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ABSTRACT: The neuromuscular transmission monitor (NTM) is a new device for measuring neurornuscular transmission during anaesthesia, We have assessed its use in comparison with a force transducer and found for single twitch and train-of-four modes that there was a strong positive correlation between the two methods. This device appears reliable in use and provides a satisfactory alternative to conventional neuromuscular monitoring.
Anaesthesia 02/2007; 40(2):146 - 151. · 2.96 Impact Factor
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ABSTRACT: Recordings of cerebral electrical activity were obtained using the cerebral function analysing monitor from eight unpremedicated patients anaesthetised with increasing concentrations of halothane in oxygen. The amplitude of the processed EEG increased at one and decreased at two minimal alveolar concentrations. The frequency distribution of the weighted EEG signal showed a linear increase of delta activity with a corresponding decrease in beta activity with increasing concentrations of halothane.
Anaesthesia 02/2007; 41(4):390 - 394. · 2.96 Impact Factor
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ABSTRACT: The bispectral index of the electroencephalogram is a measure of the hypnotic component of anaesthesia and can be used to guide the administration of anaesthesia. This study compares bispectral index-guided anaesthesia with remifentanil and either propofol or isoflurane.
Eighty consenting patients were randomly assigned to two groups. Following induction with propofol and remifentanil, anaesthesia was maintained with remifentanil/propofol or remifentanil/isoflurane. Remifentanil infusion rates were guided by haemodynamic responses--maintaining mean arterial pressure and heart rate within 20% of baseline. Propofol and isoflurane administration was guided using the bispectral index (45-60). Thirty minutes before the end of surgery, morphine was administered (0.15 mg kg(-1) intravenously). Fifteen minutes before end of surgery, propofol and isoflurane were reduced (bispectral index 60-75). At the end of surgery, the anaesthetic agents were discontinued. Groups were compared for recovery, remifentanil doses and signs of inadequate anaesthesia using the chi2-test and ANOVA (P < 0.05).
The duration of surgery was longer in the propofol/remifentanil group (121 +/- 53 versus 94 +/- 40 min). Recovery data were not different between groups. The remifentanil infusion rate was significantly lower with additional isoflurane (0.18 +/- 0.06 microg kg(-1) min(-1)) than with additional propofol (0.31 +/- 0.20 microg kg(-1) min(-1)). The propofol infusion rate was 123 +/- 48 microg kg(-1) min(-1); isoflurane concentration was 0.66 +/- 0.13%.
Bispectral index-guided anaesthesia with remifentanil plus propofol or isoflurane results in the absence of postoperative recall and a fast recovery with both drug combinations. In our patients, at comparable bispectral index-levels, haemodynamic control requires higher doses of remifentanil with propofol than with isoflurane.
European Journal of Anaesthesiology 08/2003; 20(8):624-30. · 2.23 Impact Factor
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ABSTRACT: The utility of bispectral index (BIS) monitoring to guide anesthetic administration has been demonstrated in adults. This prospective, randomized observer-blinded study was designed to evaluate the effect of BIS monitoring on anesthetic use and recovery characteristics in pediatric patients. After data collection in 38 historical controls, 202 patients age 0-18 yr were randomized into one of two groups: standard practice (SP) and BIS guided (BIS). Patients age 0-3 yr undergoing inguinal hernia repair (IH) and patients age 3-18 yr undergoing tonsillectomy and/or adenoidectomy (TA) were selected. All patients were anesthetized with sevoflurane in 60% N(2)O/O(2). Hernia patients also received a caudal epidural anesthetic before surgery. In the BIS group, anesthetic delivery was adjusted in an effort to achieve a target BIS of 45-60 during maintenance and 60-70 during the last 15 min of the procedure. BIS was recorded throughout surgery in all patients, but data were unavailable to the anesthesiologist in the SP group. In the TA patients, BIS monitoring was associated with a significant reduction in end-tidal sevoflurane concentration during maintenance (2.4 +/- 0.6%, SP and 1.8 +/- 0.4% BIS, mean +/- SD) and during the last 15 min of the procedure (2.1 +/- 0.7, SP and 1.6 +/- 0.6, BIS). There was a 25%-40% decrease in measured recovery times. In the patients 0-6 mo of age undergoing IH, sevoflurane concentrations during maintenance (2.0 +/- 0.4% SP, 0.9 +/- 0.8 BIS), during the last 15 min (1.6 +/- 0.4% SP, 0.6 +/- 0.6% BIS), and at the end of the procedure (1.1 +/- 0.6% SP, 0.3 +/- 0.3% BIS) were smaller in the BIS group. Emergence and recovery measures were unaffected by BIS titration. In the children 6 mo-3 yr of age, there were no significant differences between the SP and BIS groups in anesthetic use or recovery measures. IMPLICATIONS: Bispectral index monitoring in children results in less anesthetic use and faster recovery than standard practice.
