Influence of Anesthetics—Nitrous Oxide in Particular—on Electromyographic Response Evoked by Transcranial Electrical Stimulation of the Cortex

Neurosurgery ◽  
1989 ◽  
Vol 24 (2) ◽  
pp. 253-256 ◽  
Author(s):  
Josef Zentner ◽  
Ivan Kiss ◽  
Alois Ebner
Keyword(s):  
Nitrous Oxide ◽  
Motor Evoked Potentials ◽  
Transcranial Electrical Stimulation ◽  
Minor Effect ◽  
Oxide Mixture ◽  
Similar Reduction ◽  
Anterior Tibial ◽  
Oxygen Nitrous Oxide ◽  
A Minor ◽  
Electrical Stimuli

Abstract The influence of anesthetics usually used for neuroleptic anesthesia—nitrous oxide, fetanyl, flunitrazepam, and thiopental sodium—on motor evoked potentials (MEP) was examined in 15 patients during neurosurgical operations on the spinal cord, in 16 patients in traumatic coma, and in 6 healthy volunteers. MEP were recorded from the contralateral thenar and anterior tibial muscles in response to single transcranial electrical stimuli on the motor cortex. Intraoperatively, during neuroleptic anesthesia we found the amplitudes to be reduced to an average of 11% of the preoperative baselines for the thenar potentials, and to 7% of the preoperative baselines for the anterior tibial muscle potentials, despite a maximum stimulus strength of 750 V. A similar reduction of MEP amplitudes was observed in 6 volunteers during breathing of an oxygen/nitrous oxide mixture (34%/66%), whereas fentanyl, flunitrazepam, and thiopental had only a minor effect on MEP. We conclude that with respect to anesthesia-related suppression of amplitudes, an average of 5 to 15 electromyographic responses should be evaluated for intraoperative monitoring of MEP using the technique described here.

Effect of N2O on Sevoflurane Vaporizer Settings during Minimal- and Low-flow Anesthesia

2002 ◽  
Vol 97 (2) ◽  
pp. 400-404 ◽  
Author(s):  
Jan F. A. Hendrickx ◽  
José Coddens ◽  
Frederik Callebaut ◽  
Hermes Artico ◽  
Thierry Deloof ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Gas Flow ◽  
Low Flow ◽  
Oxide Mixture ◽  
Factors Affecting ◽  
Carrier Gas ◽  
Dial Setting ◽  
Oxygen Nitrous Oxide ◽  
Low Flow Anesthesia ◽  
Almost All

Background Uptake of a second gas of a delivered gas mixture decreases the amount of carrier gas and potent inhaled anesthetic leaving the circle system through the pop-off valve. The authors hypothesized that the vaporizer settings required to maintain constant end-expired sevoflurane concentration (Etsevo) during minimal-flow anesthesia (MFA, fresh gas flow of 0.5 l/min) or low-flow anesthesia (LFA, fresh gas flow of 1 l/min) would be lower when sevoflurane is used in oxygen-nitrous oxide than in oxygen. Methods Fifty-six patients receiving general anesthesia were randomly assigned to one of four groups (n = 14 each), depending on the carrier gas and fresh gas flow used: group Ox.5 l (oxygen, MFA), group NOx.5 l (oxygen-nitrous oxide, MFA after 10 min high fresh gas flow), group Ox1 l (oxygen, LFA), and group NOx1 l (oxygen-nitrous oxide, LFA after 10 min high fresh gas flow). The vaporizer dial settings required to maintain Etsevo at 1.3% were compared between groups. Results Vaporizer settings were higher in group Ox.5 l than in groups NOx.5 l, Ox1 l, and NOx1 l; vaporizer settings were higher in group NOx.5 l than in group NOx1 l between 23 and 47 min, and vaporizer settings did not differ between groups Ox1 l and NOx1 l. Conclusions When using oxygen-nitrous oxide as the carrier gas, less gas and vapor are wasted through the pop-off valve than when 100% oxygen is used. During MFA with an oxygen-nitrous oxide mixture, when almost all of the delivered oxygen and nitrous oxide is taken up by the patient, the vaporizer dial setting required to maintain a constant Etsevo is lower than when 100% oxygen is used. With higher fresh gas flows (LFA), this effect of nitrous oxide becomes insignificant, presumably because the proportion of excess gas leaving the pop-off valve relative to the amount taken up by the patient increases. However, other unexplored factors affecting gas kinetics in a circle system may contribute to our observations.

