Modelling Initial Patient Response for Control during General Anaesthesia

C.S. Nunes and T.F. Mendonça (Portugal)


Nonlinear modelling; drug interactions; bispectral index; anaesthesia


To model the effect of anaesthetic drugs on the brain signal Bispectral Index (BIS) is of great importance for a con trol drug infusion system during surgery. In this study, two models for BIS are applied to clinical data of 12 pa tients, considering the anaesthetic propofol and analgesic remifentanil. The first model only uses propofol and ad mits that the analgesic does not have influence on BIS. The second model uses a measure of drug interactions to obtain BIS. The objective was to use these models in clinical data (optimised per patient using nonlinear least squares) during the induction of anaesthesia and analyse if they translate the patient's behaviour under surgery. The first model did not capture the BIS trend. The second model performed well in all patients, leading to the conclusion that the analgesic has an effect on BIS. The model parameters can be further used to adjust an multivariable infusion control system to patients' individual responses, during surgery.

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