Anesthesia & Analgesia 05/2001; 92(4):877-81. · 3.29 Impact Factor
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Anesthesiology 12/2000; 93(5):1336-44. · 5.36 Impact Factor
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ABSTRACT: To examine the impact on perioperative care of routine Bispectral Index (BIS) monitoring during general anesthesia throughout an entire operating room (OR) suite.
Open, observational trial with retrospective analysis of guideline performance. Data were analyzed from 1,552 adult patients receiving general anesthesia with surgical times of at least 1 hour and who were extubated by postanesthesia care unit (PACU) discharge. Staff were trained using a simple decision matrix, which integrated BIS titration goals with anesthetic management. Unmonitored patients were compared to either BIS-monitored patients or to performance subgroups based on BIS measurements recorded during anesthetic maintenance ("deep", BIS < 50; "target", 50-65; "light", >65).
Large, urban academic/trauma center.
Demographic profiles of all groups and subgroups were similar. Anesthetic emergence, recovery times, and volatile drug use were significantly shortened or reduced only when BIS values were maintained between 50 and 65. Extubation time from end of surgery decreased by 2.1 minutes from 5.7+/-7 (37%); OR exit time decreased by 2.2 minutes from 9.3+/-6 (24%); eligibility for phase 1 PACU discharge decreased by 4 minutes from 22+/-42 (23%); and actual PACU discharge decreased by 15 minutes from 130+/-78 (7%). PACU extubation frequency decreased from 6.9% to 2.6%. Modest decreases in total intraoperative drug use were noted with an increase in PACU analgesic administration.
Routine application of BIS monitoring throughout an OR suite impacted clinical outcome only if guideline targets were met. BIS values within the last 30 minutes of surgery were not predictive of emergence or recovery. Hypnotic maintenance at BIS < 50 did not confer any clinical advantage over unmonitored cases. Anesthetic maintenance at BIS values between 50 and 65 was associated with shortened emergence and recovery from general anesthesia.
Journal of Clinical Anesthesia 10/2000; 12(6):433-43. · 1.21 Impact Factor
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ABSTRACT: The Bispectral Index (BIS) correlates well with the level of consciousness with single anesthetic drugs. We studied the effect of the interaction of propofol with alfentanil on propofol concentration and BIS associated with 50% probability of loss of consciousness and lack of recall (Cp50 and BIS50, respectively). We studied 40 consenting volunteers at two institutions who were randomly assigned to receive stepped increases of propofol (10 subjects at each site), propofol plus alfentanil 50 ng/mL (10 subjects at Emory site), or propofol plus alfentanil 100 ng/mL (10 subjects at Duke site) by using a target-controlled infusion device. Measures of sedation, BIS, deltaBIS (absolute change of BIS after a painful stimulus), memory, and drug concentration were obtained at each target drug concentration. The relation among BIS, measured drug concentration, sedation score, and presence or absence of recall was determined by linear and logistic regression for different drug regimens, and the prediction probability (Pk) was calculated. The addition of alfentanil in increasing doses did not significantly affect the BIS50 and propofol Cp50 values for loss of consciousness and lack of recall. DeltaBIS was significantly decreased by both an increase in the concentration of propofol and the presence of alfentanil. The Pk for BIS was >0.93 with all drug regimens, better than those of the target and measured propofol concentrations. We conclude that BIS correlated well with the hypnotic component of anesthesia independent of the presence of an opioid. Moreover, the level of consciousness, and, therefore, the BIS index, is affected by a painful stimulus, and this response is ablated either by opioids or increasing propofol concentration. IMPLICATIONS: In volunteers, the sedation and changes in memory function produced by propofol correlated well with changes in the Bispectral Index. This relationship was not altered by the addition of an analgesic (alfentanil). However, in moderately sedated patients who received a painful stimulus, the Bispectral Index increased, but this response was blocked by the analgesic or increasing propofol concentrations.