Oxidation of propane with oxygen, nitrous oxide and oxygen/nitrous oxide mixture over Co- and Fe-zeolites

2005 ◽  
Vol 100 (3-4) ◽  
pp. 315-319 ◽  
Author(s):  
Kateřina Novoveská ◽  
Roman Bulánek ◽  
Blanka Wichterlová
Keyword(s):  
Nitrous Oxide ◽  
Oxide Mixture ◽  
Oxygen Nitrous Oxide

Effects of Nitrous Oxide on Motor Evoked Potentials Recorded from Skeletal Muscle in Patients under Total Anesthesia with Intravenously Administered Propofol

Neurosurgery ◽  
1991 ◽  
Vol 29 (4) ◽  
pp. 558-562 ◽  
Author(s):  
David Jellinek ◽  
Michael Platt ◽  
Doreen Jewkes ◽  
Lindsay Symon
Keyword(s):  
Nitrous Oxide ◽  
Evoked Potentials ◽  
Motor Evoked Potentials ◽  
Human Subjects ◽  
Deltoid Muscle ◽  
Progressive Increase ◽  
Peak Amplitude ◽  
Onset Latency ◽  
Electrical Stimuli ◽  
Dorsal Interosseous Muscle

Abstract The effect of nitrous oxide (N2O) on motor evoked potentials (MEPs) recorded from human subjects under total intravenous anesthesia with propofol (2,6-diisopropylphenol) was studied. MEPs were recorded from the 1st dorsal interosseous muscle of the foot in nine subjects; in two of these, simultaneous recordings were made from the 2nd dorsal interosseous muscle of the hand and from the deltoid muscle. Single transcranial electrical stimuli were used in recording the MEPs. The effects of N2O were studied at concentrations from 20 to 70%. Increasing concentrations of N2O caused a progressive increase in onset latency and a fall in the peak-to-peak amplitude of the MEPs recorded from the foot. Latency values showed a significant increase above the baseline at concentrations of N2O greater than 20% (Pvalues, 0.05-0.005). The response amplitude showed a significant decrease from the baseline at concentrations of N2O greater than 50% (P values, 0.05-0.005). The 2nd dorsal interosseous muscle of the hand demonstrated a pattern of sensitivity to N2O similar to that of the 1 st dorsal interosseous muscle of the foot. The onset latency and initial peak-to-peak amplitude of the deltoid muscle were insensitive to N2O at the concentrations used. We conclude that N2O can be used as an anesthetic adjunct without a significant deleterious effect on MEPs during intraoperative monitoring in patients under propofol anesthesia, providing concentrations are maintained below 50%.

scholarly journals Halothane anaesthesia of normal and dystrophic hamsters

1975 ◽  
Vol 9 (4) ◽  
pp. 345-352 ◽  
Author(s):  
J. E. Carvell ◽  
P. J. Stoward
Keyword(s):  
Nitrous Oxide ◽  
Gas Flow ◽  
Face Mask ◽  
Open Circuit ◽  
Dystrophic Muscle ◽  
Oxide Mixture ◽  
Oxygen Nitrous Oxide ◽  
Wet Weight ◽  
Clear Plastic ◽  
Anaesthetic Mixture

Induction, carried out in a small clear-plastic box with 3·5% (v/v) halothane in 30:70 (v/v) oxygen: nitrous oxide, was quiet and rapid. Recovery was almost instantaneous. 2% halothane in the oxygen-nitrous oxide mixture was sufficient for maintenance anaesthesia. The anaesthetic mixture was given by face mask in an open circuit specially designed to function at low gas-flow rates. The halothane content of the muscle and blood after 25 min anaesthesia was estimated by gas chromatography of n-heptane extracts. The mean level(± s.e.m.) in blood was 22·8±2·7 mg/1OO ml (n=4), and in dystrophic muscle 226±36·8 mg/100 g wet weight of tissue (n=4): there was a positive correlation (r=0·94) between them ( p<:0·02).

