1Department of Anaesthesiology and Intensive Care, 2Department of ENT Surgery and 3Department of Physiology (CNRS UPRESA 5020), Centre Hospitalo-Universitaire Lyon-Sud, France*Corresponding author: Service dAnesthésie-réanimation, Centre Hospitalo-Universitaire Lyon-Sud, F-69495 Pierre-Bénite Cedex, France
Accepted for publication: September 25, 2000
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Br J Anaesth 2001; 86: 20912
Keywords: brain, electroencephalography, bispectral index; paediatrics; anaesthetics volatile, sevoflurane; monitoring, electroencephalography, bispectral index
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
This prospective study was designed to evaluate the correlation between BIS and the clinically assessed hypnotic component of anaesthesia (CA score) in children and adults patients when sevoflurane is used as the sole anaesthetic.
![]() |
Methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
All patients were admitted on the day before surgery and fasted for at 12 h before their operation. All patients received oral premedication (hydroxyzine 1 mg kg1, alprazolam 0.015 mg kg1) 2 h before surgery. On arrival in the operating room, in addition to routine monitoring (heart rate (HR), non-invasive mean arterial pressure (MAP), pulse oximetry), the EEG signal was acquired using four Zipprep electrodes (Aspect Medical Systems, Natick, MA) applied to the forehead, with one on the outer aspect of each malar bone and one at the centre of the forehead, and the ground electrode above the central electrode. The BIS value was displayed using an Aspect EEG monitor (Model A-1000; Aspect Medical Systems). A 24- (for children) or 18-gauge catheter (for adults) was inserted into a forearm vein and used for administration of fluid and drug. A 5% glucose solution (for children) or Ringers solution (for adults) was administered at 5 ml kg1 h1. Baseline values for BIS and haemodynamic variables were obtained, and then all patients breathed through a face mask connected to a semiclosed anaesthetic circuit. Fresh gas flow into the anaesthetic circuit was 6 litres min1.7 The concentrations of carbon dioxide, sevoflurane and oxygen were measured continuously using an infrared anaesthetic gas analyser (Capnomac, Helsinki, Finland), which was calibrated before anaesthesia for each patient using a standard gas mixture. Anaesthesia was induced with 4% sevoflurane in oxygen; ventilation was assisted as necessary. The inspired concentration of sevoflurane was adjusted to obtain loss of consciousness (LOC) and loss of movement. The end-tidal carbon dioxide concentration was kept between 4.67 and 5.34 kPa during the study period. Just after loss of movement and before tracheal intubation, children and adults received a bolus of alfentanil 25 µg kg1 i.v. followed by a constant infusion of 0.5 µg kg1 min1. Tracheal intubation was performed after 5% lidocaine local anaesthetic had been applied to the glottis. The BIS and hypnotic component of anaesthesia (CA score) were evaluated during the onset of sevoflurane-induced anaesthesia, i.e at LOC, every 15 s until loss of movement occurred, and on recovery of consciousness (ROC). During the onset and offset periods, the CA score was assessed clinically by using the responsiveness component of the observers assessment of alertness/sedation (OAA/S) rating scale (Table 1). From LOC until ROC, BIS was recorded continuously. The end of the recovery period was defined as the time when a patient opened their eyes on verbal command (CA=2). During surgery, sevoflurane concentrations were adjusted according to standard clinical practice to maintain haemodynamic stability and avoid patient movement, with the aim of achieving rapid recovery after surgery.
|
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
|
|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In this work, adults served as a control group for children as no studies have been done in children to our knowledge. Many studies in adults have demonstrated the ability of the BIS to define depth of sedation induced by sevoflurane7 or its ability to predict patient movement in response to skin incision during isoflurane11 or propofolnitrous oxide anaesthesia.12 13 In our study, the CA score did not include the motor response to noxious stimuli. At present, it is not acceptable to include movement in the assessment of depth of anaesthesia and to correlate it with BIS; EEG BIS is a form of cortical function monitoring which cannot predict a response to noxious stimuli mediated by subcortical structures.7 Cortical activity does not accurately predict motor response to noxious stimuli.3 14 Cortical and subcortical (motor, haemodynamic and endocrine stability) components of anaesthetic adequacy are independent of each other. For educational purposes, when it is compared with BIS, depth of anaesthesia should be referred to as the hypnotic component of anaesthesia. For this reason, in this study, BIS values were not compared with CA scores during surgery, and were only recorded to compare the two groups. Even though the BIS cannot predict directly motor response to noxious stimuli, it can serve in clinical practice as an indicator of depth of anaesthesia as defined by its hypnotic component, for lack of a more specific one. The hypnotic component of anaesthesia can be defined by a threshold of amnesia, beyond which intraoperative recall disappears. During propofol-induced sedation2, none of the patients were able to recall pictures shown during the operation at an OAA/S score of 2, with a corresponding BIS of 80.8 (8.3) (mean (SD)). In the present study, the threshold of amnesia would correspond to a CA score of 3. Further studies are necessary in order to assess the relationship between intraoperative recall and BIS during sevoflurane-induced sedation and anaesthesia. In this study, when using sevoflurane during a monitored anaesthetic technique, the anaesthetist attempted to titrate the drugs to optimize patient comfort, while maintaining cardiorespiratory stability. Further studies are needed to determine whether it will be possible to improve the administration of sevoflurane by using BIS monitoring as an adjunct to routine clinical assessment. Meanwhile, these results inform anaesthetists of the BIS value at which LOC and loss of movement occur in anaesthetized children or adults, allowing adjustment of the sevoflurane concentration to avoid undesirable recall2 or movements, and to predict recovery of consciousness if BIS is used.15 Stable anaesthetic concentrations of sevoflurane could not be obtained in this study during onset of sevoflurane-induced anaesthesia in children because of the excitation period that prohibits noxious stimulation.
