Narcotrend,bispectral index,and classical electroencephalogram variables during emergence from propofol/remifentanil anesthesia

The aim of this study was to investigate modern and classical electroencephalographic (EEG) variables in response to remifentanil and propofol infusions. We hypothesized that modern EEG variables may indicate the effects of propofol but not of remifentanil. Twenty-five patients were included in the study after the end of elective spine surgery without any surgical stimulation. Baseline values were defined with remifentanil 0.3 microg. kg(-1). min(-1) and target-controlled infusion of propofol 3.0 microg/mL. EEG changes were evaluated 1, 3, 5, 7, and 9 min after the stop of remifentanil infusion, followed by a step-by-step reduction (0.2 microg/mL) every 3 min of target-controlled infusion propofol. Narcotrend (NT; classifying EEG stages from awake to deep anesthesia), bispectral index (BIS), EEG spectral frequency bands (%), 50% (Median) and 95% percentiles (spectral edge frequency), mean arterial blood pressure, heart rate, and oxygen saturation were detected at every time point. The end of remifentanil application resulted in significant increases in %alpha, spectral edge frequency, mean arterial blood pressure, and %theta and decreases in %delta (P < 0.05). NT, BIS, Median, heart rate, and oxygen saturation were unchanged. Decreases in propofol concentration were associated with statistically significant increases in NT and BIS (P < 0.05). Thus, the sedative-hypnotic component of propofol could be estimated by modern EEG variables (NT and BIS), whereas the analgesic component provided by remifentanil was not indicated. However, during conditions without surgical stimulation, neither NT nor BIS provided an adequate assessment of the depth of anesthesia when a remifentanil infusion was used. IMPLICATIONS: We investigated modern and classical electroencephalographic (EEG) variables during emergence from propofol/remifentanil anesthesia. Modern EEG variables indicate changes of infusion in propofol, but not in remifentanil. Thus, modern EEG variables did not provide an adequate assessment of depth of anesthesia when remifentanil was used.     

Comparability of Narcotrend index and bispectral index during propofol anaesthesia

Background. The dimensionless Narcotrend^TM (NCT) index (MonitorTechnik,Germany, version 4.0), from 100 (awake) to 0, is a new indexbased on electroencephalogram pattern recognition. Transferringguidelines for titrating the Bispectral Index^TM (BIS, AspectMedical Systems, USA, version XP) to the NCT index depends ontheir comparability. We compared the relationship between BISand NCT values during propofol anaesthesia. Methods. Eighteen adult patients about to have radical prostatectomywere investigated. An epidural catheter was placed in the lumbarspace and electrodes for BIS and NCT were applied as recommendedby the manufacturers. After i.v. fentanyl 0.1 mg, anaesthesiawas induced with a propofol infusion. After intubation, patientsreceived bupivacaine 0.5% 15 ml via the epidural catheter. Forty-fiveminutes after induction, the propofol concentration was increasedto substantial burst suppression pattern and then decreased.This was done twice in each patient, and BIS and Narcotrendvalues were recorded at intervals of 5 s. The efficacy of NCTand BIS in predicting consciousness vs unconsciousness was evaluatedusing the prediction probability (P_K). Results. We collected 38 629 artefact-free data pairs of BISand NCT values from the respective 5-s epochs. Because of artefacts,another 5008 epochs had been excluded from data analysis (3855epochs for the NCT index alone, 245 epochs for the BIS aloneand 908 epochs for both indices). Mean (SD) values in awakepatients were 94 (6) for Narcotrend and 91 (8) for BIS. Withloss of the eyelash reflex, both values were significantly reduced,to 72 (9) for NCT (P<0.001) and to 77 (11) for the BIS index(P<0.001). The P_K value for loss of eyelash reflex was similarfor BIS (0.95) and NCT (0.93). Decreasing BIS values coincidedwith 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 indexin a BIS range between 100 and 50. For BIS values lower than50, a second sigmoid model with a correlation of r=0.83 wasapplied [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 sigmoidmodel: NCT index=265/(1+exp((–BSR+108)/–49); r=0.73. Conclusions. We found a sufficient correlation between BIS andNCT index, but deviations from the line of identity in someranges require attention. Therefore, a simple 1:1 transfer fromBIS to NCT values is not adequate. Our results might serve asa blueprint for the rational translation of BIS into NCT values.     

