ANTAGONISM BY FLUMAZENIL OF MIDAZOLAM-INDUCED CHANGES IN QUANTITATIVEELECTROENCEPHALOGRAPHIC DATA FROM ISOFLURANE-ANESTHETIZED DOGS

Quantitative electroencephalography (QEEG) was assessed in 5 dogs anes thetized with 1.6% end-tidal concentration of isoflurane and after sub sequent administration of the benzodiazepine midazolam (0.2 mg/kg of b ody weight, IV). Ventilation was controlled to maintain normocapnia, E ffect of the benzodiazepine antagonist, flumazenil (0.04 mg/kg, IV), o n QEEG in midazolam-isoflurane-anesthetized dogs was determined. Heart rate, arterial blood pressure, esophageal temperature, arterial pH an d blood gas tensions, end-tidal CO2 concentration, and end-tidal isofl urane concentration were monitored throughout the study. A 21-lead lin ked-ear montage was used for recording the EEG data. Quantitative EEG data were stored on an optical disk for later analysis. Values for abs olute power of EEG were determined for delta -, theta -, alpha -, and beta-frequencies. Cardiovascular variables remained stable throughout the study. Midazolam administration was associated with decreased abso lute power in all frequencies of EEG at all electrode sites. Administr ation of flumazenil antagonized midazolam-induced decreased absolute p ower of EEG in all frequencies at all electrode sites. We conclude tha t QEEG provides a noninvasive, objective measure of midazolam- and flu mazenil-induced changes in cortical activity, during isoflurane anesth esia.