Anesthesia & Analgesia 10/1998; 87(4):949-55. · 3.29 Impact Factor
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ABSTRACT: We investigated whether fentanyl decreases the serum concentrations of the steroid anesthetic eltanolone effective in producing loss of consciousness in 50% of patients (EC50induction) and in preventing movement at skin incision in 50% of patients (EC50incision). For anesthetic induction, patients received effect-site target concentrations of fentanyl 0.0, 1.5, 3.0, or 4.5 ng/mL and eltanolone 500, 750, 1000, or 1200 ng/mL. Loss of response to verbal command was assessed after 10 min. For incision, patients received effect-site target concentrations of fentanyl 0.5,1.5, 3.0, or 4.5 ng/mL and eltanolone 547-2926 ng/mL. Movement at incision was assessed at least 10 min after new targets were entered. Probability of loss of consciousness and of movement versus arterial serum concentration combinations were analyzed by logistic regression. Dixon up-down analysis was used to estimate ET50incision effective target concentration combinations. In the absence of fentanyl, anesthesia was induced in only 1 of 12 patients, which suggests that the EC50induction is >1500 ng/mL at fentanyl 0.0 ng/mL. With fentanyl (38 patients), eltanolone EC50induction was independent of fentanyl concentration, calculated as 628 ng/mL. For the incision phase (52 patients), logistic regression failed to generate a valid model. Dixon analysis (43 patients) produced an eltanolone ET50incision of 2288 ng/mL at fentanyl targets of 0.5 ng/mL, 754 ng/mL at 1.5 ng/mL, 735 ng/mL at 3.0 ng/mL, and 645 ng/mL at 4.5 ng/mL. Fentanyl reduced the serum concentration of eltanolone required to produce loss of consciousness and the target concentration of eltanolone required to prevent movement to skin incision. IMPLICATIONS: Fentanyl reduced the serum concentration of eltanolone required to produce loss of consciousness and the target concentration of eltanolone required to prevent movement to skin incision. Future interaction studies of this nature using logistic regression should model responses to hypnotic alone separately from responses to hypnotic-analgesic combinations.
Anesthesia & Analgesia 10/1998; 87(4):967-72. · 3.29 Impact Factor
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ABSTRACT: Esmolol, a short-acting beta1-receptor antagonist, decreases anesthetic requirements during propofol/N2O/morphine anesthesia. This study was designed to determine whether esmolol affects the volatile anesthetic (isoflurane) required to prevent movement to skin incision in 50% patients (minimum alveolar anesthetic concentration [MAC]) with or without an additional opioid (alfentanil). One hundred consenting adult patients were randomly divided into five treatment groups: isoflurane alone (I), I with continuous large-dose (250 microg x kg(-1) x min(-1)) esmolol (E), I with alfentanil (effect site target of 50 ng/mL) via a continuous computer-controlled infusion (A), A plus continuous small-dose (50 microg x kg(-1) x min(-1)) esmolol (A1), or A plus large-dose esmolol (A2). Anesthesia was induced via a face mask, and steady-state target end-tidal isoflurane concentrations were maintained before incision. The MAC of isoflurane alone was 1.28% +/- 0.13%. Large-dose esmolol did not significantly alter the isoflurane MAC (1.23% +/- 0.14%). Alfentanil alone significantly decreased isoflurane MAC by 25% (0.96% +/-0.09%). Adding small-dose esmolol did not further decrease MAC with alfentanil (0.96% +/- 0.13%). However, large-dose esmolol significantly decreased isoflurane MAC with alfentanil (0.74% +/- 0.09%). Esmolol and alfentanil both significantly reduced the increases in heart rate and mean arterial pressure associated with endotracheal intubation and incision. The mechanism of this effect is unknown. IMPLICATIONS: Most anesthetic techniques rely on a balance of several highly selective medications. The current results define a new anesthetic-sparing effect when volatile anesthetic, analgesic, and beta-adrenergic blocking drugs are combined.