Auditory information processing during adequate propofol anesthesia monitored by electroencephalogram bispectral index

Memory for intraoperative events may arise from inadequate anesthesia when the hypnotic state is not continuously monitored. Electroencephalogram bispectral index (BIS) enables monitoring of the hypnotic state and titration of anesthesia to an adequate level (BIS 40 to 60). At this level, preserved memory function has been observed in trauma patients. We investigated memory formation in elective surgical outpatients during target-controlled propofol anesthesia supplemented with alfentanil. While BIS remained between 40 and 60, patients listened to a tape with either familiar instances (exemplars) from two categories (Experimental [E] group, n = 41) or bird sounds (Control [C] group, n = 41). After recovery, memory was tested directly and indirectly. BIS during audio presentation was on average (+/- SD) 44 +/- 5 and 46 +/- 5 for Groups E and C, respectively. No patient consciously recalled the intraoperative period, nor were presented words recognized reliably (Group E, 0.9 +/- 0.8 hits; Group C, 0.8 +/- 0.8 hits) (P = 0.7). When asked to generate category exemplars, Group E named 2.10 +/- 1.0 hits versus 1.98 +/- 1.0 in Group C (P = 0.9). We found no explicit or implicit memory effect of familiar words presented during adequate propofol anesthesia at BIS levels between 40 and 60 in elective surgical patients. IMPLICATIONS: This study suggests that stable levels of adequate hypnosis may prevent information processing and memory formation during general anesthesia and supports the feasibility of electroencephalogram bispectral index as a monitor of adequate anesthesia.     

Auditory evoked potentials index versus bispectral index during propofol sedation in spinal anesthesia

Purpose  It is still controversial whether an electroencephalogram could be a useful monitor of sedation levels. The present study was performed to compare the bispectral index (BIS) and the auditory evoked potentials index (AAI) during light sedation with propofol infusion in spinal anesthesia. Methods  Eighty patients, aged 20 to 70 years, scheduled for surgery of the lower extremities under spinal anesthesia were assigned to one of four groups (20 patients each). Patients in the AAI propofol and BIS propofol groups were sedated with propofol infusion at an initial rate of 2 mg·kg⁻¹·h⁻¹. Propofol infusion was controlled to try to keep the observer’s assessment of alertness/sedation (OAAS) scale at 3 or 4. Patients in the AAI control and BIS control groups did not receive propofol. Results  The OAAS scales and the AAI or BIS decreased significantly in all groups during surgery, while the decrease was larger in the AAI propofol and BIS propofol groups. The AAI was significantly lower along with lower OAAS scales. There was no overlap in the AAI between OAAS scale 3 and scale 5 in the AAI propofol group, while in the BIS propofol group, no difference was observed in the BIS among OAAS scales 2, 3, 4, and 5. Conclusion  The AAI, but not the BIS, could discriminate slight changes of consciousness during light sedation with propofol infusion in patients with spinal anesthesia. This work was done at the Department of Anesthesiology, Ofuna Chuo Hospital, Kanagawa, Japan.     

Cerebral state index versus bispectral index during propofol–fentanyl–nitrous oxide anesthesia

Purpose  

The aim of this study was to compare the cerebral state index (CSI) and bispectral index (BIS) during propofol–fentanyl–nitrous oxide anesthesia.     

A case of awareness during propofol anesthesia using bispectral index as an indicator of hypnotic effect

A 77-year old, woman weighing 44 kg with mild liver dysfunction underwent lower abdominal surgery. Anesthesia was induced with propofol 60 mg and fentanyl 0.1 mg. Tracheal intubation was facilitated with vecuronium 8 mg, and the lungs were ventilated with 33% oxygen in air. The bispectral index (BIS) was continuously monitored. Anesthesia was maintained with propofol infusion and analgesia was provided by thoracic epidural infusion of lidocaine 1.5%. The infusion rate of propofol was altered to maintain the BIS value between 40 and 50. The patient was hemodynamically stable with propofol 1.5 mg.kg-1.hr-1 and the BIS value was maintained about 40 during the operation. Near the end of the operation the patient moved suddenly. Suspecting inadequate anesthesia, a total of 40 mg of propofol i.v. and 5 ml of the epidural infusion were given. Immediately before the movement the BIS value was about 40. The operation was completed 30 min later. On discharge from the operating room the patient declared that she had been awake. She had heard voices and felt the surgeon working, but had suffered no pain. The BIS is a useful indicator for hypnotic effect, but this case demonstrates that awareness might occur even when BIS value indicates adequate hypnotic state.     

