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Contains fulltext : 89815.pdf (Publisher’s version ) (Open Access) BACKGROUND: The patient state index (PSI) and the bispectral index (BIS) quantify anaesthetic depth based on the EEG using different algorithms. We compared both indices with regard to the prediction of the depth of propofol anaesthesia. METHODS: In 17 patients, propofol was infused until burst suppression occurred and stopped thereafter until BIS recovered to values above 60. This was repeated; afterwards, patients were intubated, for subsequent surgery. Without surgical stimulus, PSI and BIS were measured simultaneously and compared with the estimated effect-site concentrations of propofol. These were derived from simultaneous pharmacokinetic and -dynamic modelling in an individual two-stage and a population-based NONMEM approach. RESULTS: A close sigmoid relationship was observed between the propofol effect-site concentration and both PSI [coefficient of determination rho(2)=0.91 (sd 0.05)] and BIS [rho(2)=0.92 (0.03)], which was significantly steeper for PSI [gamma=2.2 (0.6)] than for BIS [gamma=1.8 (0.4)], and reached significantly lower values for PSI [E(max)=0.3 (1.1)] than for BIS [E(max)=5.3 (6.7)] at maximal propofol concentrations. A significantly smaller k(e0) was obtained for PSI [0.09 (0.03) min(-1)] compared with BIS [0.10 (0.02) min(-1)]. PSI and BIS correlated significantly with each other (rho(2)=0.866) and predicted propofol effect-site concentration with a comparable probability [P(K)=0.87 (0.05) and 0.86 (0.05), respectively]. NONMEM revealed E(0)=89.3 and 92.3, E(max)=1.9 and 8.6, C(e50)=1.38 and 1.92 microg ml(-1), gamma=1.6 and 1.48, and k(e0)=0.103 and 0.131 min(-1) as typical values for PSI and BIS, respectively. CONCLUSIONS: The PSI and the BIS monitors performed equally well in predicting depth of propofol anaesthesia. However, PSI was lower than BIS by approximately 10-15 points at high propofol concentrations. 01 augustus 2010

Background.Thisstudywasdesignedtoinvestigatetheimpactofbispectralindex(BIS)orA-line AAI index (based on middle-latency auditory evoked potential) monitoring on recovery times and drug consumption when compared with standard anaesthetic practice during desfluraneremifentanil anaesthesia. Methods. After having obtained approval from the institutional review board and written informed consent, 200 adult patients undergoing minor surgical procedures were randomized to receive a desflurane-remifentanil anaesthetic controlled either solely by clinical parameters or by BIS or AAI to the following target values: during maintenance of anaesthesia to a value of ‘50’ (BIS) or ‘30’ (AAI), 15 minbefore the end ofsurgery to ‘60’ (BIS)or ‘45’ (AAI). Recovery times and drug consumption were recorded by a blinded investigator. Results. Compared with standard practice, patients with BIS or AAI monitoring needed similar desfluraneconcentrations(standardpractice2.9[0.5]vol%,BIS3.3[0.9]vol%,AAI2.6[0.5]vol%), and had similar recovery times (open eyes 5.6 [2.5] min, 5.9 [3.4] min, 5.0 [3.1] min; extubation 6.3 [2.4] min, 6.6 [3.5] min, 5.6 [3.0] min; stating name 7.3 [2.4] min, 7.6 [3.5] min, 7.3 [6.6] min). Conclusions. Compared with standard anaesthetic practice BIS and AAI guided titration to the used target ranges did not result in a reduction of desflurane consumption or recovery times during minor surgery with use of remifentanil. Br J Anaesth 2005; 94: 63‐9

The bispectral index (BIS) is a complex EEG variable that combines several disparate descriptors of the EEG into a single value. Approximate entropy is a novel EEG measure that quantifies the regularity of a data time series such as EEG. We report two patients in which the EEG effect of propofol was quantified very similarly by BIS and approximate entropy. However, at the beginning of burst suppression of the EEG, BIS did not indicate an increased anaesthetic drug effect, while approximate entropy did.