The dynamic relationship between end-tidal sevoflurane concentration and BIS has been evaluated.16 17 Liu and colleagues18 showed that, with increasing sedation with benzodiazepines, there was a progressive decrease in BIS. In the present study, a sedative premedication with a benzodiazepine was given orally 2 h before anaesthesia in both children and adults, ensuring stable sedation at the time of measurement of the baseline values of BIS and CA score. These were at satisfactory high levels in both groups, which shows that premedication did not disturb the level of consciousness. It has already been shown that benzodiazepines do not shorten the time taken to achieve LOC with inhalational anaesthetic induction with sevoflurane.19 The pharmacokinetic properties of sevoflurane,8 i.e. rapid washout from body tissues and low bloodgas partition coefficient, facilitate control over the depth of anaesthesia, and a rapid and smooth induction of, and emergence from, anaesthesia. This explains why the duration of administration of this potent inhalational agent has little effect on BIS and the depth of anaesthesia at the time of ROC. Moreover, in the present study, although duration of surgery was twice as long in adults as in children, there was no significant difference between the two groups in BIS and CA score at the time of ROC.
In summary, the EEG BIS correlated with the hypnotic component of anaesthesia induced by sevoflurane in children and adult patients.
![]() |
Acknowledgement |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
2 Liu J, Singh H, White P. Electroencephalographic bispectral index correlates with intraoperative recall and depth of propofol-induced sedation. Anesth Analg 1997; 84: 1859[Abstract]
3 Sebel PS, Lang E, Rampil IJ, White PF, Cork R, Jopling M, Smith NT, Glass PSA, Manberg P. A multicenter study of bispectral electroencephalogram analysis for monitoring anesthetic effect. Anesth Analg 1997; 84: 8919[Abstract]
4 Vernon JM, Lang E, Sebel PS, Manberg P. Prediction of movement using bispectral electroencephalographic analysis during propofol/alfentanil or isoflurane/alfentanil anesthesia. Anesth Analg 1995; 80: 7805[Abstract]
5 Rampil IJ, Kim JS, Lenhardt R, Negishi C, Sessler DI. Bispectral EEG index during nitrous oxide administration. Anesthesiology 1998; 89: 6717[ISI][Medline]
6 Song D, Joshi GP, White PF. Titration of volatile anesthetics using bispectral index facilitates recovery after ambulatory anesthesia. Anesthesiology 1997; 87: 8428[ISI][Medline]
7 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]
8 Patel SS, Goa KL. Sevoflurane. A review of its pharmacodynamic and pharmacokinetic properties and its clinical use in general anaesthesia. Drugs 1996; 51: 658700[ISI][Medline]
9 Johanneson GP, Floren M, Lindahl SGE. Sevoflurane for ENT-surgery in children. A comparison with halothane. Acta Anaesthesiol Scand 1995; 39: 54650[ISI][Medline]
10 Smith I, Ding Y, White P. Comparison of induction, maintenance, and recovery characteristics of sevofluraneN2O with propofolisofluraneN2O anesthesia. Anesth Analg 1992; 74: 2539[Abstract]
11 Sebel PS, Bowles SM, Saini V, Chamoun N. EEG bispectrum predicts movements during thiopental/isoflurane anesthesia. J Clin Monit 1995; 11: 8391[ISI][Medline]
12 Kearse LA Jr, Manberg P, Chamoun M, deBros F, Zaslavsky A. Bispectral analysis of the electroencephalogram correlates with patient movement to skin incision during propofol/nitrous oxide anesthesia. Anesthesiology 1994; 81: 136570[ISI][Medline]
13 Leslie K, Sessler DI, Smith WD, Larson MD, Ozaki M, Blanchard D, Crankshaw DP. Prediction of movement during propofol/nitous oxide anesthesia. Performance of concentration, electroencephalographic, pupillary, and hemodynamic indicators. Anesthesiology 1996; 84: 5263[ISI][Medline]
14 Kochs E, Bischoff P, Pichlmeier U, Schulte am Esch J. Surgical stimulation induces changes in brain electrical activity during isoflurane/nitous oxide anesthesia. A topographic electroencephalographic analysis. Anesthesiology 1994; 80: 102634[ISI][Medline]
15 Stanski DR. Monitoring depth of anesthesia. In: Miller RD, ed. Anesthesia, 3rd Edn. New York: Churchill Livingstone, 1990; 100129
16 Billard V, Plaud B, Boulay G, Bocquet R, Debaene B. Monitoring induction and maintenance of sevoflurane anesthesia by bispectral analysis of EEG: preliminary report (abstract). Anesthesiology 1996; 85: A352
17 Olofsen E, Dahan A. The dynamic relationship between end-tidal sevoflurane and isoflurane concentrations and bispectral index and spectral edge frequency of the electroencephalogram. Anesthesiology 1999; 90: 134553[ISI][Medline]
18 Liu J, Singh H, White PF. Electroencephalogram bispectral analysis predicts the depth of midazolam-induced sedation. Anesthesiology 1996; 84: 649[ISI][Medline]
19 Muzi M, Colinco MD, Robinson BJ, Ebert JT. The effects of premedication on inhaled induction of anesthesia with sevoflurane. Anesth Analg 1997; 85: 11438[Abstract]