Remifentanil dose/electroencephalogram bispectral response during combined propofol/regional anesthesia

The effect of opioid administration on the bispectral index (BIS) during general anesthesia is controversial. Several investigators have reported BIS to be insensitive to opioid addition, whereas others have found a hypnotic response. We designed this study to examine the effect of remifentanil on BIS during combined regional/general propofol anesthesia under steady-state conditions. After Human Investigations Committee approval, 19 healthy ASA physical status I or II patients were enrolled in a prospective experimental design. Regional anesthesia was initiated and general anesthesia induced by using computer-assisted continuous infusion of propofol. Propofol was incrementally adjusted to a BIS of approximately 60. After 20 min at a stable propofol infusion rate, a remifentanil computer-assisted continuous infusion (effect-site target concentration of 0.5, 2.5, and then 10 ng/mL) was sequentially administered at stepped 15-min intervals. BIS decreased from 56 +/- 2 to 44 +/- 1, 95% spectral edge frequency from 17.9 +/- 0.5 Hz to 15.0 +/- 0.4 Hz, heart rate from 84 +/- 5 bpm to 62 +/- 4 bpm, and mean arterial blood pressure from 93 +/- 4 mm Hg to 69 +/- 3 mm Hg with increasing remifentanil concentration. A significant linear correlation between BIS, 95% spectral edge frequency, heart rate, and log (remifentanil effect-site) concentration was found. The change in baseline BIS was relatively modest but significant, suggesting that remifentanil has some sedative/hypnotic properties, or that it potentiates the hypnotic effect of propofol. IMPLICATIONS: This experiment identified a significant, dose-dependent decrease in bispectral index (BIS), 95% spectral edge frequency, heart rate, and mean arterial blood pressure with increasing remifentanil dose. The change in baseline BIS was relatively modest but significant, suggesting that remifentanil has some sedative/hypnotic properties, or that it potentiates the hypnotic effect of propofol.     

The effect of lidocaine on the bispectral index during anesthesia induction with propofol]

We investigated the effect of premixing lidocaine with propofol on a bispectral index (BIS) during propofol infusion. We studied 40 adult patients given mixture of 1% propofol 20 ml with 2 ml of normal saline (control group) or 2% lidocaine (lidocaine group) infused at 2 ml.kg-1.hr-1 for 10 minutes. Heart rate, mean arterial pressure, and BIS were measured every minute. The addition of lidocaine to propofol reduced the incidence of injection pain from 85% to 10% but did not change the induction time. Propofol significantly decreased mean arterial pressure and BIS but there was no difference between the groups. In conclusion, premixing lidocaine with propofol reduces injection pain without affecting the hypnotic effect.     

艾司洛尔对丙泊酚麻醉诱导过程中脑电双频指数的影响

目的观察艾司洛尔用于丙泊酚麻醉诱导插管时脑电双频指数(BIS)的变化。方法30例ASAⅠ或Ⅱ级患者随机分为两组,对照组静注生理盐水10ml负荷量后静滴生理盐水,用药组艾司洛尔1mg/kg稀释于生理盐水10ml静注后以250μg.kg-1.min-1微量泵输入,然后静注丙泊酚2mg/kg,当两组BIS降至40~50时静注芬太尼2μg/kg、阿曲库铵0.5mg/kg行经口明视气管插管。监测给药前、诱导前、插管前、插管后1、3、5minBIS、MAP及HR,并观察插管后各时点与插管前BIS、MAP、HR的变化差值△BIS、△MAP及△HR。结果插管前对照组及用药组BIS变化差异无显著意义。插管后1、3、5min对照组BIS较插管前显著升高,用药组BIS与插管前比较差异无显著意义,两组间比较差异有显著意义(P<0.05)。插管后对照组△BIS变化最大百分比为40%,与用药组的6.8%相比差异有极显著意义(P<0.01)。插管后1、3min对照组MAP、HR显著高于插管前,两组比较差异无显著意义;插管后对照组△MAP及△HR变化最大百分比为55%及40%,明显高于用药组的29%及15%。结论艾司洛尔用于丙泊酚麻醉诱导插管时,对插管前BIS无影响,插管后可抑制BIS的增加。     

Abnormally low bispectral index and isoelectric electroencephalogram observed after administration of small doses of propofol during induction of anesthesia

