Is the ARX index a more sensitive indicator of anesthetic depth than the bispectral index during sevoflurane/nitrous oxide anesthesia?
BACKGROUND
During general anesthesia, hypnotic components have been monitored with electroencephalogram. The bispectral index is derived from a cortical electroencephalogram, but the A-line ARX index is the electroencephalographic response to auditory stimuli. The purpose of this study was to compare the changes of the A-line ARX index and the bispectral index during sevoflurane - nitrous oxide anesthesia.


METHODS
One hundred females aged 30-60 years, and scheduled for partial mastectomy, were divided into two groups. Anesthesia was induced with sevoflurane 5% and nitrous oxide in oxygen for 3 min. A laryngeal mask airway was inserted, and anesthesia was maintained with sevoflurane 1-2% and nitrous oxide in oxygen. During surgery, the sevoflurane end-tidal concentration was kept at 0.5%, 1%, or 2% for 5 min before each measurement. Blood pressure, heart rate, and the A-line ARX index (n = 50), and the bispectral index (n = 50) were measured.


RESULTS
Blood pressure and heart rate increased following laryngeal mask airway insertion and blood pressure decreased at 2% sevoflurane in both groups similarly. The A-line ARX index, but not the bispectral index, increased significantly by laryngeal mask airway insertion and skin incision. The A-line ARX index decreased at 2% sevoflurane compared with 0.5%, while the bispectral index remained unchanged.


CONCLUSIONS
During sevoflurane-nitrous oxide anesthesia, the A-line ARX index might be a more sensitive indicator of anesthetic depth than the bispectral index.
Department of Anesthesiology, The University of Tokyo, Japan. nishit-tky@umin.ac.jp
T
T
Nishiyama
T
T
Matsukawa
K
K
Hanaoka
D000328:Adult; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation; D001794:Blood Pressure / Q000187:drug effects; D004569:Electroencephalography / Q000187:drug effects*; D005072:Evoked Potentials, Auditory; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D017214:Laryngeal Masks; D015412:Mastectomy, Segmental; D008738:Methyl Ethers; D008875:Middle Aged; D009609:Nitrous Oxide; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D009609:Nitrous Oxide