The dimensionless Narcotrend (NCT) index (MonitorTechnik, Germany, version 4.0), from 100 (awake) to 0, is a new index based on electroencephalogram pattern recognition. Transferring guidelines for titrating the Bispectral Index (BIS, Aspect Medical Systems, USA, version XP) to the NCT index depends on their comparability. We compared the relationship between BIS and NCT values during propofol anaesthesia.Eighteen adult patients about to have radical prostatectomy were investigated. An epidural catheter was placed in the lumbar space and electrodes for BIS and NCT were applied as recommended by the manufacturers. After i.v. fentanyl 0.1 mg, anaesthesia was induced with a propofol infusion. After intubation, patients received bupivacaine 0.5% 15 ml via the epidural catheter. Forty-five minutes after induction, the propofol concentration was increased to substantial burst suppression pattern and then decreased. This was done twice in each patient, and BIS and Narcotrend values were recorded at intervals of 5 s. The efficacy of NCT and BIS in predicting consciousness vs unconsciousness was evaluated using the prediction probability (P(K)).We collected 38 629 artefact-free data pairs of BIS and NCT values from the respective 5-s epochs. Because of artefacts, another 5008 epochs had been excluded from data analysis (3855 epochs for the NCT index alone, 245 epochs for the BIS alone and 908 epochs for both indices). Mean (sd) values in awake patients were 94 (6) for Narcotrend and 91 (8) for BIS. With loss of the eyelash reflex, both values were significantly reduced, to 72 (9) for NCT (P0.001) and to 77 (11) for the BIS index (P0.001). The PK value for loss of eyelash reflex was similar for BIS (0.95) and NCT (0.93). Decreasing BIS values coincided with decreasing NCT values. A sigmoid model [NCT index=52.8+26.8/(1+exp(-(BIS-78.3)/4.8))(0.4); r=0.52] described the correlation between BIS and NCT index in a BIS range between 100 and 50. For BIS values lower than 50, a second sigmoid model with a correlation of r=0.83 was applied [NCT index=6.6+45.3/(1+exp(-(BIS-29.8)/2.4)) (0.6) r=0.83]. The relationship between burst suppression ratio (BSR) and NCT index was best described by the following sigmoid model: NCT index=265/(1+exp((-BSR+108)/-49); r=0.73.We found a sufficient correlation between BIS and NCT index, but deviations from the line of identity in some ranges require attention. Therefore, a simple 1:1 transfer from BIS to NCT values is not adequate. Our results might serve as a blueprint for the rational translation of BIS into NCT values.

The Alaris AEP monitor(TM) (Alaris, UK, version 1.4) is the first commercially available auditory evoked potential (AEP) monitor designed to estimate the depth of anaesthesia. It generates an "Alaris AEP index" (AAI), which is a dimensionless number scaled from 100 (awake) to 0. This study was designed to compare AAI and BIS(TM) (Aspect, USA, version XP) values at different levels of anaesthesia.Adult female patients were premedicated with diazepam 0.15 mg kg(-1) orally on the morning of surgery. Electrodes for BIS and Alaris AEP monitoring and a headphone to give auditory stimuli were applied as recommended by the manufacturers. Anaesthesia was induced with remifentanil (0.4 microg kg(-1) min(-1)) and a propofol target-controlled infusion (Diprifusor(TM) TCI, AstraZeneca, Germany) to obtain a predicted concentration of initially 3.5 microg ml(-1). After loss of consciousness the patients were given 0.5 mg kg(-1) of atracurium. After tracheal intubation, remifentanil was given at 0.2 microg kg(-1) min(-1) and the propofol infusion was adjusted to obtain BIS target values of 30, 40, 50, and 60. AAI and BIS values were recorded and matched with the predicted propofol effect-site concentrations. Prediction probability was calculated for consciousness vs unconsciousness. Values are mean (SD).Fifty female patients, 53 (15), range 18-78 yr, ASA I or II were studied. Mean values before induction of anaesthesia were 95 (4), range 99-82 for BIS and 85 (12), range 99-55 for AAI. With loss of eyelash reflex both values were significantly reduced to 64 (13), range 83-39 for BIS (P0.05) and 61 (22), range 99-15 for AAI (P0.05). The prediction probability P(K) for consciousness vs unconsciousness (i.e. loss of eyelash reflex) was better for BIS (P(K)=0.99) than for AAI (P(K)=0.79). At a BIS of 30, 40, 50, and 60 the corresponding AAI values were 15 (6), 20 (8), 28 (11), and 40 (16), and these were significantly different.During propofol-remifentanil anaesthesia a decrease of the depth of anaesthesia as indicated by BIS monitoring is accompanied by corresponding effects shown by the AAI. However, wide variation in the awake values and considerable overlap of AAI values between consciousness and unconsciousness, suggests further improvement of the AAI system is required.