1 Department of Anaesthesiology and Intensive Care Medicine, University of Bonn, Germany. 2 Department of Anaesthesiology and Intensive Care Medicine, University of Saarland, Homburg/Saar, Germany. 3 Department of Anaesthesiology and Intensive Care Medicine, University of Hamburg-Eppendorf, Hamburg, Germany. 4 Department of Anaesthesiology and Intensive Care Medicine, University of Frankfurt, Germany. 5 Department of Anaesthesiology and Intensive Care Medicine, St-Marien-Hospital, Lünen, Germany
* Corresponding author. E-mail: jbruhn{at}mailer.meb.uni-bonn.de
Accepted for publication September 6, 2004.
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
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 min before the end of surgery 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 desflurane concentrations (standard practice 2.9 [0.5] vol%, BIS 3.3 [0.9] vol%, AAI 2.6 [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.
Keywords: anaesthetics volatile, desflurane ; analgesics opioid, remifentanil ; monitoring, bispectral index ; monitoring, A-line AAI index
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In the present multicentre study we investigated the impact of BIS and the A-line AEP monitoring on recovery times and drug consumption when compared with a standard anaesthetic practice protocol during desflurane-remifentanil anaesthesia.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
All patients were pre-medicated with midazolam 7.5 mg orally on the morning before surgery. In the operating room an i.v. canula was inserted into a larger forearm vein and standard monitors were applied. The EEG was continuously recorded using an A-2000 BIS monitor (version XP) and an A-line AEP monitor (version 1.4), simultaneously. After the skin of the forehead had been degreased with 70% isopropanol, both the BIS (BIS XP Sensor, Aspect Medical Systems, Inc.) and the AEP electrodes (Danmeter) were positioned as recommended by the manufacturers. Finally, impedances were measured for each set of electrodes to ensure optimal electrode contact.
In all the patients, anaesthesia was induced with remifentanil infusion at 0.4 µg kg1 min1 followed 5 min later by 2 mg kg1 propofol. After loss of consciousness oxygen was given by facemask ventilation, each patient received 0.1 mg kg1 of cis-atracurium, and 3 min later the trachea was intubated and the lungs were mechanically controlled ventilated to an end-tidal carbon dioxide concentration of 4.6 kPa. Immediately after intubation, remifentanil was reduced to the rate of 0.2 µg kg1 min1 and the desflurane was delivered in the inspired mixture of oxygen and air to obtain an end-tidal concentration of 3 vol%. Thereafter, desflurane was sequentially adjusted according to the predetermined target values of BIS or AAI, or clinical parameters. No more neuromuscular blocking agents were given intraoperatively.
Continuous monitoring included heart rate (HR), systemic arterial pressure, ventilatory frequency, oxygen saturation, and end-tidal concentrations of desflurane and carbon dioxide. The oxygen saturation was measured by pulse oximetry and maintained above 95%. Baseline systolic arterial pressure (SAP) was defined as the lower of the two measurements obtained the day before surgery and immediately before induction of anaesthesia. HR and blood pressure were recorded every 5 min.
During maintenance of anaesthesia, all patients were assessed for signs of inadequate anaesthesia, hypotension, or bradycardia. Inadequate anaesthesia was defined as hypertension, tachycardia or patient movement, eye opening, swallowing, grimacing, lacrimation, or sweating. The definition of adverse haemodynamic responses was adapted from Garrioch and Fitch:18 responses were classified as hypertension (SAP >40 mm Hg from baseline), hypotension (SAP <40 mm Hg from baseline), tachycardia (HR >100 beats min1), and bradycardia (HR <45 beats min1).
In the standard practice group, if anaesthesia was inadequate the desflurane concentration was increased in steps of 0.5 vol% as necessary. If this was judged insufficient, the infusion rate of remifentanil could be increased in increments of 0.05 µg kg1 min1. Hypotension, if any, was initially treated with i.v. fluid replacement; desflurane concentration was then reduced in steps of 0.5 vol%, and finally, an i.v. vasopressor (Akrinor, AWD Pharma, Dresden, Germany, 1 ml contains 100 mg cafedrine and 5 mg theodrenaline) was given at a dose chosen by the investigator.
