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ABSTRACT: Target Controlled Infusion (TCI) systems are based in drug Pharmacokinetic (Pk) and Pharmacodynamic (Pd) models implemented in an algorithm to drive an infusion device. Several studies had compare manual titration of anesthesia and TCI system use; some studies evaluate the performance of the control algorithms for TCI systems, and a considerable number of studies assess the performance of Pk/Pd models implemented into TCI systems. This study presents a set of tests to validate the performance of a TCI system as a computer-aided. The goal of the current study was to assess the performance of the TCI system, Anaesthesia Synchronization Software (ASYS), on clinical set up to evaluate communication consistence (computer - infusion device) and controller performance in real time. These measures provided quantitative and qualitative evidences of software robustness and accuracy to be used at clinical environment.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:6777-80.
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ABSTRACT: Patients with hypertension may be more prone to develop hypotension as a consequence of opioid administration under general anesthesia. The hemodynamic and bispectral index responses to a remifentanil bolus in neurosurgical hypertensive patients under target-controlled infusion with propofol and remifentanil are addressed.
Ten healthy patients and 10 patients with diagnosed hypertension under pharmacological treatment were studied. A 2 microg/kg remifentanil bolus was administered to all patients before skin incision under target-controlled infusion with propofol and remifentanil. Mean arterial pressure, heart rate, and the area under the curve for the bispectral index of the electroencephalogram were analyzed within the groups and compared between them every 30 seconds for two minutes following the bolus.
Two minutes after the remifentanil bolus, remifentanil predicted effect-site concentrations reached maximum values of 8.46+/-0.91 ng/ml and 9.74+/-1.29 ng/ml in the healthy and hypertensive patients, respectively. Both groups showed a significant decrease in mean arterial pressure, heart rate, and in the area under the curve for the bispectral index. Mean arterial pressure decreased by 17.3+/-10% and 24+/-9%, heart rate by 11.1+/-8% and 12+/-8%, and the bispectral index by 13+/-9.2% and 8.6+/-8.4% in the healthy and hypertensive patients, respectively, 120 seconds after the remifentanil bolus.
In a clinical situation in which high remifentanil doses may be required, hypertensive patients are expected to have hemodynamic and bispectral index responses similar to those observed in healthy patients.
Medical science monitor: international medical journal of experimental and clinical research 11/2009; 15(11):CR551-5. · 1.70 Impact Factor
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ABSTRACT: To investigate whether a patient's propofol effect-site concentration at return to consciousness (ROC) was related to the propofol effect-site concentration at loss of consciousness (LOC) and to patients' individual demographic parameters.
Prospective study.
Operating room.
31 ASA physical status I and II neurosurgical patients with Glasgow Coma Score > 15, and scheduled to receive total intravenous anesthesia with effect-site target controlled infusion (TCI) of propofol and remifentanil.
A constant propofol infusion was administered until LOC. At LOC, remifentanil started with a plasma concentration target of 2.5 ng mL(-1).
Propofol concentration at LOC was 4.9 +/- 1 microg mL(-1). At ROC, propofol and remifentanil concentrations were 1.16 +/- 0.3 microg mL(-1) and 3.41 +/- 1.5 ng mL(-1). Significant correlation was observed between propofol concentrations at ROC and LOC, between propofol concentration at ROC and patient age (48.7 +/- 15 yrs), and between propofol concentrations at ROC and LOC, divided by patient's age.
The correlation between propofol concentrations at ROC and LOC was improved by inclusion of patient age data.