Anesthesia & Analgesia 10/1998; 87(3):671-6. · 3.29 Impact Factor
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P S Sebel
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ABSTRACT: Electroencephalography (EEG) is used to monitor the function of the central nervous system in a variety of surgical procedures. During cardiac surgery with cardiopulmonary bypass, ischemic changes on the EEG as a result of impaired central nervous system blood supply can be noted. The EEG also may be used to monitor the functional state of the brain during and after profound hypothermic circulatory arrest. If a desired goal is to reduce cerebral metabolism using a barbiturate or other such agent, the EEG can be monitored to provide a measurable pharmacodynamic end point (burst suppression). Techniques have been developed to process the EEG signal using a computer and to improve on-line interpretation. These include fast Fourier transformation to develop a three-dimensional plot or compressed spectral array, evoked-potential monitoring, and bispectral analysis to derive a univariate descriptor of the EEG. These techniques have been used to detect awareness and indirect memory function, as well as to assess the adequacy of anesthesia. There is a good correlation between implicit memory and alterations in midlatency auditory-evoked responses. The bispectral index has been used to assess the adequacy of anesthesia as well as to detect awareness. Preliminary studies suggest that titrating the anesthetic to bispectral index levels may be useful during cardiac surgery.
Journal of Cardiothoracic and Vascular Anesthesia 05/1998; 12(2 Suppl 1):3-8. · 1.64 Impact Factor
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ABSTRACT: In clinical practice, indirect and non-specific signs are used for monitoring anaesthetic adequacy. These include haemodynamic, respiratory, muscular and autonomic signs. These measures do not indicate adequacy of anaesthesia in a reliable manner. Many attempts have been made to find a more accurate monitor. Direct monitoring of anaesthetic effect should be possible by EEG measurement. EEG information can be reduced, condensed and simplified, leading to single numbers (spectral edge frequency and median frequency). These methods appear insufficient for assessing anaesthetic adequacy. The bispectral index, derived from bispectral analysis of the EEG, is a very promising tool for measuring adequacy of anaesthesia. An alternative approach is to monitor evoked potentials. Middle latency auditory evoked potentials may be helpful in assessing anaesthetic adequacy. Both techniques need further validation.
European Journal of Anaesthesiology - Supplement 06/1997; 15:21-8.
