Adequacy of Anesthesia

Bibliography

Review articles

Johansen,J.W.; Sebel,P.S.
Development and clinical application of electroencephalographic bispectrum monitoring
Anesthesiology 2000; 93: 1336-1344
"This is an excellent review of the development of the bispectral index (BIS), and the key studies performed on its validity, performance and clinical utility up until 1999. Limitations of the BIS are also presented, and potential horizons in its use with pediatric patients as well as in the ICU are discussed."

Rampil,I.J.
A primer for EEG signal processing in anesthesia
Anesthesiology 1998; 89: 980-1002
"This article originates from the request of many anesthesiologists to learn how BIS is calculated. Dr. Rampil first presents an extensive review of EEG signal acquisition and processing methods used in anesthesia. He then moves on to describing how these methods have been applied in the calculation of BIS. The development process and the general architecture of BIS are also described."

Validity studies

Flaishon,R.; Windsor,A.; Sigl,J.; Sebel,P.S.
Recovery of consciousness after thiopental or propofol; Bispectral Index and the isolated forearm technique
Anesthesiology 1997; 86: 613-619
"Study purpose was to assess whether BIS could predict the return of consciousness in unpremedicated patients after a single bolus induction dose of thiopental (N=20) or propofol (N=20).

The return of consciousness was measured by the isolated forearm technique: first a tourniquet was applied to one arm, and before administration of neuromuscular relaxants it was inflated above the systolic blood pressure. Hence, it was possible for the patient to respond to verbal commands by squeezing that hand. In all patients, BIS showed a rapid decrease, then gradual increase until return of consciousness. No patients with BIS less than 58 were conscious. On the average, the return to consciousness occurred at BIS of 80 for propofol and at BIS of 81 for thiopental."

Glass,P.S.; Bloom,M.; Kearse,L.; Rosow,C.; Sebel,P.; Manberg,P.
Bispectral analysis measures sedation and memory effects of propofol, midazolam, isoflurane, and alfentanil in healthy volunteers
Anesthesiology 1997; 86: 836-847
"This key paper validates the performance of BIS (version 3.0), and reports the results from a multicenter study. It presents relation among BIS, measured drug concentrations and increasing levels of sedation. A total of 72 healthy volunteers were enrolled in the study, each receiving one of the anesthetic drugs studied (propofol, isoflurane, midazolam, and alfentanil).

The pooled BIS values at which 50% and 95% of participants were unconscious were 67 and 50, respectively. Alfentanil data was excluded from the pooled analysis, as none of the study subjects lost consciousness. Close correlation was found between BIS and the level of responsiveness, and BIS could well predict the loss of consciousness. The authors conclude that BIS may be a valuable monitor of the level of sedation and loss of consciousness for propofol, midazolam, and isoflurane."

Degoute,C.S.; Macabeo,C.; Dubreuil,C.; Duclaux,R.; Banssillon,V.
EEG bispectral index and hypnotic component of anesthesia induced by sevoflurane: comparison between children and adults
British Journal of Anesthesia 2001; 86: 209-212
"This study was designed to evaluate the correlation of BIS and the hypnotic component of sevoflurane anesthesia in two study groups (27 children and 27 adults). In either study groups, BIS values at return of consciousness did not different from values at the loss of consciousness. There was a close correlation between the BIS and the hypnotic component of anesthesia."

Riker,R.R.; Fraser,G.L.; Simmons,L.E.; Wilkins,M.L.
Validating the Sedation-Agitation Scale with the Bispectral Index and Visual Analog Scale in adult ICU patients after cardiac surgery
Intensive Care Medicine 2001; 27: 853-858
"The objective of this study was to validate the Sedation-Agitation Scale (SAS) with the Visual Analog Scale (VAS) and BIS in adult ICU patients. Thirty-nine adult patients were studied after cardiac surgery. SAS exhibited a good correlation both with the BIS and with the VAS. A small percentage of ICU patients not receiving neuromuscular blockade, demonstrated above average frontal electromyogram (EMG) power, which reduced correlation between SAS and BIS. In general, SAS and BIS proved to be valid measures of wakefulness after cardiac surgery."

Drug interaction studies

Lysakowski,C.; Dumont,L.; Pellegrini,M.; Clergue,F.; Tassonyi,E.
Effects of fentanyl, alfentanil, remifentanil and sufentanil on loss of consciousness and Bispectral Index during propofol induction of anesthesia
British Journal of Anaesthesia 2001; 86: 523-527
"In five study groups (15 unpremedicated patients in each), BIS, sedation score and hemodynamic variables were recorded to determine the effect of propofol in the presence of fentanyl, alfentanil, remifentanil, sufentanil or placebo. Opioids were first administered by target-controlled infusion (TCI), to obtain predicted effect-site concentrations. Thereafter, propofol TCI was started, and gradually adjusted to reach three predicted effect-site concentration levels. In the presence of opioids, loss of consciousness (LOC) occurred at a lower concentration of propofol and at a higher BIS50 (i.e. the BIS value associated with 50% probability of LOC) compared with placebo. It was concluded that the clinical hypnotic effect of propofol was enhanced by the opioid analgesics, but BIS did not reflect that increased hypnotic effect."

