Document Detail

Hyperventilation-induced hypocapnia changes the pattern of electroencephalographic bicoherence growth during sevoflurane anaesthesia.
MedLine Citation:
PMID:  18791187     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Hyperventilation, with the resulting hypocapnia, reduces cerebral blood flow and causes slowing of the EEG activity. However, neuronal oscillating properties including the thalamocortical network during hyperventilation have not been elucidated. To assess these features provoked by hyperventilation, the present study examined quadratic phase coupling features by means of bicoherence analysis. METHODS: Twenty-two patients were anaesthetized using sevoflurane 1.5% combined with remifentanil or epidural anaesthesia. After a stable normocapnic period, hypocapnia was induced by hyperventilation, and the raw EEG signals were collected. Bispectral analysis (bicoherence) and power spectrum analysis were performed before and after hypocapnia. RESULTS: Mean (sd) peak bicoherence in the delta- area increased from 35.6 (10.9)% during normocapnia to 43.8 (10.9)% during hypocapnia (P<0.05), whereas mean (sd) peak bicoherence in the alpha area decreased from 42.8 (14.4)% during normocapnia to 37.5 (12.3)% during hypocapnia (P<0.05). Normalized power in the delta- frequencies on the power spectrum increased from 60.2 (13.1)% to 72.5 (12.7)% (P<0.05). Bispectral index and spectral edge frequency changed from 45.9 (7.0) to 40.1 (5.6) (P<0.05) and from 15.0 (2.3) to 14.0 (2.5) Hz (P<0.05), respectively. No significant differences in these values were observed between the two types of anaesthesia. CONCLUSIONS: Hypocapnia enlarged bicoherence growth in the delta- frequency range, suggesting the contribution of subcortical oscillating mechanisms in regulating EEG during hyperventilation.
K Hayashi; M Fujikawa; T Sawa
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-09-12
Journal Detail:
Title:  British journal of anaesthesia     Volume:  101     ISSN:  1471-6771     ISO Abbreviation:  Br J Anaesth     Publication Date:  2008 Nov 
Date Detail:
Created Date:  2008-10-15     Completed Date:  2008-11-18     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0372541     Medline TA:  Br J Anaesth     Country:  England    
Other Details:
Languages:  eng     Pagination:  666-72     Citation Subset:  IM    
Department of Anesthesiology, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kamigyo-ku, Kyoto 602-0841, Japan.
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MeSH Terms
Anesthetics, Inhalation / pharmacology*
Carbon Dioxide / blood
Electroencephalography / drug effects*
Hyperventilation / physiopathology*
Hypocapnia / blood,  physiopathology*
Methyl Ethers / pharmacology*
Middle Aged
Monitoring, Intraoperative / methods
Partial Pressure
Signal Processing, Computer-Assisted
Reg. No./Substance:
0/Anesthetics, Inhalation; 0/Methyl Ethers; 124-38-9/Carbon Dioxide; 28523-86-6/sevoflurane

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