Quantification of epileptiform electroencephalographic activity during sevoflurane mask induction.
BACKGROUND
Sevoflurane may induce epileptiform electroencephalographic activity leading to unstable Bispectral Index numbers, underestimating the hypnotic depth of anesthesia. The authors developed a method for the quantification of epileptiform electroencephalographic activity during sevoflurane anesthesia.


METHODS
Electroencephalographic data from 60 patients under sevoflurane mask induction were used in the analysis. Electroencephalographic data were visually classified. A novel electroencephalogram-derived quantity, wavelet subband entropy (WSE), was developed. WSE variables were calculated from different frequency bands. Performance of the WSE in detection and quantification of epileptiform electroencephalographic activity and the ability of the WSE to recognize misleading Bispectral Index readings caused by epileptiform activity were evaluated.


RESULTS
Two WSE variables were found to be sufficient for the quantification of epileptiform activity: WSE from the frequency bands 4-16 and 16-32 Hz. The lower frequency band was used for monophasic pattern monitoring, and the higher frequency band was used for spike activity monitoring. WSE values of the lower and higher bands followed the time evolution of epileptiform activity with prediction probabilities of 0.809 (SE, 0.007) and 0.804 (SE, 0.007), respectively. In deep anesthesia with epileptiform activity, WSE detected electroencephalographic patterns causing Bispectral Index readings greater than 60, with event sensitivity of 97.1%.


CONCLUSIONS
The developed method proved useful in detection and quantification of epileptiform electroencephalographic activity during sevoflurane anesthesia. In the future, it may improve the understanding of electroencephalogram-derived information by assisting in recognizing misleading readings of depth-of-anesthesia monitors. The method also may assist in minimizing the occurrence of epileptiform activity and seizures during sevoflurane anesthesia.
Särkelä
Mika O K
MO
GE Healthcare Finland Oy, Helsinki, Finland. mika.sarkela@ge.com
Ermes
Miikka J
MJ
van Gils
Mark J
MJ
Yli-Hankala
Arvi M
AM
Jäntti
Ville H
VH
Vakkuri
Anne P
AP
D000328:Adult; D000769:Anesthesia, Inhalation / Q000295:instrumentation / Q000379:methods; D004569:Electroencephalography / Q000187:drug effects*; D006801:Humans; D017214:Laryngeal Masks; D008738:Methyl Ethers / Q000008:administration & dosage*; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods; D000077149:Sevoflurane
D008738:Methyl Ethers; D000077149:Sevoflurane