Brazilian Journal of Anesthesiology
https://app.periodikos.com.br/journal/rba/article/doi/10.1590/S0034-70942002000300001
Brazilian Journal of Anesthesiology
Scientific Article

Ação do óxido nitroso no sistema nervoso central: estudo eletrofisiológico como agente único e como agente coadjuvante

Nitrous oxide action on the central nervous system: electrophysiological study as a sole agent or a coadjuvant

Verônica Vieira da Costa; Renato Ângelo Saraiva

http://dx.doi.org/10.1590/S0034-70942002000300001 Braz J Anesthesiol, vol.52, n3, p.255-271, 2002
PDF Português
PDF English
Downloads: 2
Views: 1486

Resumo

JUSTIFICATIVA E OBJETIVOS: O óxido nitroso é o agente anestésico inalatório mais utilizado em todo o mundo. Seu mecanismo de ação é bastante discutido, com base em resultados experimentais e em evidências clínicas. O objetivo deste estudo é avaliar a ação eletrofisiológica deste fármaco no Sistema Nervoso Central através de monitorização específica. MÉTODO: Foram estudados vinte e cinco pacientes de ambos os sexos, com idades entre 6 e 25 anos, submetidos à cirurgia ortopédica ou plástica reparadora, os quais foram monitorizados com índice bispectral do eletroencefalograma (BIS) e potencial evocado somatossensitivo (PESS) durante a anestesia. Foram realizados registros basais do BIS e do PESS, bem como após o uso do óxido nitroso em fracionais alveolares (FA) de 30%, 50% e 66%. Em seguida o óxido nitroso era descontinuado e administrado aleatoriamente isoflurano ou desflurano em 0,5 CAM e 1 CAM. Mantinha-se 1 CAM do determinado agente e o óxido nitroso era novamente administrado nas mesmas concentrações anteriores. RESULTADOS: O óxido nitroso quando utilizado como agente único, produz uma redução no BIS que, embora seja estatisticamente significante, não expressa um estado de hipnose. Esta redução também ocorre quando utilizado como agente coadjuvante mas sem importância clínica. Como agente único, o óxido nitroso deprimiu significantemente a amplitude das ondas cerebrais, sem promover aumento na latência. O isoflurano e desflurano reduziram a amplitude e aumentaram a latência das ondas cerebrais. A associação do óxido nitroso a estes agentes, intensificou ainda mais estes efeitos nas ondas corticais. Não houve alteração significativa das ondas periférica e medular do PESS. CONCLUSÕES: O óxido nitroso tem uma pequena ação hipnótica, que não é captada completamente pelo BIS. Tem ação acentuada nas estruturas corticais, tanto como agente único como associado ao isoflurano e desflurano, o que pode explicar o seu bom efeito analgésico.

Palavras-chave

ANESTÉSICOS, ANESTÉSICOS, MONITORIZAÇÃO, MONITORIZAÇÃO

Abstract

BACKGROUND AND OBJECTIVES: Nitrous oxide is the most widely used inhalational anesthetic worldwide. Its action mechanism is broadly discussed based on results of experimental studies and clinical evidences. The purpose of this study was to evaluate, through specific monitoring, nitrous oxide electrophysiological action on the central nervous system. METHODS: Twenty-five patients of both genders, aged 6 to 25 years, undergoing orthopedic or corrective plastic surgery, were monitored by electroencephalogram bispectral index (EEG-BIS) and somatosensory evoked potential (SEP) during anesthesia. BIS and SEP baseline values were recorded, as well as after fractional alveolar (FA) 30%, 50% and 66% nitrous oxide administration. Then, nitrous oxide was withdrawn and isoflurane or desflurane were randomly administered in 0.5 and 1 MAC. While maintaining 1 MAC of one of those agents, nitrous oxide was again administered in the same previous concentrations. RESULTS: Nitrous oxide as sole agent caused a BIS decrease which, although statistically significant, did not represent a hypnotic state. This decrease was also observed when nitrous oxide was used as a coadjuvant agent, however without clinical significance. As sole agent, nitrous oxide significantly depressed brain waves amplitude, with no increase in onset time. Isoflurane and desflurane decreased the amplitude and increased onset time of brain waves. The association of nitrous oxide to those agents further increased these effects on cortical waves. There were no significant changes in peripheral and spinal cord SEP waves. CONCLUSIONS: Nitrous oxide has a minor hypnotic action, which is not completely captured by EEG-BIS. It has a pronounced action on cortical structures, both as sole agent or associated to isoflurane or desflurane, which may explain its satisfactory analgesic effect.

