Browsing by Author "Castro, A."
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- Correlation between clinical signs of depth of anaesthesia and cerebral state index responses in dogs during induction of anaesthesia with propofolPublication . Ribeiro, L. M.; Ferreira, D. A.; Brás, S.; Castro, A.; Nunes, Catarina S.; Amorim, Pedro; Antunes, L. M.The cerebral state index (CSI) is used for monitoring EEG and depth of anaesthesia. The objective of this study was to analyse the correlation between ocular reflexes, CSI and estimated propofol plasma concentrations (PropCP) in dogs during induction of anaesthesia with propofol. Fourteen dogs were premedicated with acepromazine 0.05 mg kg1 IM. Anaesthesia was induced with a 200 ml h1 propofol 1% constant infusion rate until loss of corneal reflex using RugLoop II software with Beths’ pharmacokinetic model to estimate PropCp. Palpebral reflex (PR) and the corneal reflex (CR) were tested every 30 s and classified as present (+) or absent (), and eyeball position was registered as rotated ventromedialy (ERV) or centred (EC). Heart rate (HR), mean arterial pressure (MAP) and CSI values were analyzed from baseline before the beginning of propofol infusion (T0) until loss of CR; CSI and PropCp, CSI and anaesthetic planes, and PropCp and anaesthetic planes were compared using correlation analysis. PropCp reached 7.65 ± 2.1 lg ml1 at the end of the study. CSI values at T0 were 89.2 ± 3.8. Based on the observation of ocular reflexes and eyeball position, it was possible to define five anaesthetic planes: A (superficial) to E (deep), being A (PR+/CR+/EC), B (PR+/ERV/CR+), C (PR/ERV/CR+), D (PR/EC/CR+) and E (PR/EC/CR). There was a significant correlation between PropCp and the anaesthetic planes (R = 0,861; P < 0.01). No significant correlation was observed between CSI and the anaesthetic planes or between CSI and PropCp. MAP decreased significantly from T0 until loss of corneal reflex (from 98 ± 14 mmHg to 82 ± 12 mmHg); HR did not change significantly (from 101 ± 30 bpm to 113 ± 16 bpm). The CSI monitoring was not consistent with the clinical observations observed in the different stages of depth anaesthesia. This could limit the use of CSI for monitoring depth of anaesthesia with propofol.
- Modelling the dynamics of depth of anaesthesia: cerebral state index in dogsPublication . Bressan, Nadja; Castro, A.; Bras, S.; Ribeiro, L.; Ferreira, D. A.; Silva, A.; Antunes, L.; Nunes, Catarina S.The goal of this study was to obtain models that described the relation between the anaesthetic drug infusions (propofol) and an electroencephalogram (EEG) derived index (Cerebral State Index - CSI) during general anaesthesia in dogs. The first phase integrated the adaptation of hardware for EEG acquisition and exploration for the best electrodes position in dogs skull. The clinical protocol implementation and data collection were the next steps followed by CSI modeling. CSI showed adequate response to changes in drug infusion, reflecting the changes of depth of anaesthesia in dogs. The models obtained adjusted well to the original CSI data and also predicted the CSI trend during surgery. Using this monitor in current practice might improve quality in the anaesthesia procedure providing a useful tool to administer a correct sedation.
- A wavelet based method for steady-state detection in anesthesiaPublication . Castro, A.; Almeida, F. G.; Amorim, Pedro; Nunes, Catarina S.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.