Untitled

Funder

Organizational Unit

Publications

Modelling drugs' pharmacodynamic interaction during general anaesthesia: the choice of pharmacokinetic model

Publication . Nunes, Catarina S.; Mendonça, Teresa F.; Antunes, Luís; Ferreira, David A.; Lobo, Francisco; Amorim, Pedro

The effect of drugs’ interaction on the brain signal Bispectral Index (BIS) is of great importance for an anaesthesia control drug infusion system. In this study, two renowned pharmacokinetic (PK) models for propofol are compared, in order to evaluate its influence on the performance/predictably of a drug interaction model for BIS, considering data of 45 patients. The model was fitted per patient during anaesthesia induction, and tested for prediction under surgery. The results showed that the choice of PK model had influence on the overall performance. In the prediction phase, only one PK model presented good results with small errors.

2006Book part

Open access

Predictive adaptive control of the bispectral Index of the EEG (BIS): using the intravenous anaesthetic drug propofol

Publication . Nunes, Catarina S.; Mendonça, Teresa F.; Magalhães, Hugo; Lemos, João M.; Amorim, Pedro

The problem of controlling the level of unconsciousness measured by the Bispectral Index of the EEG (BIS) of patients under anaesthesia, 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 order to tackle the high uncertain 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 remifentanil disturbance, different reference values and noise. A reduction of propofol consumption was also observed when comparing to the real clinical dose used for a similar BIS trend.

2006Conference object

Open access

Remifentanil bolus dose is a safe procedure to control intense noxious stimuli in hypertensive neurosurgical patients

Publication . Ferreira, David A.; Nunes, Catarina S.; Lobo, Francisco; Antunes, Luís M.; Amorim, Pedro

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 µg/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.

2009Journal article

Open access

Brain monitoring in dogs using the cerebral state index during the induction of anaesthesia via target-controlled infusion of propofol

Publication . Ribeiro, Lénio M.; Ferreira, David A.; Bressan, Nadja; Nunes, Catarina S; Amorim, Pedro; Antunes, Luis M.

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.

2008Journal article

Restricted access

Regular clinical use bispectral index monitoring may result in lighter depth of anesthesia as reflected in average higher bispectral index values

Publication . Nunes, Catarina S.; Ferreira, David A.; Antunes, Luís M.; Amorim, Pedro

2005Journal article

Open access