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P S Sebel
Canadian Journal of Anaesthesia 06/1997; 44(5 Pt 2):R124-30. · 2.35 Impact Factor
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ABSTRACT: Bispectral analysis (BIS) of the electroencephalogram (EEG) has been shown in retrospective studies to predict whether patients will move in response to skin incision. This prospective multicenter study was designed to evaluate the real-time utility of BIS in predicting movement response to skin incision using a variety of general anesthetic techniques. Three hundred patients from seven study sites received an anesthetic regimen expected to give an approximately 50% movement response at skin incision. EEG was continuously recorded via an Aspect B-500 monitor and BIS was calculated in real time from bilateral frontocentral channels displayed on the monitor. Half of the patients were randomized to a treatment group in which anesthetic drug doses were increased to produce a lower BIS. In the control group, BIS was recorded, but no action taken on the data displayed. A determination of movement in response to skin incision was made in the 2 min succeeding incision. Retrospective pharmacodynamic modeling was performed using STANPUMP to estimate effect-site concentrations of intravenously administered anesthetics. BIS values were significantly higher in the control group (66 +/- 19) versus the BIS-guided group, in which additional anesthesia was administered to produce a lower BIS (51 +/- 19). The movement response rate was significantly higher in the control group at 43% compared with 13% in the BIS-guided group, but response rates were low at sites which used larger doses of opioids. Logistic regression analysis showed that BIS, estimated opioid effect-site concentrations, and heart rate (in that order) were the best predictors of movement at skin incision. This study demonstrates that dosing anesthetic drugs to lower BIS values achieves a lower probability of movement in response to surgical stimulation. BIS is a significant predictor of patient response to incision, but the utility of the BIS depends on the anesthetic technique being used. When drugs such as propofol or isoflurane are used as the primary anesthetic, changes in BIS correlate with the probability of response to skin incision. When opioid analgesics are used, the correlation to patient movement becomes much less significant, so that patients with apparently "light" EEG profiles may not move or otherwise respond to incision. Therefore, the adjunctive use of opioid analgesics confounds the use of BIS as a measure of anesthetic adequacy when movement response to skin incision is used as the primary end point.
Anesthesia & Analgesia 05/1997; 84(4):891-9. · 3.29 Impact Factor
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ABSTRACT: Currently, there exists no effective monitor that can predict the probability of a patient being conscious during general anesthesia. The electroencephalogram-derived bispectral index (BIS) is a promising new method to assess anesthetic adequacy. This study used the BIS to predict the probability of recovery of consciousness after a single bolus induction dose of propofol or thiopental.
Twenty unpremedicated surgical patients were anesthetized with 4 mg/kg thiopental and 20 patients with 2 mg/kg propofol. The BIS was monitored throughout the study. After induction, before administration of neuromuscular blocking agent, a tourniquet was applied to one arm and inflated above the systolic blood pressure. This allowed preservation of the ability to move the hand after neuromuscular blocking agent onset. Patients were then prompted to squeeze the investigator's hand every 30 s, until they responded to the request. At the time of response, anesthesia was reinduced and the study terminated.
The BIS at loss of consciousness and recovery of a response was not statistically different between propofol and thiopental. No patient with a BIS less than 58 was conscious. In both groups, a BIS of less than 65 signified a less than 5% probability of return of consciousness within 50 s.
The BIS can be used to predict probability of recovery of consciousness after a single injection of either thiopental or propofol.
Anesthesiology 04/1997; 86(3):613-9. · 5.36 Impact Factor
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ABSTRACT: Although beta blockers have been used primarily to decrease unwanted perioperative hemodynamic responses, the sedative properties of these compounds might decrease anesthetic requirements. This study was designed to determine whether esmolol, a short-acting beta 1-receptor antagonist, could reduce the propofol concentration required to prevent movement at skin incision.
Sixty consenting patients were premedicated with morphine, and then propofol was delivered by computer-assisted continuous infusion along with 60% nitrous oxide. Patients were randomly divided into three groups, propofol alone, propofol plus low-dose esmolol (bolus of 0.5 mg/kg, then 50 micrograms.kg-1.min-1), and propofol plus high-dose esmolol (bolus of 1 mg/kg, then 250 micrograms.kg-1.min-1). Two venous blood samples were drawn at equilibrium. The serum propofol concentration that prevented movement to incision in 50% of patients (Cp50) was calculated by logistic regression.
The propofol Cp50 with nitrous oxide was 3.85 micrograms/ ml. High-dose esmolol infusion was associated with a significant reduction in the Cp50 to 2.80 micrograms/ml (P < 0.04). Propofol computer-assisted continuous infusion produced stable serum concentrations with a slight positive blas. Esmolol did not alter the serum propofol concentration. No intergroup differences in heart rate or blood pressure response to intubation or incision were found.
Esmolol significantly decreased the anesthetic requirement for skin incision. The components and mechanism of this interaction remain unclear. A simple pharmacokinetic interaction between esmolol and propofol does not explain the Cp50 reduction. These results demonstrate an anesthetic-sparing effect of a beta-adrenergic antagonist in humans under clinically relevant conditions.
