Background and Goal of study: The electroencephalogram (EEG) changes from birth to elderly alter in the composition of the EEG signal during general anesthesia. In elderly patients, a decreased of the dominant frequency compared with younger patients has been reported. However, it was unknown that age-related differences in EEG using inhalational anesthetics such as sevoflurane, isoflurane or desflurane. In this study, we investigated that age-related difference in the EEG by 1 minimum alveolar concentration (MAC) during general anesthesia.

Methods: Patients (ASA-PS: I-II, 0-90 yrs) were scheduled for oral maxillofacial surgery were enrolled. Patients were divided into three groups with children group (age from 1 to 15 yrs), adult group (age from 16 to 59 yrs) and elderly group (age from 60 to 90 yrs). Patients with psychological disease and an inability to communicate were excluded. After intubation, inhalational anesthetics (sevoflurane, isoflurane or desflurane) was maintained at 1 MAC according to patient’s age. The raw EEG signal was recorded. BIS value, frequency and amplitude were recorded.

Results and discussion: A total of 180 patients were included; children, adult and elderly patients were each one by 20 in sevoflurane, isoflurane and desflurane groups. In children group, BIS value (35.2-50.0) was significantly higher than adult (31.4-35.5), elderly (40.1-42.6) groups (P<0.05). In adult group, frequency (11.4-12.0 Hz) and amplitude (16.0-19.5 micro volt) were lower than children group (13.8-17.2 Hz, 30.5-35.8 micro volt) (P>0.05). However, there were higher frequency in elderly group (11.9-13.5 Hz) than adult group (P<0.05). These parameter were similar to three inhalational anesthetics. BIS, amplitude and frequency in sevoflurane were tended to be higher compared to other inhalational anesthetics. It was predicted that aged patients had a smaller EEG parameters compared with younger patients. However, in elderly, frequency was increased 10% compared to adult. It might be influenced on the change of brain wave activities of α and β bands at 1MAC. Therefore, BIS value in adult patients was low 10-20% compared to aged patients. 

Conclusion: Age-dependent EEG using three inhalational anesthetics at 1 MAC was same result as a decreased in amplitude. However, BIS value and frequency were not true of age dependent.

05 / The age-related EEG at 1 MAC inhalational anesthetics during general anesthesia.