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Comparison of bispectral index and spectral entropy during isoflurane and medetomidine general anaesthesia in horses
Author(s) -
NavarreteCalvo Rocío,
Morgaz Juan,
GómezVillamandos Rafael J.,
QuirósCarmona Setefilla,
Domínguez Juan M.,
RuizLópez Patricia,
Granados María M.
Publication year - 2020
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/evj.13234
Subject(s) - bispectral index , anesthesia , isoflurane , medetomidine , sedation , medicine , approximate entropy , general anaesthesia , entropy (arrow of time) , heart rate , physics , quantum mechanics , blood pressure
Background The bispectral index (BIS) has been evaluated as an indicator of central nervous system (CNS) depression in horses during general anaesthesia. The spectral entropy is another electroencephalographic device and it has not been evaluated yet in horses. Objectives To determine if spectral entropy can assess anaesthetic depth during the different phases of anaesthesia, define the value of state and response entropy during surgical plane of anaesthesia and compare them with BIS. Study design Clinical, prospective, non‐blinded observational study. Methods Thirty‐five horses ASA I or II undergoing scheduled surgical procedure were used. BIS and electromyography (EMG) with a BIS monitor and state and response entropy with a spectral entropy monitor were recorded at baseline after receiving 5 µg/kg bwt i.v. of medetomidine (sedation period), during the anaesthetic maintenance with isoflurane and medetomidine (intraoperative period) and once the trachea was extubated (recovery period). A general linear model for repeated measurements was employed. Correlation and agreement between methods were also assessed. Data are presented as mean ± SD. Results State entropy, response entropy and EMG showed significant differences according to the anaesthetic period ( P < .001). There was no significant difference in BIS between baseline and sedation period, but there were differences between the remainder of the periods ( P < .001). BIS (53.4 ± 11.2) was significantly higher ( P < .001) than response entropy (35.1 ± 7.1) and state entropy (27.4 ± 4.8) during surgical plane of anaesthesia. The ICC between BIS and response entropy was 0.56 and between BIS and state entropy was 0.43, without agreement between them. Main limitations The need to shave the skin in contact with the sensors and the difficulty in taking measurements during recovery period. Conclusions Spectral entropy can be used to detect the different periods of an anaesthetic protocol, with the lowest values during the intraoperative period. A low correlation and no concordance were observed between both methods.