Optimal cutoff points of entropy indices for use in predicting responses elicited during determination of minimum alveolar concentration of sevoflurane in dogs.

Abstract

To investigate values of spectral indices for use in predicting responses in dogs during determination of minimum alveolar concentration (MAC) of sevoflurane. 15 healthy German Shepherd Dogs. PROCEDURES :Sevoflurane MAC was determined by use of tail clamping. Entropy indices consisting of response entropy and state entropy were recorded during MAC determination. Optimal cutoff points of response entropy and state entropy for use in predicting responses to tail clamping were analyzed with multiple logistic regression. Sevoflurane MAC ranged from 1.8% to 2.6% (mean ± SD, 2.2 ± 0.3%). Response entropy and state entropy were significantly higher during positive responses to tail clamping (88 ± 2 and 76 ± 2, respectively) than during negative responses to tail clamping (63 ± 3 and 52 ± 3, respectively). The difference between the 2 entropy indices did not differ between positive (11 ± 1) and negative (13 ± 1) responses to tail clamping. Response entropy and state entropy served as independent predictors of a positive response, with areas under the curve for receiver operating characteristic curves 0.810 (95% confidence interval, 0.716 to 0.903) and 0.828 (95% confidence interval, 0.741 to 0.916), respectively. Optimal cutoff points to predict a positive response were 75 for response entropy and 65 for state entropy, which corresponded to mean ± SD ORs of 25.2 ± 15.6 and 14.9 ± 7.9, respectively. Response entropy and state entropy were good predictors of responses to tail clamping elicited during determination of sevoflurane MAC in healthy dogs.