title: Isoflurane and sevoflurane decrease entropy indices more than halothane at equal MAC values.
abstract: Recently, bispectral index (BIS) values were demonstrated to be different for various anesthetics as a result of differential effects on electroencephalographic (EEG) signals. Entropy is similar to the BIS monitor, as both process raw EEG to derive a number. We hypothesized that entropy may also be anesthetic agent-specific. Thirty adult patients undergoing spinal surgery were randomized to receive halothane, isoflurane, or sevoflurane. Entropy indices were recorded at various minimum alveolar concentration (MAC) values-0.5, 0.75, 1.0 and 1.5-both during wash-in and wash-out of the agent. Heart rate (HR), mean arterial blood pressure (MAP), response entropy (RE), and state entropy (SE) were noted. Statistical analysis was done using a one-way analysis-ofvariance test. P values less than 0.05 were considered significant. Ten patients in each group completed the study. The demographics and baseline values of HR, MAP, RE, and SE were comparable in all three groups. During the study period, for a given MAC value, both RE and SE remained low in the isoflurane and sevoflurane groups compared to the halothane group. For a given MAC, the RE and SE were comparable during wash-in and wash-out phases. Halothane produced higher entropy values as compared to isoflurane and sevoflurane at equivalent MAC levels.
authors.affiliation: Department of Neuroanaesthesiology, Neurosciences Center, 7th floor, All India Institute of Medical Sciences, New Delhi, 110029, India.
authors.forename: Hemanshu
authors.initials: H
authors.lastname: Prabhakar
authors.forename: Zulfiqar
authors.initials: Z
authors.lastname: Ali
authors.forename: Parmod K
authors.initials: PK
authors.lastname: Bithal
authors.forename: Girija P
authors.initials: GP
authors.lastname: Rath
authors.forename: Deepak
authors.initials: D
authors.lastname: Singh
authors.forename: Hari H
authors.initials: HH
authors.lastname: Dash
mesh_terms: D000293:Adolescent; D000328:Adult; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000493:pharmacokinetics; D001794:Blood Pressure / Q000187:drug effects; D004569:Electroencephalography / Q000187:drug effects; D019277:Entropy; D005260:Female; D006221:Halothane / Q000008:administration & dosage / Q000493:pharmacokinetics; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage / Q000493:pharmacokinetics; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage / Q000493:pharmacokinetics; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000378:metabolism*; D000077149:Sevoflurane; D055815:Young Adult
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane; D006221:Halothane