Nitrous oxide induces paradoxical electroencephalographic changes after tracheal intubation during isoflurane and sevoflurane anesthesia.
In this randomized, double-blind, controlled study, we tested the hypothesis that nitrous oxide (N2O) affects bispectral index (BIS) and 95% spectral edge frequency (SEF95) in response to tracheal intubation during anesthesia with isoflurane and sevoflurane. In protocol 1, we randomly allocated 90 ASA physical status I patients to 6 groups (n = 15 each). Anesthesia was induced with isoflurane or sevoflurane with 0%, 33%, or 66% N2O. The concentration of isoflurane and sevoflurane was gradually increased and end-tidal concentrations were maintained at 1.1% and 1.7%, respectively. Tracheal intubation was performed 12 min after induction of anesthesia. BIS was significantly increased 1 min after tracheal intubation compared before laryngoscopy in patients receiving only isoflurane or sevoflurane (P = 0.001 and 0.007, respectively). In patients receiving 66% N2O-isoflurane or 66% N2O-sevoflurane, both BIS and SEF95 were significantly decreased after tracheal intubation and significantly lower than in those patients receiving only isoflurane or sevoflurane, respectively (P < 0.01 for both). In protocol 2, 3 microg/kg of IV fentanyl completely abolished the decrease of BIS and SEF95 after tracheal intubation during anesthesia with 66% N2O-isoflurane and 66% N2O-sevoflurane (n = 10). We conclude that 66% N2O induced a paradoxical decrease of BIS in response to tracheal intubation during anesthesia with isoflurane and sevoflurane.
Oda
Yutaka
Y
Department of Anesthesiology and Intensive Care Medicine, Graduate School of Medicine, Osaka City University, Osaka, Japan. odayou@msic.med.osaka-cu.ac.jp
Tanaka
Katsuaki
K
Matsuura
Tadashi
T
Hase
Ichiro
I
Nishikawa
Kiyonobu
K
Asada
Akira
A
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D000769:Anesthesia, Inhalation / Q000379:methods / Q000706:statistics & numerical data*; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D016009:Chi-Square Distribution; D004311:Double-Blind Method; D004569:Electroencephalography / Q000187:drug effects* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal / Q000706:statistics & numerical data*; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D008875:Middle Aged; D009609:Nitrous Oxide / Q000494:pharmacology*; D000077149:Sevoflurane
D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane; D009609:Nitrous Oxide