Anesthesiology 02/1997; 86(2):364-71. · 5.36 Impact Factor
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ABSTRACT: Remifentanil is a new micro-specific opioid receptor agonist currently under investigation. The interaction between opioids and volatile anesthetics is complex. Defining this interaction provides a basis for more rational dosing schemes when such combinations are used for anesthesia and allows the anesthetic potency of remifentanil relative to other opioids to be determined.
Two centers enrolled a total of 220 patients. Patients were randomized to receive a target concentration of remifentanil via a computer-assisted continuous infusion device of either 0.0, 0.5, 1.0, 1.5, 2.0, 4.0, 8.0, 16.0, and 32.0 ng/ml initiated before the administration of isoflurane. Patients were also stratified by groups 18-30, 31-55, and 56-65 yr. After induction of anesthesia with isoflurane the initial patient in each dose group was assigned an age-adjusted isoflurane concentration. The isoflurane concentration for each subsequent patient was adjusted according to the up/down technique until a minimum of 12 patients were enrolled in each group. Arterial blood samples for remifentanil whole blood concentrations were obtained. The patient was observed for purposeful movement for up to 1 min after skin incision. The minimum alveolar concentration (MAC) of isoflurane (0 ng/ml remifentanil group) and MAC reduction of isoflurane by remifentanil were determined.
The MAC of isoflurane alone was 1.3%. Remifentanil caused an exponential reduction in the MAC of isoflurane with 1.37 ng/ml remifentanil a 77% reduction and 32 ng/ml a 91% reduction of isoflurane MAC.
The MAC reduction of isoflurane by remifentanil is similar to that produced by other opioids. Although remifentanil was given at extremely high concentrations in the absence of isoflurane, it did not provide adequate anesthesia. A 50% isoflurane MAC reduction is produced by 1.37 ng/ml remifentanil whole blood concentration compared to previously published plasma concentrations of fentanyl of 1.67 ng/ml or sufentanil of 0.14 ng/ml.
Anesthesiology 11/1996; 85(4):721-8. · 5.36 Impact Factor
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ABSTRACT: This study was designed to confirm the effect of therapeutic intraoperative auditory suggestion on recovery from anesthesia, to establish the effect of preoperative suggestion, and to assess implicit memory for intraoperative information using an indirect memory task. Sixty consenting unpremedicated patients scheduled for elective gynecologic surgery were randomly divided into three equal groups: Group 1 received a tape of therapeutic suggestions preoperatively, and the story of Robinson Crusoe intraoperatively; Group 2 heard the story of Peter Pan preoperatively and therapeutic suggestions intraoperatively; Group 3 heard the Crusoe story preoperatively and the Peter Pan story intraoperatively. A standardized anesthetic technique was used with fentanyl, propofol, isoflurane, and nitrous oxide. After surgery, all patients received patient-controlled analgesia (PCA) with a standardized regimen. In the 24 h postsurgery, morphine use was recorded every 6 h and at 24 h an indirect memory test (free association) was used to test for memory of the stories. Anxiety scores were measured before surgery and at 6 and 24 h postsurgery. There were no significant differences between groups for postoperative morphine use, pain or nausea scores, anxiety scores, or days spent in hospital after surgery. Seven of 20 patients who heard the Pan story intraoperative gave a positive association with the word "Hook," whereas 2 of 20 who did not hear the story gave such an association. Indirect memory for the Pan story was established using confidence interval (CI) analysis. (The 95% CI for difference in proportion did not include zero). No indirect memory for the Crusoe story could be demonstrated. This study did not confirm previous work which suggested that positive therapeutic auditory suggestions, played intraoperatively, reduced PCA morphine requirements. In contrast, a positive implicit memory effect was found for a story presented intraoperatively.