Keywords

ANESTHETICS, ANESTHETICS, MONITORING, MONITORING

References

Hornbein TF, Eger EI II, Winter PM. The minimum alveolar concentration of nitrous oxide in man. Anesth Analg. 1982;61:553-556.

Eger II EI, Brandstater B, Saidman LJ. Equipotent alveolar concentrations of methioxyflurane, halothane, diethyl ether, fluoxene, cyclopropane, xenon and nitrous oxide in the dog. Anesthesiology. 1965;26:771-777.

Zancy JP. Time course of effects of brief inhalations of nitrous oxide in normal volunteers. Addiction. 1994;89:831-839.

Frost E. Nitrous Oxide: N2O. 1985:1-22.

Eger II EI, Larson Jr CP. Anaesthetic solubility in blood and tissues: values and significance. Br J Anaesth. 1964;36:140-149.

Saidman LJ, Eger II EI. Effect of nitrous oxide and of narcotic premedication on the alveolar concentration of halothane required for anesthesia. Anesthesiology. 1964;25:302-306.

Thornton JA, Fleming JS, Goldberg AD. Cardiovascular effects of 50% nitrous oxide and 50% oxygen mixture. Anaesthesia. 1973;28:484-489.

Eger II EI. Nitrous Oxide: N2O. 1985:57-67.

Porkkala T, Jäntti V, Kaukinen S. Nitrous oxide has different effects on the EEG and somatosensory evoked potentials during isoflurane anesthesia in patients. Acta Anaesthesiol Scand. 1997;41:497-501.

Sebel PS, Flynn PJ, Ingram DA. Effect of nitrous oxide on visual, auditory and somatosensory evoked potentials. Br J Anaesth. 1984;56:1403-1407.

Clark DL, Rosner BS. Neurophysiologic effects of general anesthetics: I. The electroencephalogram and sensory evoked responses in man. Anesthesiology. 1973;38:564-582.

Horkey J, Bustillo F, Norton ML. Evaluation of the effects of nitrous oxide in man. Anesth Prog. 1973;20:16-19.

Levy WJ. Effect of epoch length on power spectrum analysis of the EEG. Anesthesiology. 1987;66:489-495.

Eger II EI, Lampe GH, Wauk LZ. Clinical pharmacology of nitrous oxide: an argument for its continued use. Anesth Analg. 1990;71:575-585.

Eger II EI. Respiratory Effects of Nitrous Oxide. Nitrous Oxide/N2O. 1985:109-123.

Kearse L, Rosow P, Sebel P. The bispectral index correlates with sedation/hypnosis and recall: comparison using multiple agents. Anesthesiology. 1995;83.

Flaishon R, Windsor A, Sigl J. Recovery of consciousness after thiopental or propofol: Bispectral index and the isolated forearm technique. Anesthesiology. 1997;86:613-619.

Rampil IJ, Kim J, Lenhardt R. Bispectral EEG index during nitrous oxide administration. Anesthesiology. 1998;89:671-677.

Barr G, Jakobsson JG, Öwall A. Nitrous oxide does not alter bispectral index: study with nitrous oxide as sole agent and as an adjunct to i.v. anaesthesia. Br J Anaesth. 1999;82:827-830.

Glass PS, Bloom M, Kearse L. Bispectral analysis measures sedation and memory effects of propofol, midazolam, isoflurane, and alfentanil. Anesthesiology. 1997;86:836-847.

