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- Do we have today a reliable method to detect the moment of loss of consciousness during induction of general anaesthesia?Publication . Ferreira, Ana Isabel Leitão; Nunes, Catarina S.; Mendes, Joaquim; Amorim, PedroThis review aims to give an overview of the current state of monitoring depth of anaesthesia and detecting the moment of loss of consciousness, from the first clinical signs involved in anaesthesia to the latest technologies used in this area. Such techniques are extremely important for the development of automatic systems for anaesthesia control, including preventing intraoperative awareness episodes and overdoses. A search in the databases Pubmed and IEEE Xplore was performed using terms such anaesthetic monitoring, depth of anaesthesia, loss of consciousness, as well as anaesthesia indexes, namely BIS. Despite the several methods capable of monitoring the hypnotic state of anaesthesia, there is still no methodology to accurate detect the moment of loss of consciousness during induction of general anaesthesia.
- EEG signatures at the transition between conscious and unconscious state during induction of general anesthesia with remifentanil and propofolPublication . Ferreira, Ana Isabel Leitão; Mendes, Joaquim; Amorim, Pedro; Nunes, Catarina S.The precise identification of the moment of Loss Of Consciousness (LOC) during the induction phase of general anesthesia is of extreme importance for the individualization of drug doses. In the lack of an objective method to assess this moment, the development of a new methodology is needed. In this observational study, Electroencephalogram (EEG) signatures that were associated with the moment of LOC are examined as a starting point, so as to create a robust model for tracking the dynamic changes between conscious and unconscious states. The data from 12 patients under general anesthesia for neurosurgical procedures with remifentanil and propofol, are used is this study. Multitaper spectrograms were computed to observe the dynamics of EEG oscillations before and after LOC. At LOC, a decrease in gamma power and an increase in delta and alpha bands were identified.
- Towards personalized anesthesia: predictive factors for propofol requirements for loss of consciousnessPublication . Nunes, Catarina S.; Ferreira, Ana Isabel Leitão; Correia, Rui P.; Amorim, Pedro
- The influence of two different drug infusion profiles on the pharmacodynamics model performancePublication . Ferreira, Ana Isabel Leitão; Nunes, Catarina S.; Gabriel, J.; Amorim, PedroTo model the effect of anesthetic drugs on the Bispectral Index (BIS) of the EEG is of great importance for a reliable predictive response model during surgery. In this study, the impact of using two different drug infusion profiles in a pharmacodynamics interaction model was studied and the methods were compared with respect to their performance. Clinical data of 22 patients were considered. The interaction model was optimized per patient using nonlinear least squares during the induction of anesthesia, and tested for prediction abilities of test patients. In the optimization phase, all models could follow the BIS trend with errors not significantly differ- ent from zero. In the test data the choice of drug infusion pro- file proved to have a significant impact, showing that the per- formance is greatly influenced by the interaction. Results also show a time delay between the BIS signal and the Modeled BIS in both groups. This delay corresponds to a delay in the dy- namics of the patient and could be related to the delay in BIS processing time. This work is an important step to predict the effect of anesthetic drugs.
- Neuro-fuzzy models to predict the required propofol amount for loss of consciousness during general anesthesia: a preliminary studyPublication . Ferreira, Ana Isabel Leitão; Mendes, Joaquim; Amorim, Pedro; Nunes, Catarina S.This study presents several models to predict the total amount of the anesthetic drug propofol required to achieve loss of consciousness during the induction phase of anesthesia, considering different clinical variables. The data from 49 patients under anesthesia for neurosurgical procedures, were used in this study. Takagi-Sugeno-Kang (TSK) fuzzy models were used to describe the effect of clinical variables on the amount of propofol required for loss of consciousness. The parameters of the TSK models were optimized using an Adaptive Network-Fuzzy Interference System. All models were trained with the data of 35 patients and tested with the data of 14 patients. These models proved to have reasonable prediction properties. The fuzzy model with the best balanced performance used only two inputs: the systolic arterial pressure and the Bispectral Index of the EEG.
- Individualized anesthesia: independent predictive factors for the propofol induction targetPublication . Nunes, Catarina S.; Ferreira, Ana Isabel Leitão; Correia, Rui P.; Amorim, Pedro