EEG Entropy Values During Isoflurane, Sevoflurane and Halothane Anesthesia With and Without Nitrous Oxide

Prabhakar, Hemanshu; Ali, Zulfiqar; Bithal, Parmod K.; Singh, Gyaninder Pal; Laithangbam, Pradip K.; Dash, Hari H.

doi:10.1097/ana.0b013e318192d60e

Cited by 15 publications

(11 citation statements)

References 10 publications

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“…Mean RE and SE during 0.6 % Isoflurane and 66 % nitrous oxide maintenance anaesthesia were found to be 53.5 and 55.1 respectively in lumbar spine surgery patients [1]. Our patient would be expected to have slightly lower values while using 0.8 % Isoflurane.…”

Section: Discussionmentioning

confidence: 53%

ECG contamination of EEG signals: effect on entropy

Chakrabarti

Bansal

2015

J Clin Monit Comput

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Entropy™ is a proprietary algorithm which uses spectral entropy analysis of electroencephalographic (EEG) signals to produce indices which are used as a measure of depth of hypnosis. We describe a report of electrocardiographic (ECG) contamination of EEG signals leading to fluctuating erroneous Entropy values. An explanation is provided for mechanism behind this observation by describing the spread of ECG signals in head and neck and its influence on EEG/Entropy by correlating the observation with the published Entropy algorithm. While the Entropy algorithm has been well conceived, there are still instances in which it can produce erroneous values. Such erroneous values and their cause may be identified by close scrutiny of the EEG waveform if Entropy values seem out of sync with that expected at given anaesthetic levels.

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Section: Discussionmentioning

confidence: 53%

ECG contamination of EEG signals: effect on entropy

Chakrabarti

Bansal

2015

J Clin Monit Comput

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“…17 The patients in our study received midazolam as premedication and propofol as induction agent. In some studies, no premedication was allowed, 7,11,24 while in others, intravenous induction agents were avoided and anaesthesia was induced using a volatile anaesthetic and/or N 2 O. 2,5,10 Although GABA A agonists, such as midazolam, may decrease the analgesic effect of N 2 O, a small dose (7.5 mg) was administered two hours preoperatively in our study.…”

Section: Resultsmentioning

confidence: 93%

“…Surgical stimuli increase cortical electrical activity as measured by BIS, SEF95 and median power frequency. 27 Using the same entropy module as we did during surgical stimulation, Soto et al 24 and Prabhakar et al 7 found increased entropy after the addition of N 2 O during volatile agent administration. Prabhakar et al 7 observed an increase in entropy in the presence of N 2 O 66% and iso urane or sevo urane adjusted to an EMAC of 1.0 but a nonsigni cant decrease when end-tidal vapour concentrations were kept constant at 1.1% and 2% with the addition of N 2 O 66% (1.5 EMAC).…”

mentioning

confidence: 78%

“…27 Using the same entropy module as we did during surgical stimulation, Soto et al 24 and Prabhakar et al 7 found increased entropy after the addition of N 2 O during volatile agent administration. Prabhakar et al 7 observed an increase in entropy in the presence of N 2 O 66% and iso urane or sevo urane adjusted to an EMAC of 1.0 but a nonsigni cant decrease when end-tidal vapour concentrations were kept constant at 1.1% and 2% with the addition of N 2 O 66% (1.5 EMAC). Our ndings concur partly with the nding of Soto et al 24 During laparoscopy, they demonstrated a dual effect of N 2 O on entropy: When > 65% N 2 O was added to 2% sevo urane, entropy decreased.…”

mentioning

confidence: 78%

“…6 In contrast, when the alveolar concentration of sevo urane or iso urane or halothane was kept at 1 MAC, the addition of N 2 O 66% resulted in increased entropy, but there was no change at 1.5 MAC of those agents . 7 It therefore appears that the effect of N 2 O on entropy depends on the relative concentrations of the concomitantly administered volatile agent and N 2 O.…”

Section: Introductionmentioning

confidence: 99%

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Entropy of the electroencephalogram as applied in the M-Entropy S/5™ Module (GE Healthcare) during increases in nitrous oxide and constant sevoflurane concentrations

Smith

Spijkerman

Becker

et al. 2010

Southern African Journal of Anaesthesia and Analgesia

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Background: It has been suggested that spectral entropy of the electroencephalogram as applied in the M-Entropy S/5 TM Module (GE Healthcare) does not detect the effects of nitrous oxide (N 2 O). The aim of this study was to investigate the effect on entropy by graded increases in N 2 O concentrations in the presence of a constant concentration of sevo urane, in the absence of surgical stimulation. Method: This single-blind, randomised study was conducted at an altitude of approximately 1 400 m. Patients received sevo urane 2% (1.7% at sea level) and N 2 O, at end-tidal concentrations of 0%, 10%, 20%, 30%, 40%, 50%, 60% or 70% (equivalent to 8.5%, 17%, 25.5%, 34%, 42.6%, 51.1% and 59.6% at sea level). Entropy was measured before, during and after N 2 O administration. The absolute changes and ratios o f entropy relative to the baseline were calculated. Between-and within-group comparisons were made using analysis of variance and covariance. Results: None of the entropy variables differed signi cantly within and between groups before and after N 2 O administration. Within-group analysis revealed that entropy during N 2 O administration was signi cantly lower than before or after N 2 O administration (P < 0.007). While a minor clinical but statistically signi cant linear relationship was observed between increasing N 2 O concentration and decreasing entropy from N 2 O 0% to 60%, a steeper and clinically important decrease (relative change > 20%) was noted at N 2 O > 60% (> 51% at sea level). Conclusions: The M-Entropy Module S/5TM responds to increasing concentrations of N 2 O in the presence of 2% (1.7% at sea level) sevo urane, in the absence of surgical stimulation. There is a linear relationship between increasing N 2 O concentrations and decreasing entropy with a steep and clinically important decrease at N 2 O > 60% (> 51% at sea level). The in uence of ambient pressure on the partial pressures, which determine the effects of anaesthetic agents, must be taken into account.

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