Influence of Halothane, Enflurane, and Isoflurane on Motor Evoked Potentials

Zentner, Josef; Albrecht, Thomas; Heuser, D.

doi:10.1097/00132586-199308000-00022

Cited by 14 publications

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“…As these values are close to the degree of action potential depression obtained in our study, it seems very likely that the effects of halothane and isoflurane on human brain metabolism reflect, or even largely result from, changes in spontaneous action potential firing. Zentner and coworkers (Zentner et al ., 1992) investigated the effects of halothane, isoflurane and enflurane on muscle contractions triggered by electric stimulation of the motor cortex in awake and anaesthetized rats. Concentrations of volatile anaesthetics close to the MAC awake attenuated evoked responses by roughly 50%.…”

Section: Discussionmentioning

confidence: 99%

Neocortex is the major target of sedative concentrations of volatile anaesthetics: strong depression of firing rates and increase of GABA_A receptor‐mediated inhibition

Hentschke

Schwarz

Antkowiak

2005

Eur J of Neuroscience

162

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General anaesthetics cause sedation, amnesia and hypnosis. Although these clinically desired actions are indicative of an impairment of neocortical information processing, it is widely held that they are to a large part mediated by subcortical neural networks. Anaesthetic action on brain stem, basal forebrain and thalamus, all of which are known to modulate cortical excitability, would thus ultimately converge on neocortex, perturbing and reducing action potential activity therein. However, as neocortex harbours molecular targets of anaesthetics in high densities, notably GABA(A) receptors, neocortex itself should be very sensitive to anaesthetics. Here, we performed experiments to reveal the extent to which neocortex proper is a relevant target of the low concentrations of volatile anaesthetics causing sedation and hypnosis. We compared the effects of isoflurane, enflurane and halothane on spontaneous action potential activity of rat neocortical neurons in vivo and in isolated cortical networks in vitro, i.e. in the presence and absence of subcortical arousal systems. We observed that the anaesthetics decreased spontaneous firing of neurons via intracortical mechanisms; concentrations inducing hypnosis in humans reduced discharge rates both in vivo and in vitro to the same extent, approximately 50%. This decrease in neuronal activity was paralleled by a significant enhancement of neocortical GABA(A) receptor-mediated inhibition. These findings challenge the notion of predominantly subcortical effects of volatile anaesthetics and suggest that intracortical targets, among them neocortical GABA(A) receptors, mediate the sedative and hypnotic properties of volatile anaesthetics.

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Section: Discussionmentioning

confidence: 99%

Neocortex is the major target of sedative concentrations of volatile anaesthetics: strong depression of firing rates and increase of GABA_A receptor‐mediated inhibition

Hentschke

Schwarz

Antkowiak

2005

Eur J of Neuroscience

162

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“…All halogenated inhalational agents produce a dose-related increase in latency and reduction in the amplitude of cortically recorded SSEPs [28,74]. It is also noteworthy that cortical SSEPs are more sensitive to interference than are subcortical or peripherally acquired potentials.…”

Section: Halogenated Anestheticsmentioning

confidence: 97%

Current approach on spinal cord monitoring: the point of view of the neurologist, the anesthesiologist and the spine surgeon

2007

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Optimal outcome in spine surgery is dependent of the coordination of efforts by the surgeon, anesthesiologist, and neurophysiologist. This is perhaps best illustrated by the rising use of intraoperative spinal cord monitoring for complex spine surgery. The challenges presented by neurophysiologic monitoring, in particular the use of somatosensory and motor evoked potentials, requires an understanding by each member for the team of the proposed operative procedure as well as an ability to help differentiate clinically important signal changes from false positive changes. Surgical, anesthetic, and monitoring issues need to be addressed when relying on this form of monitoring to reduce the potential of negative outcomes in spine surgery. This article provides a practical overview from the perspective of the neurophysiologist, the anesthesiologist, and the surgeon on the requirements which must be understood by these participants in order to successfully contribute to a positive outcome when a patient is undergoing complex spine surgery.

