Monitoring and Control in Anaesthesia: an Implementation Example

Transcription

1 Case Study: Depth of Anaesthesia (DOA) Anaesthesia includes paralysis, unconsciousness (i.e. DOA) and analgesia; Monitoring and Control in Anaesthesia: an Implementation Example Catarina S. Nunes Department of Applied Mathematics Faculty of Sciences, University of Porto, Portugal Balanced anaesthesia, i.e. use of 3 drugs; DOA direct measurements are not available; The Bispectral Index (BIS) of the Electroencephalogram (EEG), a multivariable regression model combining different features into a linear numeric index, ranging from 0 (isoelectric EEG) to 100 (fully awake). Auditory evoked potentials (AEP), i.e. evoked brain potentials, are used to measure DOA (AEP are EEG responses to clicks applied to both ears). State Entropy: EEG and EMG processing using Spectral Entropy. Research Awareness Main Investigation topics Modelling, identification and forecasting methods Data analysis, clustering and knowledge extraction Neural and decision support networks Mathematical aspects of control systems design Fault detection and alarm systems Development and implementation of hybrid control algorithms Software development Medical Applications Automatic control of drug delivery systems Decision support and control in anaesthesia Modelling and control of physiologic variables Anesthesia awareness is the phenomenon of being mentally alert (and terrified) while supposedly under full general anesthesia. The patient is paralyzed, unable to speak, and totally helpless to communicate his/her awareness. Actual cutting pain may or may not be present. The mission of the Anesthesia Awareness Campaign is to prevent patients (even one) from experiencing anesthesia awareness and its consequences through education, prevention, and empowerment by replacing ignorance or fear with knowledge. Anesthesia awareness continues to be reported between times daily in the United States, in addition to an unknown number worldwide. Researchers believe that anesthesia awareness is under-reported by 50%-100% and occurs between 4-6 times more often in pediatric surgeries

2 AIM Research Team DEPTH OF ANAESTHESIA Model Variability Reference Error Action Unconsciousness Control University of Trás-os-Montes & Alto Douro (Department of Veterinary) Luís Antunes David A. Ferreira Animal Hospital of Porto Lénio Ribeiro (also PhD Student) Institute of Molecular and Celular Biology (Animal Welfare) Ana Olsen, Ana MariaValentim (Scholarship) Drug Interaction Analgesia PhD Students: Heber Alves University Fernando Pessoa Porto (Pharmacology) Pedro Barata Institute of Oncology (Genetics) Rui Medeiros Research Team Case Study: Depth of Anaesthesia (DOA) Faculty of Sciences (Department of Applied Mathematics) Hospital Geral de Santo António (Department of Anaesthesiology) clinician Catarina S. Nunes Teresa Feio Mendonça Scholarships: Nadja Bressan Ana Castro PhD Students: Susana Brás Pedro Amorim Francisco Lobo (also PhD Student) Neurosurgery: Isabel Alexandra Santos Manuela Casal Leónia Ferreira Urology: Eduarda Amadeu Paula Sá Couto Fátima Martins computer infusion control pump algorithm disturbances intravenous administration sensor induced effect patient time varying observation noise Control objective: tracking a reference level Global main features:!high interindividual variability!input constraints in the control action!level noise in measurements!high degree of reliability!good performance!time varying parameters 3 4

3 Pharmacodynamic Drug Interactions Interaction Model Zero-interaction: the effect of the combination is the sum of the effects of the individual agents; Synergistic: the effect of the combination is greater than that expected as based on the concentration effect relationships of the individual agents; Antagonistic: the effect of the combination is less than the sum of the effects of the individuals; Propofol (anaesthetic) and Remifentanil (analgesic) have a synergistic interaction. Effect = Normalised concentrations to the respective potencies Number of units (U) associated with 50% of maximum effect at ratio " Potency of the mixture Bruhn, J.; et al., 2003, Anesthesiology, vol. 98, pp Initial Patient Response Anaesthesiologist! 15 minutes (non-steady state) BIS BIS Goal: Extracting from initial data Patient individual features minutes minutes Control Modelling Real BIS values 45 Patients Modelled BIS Nunes CS, Mendonça TF, Antunes L, Ferreira DA, Lobo F, Amorim P. Modelling Drug s Pharmacodynamic Interaction during General Anaesthesia: the choice of Pharmacokinetic Model. Modelling and Control in Biomedical Systems 2006 (Including Biological Systems). D. D. Feng, O. Dubios, J. Zaytoon and E. Carson, eds. Oxford, United Kingdom, Elsevier Science Ltd: ,

4 Predictive Adaptive Control of the Bispectral Index of the EEG (BIS) - using the intravenous anaesthetic drug propofol Mendonça T, Nunes CS, Magalhães H, Lemos JM, Amorim P: Predictive Adaptive Control of Unconsciousness Exploring Remifentanil as an Accessible Disturbance. Proceedings of the IEEE International Conference on Control Applications, CCA06, Munich, Germany, October 4-6, pp , LNAI 4253 (Springer), Part 2: pp , MUSMAR Fuzzy Logic ANFIS Modelling BIS Journal of Intelligent and Fuzzy Systems 16(1):15-22,

5 Trainning Data Testing Data 9