Journal of clinical anesthesia 03/2009; 21(1):3-8. · 1.32 Impact Factor
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BIOSIGNALS 2009 - Proceedings of the International Conference on Bio-inspired Systems and Signal Processing, Porto, Portugal, January 14-17, 2009; 01/2009
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ABSTRACT: With the recent concern on patient's outcome following general anesthesia, automatic control of drugs has been a field of interest. The Bispectral Index (BIS) is an EEG based hypnosis monitor, in current use at the operating theatre as a guiding tool for the anesthesiologist to titrate drugs, and prevent awareness. When trying to model a certain process, it's very important to obtain information of the system behavior under steady-state conditions. In this study the hypnotic and analgesic drugs' effect on the hypnosis index BIS was analyzed, in order to obtain steady-state information of the system response (inputs-output), and in the future model the drugs combined effect. A steady-state index was obtained using a wavelet analysis technique for trend detection. This tool may be used in the future to model the drug's combined effect on the hypnosis indices, and also to bring some insight on disturbances not related to drug changes.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:954-7.
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ABSTRACT: Target Controlled Infusion (TCI) systems are based in drug pharmacokinetic and pharmacodynamic models implemented in an algorithm to drive an infusion pump. Infusion control algorithms have been designed, implemented and validated for several anesthetic drugs, devices and controllers. The maintenance phase in these algorithms is represented by an equation that compensates the loss of drug from the central compartment and maintains the set target concentration. The goal of the current study was to improve existing TCI software with a new method for the maintenance phase. We compared and analyzed two different methods to find the more efficient method for the maintenance phase in an open-loop control TCI system.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:6234-7.
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ABSTRACT: The problem of controlling the level of unconsciousness measured by the Bispectral Index (BIS) of the EEG of patients under anaesthesia is considered. The manipulated variable is the infusion rate of the hypnotic drug propofol. In order to tackle the high uncertainties present in the system, the predictive adaptive controller MUSMAR is used. The performance of the controller is illustrated by means of simulations with 50 patient individual adjusted models (nonlinear models), which incorporate the effect of the drugs interaction on BIS. This work presents a feasibility study of the control of the BIS exploring the above ideas. These results show that such a control structure can be adequate to control the BIS signal during total intravenous anaesthesia. The controller was able to adequately achieve and maintain the BIS signal with different patient dynamics, reference values and noise. A major challenge for the automation of anaesthesia consists of replicating the experience of the anaesthetist. Clearly, this calls for the use of feedforward from measurable signals correlated with disturbances (e.g. electromyography—EMG, analgesic drug). The results also show that the analgesic and EMG have different influences on the performance and therefore carry different but relevant information. Copyright © 2008 John Wiley & Sons, Ltd.
International Journal of Adaptive Control and Signal Processing 11/2008; 23(5):485 - 503. · 0.91 Impact Factor
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ABSTRACT: The aim of this study was to evaluate the correlation between the cerebral state index (CSI) and the estimated propofol plasma concentrations in dogs during induction of anaesthesia. Fifteen healthy dogs undergoing scheduled routine surgical procedures were enrolled in this study. Target controlled infusion (TCI) software, based on the pharmacokinetic model for propofol, was used to control the syringe pump and to estimate plasma propofol concentrations (PropCp) and the CSI values every five-seconds. Three electrodes placed in the centre of the forehead, on the left side of the forehead and on the left mastoid were used to collect the electroencephalographic (EEG) signal converted by the cerebral state monitor into the CSI. The cerebral electrical changes induced by increasing propofol concentrations appear to be detected by CSI monitoring in dogs. The negative correlation between CSI and PropCp demonstrates that the CSI could be used to assess electrical brain activity in dogs during the induction of anaesthesia with propofol.
Research in Veterinary Science 11/2008; 85(2):227-32. · 1.65 Impact Factor
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Nadja Bressan,
Ana Castro,
Carlos Braga,
Jose Lages,
Nuno R. Silva,
Paulo Portela,
Pedro Miranda,
Sergio Oliveira,
Joaquim Mendes, Pedro Amorim,
Catarina S. Nunes
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ABSTRACT: This work presents the improvement of a software for a clinical setup, the Anesthesia Synchronization Software (ASYS). The first version presented the data acquisition from cerebral monitors and a partial control with Target Controlled Infusion (TCI) system. Based on pharmacokinetic models, the effect-site and plasma concentrations can be related with the drug dose infused and vice versa. This later version comes with the implementation of the hemodynamic monitor always present in operating rooms and with the full TCI system developed to determine the infusion rates of the drug which are given as commands to the infusion pumps.