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“…Routine balanced anesthesia with inhalational anesthetic agents and a muscle relaxant has various side effects on somatosensory evoked potentials and motoric evoked potentials (MEP). Inhalational anesthetics such as halothane, enflurance and isoflurane significantly reduce the amplitude of early cortical SEP responses after stimulation of the median or tibial nerve (N20 ± P25, P37 ± N45) [9] and have a dose-dependent suppressive effect on the electromyographic responses after direct cortical stimulation [10]. Additionally, muscle relaxants prevent the peripheral muscles from contracting after the primary motor cortex is stimulated and from obtaining an adequate EMG response.…”

Section: Anesthesiamentioning

confidence: 99%

Neuronavigation Combined with Electrophysiological Monitoring for Surgery of Lesions in Eloquent Brain Areas in 42 Cases: A Retrospective Comparison of the Neurological Outcome and the Quality of Resection with a Control Group with Similar Lesions

Reithmeier

Krammer

Gumprecht

et al. 2003

Minim Invasive Neurosurg

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The purpose of this study was to achieve a more radical resection of tumors in the area of the motor cortex via minimal craniotomy using a combination of neuronavigation and neurophysiological monitoring with direct electrical cortical stimulation and to compare retrospectively the clinical outcome and postoperative magnetic resonance imaging with a control group that was operated on in our service when the combination of these monitoring techniques was not available. A total of 42 patients with tumors in or near the central region underwent surgery with neuronavigation guidance and neurophysiological monitoring. The primary motor cortex was identified intraoperatively by the somatosensory evoked phase reversal method and direct cortical stimulation. The functional areas were transferred into the neuronavigation system. By stimulating the identified primary motor cortex and displaying the motor area in the operating microscope a permanent control of the motor function was possible during the whole operation. Using these techniques a more radical tumor resection - evaluated by postoperative MRI - was achieved in the study group (p = 0.04) and also a trend toward a better neurological outcome.

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Influence of Halothane, Enflurane, and Isoflurane on Motor Evoked Potentials

Cited by 14 publications

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Neocortex is the major target of sedative concentrations of volatile anaesthetics: strong depression of firing rates and increase of GABA_A receptor‐mediated inhibition

Neocortex is the major target of sedative concentrations of volatile anaesthetics: strong depression of firing rates and increase of GABA_A receptor‐mediated inhibition

Current approach on spinal cord monitoring: the point of view of the neurologist, the anesthesiologist and the spine surgeon

Neuronavigation Combined with Electrophysiological Monitoring for Surgery of Lesions in Eloquent Brain Areas in 42 Cases: A Retrospective Comparison of the Neurological Outcome and the Quality of Resection with a Control Group with Similar Lesions

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Influence of Halothane, Enflurane, and Isoflurane on Motor Evoked Potentials

Cited by 14 publications

References 0 publications

Neocortex is the major target of sedative concentrations of volatile anaesthetics: strong depression of firing rates and increase of GABAA receptor‐mediated inhibition

Neocortex is the major target of sedative concentrations of volatile anaesthetics: strong depression of firing rates and increase of GABAA receptor‐mediated inhibition

Current approach on spinal cord monitoring: the point of view of the neurologist, the anesthesiologist and the spine surgeon

Neuronavigation Combined with Electrophysiological Monitoring for Surgery of Lesions in Eloquent Brain Areas in 42 Cases: A Retrospective Comparison of the Neurological Outcome and the Quality of Resection with a Control Group with Similar Lesions

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Neocortex is the major target of sedative concentrations of volatile anaesthetics: strong depression of firing rates and increase of GABA_A receptor‐mediated inhibition

Neocortex is the major target of sedative concentrations of volatile anaesthetics: strong depression of firing rates and increase of GABA_A receptor‐mediated inhibition