Entropy indices vs the bispectral index (TM) for estimating nociception during sevoflurane anaesthesia

Tokyo Women's Medical University, Edo, Tōkyō, Japan
BJA British Journal of Anaesthesia (Impact Factor: 4.85). 06/2006; 96(5):620-6. DOI: 10.1093/bja/ael050
Source: PubMed


It is now possible to acquire and process raw EEG and frontal EMG signals to produce two spectral-entropy-based indices (response entropy and state entropy) reflective of analgesic and hypnotic levels during general anaesthesia (with the Datex-Ohmeda S/5 Entropy Module, Datex-Ohmeda, Helsinki, Finland). However, there are no data available on the accuracy of the Entropy Module in estimating nociception during sevoflurane anaesthesia.
Forty female patients were enrolled in the present study. Each patient was allocated randomly to one of four end-tidal sevoflurane concentration (ET(sev)) groups (1.3, 1.7, 2.1 or 2.5%). A BIS Sensor (Aspect Medical Systems, Newton, MA) and an Entropy Sensor (Datex-Ohmeda) were applied side-by-side to the forehead. The bispectral index (A-2000 BIS Monitor, version 3.4, Aspect Medical Systems), response entropy, state entropy and patient movement were observed after electrical stimulation (20, 40, 60 and 80 mA, 100 Hz, 5 s) and after skin incision during sevoflurane anaesthesia (1.3, 1.7, 2.1 or 2.5%). Accuracy of the EEG variables in differentiating the intensity of electrical stimulation was estimated by the prediction probability (P(K)) values.
Response entropy and state entropy [median, (range)] before skin incision were significantly lower in patients who did not move [29 (15-41) and 24 (14-41)] than in those that did [38 (24-53) and 37 (24-52)], but there was no significant difference in BIS. All EEG variables increased significantly (P<0.0001 for all) with increases in the intensity of electrical stimulation. The difference between response entropy and state entropy increased with increases in the electrical stimulation (P<0.0001). However, no EEG variables could differentiate the intensity of the electrical stimulations accurately because of low P(K)-values (P(K)<0.8).
Noxious stimulation increased the difference between response entropy and state entropy. However, an increase in the difference does not always indicate inadequate analgesia and should be interpreted carefully during anaesthesia.

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    • "Clinical endpoints, such as movement in response to nociceptive stimulation, are commonly used as an indicator of inadequate analgesia [23] but are also unreliable and suppressed by muscle relaxants [24]. Some electroencephalographic (EEG-) derived variables, such as Entropy, especially the difference between state entropy (SE) and response entropy (RE), are proposed to be useful for evaluating the nociceptive component of anaesthesia [17] [25] [26]. Additionally, changes in skin conductivity and photoplethysmographic pulse wave amplitude or pulse wave reflex have been suggested as indicators of stress or nociception [27] [28]. "
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    ABSTRACT: Eighty patients undergoing elective ear-nose-throat surgery were enrolled in the present study to investigate the relationship between surgical pleth index (SPI) and stress hormones (ACTH, cortisol, epinephrine, norepinephrine) during general anaesthesia which was induced and maintained with propofol and remifentanil using a target-controlled infusion. The study concluded that the SPI had moderate correlation to the stress hormones during general anaesthesia, but no correlation during consciousness. Furthermore, SPI values were able to predict ACTH values with high sensitivity and specificity.
    The Scientific World Journal 09/2012; 2012(4):879158. DOI:10.1100/2012/879158 · 1.73 Impact Factor
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    • "In some studies, noxious pain like tracheal intubation increases spectral entropy, especially RE rather than BIS [12,13], since noxious pain is relevant to increases EMG activity [14]. By comparison, we investigated BIS, RE and SE values during induction of anesthesia, and not in anesthetized patients. "
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    ABSTRACT: Etomidate frequently induces myoclonus, so it may affect electromyographics (EMG). And EMG commonly has an effect on the bispectral index scale (BIS) and spectral entropy. This study was performed to compare the effect of etomidate on BIS, response entropy (RE) and state entropy (SE) during induction of anesthesia. Fifty patients (ASA I or II) scheduled for elective surgery were included in this study. Anesthesia was induced with etomidate (0.3 mg/kg) and rocuronium (0.6 mg/kg). Patients also inhaled 4 vol% sevoflurane and 100% oxygen and, then intubated. BIS, RE, SE and Modified Observer's Assessment of Alertness/Sedation Scale (MOAA/S) were measured 4 times (before injection of etomidate [T0], at loss of eyelash reflex [T1], 90 seconds after rocuronium injection [T2], and after intubation [T3]). We also checked whether myoclonus occurred. Baseline values (T0) were 93.1 ± 4.7 for BIS, 95.8 ± 3.7 for RE and, 87.3 ± 3.5 for SE. In comparison with T0, there were significantly differences in BIS (50.2 ± 16.3), RE (76.8 ± 18.5) and SE (66.3 ± 17.4) at T1 (all P < 0.05). There were no significant differences at T2 and T3. Thirty one patients had myoclonus. At the occurrence of myoclonus, RE and SE values significantly increased but not BIS (P < 0.05). In patients with myoclonus, at the loss of consciousness, spectral entropy did not decrease where as BIS did, suggesting that BIS may evaluate hypnotic levels better than spectral entropy during induction of anesthesia with etomidate.
    Korean journal of anesthesiology 03/2012; 62(3):230-3. DOI:10.4097/kjae.2012.62.3.230
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    • "Clinical endpoints , such as movement reaction in response to nociceptive stimulus, can be used as an indicator of inadequate analgesia [2], but it is not very useful during operation when patients are paralysed. Some electroencephalographic (EEG)-derived parameters, such as Entropy, are suggested to reflect also the nociceptive component of anesthesia [3] [4] [5]. Changes in skin conductivity and suppression of photoplethysmographic pulse wave amplitude (PPWA) have also been proposed as indicators of nociception [6] [7]. "
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    ABSTRACT: The performance of recently introduced Surgical Stress Index (SSI), based on heart rate and photoplethysmography, was estimated during sevoflurane-fentanyl and isoflurane-fentanyl anesthesia during surgical procedures. Forty ASA I-III patients were enrolled. Anesthesia was induced with fentanyl 2 mug kg(-1) and thiopentone 3-5 mg kg(-1). Tracheal intubation was performed 5 minutes after fentanyl bolus. Patients were randomly allocated to receive sevoflurane (n = 20) or isoflurane (n = 20) in 30% oxygen/air. State entropy was kept at 40-60, target being 50. During surgery, fentanyl boluses 1.5 mug kg(-1) were given at 30-40-minute intervals. SSI increased significantly after intubation. During surgery, the decrease of SSI after fentanyl boluses was similar in sevoflurane and isoflurane groups but SSI values were higher in sevoflurane than in isoflurane group. Tracheal intubation, skin incision, and surgical stimuli increased SSI from baseline, indicating that nociceptive stimuli increase SSI. Fentanyl boluses during surgery decreased SSI, indicating that increasing analgesia decreases SSI.
    Anesthesiology Research and Practice 04/2010; 2010. DOI:10.1155/2010/810721
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