Engineering in Medicine and Biology Society, 2008. EMBS 2008. 30th Annual International Conference of the IEEE; 09/2008
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ABSTRACT: To compare propofol-predicted effect-site concentrations (PropCe) and bispectral index (BIS) of the electroencephalogram during induction of anesthesia in patients with small brain tumors and to analyze BIS and PropCe at loss of consciousness (LOC).
Prospective investigation.
Operating theater of a university hospital.
26 ASA physical status I and II patients, 13 of whom were scheduled for nontumor spinal surgeries, and the other 13, for brain surgery for small brain tumor removal.
Anesthesia was induced with a propofol 1% constant infusion rate of 200 mL/h until LOC.
BIS, PropCe, heart rate, and mean arterial pressure were analyzed at the beginning of the propofol infusion and every 30 seconds during induction.
The BIS values were significantly higher in patients with brain tumors in the period from 150 to 210 seconds, with PropCe similar to patients without brain tumors. Loss of consciousness occurred 3.6 +/- 0.8 minutes in patients without brain tumors and 3.9 +/- 0.7 minutes in patients with brain tumors. No differences were observed between groups in the time to LOC (3.6 +/- 0.8 in group 1 vs 3.9 +/- 0.7 in group 2) or in BIS at LOC (48.7 +/- 11.4 in group 1 vs 58.6 +/- 21.7 in group 2).
For similar propofol concentrations, patients with small brain tumors show higher BIS values on induction of anesthesia with propofol.
Journal of Clinical Anesthesia 04/2008; 20(2):116-21. · 1.21 Impact Factor
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ABSTRACT: The effect of drugs' interaction on the hemo-dynamic variables is of great importance when considering patient's safety and stability. It is also important for control infusion systems during anesthesia. In this article, an adaptive-network fuzzy inference system is used to model the effect of two drugs (propofol and remifentanil) on the mean arterial pressure and heart rate. The clinical data of 45 patients is used to train and test the model. The use of subtractive clustering improved the model performance on the testing data set. The fuzzy model is able to capture the synergistic interaction between the two drugs, but other influences were detected.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2008; 2008:5814-7.
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ABSTRACT: Nowadays general anesthesia is maintained using as the controller the human intervention, relying only on the quick and certain response of the anesthesiologist to the surrounding conditions, in order to provide the adequate state of anesthesia for the three main components - hypnosis, analgesia and paralysis. One of the most advantageous breakthroughs in anesthesia has been the appearance of depth of anesthesia monitors, assisting anesthesiologists in the hard job of knowing the hypnotic state of a patient. This information allows a way of closing the loop for administration of the hypnotic drug, and a more secure maintenance of hypnosis. The objective of this work was to apply sliding-mode control techniques to the model structure of the hypnotic in the human body (measured by the effect), and evaluate the robustness of this method to expected deviations from the average patient.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2008; 2008:5810-3.
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Nadja Bressan,
Ana Castro,
Carlos Braga,
Jose Lages,
Nuno R Silva,
Paulo Portela,
Pedro Miranda,
Sergio Oliveira,
Joaquim Mendes, Pedro Amorim,
Catarina S Nunes
[show abstract]
[hide abstract]
ABSTRACT: This work presents the improvement of a software for a clinical setup, the Anesthesia Synchronization Software (ASYS). The first version presented the data acquisition from cerebral monitors and a partial control with Target Controlled Infusion (TCI) system. Based on pharmacokinetic models, the effect-site and plasma concentrations can be related with the drug dose infused and vice versa. This later version comes with the implementation of the hemodynamic monitor always present in operating rooms and with the full TCI system developed to determine the infusion rates of the drug which are given as commands to the infusion pumps.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2008; 2008:5543-7.