Detsch O, Schneider G, Kochs E. Increasing isoflurane concentration may cause paradoxical increases in the EEG bispectral index in surgical patients. Br J Anaesth. 2000;84:33-37.

Yli-Hankala A, Lindgren L, Porkkala T. Nitrous oxide-mediated activation of the EEG during isoflurane anaesthesia in patients. Br J Anaesth. 1993;70:54-57.

Sebel P, lang E, Rampil L. A multicenter study of bispectral encephalogram analysis for monitoring anesthetic effect. Anesth Analg. 1997;84:891-899.

Kearse LA, Rosow C, Zaslavsky A. Bispectral analysis of the electroencephalogram predicts conscious processing of information during propofol sedation and hypnosis. Anesthesiology. 1998;88:25-34.

Lam AM, Sharar SR, Mayberg TS. Isoflurane compared with nitrous oxide anaesthesia for intraoperative monitoring of somatosensory-evoked potentials. Can J Anaesth. 1994;41:295-300.

Samra SK, Vanderzant CW, Domer PA. Differential effects of isoflurane on human median nerve somatosensory evoked potentials. Anesthesiology. 1987;66:29-35.

Sloan TB, Koht A. Depression of cortical somatosensory evoked potentials by nitrous oxide. Br J Anaesth. 1985;57:849-852.

Thornton C, Creagh-Barry P, Jordan C. Somatosensory and auditory evoked responses recorded simultaneously: differential effects of nitrous oxide and isoflurane. Br J Anaesth. 1992;68:508-514.

Pathak KS, Ammadio M, Kalamchi A. Effects of halothane, enflurane, and isoflurane on somatosensory evoked potentials during nitrous oxide anesthesia. Anesthesiology. 1987;66:753-757.

Peterson DO, Drummond JC, Todd MM. Effects of halothane, enflurane, isoflurane, and nitrous oxide somatosensory evoked potentials in humans. Anesthesiology. 1986;65:35-40.

Schindler E, Muller M, Zickmann B. Modulation of somatosensory evoked potentials under various concentrations of desflurane with and without nitrous oxide. J Neurosurg Anesthesiol. 1998;10:218-223.

Lam AM, Manninen PH, Ferguson GG. Monitoring electrophysiological function during carotid endarterectomy: a comparison of somatosensory evoked potentials and conventional EEG. Anesthesiology. 1991;75:15-21.

Costa VV, Saraiva RA, Almeida AC. The effect of nitrous oxide on the inhibition of somatosensory evoked potentials by sevoflurane in children. Anaesthesia. 2001;56:202-207.

Mason DG, Higgins D, Boyd SG. Effects of isoflurane anaesthesia on the median nerve somatosensory evoked potential in children. Br J Anaesth. 1992;69:562-566.

Stejaskal L, Traunicek K, Sourek V. Somatosensory evoked potentials in deep hypothermia. Appl Neurophysiol. 1980;43:1-7.

Dubois M, Coppola R, Buchsbaum MS. Somatosensory evoked potential during whole body hyperthermia in human. Electroencephalogr Clin Neurophysiol. 1981;52:157-162.

Angel A. Central neuronal pathways and the process of anaesthesia. Br J Anaesth. 1993;71:148-163.

Roald OK, Forsman M, Heier MS. Cerebral effects of nitrous oxide when added to low and high concentrations of isoflurane in the dog. Anesth Analg. 1991;72:75-79.

Algotsson L, Messeter K, Rosén I. Effects of nitrous oxide on cerebral haemodynamics and metabolism during isoflurane anaesthesia in man. Acta Anaesthesiol Scand. 1992;36:46-52.

5dd58d060e88253855c8fca6 rba Articles
Links & Downloads
2352-2291 (Electronic) 0104-0014 (Printed)
Braz J Anesthesiol ©2024 All rights reserved.

Braz J Anesthesiol

Share this page
Page Sections