In the AAI and BIS groups, desflurane during maintenance of anaesthesia was continuously adjusted according to a target value of 50 for BIS or 30 for AAI. In case anaesthesia was judged inadequate despite these BIS or AAI target values, the infusion rate of remifentanil could be increased in increments of 0.05 µg kg1 min1. Hypotension was initially treated with i.v. fluid replacement and finally, the i.v. vasopressor was given. In all groups bradycardia was treated with 0.5 mg of atropine.
In all patients, irrespective of the individual group assignment, both BIS values and AAI values were continuously recorded as data pairs in intervals of 5 min by an independent investigator. In the standard practice group both the monitors were covered behind a curtain and invisible to the attending anaesthesiologist, whereas in the BIS or AAI groups either only the BIS monitor or only the AEP monitor was uncovered. All participating anaesthetists were familiar with the use of brain monitors.
Fifteen minutes before the expected end of surgery, desflurane was reduced in all the patients to facilitate rapid emergence from anaesthesia, whereas the remifentanil infusion rate remained unchanged throughout the end of the procedure. In the BIS and AAI groups, desflurane concentration was adjusted to a value of 60 for BIS or 45 for AAI, whereas in the standard protocol group it was reduced as much as was clinically judged possible without allowing for intraoperative awakening. Simultaneously, complete neuromuscular recovery was ensured by neuromuscular monitoring, and all patients received a 100 ml infusion of NaCl 0.9% containing metamizol 25 mg kg1 for postoperative pain relief.
The delivery of anaesthetic was stopped at the end of surgery, which was defined as the final surgical suture. Emergence from anaesthesia was assessed by measuring the times to spontaneous opening of eyes, extubation, stating the name, and arrival at the post-anaesthesia care unit. Recovery times were recorded by a blinded investigator. Finally, all patients were visited in the postanaesthesia care unit and on the first and third postoperative day and interviewed about intraoperative recall.
End-points and statistical analysis
The primary end-point of this study was defined as the time taken to spontaneous opening of eyes. Statistical analysis included comparisons of patient characteristics, duration of anaesthesia, end-tidal desflurane concentrations, recovery times, and remifentanil consumption. For nominal data statistical analysis was performed by means of a 2-test, for numerical data by one way analysis of variance (ANOVA) with StudentNewmanKeuls test for multiple comparisons. All tests were two-tailed with statistical significance defined as P<0.05; data are presented as mean (SD). Statistical calculations were done using SigmaStat 2.03 and SigmaPlot 2000 computer software (both SPSS GmbH, Erkrath, Germany).
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
|
|
|
|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
At first look these findings seem to be surprising and disappointing compared with previous studies, which found more favourable results for EEG-guided anaesthesia.713 The following issues must be discussed and may explain the differences with the previous studies.
In general, significant differences between the standard practice group and the monitoring groups are easier to find if the EEG/AEP parameter values are lower in the standard practice group indicating relatively too deep anaesthesia. The mean BIS value in our control group was 47 (14) and this was in good accordance with the mean BIS values in the control groups of previous studies using desflurane, that is 40 (11),19 45 (9),20 and 44 (1.1).12 It is important to exclude a potential investigator bias in the standard practice group: learning contamination bias21 may occur as a problem of unintended improvement of standard clinical practice patterns associated with the introduction of a new monitor device. Furthermore, results may be influenced by subtle investigator bias leading to an overestimation of the difference between standard practice and the device-monitored groups.
While the mean BIS value in the control group during maintenance of anaesthesia was similar to previous studies, the mean BIS value in the BIS group of the present study was 45 (9) and thereby lower than in previous studies using desflurane. Of note, the mean BIS value is obviously correlated with the amount of reduction of desflurane consumption which was 9% at a mean BIS value of 46,20 17% at a mean BIS value of 49,19 and 30% at a mean BIS value of 60.12 Considering the low mean BIS value in the BIS group of our study, the missing reduction of the desflurane consumption may well be explained.
