Modelling of BIS-Index Dynamics for Total Intravenous Anesthesia Simulation in Matlab-Simulink

摘要

The anesthesiologic technique, where substances are injected intravenously, is known as total intravenous anesthesia (TIVA). The anesthesiologist's task is to carefully assess the depth of anesthesia (DoA) and adjusts the injection of intravenous anesthetic agents accordingly. In the paper, we present a framework for studying DoA dynamics within the Matlab-Simulink environment. DoA can be indirectly measured by bispectral index (BIS index), which is calculated from appropriate electroencephalographic (EEG) signals, and is assumed to be influenced primarily by inflow of propofol. The 3-compartmental model is presented and the 4th (virtual) compartment dealing with the effect-site model is introduced. Next, the pharmacodynamic model structure is presented and the BIS-index effect output is formulated. The relevant parameters based on patient's age, weight, height and gender are established. The model is verified by comparing the simulation results to the data obtained during an actual target-controlled anesthetic application of intravenously administered propofol (total duration approx. 70 minutes). The data were recorded by an Orchestra Base Primea infusion workstation and a Lidco monitor. The data parser and the model developed in the Matlab-Simulink environment provide a basis for further refining the dynamic model and for development and validation of closed-loop control approaches for DoA. The presented model allows conducting simulations and tests of various scenarios of propofol administration within the Matlab-Simulink environment with the goal of a deeper insight into the mechanisms of DoA dynamics. This will lead to better administration methods that will benefit the patient, relieve the workload and allow the anesthesiologist to focus on the critical aspects of the procedure.