Effects of Halothane on Motor Evoked Potential Recorded in the Extradural Space

Loughnan, B.A.; Anderson, Sharon K.; Hetreed, M.; Weston, P. F.; Boyd, Stewart; Hall, G.M.

doi:10.1093/bja/63.5.561

Cited by 34 publications

(7 citation statements)

References 16 publications

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“…In the former, there would be a change in the descending corticospinal volley recorded using extradural electrodes; in the latter there would be no such change. Loughnan and colleagues [19] have reported that halothane and propofol do not alter the corticospinal volley in extradural recordings, but these findings did not accord with our anecdotal experience.…”

contrasting

confidence: 85%

“…It is unlikely that fentanyl can cause the increase in I waves and thus the changes are attributed to isoflurane withdrawal. In addition, Loughnan and co-workers [19] observed infrequent small I waves when using halothane or propofol in addition to nitrous oxide. These observations suggest that depression of I waves may represent a fundamental difference in effect between an anaesthetic agent which primarily produces unconsciousness, such as the volatile agents or propofol, and one which has a large analgesic component to its action, such as nitrous oxide or an opioid.…”

Section: Discussionmentioning

confidence: 99%

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Some Effects of Isoflurane on I Waves of the Motor Evoked Potential

Hicks¹,

Woodforth²,

Crawford³

et al. 1992

British Journal of Anaesthesia

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We have investigated the effects of isoflurane anaesthesia on the motor evoked potential recorded in the extradural space during corrective spinal surgery in 15 patients. Isoflurane was added to a nitrous oxide in oxygen mixture supplemented with fentanyl and a neuromuscular blocking agent. Isoflurane was administered to achieve end-tidal concentrations of 2%, 1% and 0% in all patients, and also of 1.5% and 0.5% in nine patients. Transcranial electrical stimulation of the motor cortex was used to elicit descending volleys in corticospinal axons (the motor evoked potential). With stimuli of 450-750 V and no isoflurane, multiple I waves were always seen following the D wave. In all patients the number of I waves decreased and individual I waves became smaller in amplitude the greater the isoflurane concentration, but there were only minor changes in the D wave. The greatest depressant effect on I waves occurred at an end-tidal concentration of 0.5%. Given that I waves are an index of synaptic transmission, anaesthetic-induced changes in I waves may provide a useful model for the neuronal events underlying anaesthesia-induced unconsciousness.

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contrasting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Some Effects of Isoflurane on I Waves of the Motor Evoked Potential

Hicks¹,

Woodforth²,

Crawford³

et al. 1992

British Journal of Anaesthesia

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“…The belief that the D wave produced by electrical stimulation does not change when the excitability of motor cortex changes is supported by observations on the effects of withdrawing inhalational anaesthetics (Loughnan, Anderson, Hetreed, Weston, Boyd & Hall, 1989), observations not consistent with our own unpublished experience. The present study was therefore undertaken to test the assumption that the corticospinal volley evoked by transcranial electrical stimulation is resistant to changes in motor cortex excitability.…”

Section: Introductionmentioning

confidence: 57%

Corticospinal volleys evoked by electrical stimulation of human motor cortex after withdrawal of volatile anaesthetics.

Hicks

Burke

Stephen

et al. 1992

The Journal of Physiology

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SUMMARY1. In twenty-two neurologically normal patients undergoing surgery for scoliosis, corticospinal volleys to transcranial electrical stimulation of the motor cortex were recorded from the spinal cord using epidural electrodes. While anaesthesia was maintained by nitrous oxide and narcotics, volatile anaesthetics were withdrawn to determine whether such agents had a depressant effect on the evoked corticospinal volley.2. Profound changes were documented in liminal D waves, there being an increase in amplitude averaging 392 % following withdrawal of the volatile anaesthetic. There was a proportionately smaller increase (averaging 26 %) in supraliminal D waves; these had a complex bifid or trifid shape indicating that some corticofugal axons were being activated deep to cortex. In general the effect on the D wave of withdrawing the anaesthetic agent was similar to that of increasing stimulus intensity.3. Withdrawal of isoflurane dramatically increased the number of I waves and their mean amplitude. In the absence of isoflurane, I3 (mean latency 3-5 ms after the D wave) became the dominant I wave. The amplitude of I2 (mean latency 2-2 ms) became slightly smaller. The change in I waves could not be likened to an increase in stimulus intensity, because I waves invariably increase in, or remain of the same, amplitude as stimulus intensity is increased.4. These findings indicate that changes in motor cortex excitability can result in major changes in the corticospinal volley produced by transcranial electrical stimulation, affecting both the D wave and I waves. They caution against identifying a cortical action solely on the basis of a change in the responses to magnetic stimulation of motor cortex but no such change to electrical stimulation.

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“…It has been reported that muscle MEPs are suppressed by midazolam, volatile anesthetics, and even propofol in a dose-dependent manner. 4,9,10,12,14,16,20,21,25,28,29 Since muscle MEPs are known to be sensitive to volatile anesthetics, intravenous anesthetics are preferentially used during muscle MEP monitoring. 12,25 The bispectral index (BIS) is one of several methods used to monitor the depth of anesthesia.…”

mentioning

confidence: 99%

The influence of depth of anesthesia on motor evoked potential response during awake craniotomy

Ohtaki¹,

Akiyama²,

Kanno³

et al. 2017

JNS

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OBJECTIVE Motor evoked potentials (MEPs) are a critical indicator for monitoring motor function during neurological surgery. In this study, the influence of depth of anesthesia on MEP response was assessed. METHODS Twenty-eight patients with brain tumors who underwent awake craniotomy were included in this study. From a state of deep anesthesia until the awake state, MEP amplitude and latency were measured using 5-train electrical bipolar stimulations on the same site of the precentral gyrus each minute during the surgery. The depth of anesthesia was evaluated using the bispectral index (BIS). BIS levels were classified into 7 stages: < 40, and from 40 to 100 in groups of 10 each. MEP amplitude and latency of each stage were compared. The deviation of the MEP measurements, which was defined as a fluctuation from the average in every BIS stage, was also considered. RESULTS A total of 865 MEP waves in 28 cases were evaluated in this study. MEP amplitude was increased and latency was decreased in accordance with the increases in BIS level. The average MEP amplitudes in the > 90 BIS level was approximately 10 times higher than those in the < 40 BIS level. Furthermore, the average MEP latencies in the > 90 BIS level were 1.5-3.1 msec shorter than those in the < 60 BIS level. The deviation of measured MEP amplitudes in the > 90 BIS level was significantly stabilized in comparison with that in the < 60 BIS level. CONCLUSIONS MEP amplitude and latency were closely correlated with depth of anesthesia. In addition, the deviation in MEP amplitude was also correlated with depth of anesthesia, which was smaller during awake surgery (high BIS level) than during deep anesthesia. Therefore, MEP measurement would be more reliable in the awake state than under deep anesthesia.

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Effects of Halothane on Motor Evoked Potential Recorded in the Extradural Space

Cited by 34 publications

References 16 publications

Some Effects of Isoflurane on I Waves of the Motor Evoked Potential

Some Effects of Isoflurane on I Waves of the Motor Evoked Potential

Corticospinal volleys evoked by electrical stimulation of human motor cortex after withdrawal of volatile anaesthetics.

The influence of depth of anesthesia on motor evoked potential response during awake craniotomy

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