We describe a case in which an unexpectedly, abnormally low bispectral index value (BIS = 4) and an almost isoelectric electroencephalogram (EEG) pattern were observed during typical induction of anesthesia with propofol. Starting 2 min after the beginning of propofol administration (1.26 mg kg⁻¹), the EEG recordings showed burst and suppression pattern for the next 12 min. The EEG during this period was characterized by gradual prolongation of suppression periods until the appearance of the isoelectric line. After that, burst activity returned and eventually the burst suppression pattern disappeared. We excluded the possibility of ischemic brain damage, and the evidence increasingly points toward a greater sensitivity to propofol. The findings described in this case report support the thesis that there is a wide variability in the responses of patients to propofol that cannot be detected without continuous monitoring of cortical electrical activity.     

Sudden increase in bispectral index during propofol anesthesia in three patients

We report 3 patients who developed a sudden unpredicted increase in bispectral index (BIS) value during propofol and fentanyl anesthesia. The patients were induced with propofol 2-mg.kg-1 and fentanyl 2-micrograms.kg-1 and muscle relaxation was obtained by vecuronium 0.12-mg.kg-1. During induction of anesthesia, BIS value went down to below 50 in all three cases, and anesthesia was maintained by continuous infusion of propofol at a rate of 5 mg.kg-1.hr-1 and intermittent administration of fentanyl. Forty to sixty min after starting the operation, BIS value increased suddenly (up to 80) and the body movement of the patients was observed. The serum concentration of propofol was approximately 2.5 micrograms.ml-1. All patients were successfully treated with increasing the infusion rate of propofol and additional administration of fentanyl. No clear recall or explicit memory during operation was observed after anesthesia, but, anesthesiologists might have to pay more attention to unpredictable changes of anesthetic depth during propofol anesthesia using target controlled infusion.     

The effect of fentanyl on hemodynamic and bispectral index changes during anesthesia induction with propofol

STUDY OBJECT: To investigate the changes in hemodynamics and hypnotic levels during propofol infusion and tracheal intubation with and without fentanyl. DESIGN: Randomized, double-blinded study. SETTING: Teaching hospital. PATIENTS: 40 ASA physical status I adult patients scheduled for elective surgery. INTERVENTIONS: Patients were anesthetized with either propofol (Group P; n = 20) or 2 microg/kg of fentanyl IV followed by propofol (Group PF; n = 20). Propofol was infused at 20 mg/kg/hr throughout the study, and tracheal intubation was performed 10 minutes after the start of propofol infusion. MEASUREMENT AND MAIN RESULTS: Bispectral index monitoring (BIS) progressively decreased to about 50 in both groups during infusion of propofol, but no difference was found between the two groups. After tracheal intubation, BIS significantly increased but remained below 60 in both groups. Hypertensive responses to intubation were fewer in Group PF than Group P. CONCLUSIONS: Propofol administration 20 mg/kg/hr for 10 minutes is suitable in suppressing arousal reactions to tracheal intubation, but the addition of fentanyl is required to blunt the hemodynamic responses.     

听觉诱发电位指数、脑电双频指数对异丙酚麻醉下患者术中体动反应的预测

目的评价听觉诱发电位指数(AAI)、脑电双频指数(BIS)预测异丙酚麻醉下患者术中体动反应的可能性。方法择期行妇科手术全麻患者28例,ASAⅠ或Ⅱ级,年龄24-62岁,体重46- 71 kg,术前2 h口服咪达唑仑10 mg,入室后以血浆靶浓度3．5μg/ml靶控输注异丙酚、静脉注射芬太尼2μg／kg及维库溴铵0．1 mg／kg麻醉诱导,气管插管后,调整异丙酚血浆靶浓度维持BIS 40-60。切皮后不再追加肌松剂,观察患者术中头面部及四肢的体动反应,记录体动反应发生前、后2min内BIS、AAI的最大值(BISmax、AAImax)及此时段内BIS>75、AAI>40的次数及出现时间。记录术中当BIS>75、AAI>40时前、后2 min内有无体动反应发生及发生时间。结果12例出现体动反应,体动前、后2 min内BISmax为63±16(4例BIS>75,33．3％),AAImax为48±11(12例AAI>40,100％)。麻醉维持过程中,出现14次BIS>75,并发体动反应4次(28．5％),BIS反应时间较体动时间滞后(84±19)s;出现AAI>40者28次,并发体动者12次(42．8％),AAI反应时间较体动时间滞后(13±3)s。结论异丙酚麻醉下BIS、AAI反应时间较体动发生时间滞后,不能预测术中体动反应的发生。     