Anesthesia & Analgesia 02/1996; 82(1):148-52. · 3.29 Impact Factor
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ABSTRACT: Remifentanil is a new potent opioid analgesic that undergoes rapid esterase metabolism. The purpose of this study was to investigate hemodynamic responses to 2-30 micrograms/kg remifentanil (escalating doses) injected as a bolus over 1 min during general anesthesia. After general anesthesia with endotracheal intubation, placement of a radial artery catheter, and pretreatment with glycopyrrolate, remifentanil 2, 5, 15, or 30 micrograms/kg (six patients, three male and three female per group) was administered over 1 min. Arterial blood pressure and heart rate were measured noninvasively before drug administration, after drug administration, and then every minute for 5 min. Arterial blood was taken for histamine determinations before drug administration and then at 1, 3, and 5 min after drug administration. Administration of remifentanil was associated with a reduction in systolic blood pressure from 134 +/- 18 to 91 +/- 16 mm Hg and heart rate from 99 +/- 20 to 69 +/- 21 bpm and was not associated with alterations in histamine concentration.
Anesthesia & Analgesia 06/1995; 80(5):990-3. · 3.29 Impact Factor
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ABSTRACT: Conventional electroencephalographic (EEG) analysis techniques do not use the phase information from the Fourier analysis. This study used a new technique of EEG analysis, bispectral analysis, which measures interfrequency phase relationships in the EEG. Using a reference database, and a process of multivariate discriminant analysis, we developed a univariate bispectral variable, the bispectral index (BIS). This study was designed to test the efficacy of BIS in predicting movement to incision during either an isoflurane/alfentanil anesthetic or a propofol/alfentanil anesthetic technique. Fifty consenting patients were randomized to two groups; one received isoflurane/alfentanil and the other, propofol/alfentanil for anesthesia. EEG was recorded using a microcomputer system and the data were analyzed off-line. Hemodynamic variables were also recorded. After skin incision, each patient was observed carefully for 2 min to detect purposeful movement. A significant difference was found between the BIS values for movers versus nonmovers within each of the two treatment groups (P < or = 0.002). However, isoflurane/alfentanil nonmovers could not be distinguished from propofol/alfentanil movers (P < or = 0.180), suggesting a treatment group effect independent of response classification. Preincision hemodynamic variables did not predict patient movement in response to skin incision. These findings suggest the possibility that different anesthetics have different effects on BIS, and thus BIS may not be independent of the anesthetic. Interfrequency phase coupling, a nonlinear feature of the EEG which is measured with bispectral analysis, may contain clinically useful information for the assessment of anesthetic adequacy. In this study, BIS was a better predictor of patient response than other currently available variables including hemodynamic status.
Anesthesia & Analgesia 04/1995; 80(4):780-5. · 3.29 Impact Factor
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ABSTRACT: The objective of our study was to test the efficacy of the bispectral index (BIS) compared with spectral edge frequency (SEF), relative delta power, median frequency, and a combined univariate power spectral derivative in predicting movement to incision during isoflurane/oxygen anesthesia.
A total of 42 consenting patients were assigned to 3 groups, isoflurane 0.75, 1.0, and 1.25 minimal alveolar concentration (MAC). Anesthesia was induced with thiopental and maintained with the appropriate end-tidal concentration of isoflurane. The electroencephalogram (EEG) was recorded using a microcomputer system, and data were analyzed off-line. The EEG during the 2 min before incision was analyzed. Following skin incision, each patient was carefully observed for 60 sec to detect occurrence of purposeful movement.
For all groups combined, there was a statistically significant difference for BIS (p < 0.0001) and also for relative delta power (p < 0.016) between movers and nonmovers. There was a statistically significant difference between movers and nonmovers at 1.25 MAC isoflurane for BIS (p < 0.01). There were no other significant differences for any other EEG variable at any concentration of isoflurane. No EEG variable showed a relationship to isoflurane concentration.
When bispectral analysis of the EEG was used to develop a retrospectively determined index, there was an association of the index with movement. Thus, it may be a useful predictor of whether patients will move in response to skin incision during anesthesia with isoflurane/oxygen.
Journal of Clinical Monitoring 03/1995; 11(2):83-91.