The mean BIS values in the AAI group were higher than the mean BIS values in the BIS group. This finding underlines the difficulties that arise when different neurophysiologic parameters with different algorithms are compared. The AAI target values of the present study were chosen as recommended by the manufacturer of the A-line AEP monitor.22 The published studies have shown similar results to our present finding that a BIS value of 50 is equivalent to an AAI value lower than 30. While titrating propofol to a BIS of 50, Kreuer and colleagues23 reported a mean AAI of 28 and a median AAI of 26 using the same AAI software version as in the present study. At a mean BIS value of 49 Recart and colleagues19 found a mean corresponding AAI value of 16; however, the software version in this study was not reported. Thereby, higher mean BIS values in the AAI group resulted in lower end-tidal desflurane concentrations reaching statistical significance at some time points during maintenance of anaesthesia.
Respective considerations can be made for the last 15 min before the end of surgery: we chose target values of 45 for AAI and 60 for BIS for the last 15 min. While titrating propofol to a BIS of 60 Kreuer and colleagues23 recently reported a mean AAI of 40, which is clearly below the AAI target value of 45 as used in the present study.
With desflurane and remifentanil we used the fastest combination of anaesthetic drugs, which is presently available.25 Previous studies with desflurane used fentanyl12 19 24 or fentanyl with top-up remifentanil.20 Consecutively, the recovery in our control group with a time to extubation of 6.3 (2.4) min was faster than in the control group of other desflurane studies with extubation times up to 11 (10) min.20 Thereby, with desflurane-remifentanil a further reduction of recovery times by means of neurophysiologic parameter monitoring is obviously more difficult to obtain when compared with an anaesthetic technique based on higher doses of the inhaled anaesthetic or propofol.
It is well known that the hypnotic component of anaesthesia is better reflected by the EEG or AEP than the analgesic component of anaesthesia.6 24 Therefore, it might be speculated that EEG- or AEP-guided titration of anaesthesia is clinically more useful for a hypnotic-based anaesthetic regimen (low-dose analgesics, e.g. fentanyl, combined with high-dose hypnotics, e.g. 1 MAC volatile anaesthetics) than for a more analgesic-based regimen (high-dose analgesics, e.g. remifentanil, combined with low-dose hypnotics, e.g. 0.5 MAC volatile anaesthetics), which was used in this study.
In conclusion, we evaluated the influence of BIS and AAI guidance on the titration of desflurane-remifentanil anaesthesia in comparison with a standard practice protocol. BIS and AAI-guided titration did not result in a significant reduction of recovery times or desflurane consumption during minor surgery with use of remifentanil.
![]() |
Footnotes |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
This study was presented in part at the European Society of Anaesthesiologists meeting, 2004, Lisbon, Portugal.
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
2 Iselin-Chaves I, Flaishon R, Sebel P, et al. The effect of the interaction of propofol and alfentanil on recall, loss of consciousness and the bispectral index. Anesth Analg 1998; 87: 94955[Abstract]
3 Katoh T, Suzuki A, Ikeda K. Electroencephalographic derivatives as a tool for predicting the depth of sedation and anesthesia induced by sevoflurane. Anesthesiology 1998; 88: 64250[ISI][Medline]
4 Kearse I, Rosow C, Zaslavsky A, Connors P, Dershwitz M, Denman W. Bispectral analysis of the electroencephalogram predicts conscious processing of information during propofol sedation and hypnosis. Anesthesiology 1998; 88: 2534[ISI][Medline]
5 Liu J, Singh H, White PF. Electroencephalogram bispectral analysis predicts the depth of midazolam-induced sedation. Anesthesiology 1996; 84: 649[ISI][Medline]