Correlation and agreement between bispectral index and state entropy of the electroencephalogram during propofol anaesthesia

Background. Bispectral index (BIS) and state entropy (SE) monitorhypnosis. We evaluated the correlation and the agreement betweenthose parameters during propofol anaesthesia and laryngoscopywith and without muscle relaxation. Methods. A total of 25 patients were anaesthetized with propofol.At steady state (SS: BIS 40–50), they randomly receivedrocuronium (R) or saline (S); 3 min thereafter, a 20 s laryngoscopywas performed. Correlation (regression analysis) and agreement(Bland–Altman analysis) were evaluated before induction(baseline), at loss of eyelash reflex (LER), at SS and duringthe first 3 min after laryngoscopy (L). Results. The correlation coefficient r (95% CI), the mean difference(MD) (95% CI), and the limits of agreement [lower-upper limitsof 95% CI of MD (SD 1.96)] between BIS and SE were as follows.Overall recordings: 0.87 (0.83 to 0.90), 2.5 (1.2 to 3.0), and[–19.5 to 24.6]; Baseline: 0.45 (0.06 to 0.72), 7.6 (6.0to 9.2), and [–2.7 to 17.9]; LER: 0.74 (0.47 to 0.88),8.3 (3.5 to 13.2), and [–22.6 to 39.3]; SS, all patients:0.41 (0.14 to 0.63), 2.0 (–0.5 to 4.6), and [–19.0to 23.3]; SS, Group S: 0.36 (–0.07 to 0.68), 1.9 (–2.5to 6.3), and [–25.0 to 28.8]; SS, Group R: 0.63 (0.32to 0.82), 0.2 (–2.0 to 2.3), and [–14.0 to 14.4];L, all patients: 0.49 (0.32 to 0.63), 0.7 (–1.6 to 3.0),and [–25.6 to 27.1]; L, Group S: 0.41 (0.13 to 0.63),2.3 (–2.4 to 7.1), and [–36.7 to 41.3]; L, GroupR: 0.72 (0.56 to 0.83), –0.6 (–2.2 to 1.0), and[–14.3 to 13.1]. The correlation was good except for SSin Group S. The MD was significantly different from 0 for overallrecordings, during baseline and LER, but not for the other conditions.The agreement was poor except for baseline, and SS and L inGroup R. Conclusions. BIS and SE are globally well correlated. In contrast,agreement is poor as differences of more than 20 units are frequentlyobserved, except for awake and paralysed patients.     

The changes of bispectral index induced by administration of midazolam during propofol anesthesia

The effect of the additional administration of midazolam or flumazenil on bispectral index (BIS) during propofol anesthesia was investigated in 22 scheduled surgical patients. Midazolam 10 or 30 micrograms.kg-1, or flumazenil 6 or 12 micrograms.kg-1 was injected to the patients to evaluate their effect on BIS after achieving steady state of hypnosis more than 1 hr of propofol anesthesia with 5 mg.kg-1.hr-1. The only midazolam 30 micrograms.kg-1 significantly reduced BIS value from 47.8 +/- 8.6 to 36.8 +/- 6.5. The synergistic interaction between midazolam and propofol assessed by BIS might be less clear than that assessed by hypnotic dose of propofol using psychopharmacological investigation.     

Performance of the ARX-derived auditory evoked potential index as an indicator of anesthetic depth: a comparison with bispectral index and hemodynamic measures during propofol administration

BACKGROUND: Autoregressive modeling with exogenous input of middle-latency auditory evoked potential (A-Line autoregressive index [AAI]) has been proposed for monitoring anesthetic depth. The aim of the current study was to compare the accuracy of this new index with the Bispectral Index (BIS), predicted effect-site concentration of propofol, and hemodynamic measures. METHODS: Twenty female patients scheduled for ambulatory gynecologic surgery received effect compartment controlled infusion of propofol. Target effect-site concentration was started at 1.5 microg/ml and increased every 4 min by 0.5 microg/ml. At every step, sedation level was compared with monitoring values using different clinical scoring systems and reaction to noxious stimulus. RESULTS: Bispectral Index, AAI, and predicted propofol effect-site concentration were accurate indicators for the level of sedation and loss of consciousness. Hemodynamic variables were poor indicators of the hypnotic-anesthetic status of the patient. BIS correlated best with propofol effect-site concentration, followed by AAI. Hemodynamic measurements did not correlate well. No indicators predicted reaction to noxious stimulus. Poststimulus, BIS and AAI showed an increase as a result of arousal. This reaction occurred more rapidly with the AAI than with BIS. CONCLUSION: Bispectral Index, AAI, and predicted propofol effect-site concentration revealed information on the level of sedation and loss of consciousness but did not predict response to noxious stimulus.     