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ABSTRACT: The effect of drugs' interaction on the brain signal Bispectral Index (BIS) is of great importance for an anesthesia control drug infusion system. In this study, the objective was to inspect the influence of patient's heart rate on the effect of the drugs on BIS. With this goal, the patient's heart rate was incorporated in an drug interaction model. The model was fitted per patient during anesthesia induction, and tested for prediction under surgery. The results showed that the model with time changing parameters incorporating patient's heart rate has a better performance than a non adjusted model. Three clusters of models were also identified using the fuzzy c-means algorithm. These clusters will help to distinguish between different patients' dynamics.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:6480-3.
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ABSTRACT: This work presents the development of a software for data acquisition and control (ASYS) on a clinical setup. Similar to the industrial Supervisory Control And Data Acquisition (SCADA) the software assembles a Target Controlled Infusion (TCI) monitoring and supervisory control data in real time from devices in a surgical room. The software is not a full controller since the TCI systems comprehend permanent interaction from the anesthesiologist. Based on pharmacokinetic models, the effect-site and plasma concentrations can be related with the drug dose infused and vice versa. The software determines the infusion rates of the drug which are given as commands to the infusion pumps. This software provides the anesthesiologist with a trustworthy tool for managing a safe and balanced anesthesia. Since it also incorporates the acquisition and display of patients brain signals.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:5298-301.
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ABSTRACT: The problem of controlling the level of depth of anesthesia measured by the Bispectral Index (BIS) of the electroencephalogram of patients under general anesthesia, is considered. It is assumed that the manipulated variable is the infusion rate of the hypnotic drug propofol, while the drug remifentanil is also administered for analgesia. Since these two drugs interact, the administration rate of remifentanil is considered as an accessible disturbance in combination with the level of electromyography (EMG) that also interferes with the BIS signal. In order to tackle the high uncertainty present on the system, the predictive adaptive controller MUSMAR is used. The performance of the controller is illustrated by means of simulation with 45 patient individual adjusted models, which incorporate the effect of the drugs interaction on BIS. This controller structure proved to be robust to the EMG and remifentanil disturbances, patient variability, changing reference values and noise.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:1574-7.
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ABSTRACT: Because of the complexity of raw electroencephalogram (EEG), for the anesthesiologist it is very difficult to evaluate the patient's hypnosis state. Because of this, several depth of anesthesia monitors have been developed, and are in current use at the operating room (OR). These monitors convert the information supplied by the EEG or derived signals into a simple, easy to understand index. Nowadays, general anesthesia is controlled only by the clinician, which decides what is the best drug combination for the patient, regarding all information given by monitors and sensors in the OR. In this work, we collected data from two study groups with auditory evoked potentials (AEP) monitoring, and Entropy (SE) monitoring. A model was fitted to the signals and the Hill equation parameters adjusted, in both study groups. The objective was to predict hypnosis indices, regarding only the drugs administered to a patient, and capture the initial individual patient characteristics that might influence the drugs interaction in the human body. Hypnotic and analgesic drugs interact in different ways throughout the anaesthesia stages. The models obtained captured the different dynamic interaction of drugs, during the induction and maintenance phases, demonstrating that the model must have incorporated all this information in order to perform satisfactorily. Other information like haemodynamic variables might be included in the search for the optimum model.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:1949-52.
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ABSTRACT: The problem of controlling the level of unconsciousness measured by the BIS index of patients under anesthesia, is considered. It is assumed that the manipulated variable is the administration rate of propofol, while remifentanil is also administered for analgesia. Since these two drugs interact, the administration rate of remifentanil is considered as an accessible disturbance. A predictive adaptive controller structure that explores this fact is proposed and illustrated by means of simulation.
Computer Aided Control System Design, 2006 IEEE International Conference on Control Applications, 2006 IEEE International Symposium on Intelligent Control, 2006 IEEE; 11/2006
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Anesthesiology 01/2006; 103(6):1320-1. · 5.36 Impact Factor
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Knowledge-Based Intelligent Information and Engineering Systems, 10th International Conference, KES 2006, Bournemouth, UK, October 9-11, 2006, Proceedings, Part II; 01/2006