Effects of Isoflurane and Desflurane on Neurogenic Motor- and Somatosensory-evoked Potential Monitoring for Scoliosis Surgery

1996 ◽  
Vol 85 (5) ◽  
pp. 1013-1019 ◽  
Author(s):  
Jean-Marc Bernard ◽  
Yann Pereon ◽  
Guillemette Fayet ◽  
Pierre Guiheneuc
Keyword(s):  
Spinal Cord ◽  
Nitrous Oxide ◽  
Evoked Potentials ◽  
Stimulus Intensity ◽  
Somatosensory Evoked Potentials ◽  
Evoked Potential ◽  
Motor Evoked Potentials ◽  
Volatile Anesthetic ◽  
Anesthetic Agents ◽  
Oxygen Nitrous Oxide

Background Most techniques used to monitor spinal cord tracts are sensitive to the effects of anesthesia, particularly to volatile anesthetic agents. The aim of this prospective study was to show that evoked potentials recorded from the peripheral nerves after spinal cord stimulation, so-called neurogenic motor evoked potentials, are resistant to clinical concentrations of isoflurane or desflurane, compared with somatosensory-evoked potentials. Methods Twenty-three patients were studied during surgery to correct scoliosis. The background anesthetic consisted of a continuous infusion of propofol. Isoflurane (n = 12) or desflurane (n = 11) were then introduced to achieve 0.5 and 1.0 end-tidal minimum alveolar concentrations (MAC), both in 50% oxygen-nitrous oxide and in 100% oxygen. Somatosensory-evoked potentials were elicited and recorded using a standard method, defining cortical P40 and subcortical P29. Neurogenic motor-evoked potentials were elicited by electric stimulation of the spinal cord via needle electrodes placed by the surgeon in the rostral part of the surgical field. Responses were recorded from needle electrodes inserted in the right and left popliteal spaces close to the sciatic nerve. Stimulus intensity was adjusted to produce a supramaximal response; that is, an unchanged response in amplitude with subsequent increases in stimulus intensity. Measurements were obtained before introducing volatile agents and 20 min after obtaining a stable level of each concentration. Results Isoflurane and desflurane in both 50% oxygen-nitrous oxide and 100% oxygen were associated with a significant decrease in the amplitude and an increase in the latency of the cortical P40, whereas subcortical P29 latency did not vary significantly. Typical neurogenic motor-evoked potentials were obtained in all patients without volatile anesthetic agents, consisting of a biphasic wave, occurring 15 to 18 ms after stimulation, with an amplitude ranging from 1.3 to 4.1 microV. Latency or peak-to-peak amplitude of this wave was not significantly altered with isoflurane and desflurane, either in the presence or in the absence of nitrous oxide. Conclusions Compared with cortical somatosensory-evoked potentials, neurogenic motor-evoked potential signals are well preserved in patients undergoing surgery to correct scoliosis under general anesthesia supplemented with isoflurane or desflurane in concentrations as great as 1 MAC.

Noninvasive Motor Evoked Potential Monitoring During Neurosurgical Operations on the Spinal Cord

Neurosurgery ◽  
1989 ◽  
Vol 24 (5) ◽  
pp. 709-712 ◽  
Author(s):  
Josef Zentner
Keyword(s):  
Spinal Cord ◽  
Motor Evoked Potentials ◽  
False Negative ◽  
Evaluation Criteria ◽  
Motor Evoked Potential ◽  
Neurological Status ◽  
Neurological Complications ◽  
Transcranial Electrical Stimulation ◽  
Descending Pathways ◽  
Anterior Tibial

ABSTRACT We present the results of monitoring descending pathways with motor evoked potentials (MEP) in 50 patients during neurosurgical operations on the spinal cord. The electromyographic responses of the anterior tibial muscles were recorded. In addition, in 24 patients responses of the thenar muscles after transcranial electrical stimulation of the motor cortex were recorded. Usually, the averages of 5 to 15 signals were evaluated. Although potentials were obtained preoperatively in all 50 patients, during neuroleptanesthesia intraoperative recording from the anterior tibial muscles was possible in 43 patients (86%) and from the thenar muscles in 21 patients (87.5%). Amplitudes were superior to latencies as evaluation criteria for intraoperative changes in potentials. On the basis of acceptable changes in amplitudes of up to 50% at the end of the operation, 16 recordings from the thenar muscles (76.2%) and 35 from the anterior tibial muscles (81.4%) correlated correctly with the postoperative neurological status; there were false positive results in 5 (23.8%) and 8 (18.6%) patients, respectively. We did not observe false negative findings. Postoperative neurological complications coincided in every case with permanent reduction in amplitudes of more than 50% of the base lines or with intraoperative loss of potentials as observed in 3 and 1 patient, respectively. MEP monitoring during neurosurgical operations on the spinal cord is a sensitive method for early detection of impending neurological complications. Major problems are the influence of anesthesia and the definition of acceptable limits for changes in amplitudes.

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