6 Bruhn J, Bouillon TW, Radulescu L, Hoeft A, Bertaccini E, Shafer SL. Correlation of approximate entropy, bispectral index, and spectral edge frequency 95 (SEF95) with clinical signs of anesthetic depth during coadministration of propofol and remifentanil. Anesthesiology 2003; 98: 6217[CrossRef][ISI][Medline]
7 Bannister CF, Brosius KK, Sigl JC, Meyer BJ, Sebel PS. The effect of bispectral index monitoring on anesthetic use and recovery in children anesthetized with sevoflurane in nitrous oxide. Anesth Analg 2001; 92: 87781
8 Gan TJ, Glass PS, Windsor A, et al. Bispectral index monitoring allows faster emergence and improved recovery from propofol, alfentanil, and nitrous oxide anesthesia. Anesthesiology 1997; 87: 80815[CrossRef][ISI][Medline]
9 Johansen JW, Sebel PS, Sigl JC. Clinical impact of hypnotic-titration guidelines based on EEG bispectral index (BIS) monitoring during routine anesthetic care. J Clin Anesth 2000; 12: 43343[CrossRef][ISI][Medline]
10 Kreuer S, Biedler A, Larsen R, Altmann S, Wilhelm W. Narcotrend monitoring allows faster emergence and a reduction of drug consumption in propofol-remifentanil anesthesia. Anesthesiology 2003; 99: 3441[ISI][Medline]
11 Pavlin DJ, Hong JY, Freund PR, Koerschgen ME, Bower JO, Bowdle TA. The effect of bispectral index monitoring on end-tidal gas concentration and recovery duration after outpatient anesthesia. Anesth Analg 2001; 93: 6139
12 Song D, Joshi GP, White PF. Titration of volatile anesthetics using bispectral index facilitates recovery after ambulatory anesthesia. Anesthesiology 1997; 87: 8428[ISI][Medline]
13 Yli-Hankala A, Vakkuri A, Annila P, Korttila K. EEG bispectral index monitoring in sevoflurane or propofol anaesthesia: analysis of direct costs and immediate recovery. Acta Anaesthesiol Scand 1999; 43: 5459[CrossRef][ISI][Medline]
14 Alpiger S, Helbo-Hansen HS, Jensen EW. Effect of sevoflurane on the mid-latency auditory evoked potentials measured by a new fast extracting monitor. Acta Anaesthesiol Scand 2002; 46: 2526[CrossRef][ISI][Medline]
15 Gajraj RJ, Doi M, Mantzaridis H, Kenny GN. Analysis of the EEG bispectrum, auditory evoked potentials and the EEG power spectrum during repeated transitions from consciousness to unconsciousness. Br J Anaesth 1998; 80: 4652[CrossRef][ISI][Medline]
16 Assareh H, Anderson RE, Uusijärvi J, Jakobsson J. Sevoflurane requirements during ambulatory surgery: a clinical study with and without AEP-guidance. Acta Anaesthsiol Scand 2002; 46: 4959[CrossRef][ISI][Medline]
17 Määttänen H, Anderson R, Uusijärvi J, Jakobsson J. Auditory evoked potential monitoring with AAI-index during spinal surgery: decreased desflurane consumption. Acta Anaesthesiol Scand 2002; 46: 8826[CrossRef][ISI][Medline]
18 Garrioch MA, Fitch W. Anaesthesia for carotid artery surgery. Br J Anaesth 1993; 71: 56979[ISI][Medline]
19 Recart A, Gasanova I, White PF, Thomas T, Ogunnaike B, Hamza M, Wang A. The effect of cerebral monitoring on recovery after general anesthesia: a comparison of the auditory evoked potential and bispectral index devices with standard clinical practice. Anesth Analg 2003; 97: 166774
20 Luginbühl M, Wüthrich S, Petersen-Felix S, Zbinden AM, Schnider TW. Different benefit of bispectral index (BIS) in desflurane and propofol anaesthesia. Acta Anaesthesiol Scand 2003; 47: 16373
21 Roizen MF, Toledano A. Technology assessment and the learning contamination bias. Anesth Analg 1994; 79: 4102[ISI][Medline]
23 Kreuer S, Bruhn J, Larsen R, Hoepstein M, Wilhelm W. Comparison of Alaris AEP index and bispectral index during propofol-remifentanil anaesthesia. Br J Anaesth 2003; 91: 33640
24 Recart A, White PF, Wang A, Gasanova I, Byerly S, Jones SB. Effect of auditory evoked potential index monitoring on anesthetic drug requirements and recovery profile after laparoscopic surgery. Anesthesiology 2003; 99: 8138[CrossRef][ISI][Medline]
25 Wilhelm W, Wrobel M, Kreuer S, Larsen R. Remifentanil. An update. Anaesthesist 2003; 52: 47394[ISI][Medline]