The effects of nitrous oxide on the auditory evoked potential index during sevoflurane anaesthesia

Barr, G.; Anderson, R. E.; Jakobsson, Jan

doi:10.1046/j.1365-2044.2002.02693.x

Cited by 20 publications

(11 citation statements)

References 18 publications

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“…An anaesthetic depth index of less than 35 was associated with a lack of response to deep pain 18 . An AAI index of less than 30 is associated with adequate anaesthesia in humans 3 . This correlates well with the AAI Index values recorded in our adequately anaesthetised patients.…”

Section: Discussionmentioning

confidence: 99%

“…The late cortical response occurs more than 80 ms after the stimulus and is a result of frontal cortex processing of the signal 34 . The auditoryevoked potential can be analysed by measurement of the amplitude and latencies of waves recorded 10-100 ms after auditory stimulation 3 . A regression model with exogenous input (ARX model) is used to analyse these amplitudes and latencies to derive a dimensionless number between 0 and 100 known as the A-line ARX-Index (AAI Index) 16 .…”

Section: Introductionmentioning

confidence: 99%

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Does the A-line ARX-Index provide a reasonable assessment of anaesthetic depth in dogs undergoing routine surgery?

Joubert

2004

J. S. Afr. Vet. Assoc.

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The monitoring of anaesthetic depth is usually based on the subjective assessment of the patient. An objective assessment of anaesthesia has only recently become possible. The auditory-evoked response has predictable changes in response to increasing doses of anaesthetic agents. Recent advances have brought about a regression model with exogenous input of the auditory-evoked response, the A-line ARX-Index (AAI Index). The AAI Index is a dimensionless number between 0 and 100. This technology has been incorporated into the AEP(auditory-evoked potential) monitor that is utilised to assess anaesthetic depth in humans. This study was undertaken to determine if the AEP monitor was useful in dogs. Ten dogs were enrolled in the study. After a full clinical and otoscopic examination, dogs were premedicated with acetylpromazine and morphine. Anaesthesia was induced with thiopentone and maintained with halothane. End-tidal carbon dioxide, temperature, pulse oximetry, blood pressure and the electrocardiogram were monitored and recorded every 5 minutes. Anaesthetic depth was assessed as either being adequate or inadequate by the anaesthetist during surgery. An AEP monitor was attached to the patient and automatically collected AAI Index data. The anaesthetist was blinded to the AEP monitor. Following the completion of the surgical procedure, the patient was allowed to wake up with the AEP monitor attached. The AAI Index was analysed to compare adequate with inadequate anaesthesia during the period of surgery and awake with sleep data during recovery. All AAI Index values associated with inadequate anaesthesia were greater than 31 while adequate values were less than 35. The difference between the groups was statistically significant and the power was 0.97. Statistically, the awake and sleep values were significantly different with a power of 0.99. From this study it can be concluded that the AAI Index shows good prospect for the evaluation of anaesthetic depth in dogs undergoing surgery.A larger study is needed to confirm these results.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Does the A-line ARX-Index provide a reasonable assessment of anaesthetic depth in dogs undergoing routine surgery?

Joubert

2004

J. S. Afr. Vet. Assoc.

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“…Darüber hinaus konnte gezeigt werden, dass sowohl die Applikation von Lachgas als auch von Remifentanil unter Sevoflurananästhesie ohne Veränderungen des AAI blieb [6,87].…”

Section: Limitierungenunclassified

Messung der Narkosetiefe

2007

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One of the most important mandates of the anaesthesiologist is to control the depth of anaesthesia. An unsolved problem is that a straight definition of the depth of anaesthesia does not exist. Concerning this it is rational to separate hypnosis from analgesia, from muscle relaxation and from block of cardiovascular reactions. Clinical surrogate parameters such as blood pressure and heart rate are not well-suited for a valid statement about the depth of hypnosis. To answer this question the brain has become the focus of interest as the target of anaesthesia. It is possible to visualize the brain's electrical activity from anelectroencephalogram (EEG). The validity of the spontaneous EEG as an anesthetic depth monitor is limited by the multiphasic activity, especially when anaesthesia is induced (excitation) and in deep anaesthesia (burst suppression). Recently, various commercial monitoring systems have been introduced to solve this problem. These monitoring systems use different interpretations of the EEG or auditory-evoked potentials (AEP). These derived and calculated variables have no pure physiological basis. For that reason a profound knowledge of the algorithms and a validation of the monitoring systems is an indispensable prerequisite prior to their routine clinical use. For the currently available monitoring systems various studies have been reported. At this time it is important to know that the actual available monitors can only value the sedation and not the other components of anaesthesia. For example, they cannot predict if a patient will react to a painful stimulus or not. In the future it would be desirable to develop parameters which allow an estimate of the other components of anaesthesia in addition to the presently available monitoring systems to estimate sedation and muscle relaxation. These could be sensoric-evoked potentials to estimate analgesia and AEPs for the detection of awareness.

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“…The MLAEP has been reported to be an insensitive marker of opioid and nitrous oxide effect. 22,23 BIS was reported to decrease from 47.7 to 39.8 by increasing nitrous oxide concentration from 0 to 60% during sevoflurane anesthesia, 24 while it did not change with the addition of nitrous oxide to isoflurane anesthe-sia. 25 The addition or withdrawal of nitrous oxide during constant sevoflurane anesthesia was found to cause only minor changes in the AAI.…”

Section: Me Et Th Ho Od Ds Smentioning

confidence: 99%

“…25 The addition or withdrawal of nitrous oxide during constant sevoflurane anesthesia was found to cause only minor changes in the AAI. 23 With fentanyl or nitrous oxide, MLAEP have been reported to remain nearly unchanged. 26 In the present study, we could not differentiate the effects of each anesthetic on the BIS and the AAI.…”

Section: Me Et Th Ho Od Ds Smentioning

confidence: 99%

L’index «A-line ARX» peut être un détecteur plus sensible du réveil que l’index bispectral pendant l’anesthésie avec propofol-fentanyl-protoxyde d’azote: une recherche préliminaire

Nishiyama

Hanaoka

2004

Can J Anesth/J Can Anesth

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The effects of nitrous oxide on the auditory evoked potential index during sevoflurane anaesthesia

Cited by 20 publications

References 18 publications

Does the A-line ARX-Index provide a reasonable assessment of anaesthetic depth in dogs undergoing routine surgery?

Does the A-line ARX-Index provide a reasonable assessment of anaesthetic depth in dogs undergoing routine surgery?

Messung der Narkosetiefe

L’index «A-line ARX» peut être un détecteur plus sensible du réveil que l’index bispectral pendant l’anesthésie avec propofol-fentanyl-protoxyde d’azote: une recherche préliminaire

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