Struys,M; Verhaeghen,D; De Neve,N; Jensen,E; Mortier E.
Influence of increasing remifentanil concentrations on the accuracy of depth of anesthesia measures during propofol administration: comparison between BIS, auditory evoked potentials and propofol effect-site concentration
Abstracts of the 10th Congress of the International Society for Anesthetic Pharmacology (ISAP, October 2001), New Orleans, USA.
"Forty-five patients were allocated to one of three groups receiving remifentanil at different infusion rates, and the propofol TCI was increased in steps. BIS was recorded and the level of sedation was assessed by the OAAS score, eyelash reflex, and reaction to painful stimulus.

At LOC, lower propofol concentrations and higher measured values for BIS were found for groups receiving higher doses of remifentanil. Similar results were found for detection of loss of response to noxious stimulus."

Utility analysis

Song,D.; Joshi,G.P.; White,P.F.
Titration of volatile anesthetics using bispectral analysis index facilitates recovery after ambulatory anesthesia
Anesthesiology 1997; 87: 842-848
"The authors studied the effects of BIS monitoring on usage of volatile anesthetics and recovery profile in four groups of outpatients (15 in each), undergoing laparoscopic tubal ligation. There were two BIS guided groups, where anesthesia was maintained either with desflurane or sevoflurane, together with N2O and fentanyl, and volatile anesthetics were adjusted to reach the BIS level of 60. In addition, there were two control groups where BIS values were not shown, but the same anesthetics utilized; the clinician administered volatile anesthetics according to standard clinical practice.

During the maintenance phase, the BIS values were significantly lower in the control groups (mean=42) compared with the BIS titrated groups (mean=60).

The volatile anesthetic usage in the BIS-titrated groups was 30-38% lower (P < 0.05) compared with the control groups. Awakening times were shorter in the BIS groups compared with the controls."

Gan,T.J.; Glass,P.S.; Windsor,A.; Payne,F.; Rosow,C.; Sebel,P.; Manberg,P.
Bispectral Index monitoring allows faster emergence and improved recovery from propofol, alfentanil, and nitrous oxide anesthesia
Anesthesiology 1997; 87: 808-815
"Study objective was to determine if addition of BIS monitoring to standard anesthetic practice would result in improvements in the conduct of anesthesia or in patient outcomes. A total of 302 patients receiving a propofol-, alfentanil-, nitrous oxide anesthetic were enrolled to this multi-center study. First, the preexisting practice and patient outcomes at the four institutions were assessed. Subsequent patients were randomized to the standard practice (SP group) or standard practice plus BIS monitoring (BIS group). In the BIS group, titration of propofol was based on the monitored BIS values, whereas in the SP group, clinical signs were the guideline. There was no significant difference in the incidence of intraoperative responses between the groups.

Compared to SP group, the BIS group demonstrated reduced propofol infusion rates, reduced total amount of propofol used and faster emergence from anesthetics. In addition, greater percentage of the BIS group patients were oriented on arrival to PACU (p<0.02), and they also became eligible for discharge sooner (p<0.04)."

Methods of memory studies

Lubke,G.H.; Kerssens,C.; Phaf,H.; Sebel,P.S.
Dependence of explicit and implicit memory on hypnotic state in trauma patients
Anesthesiology 1999; 90: 670-680
"This article demonstrates how intraoperative memory formation can be studied, using e.g. word completion tests, and how both explicit and implicit memory can be assessed separately. Trauma patients were chosen. Anesthesia was induced with etomidate, and maintained with isoflurane, fentanyl, and neuromuscular blocking agents. During surgery, a list of words was played via headphones, and several commonly used indicators of anesthetic effect, including BIS, were recorded during word presentation.

General memory performance declined with decreasing BIS values, but none of the other indicators of hypnotic state were related to general memory performance. The clear finding of the study was that memory was related to the depth of hypnosis, and auditory information processing occurred at bispectral index levels between 60 and 40. The authors conclude that the observed memory performance should be interpreted in terms of implicit memory."

Ghoneim, M (Ed.)
Awareness during anesthesia (textbook)
Butterworth-Heinemann Publishers, 2001. ISBN 0-7506-7201-3
"This textbook is a comprehensive collection of facts and current knowledge in the field. Topics to mention here include memory, plus explicit and implicit learning during anesthesia."

Last updated: 1 November 2001Created
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