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Time‐varying spectral analysis revealing differential effects of sevoflurane anaesthesia: non‐rhythmic‐to‐rhythmic ratio
Author(s) -
LIN Y.T.,
WU H.T.,
TSAO J.,
YIEN H.W.,
HSEU S.S.
Publication year - 2014
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/aas.12251
Subject(s) - sevoflurane , rhythm , medicine , bispectral index , anesthesia , general anaesthesia , electroencephalography , contingent negative variation , propofol , psychiatry
Background Heart rate variability ( HRV ) may reflect various physiological dynamics. In particular, variation of R ‐ R peak interval ( RRI ) of electrocardiography appears regularly oscillatory in deeper levels of anaesthesia and less regular in lighter levels of anaesthesia. We proposed a new index, non‐rhythmic‐to‐rhythmic ratio ( NRR ), to quantify this feature and investigated its potential to estimate depth of anaesthesia. Methods Thirty‐one female patients were enrolled in this prospective study. The oscillatory pattern transition of RRI was visualised by the time‐varying power spectrum and quantified by NRR . The prediction of anaesthetic events, including skin incision, first reaction of motor movement during emergence period, loss of consciousness ( LOC ) and return of consciousness ( ROC ) by NRR were evaluated by serial prediction probability ( P K ) analysis; the ability to predict the decrease of effect‐site sevoflurane concentration was also evaluated. The results were compared with B ispectral I ndex ( BIS ). Results NRR well‐predicted first reaction ( P K > 0.90) 30 s ahead, earlier than BIS and significantly better than HRV indices. NRR well‐correlated with sevoflurane concentration, although its correlation was inferior to BIS , while HRV indices had no such correlation. BIS indicated LOC and ROC best. Conclusions Our findings suggest that NRR provides complementary information to BIS regarding the differential effects of anaesthetics on the brain, especially the subcortical motor activity.