肌松药对异丙酚诱导期脑电熵和脑电双频指数的影响

目的：探讨维库溴铵、琥珀胆碱对异丙酚诱导期脑电熵和脑电双频指数（bispectral index,BIS）的影响。方法：靶控输注异丙酚进行诱导,当患者OAA/S评分≤1分时置入喉罩,机械通气。调节异丙酚靶控浓度,使效应室浓度（effect-site concentration,Ce）维持在2.0μg/mL或3.0μg/mL,稳定5min。维库溴铵2.0组（V2.0组）和维库溴铵3.0组（V3.0组）分别在异丙酚Ce稳定在2.0μg/mL或3.0μg/mL时静脉推注维库溴铵0.1mg/kg,琥珀胆碱2.0组（S2.0组）和琥珀胆碱3.0组（S3.0组）则静脉推注琥珀胆碱1mg/kg,两组对照组（C2.0组,C3.0组）给予等容量的生理盐水。记录麻醉诱导前、肌松药静脉推注前（基础值）及静脉给药后第1～5分钟的BIS、反应熵（respect entropy,RE）、状态熵（state entropy,SE）。结果：与基础值比较,V2.0组、S2.0组和C2.0组静脉给药后BIS、RE、SE下降（P〈0.05）,V3.0组和S3.0组各指标变化差异无统计学意义（P〉0.05）。S2.0组和S3.0组在给予琥珀胆碱后第2分钟时点RE、SE升高（P〈0.05）,但BIS变化差异无统计学意义（P〉0.05）。V2.0组、V3.0组、S2.0组和S3.0组分别与相同异丙酚Ce对照组比较,静脉推注肌松药前后SE、BIS差异均无统计学意义（P〉0.05）,仅RE在给予琥珀胆碱后第2分钟时点升高（P〈0.05）。结论：肌松药对脑电熵和BIS的影响与镇静深度有关,在较浅的镇静状态下,肌松药可引起BIS、RE、SE数值下降;肌松药对脑电熵和BIS的影响与肌松药的种类无关。     

Narcotrend or bispectral index monitoring during desflurane-remifentanil anesthesia: a comparison with a standard practice protocol

Bispectral Index (BIS) (Aspect Medical Systems, Newton, MA) and Narcotrend (MonitorTechnik, Bad Bramstedt, Germany) are monitoring devices that were, as others, designed to assess the depth of anesthesia. Meanwhile, a number of studies indicate that with total IV anesthesia, BIS and Narcotrend have comparable effects on drug consumption and recovery times whereas comparative clinical data for volatile anesthetics are still missing. Therefore, we designed the present prospective, randomized, and double-blinded study to compare the effects of BIS and Narcotrend monitoring during desflurane-remifentanil anesthesia and versus a standard anesthetic practice protocol. One-hundred-twenty adult patients scheduled for minor orthopedic surgery were randomized to receive a desflurane-remifentanil anesthetic controlled either by Narcotrend or by BIS or solely by clinical variables. Anesthesia was induced with 0.4 microg x kg(-1) x min(-1) remifentanil and 2 mg/kg propofol. After tracheal intubation, remifentanil was infused at a constant rate of 0.2 microg x kg(-1) x min(-1) whereas desflurane in 1.5 L/min O(2)/air was adjusted according to clinical variables or the following target values: during maintenance of anesthesia to a value of "D(0)" (Narcotrend) or "50" (BIS), 15 min before the end of surgery to "C(1)" (Narcotrend) or "60" (BIS), whereas in the standard protocol group, desflurane was controlled according to clinical variables, e.g., heart rate, arterial blood pressure, movements. Recovery times and desflurane consumption were recorded by a blinded investigator. The desflurane vaporizer was weighed before and after anesthesia and consumption per minute was calculated. Data are mean +/- sd. The groups were comparable for demographic data, duration of anesthesia, and mean remifentanil dosages. Compared with standard practice, patients with Narcotrend or BIS monitoring needed significantly less desflurane (standard practice 443 +/- 71 mg/min, Narcotrend 374 +/- 124 mg/min, BIS monitoring 416 +/- 99 mg/min desflurane [both P < 0.05]). However, recovery times were not significantly different between the groups, e.g., opening of eyes 4.7 +/- 2.2 versus 3.7 +/- 2.0 versus 4.2 +/- 2.1 min. During desflurane-remifentanil anesthesia, Narcotrend and BIS monitoring seem to be equally effective compared with standard anesthetic practice: BIS and Narcotrend allow for a small reduction of desflurane consumption whereas recovery times are only slightly reduced. IMPLICATIONS: Monitoring the electroencephalogram with Narcotrend or Bispectral Index during desflurane-remifentanil anesthesia only slightly reduces recovery times when compared with a standard practice protocol.     

