Canadian Journal of Anaesthesia

, Volume 48, Issue 10, pp 958–962 | Cite as

Values of the bispectral index do not parallel the hemodynamic response to the rapid increase in isoflurane concentration

  • Masayasu Nakayama
  • Michiko Hayashi
  • Hiromichi Ichinose
  • Shuji Yamamoto
  • Noriaki Kanaya
  • Akiyoshi Namiki
General Anesthesia



To investigate the changes in hemodynamic variables and bispectral index (BIS) in response to a rapid increase in isoflurane or sevoflurane concentration.


Thirty adult patients were anesthetized with either isoflurane (isoflurane group) or sevoflurane (sevoflurane group). Two minutes after induction of anesthesia with thiamylal, the inspired concentrations of isoflurane and sevoflurane were rapidly increased from 0.5 minimum alveolar anaesthetic concentration (MAC) to 3 MAC and maintained for five minutes. Heart rate (HR), mean arterial pressure (MAP), and BIS were measured every minute.


An increase in the anesthetic concentration caused increases in HR and MAP in the isoflurane group and a decrease in MAP in the sevoflurane group. Consequently HR and MAP in the isoflurane group were significantly higher than those in the sevoflurane group. After inhalation of high concentrations, BIS significantly and progressively decreased in both groups.


BIS values decrease after a step increase in volatile agent concentration, whether or not a hyperdynamic action occurs.


Examiner les changements des variables hémodynamiques et de l’index bispectral (BIS) en réponse à une augmentation rapide de la concentration d’isoflurane ou de sévoflurane.


Trente patients adultes ont été anesthésiés avec de l’isoflurane ou du sévoflurane et ainsi répartis en deux groupes. Deux minutes après l’induction de l’anesthésie avec du thiamylal, les concentrations d’isoflurane et de sévoflurane inspirées ont été rapidement augmentées d’une concentration alvéolaire minimale de 0,5 (CAM) à 3 MAC et maintenue pendant cinq minutes. La fréquence cardiaque (FC), la tension artérielle moyenne (TAM) et le BIS ont été mesurés à chaque minute.


Une augmentation de la concentration de l’anesthésique a entraîné une augmentation de la FC et de la TAM dans le groupe isoflurane et une baisse de la TAM dans le groupe sévoflurane. Par conséquent, la FC et la TAM ont été significativement plus élevées dans le groupe isoflurane que dans le groupe sévoflurane. Après l’inhalation de fortes concentrations, le BIS a diminué de façon progressive et significative dans les deux groupes


Les valeurs du BIS diminuent à la suite d’une augmentation rapide de la concentration de l’anesthésique volatil, qu’une réaction hyperdynamique survienne ou non.


Isoflurane Mean Arterial Pressure Sevoflurane Desflurane Bispectral Index 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Les valeurs de l’index bispectral ne correspondent pas a la réponse hémodynamique à la suite de l’augmentation rapide de la concentration d’isoflurane


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Copyright information

© Canadian Anesthesiologists 2001

Authors and Affiliations

  • Masayasu Nakayama
    • 1
  • Michiko Hayashi
    • 1
  • Hiromichi Ichinose
    • 1
  • Shuji Yamamoto
    • 2
  • Noriaki Kanaya
    • 2
  • Akiyoshi Namiki
    • 2
  1. 1.Division of AnesthesiaObihiro Kosei HospitalSapporoJapan
  2. 2.Sapporo Medical University School of MedicineSapporoJapan

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