatically controls the right dose according to the measured and desired values.

In order to validate the technique, the researchers successfully carried out simulations using various models they developed themselves, and also tested it on 15 volunteer patients, aged between 30 and 60. "The first results obtained both in surgery and in the simulations, show that the system operates very satisfactorily, and has surgical applications with well-founded expectations of success", says Albino Méndez.

The scientists hope that the method will help to improve anaesthetic-dosing performance during operations and will improve patient recovery times, as well as reducing the costs of operations. The immediate challenges for the team, aside from further developing the algorithmic part of the system, are to incorporate analgesia and muscle relaxation variables into the platform in order to provide anaesthetists with a comprehensive tool.; Source: FECYT - Spanish Foundation for Science and Technology