The effect of encephalogram bispectral index monitoring during total intravenous anesthesia with propofol in outpatient surgery]

OBJECTIVE: To assess the effect of monitoring the encephalogram bispectral index (BIS) during outpatient surgery. Outcome measures were amount of propofol administered, awakening and discharge. MATERIAL AND METHODS: Forty consecutive outpatient surgery patients were studied. The patients gave informed consent and received general intravenous anesthesia with propofol administered through a laryngeal mask using a computerized system (Diprifusor(R)). Two groups were formed: in group A, BIS was monitored, although the information was hidden from the anesthesiologists, who used the usual signs (loss of blinking reflex, pupil size and hemodynamic response) to guide anesthesia; in group B the anesthesiologists used BIS monitoring to guide propofol administration. Measurements were blood pressure, heart rate and BIS at six times during the procedure (T1-T6). Other data recorded were age, weight, height, propofol consumption in relation to weight and duration of procedure, consumption of rocuronium and alfentanil, duration of propofol infusion, time from withdrawal of propofol until eye opening, duration of stay in the post-anesthesia intensive care unit and time until total recovery. A questionnaire assessed the presence of intraoperative awareness and degree of satisfaction. The data were analyzed by Student's t and a chi square tests, with statistical significance at p < 0.05. RESULTS: Demographic variables (age, weight and height) were similar, as were duration of propofol infusion, total dose of alfentanil and rocuronium, evolution of blood pressure and heart rate. Statistically significant differences in BIS were observed at two times, T4 and T5; total propofol administered was 32.6% lower in group B; and time until eye opening was significantly shorter in group B. No significant differences were observed for time until full recovery. No instances of intraoperative awareness were reported and satisfaction was high in both groups. CONCLUSION: BIS monitoring allows for propofol titration that leads to a mean reduction of 32.6% in consumption, shortening the time until eye opening without causing intraoperative awareness or reducing patient satisfaction.     

Spectral entropy and bispectral index as measures of the electroencephalographic effects of propofol

Recently, Datex-Ohmeda introduced the Entropy Moduletrade mark for measuring depth of anesthesia. Based on the Shannon entropy of the electroencephalogram, state entropy (SE) and response entropy (RE) are computed. We investigated the dose-response relationship of SE and RE during propofol anesthesia in comparison with the Bispectral Indextrade mark (BIS). Twenty patients were studied without surgical stimulus. Anesthesia was induced by a constant propofol infusion of 2000 mg/h (451 +/- 77 microg x min(-1) x kg(-1)) via a large forearm vein. Propofol was infused until substantial burst suppression occurred (more than 50%) or mean arterial blood pressure decreased to <60 mm Hg. Hereafter, infusions were stopped until recovery of BIS values up to 60 was reached. Subsequently, the constant propofol infusion of 2000 mg/h was restarted to increase depth of anesthesia and again decreased (infusion was stopped) within the BIS value range of 40-60. The coefficient of determination (R2) and the prediction probability (P(K)) were calculated to evaluate the performance of SE, RE, and BIS to predict changing propofol effect-site concentrations. R2 values for SE, RE, and BIS of 0.88 +/- 0.08, 0.89 +/- 0.07, and 0.92 +/- 0.06, respectively, were similar. The calculated P(K) values, however, revealed a significant difference between SE and RE compared with BIS, with P(K) = 0.77 +/- 0.09, 0.76 +/- 0.10, and 0.84 +/- 0.06, respectively. BIS seems to show slight advantages in predicting propofol effect-site concentrations compared with SE and RE, as measured by P(K) but not as measured by R2.