EFFECTS OF ALTERED ARTERIAL CARBON-DIOXIDE TENSION ON QUANTITATIVE ELECTROENCEPHALOGRAPHY IN HALOTHANE-ANESTHETIZED DOGS

Quantitative electroencephalography was assessed in 6 dogs anesthetize d with 1.8% end-tidal halothane, under conditions of eucapnia, hypocap nia, and hypercapnia. Ventilation was controlled in each condition. He art rate, arterial blood pressure, core body temperature, arterial pH, blood gas tensions, end-tidal CO2 tension, and end-tidal halothane co ncentration were monitored throughout the study. A 21-lead linked-ear montage was used for recording the EEG. Quantitative electroencephalog raphic data were stored on an optical disk for analysis at a later dat e. Values for absolute power of the EEG were determined for delta, the ta, alpha, and beta frequencies. Hypocapnia was achieved by hyperventi lation. Hypercapnia was achieved by titration of 5% CO2 to the inspire d gas mixture. Hypercapnia was associated with an increase in the abso lute power of the delta band. Hypocapnia caused an increase in the abs olute power of delta, theta, and alpha frequencies. Quantitative elect roencephalographic data appear to be altered by abnormalities in arter ial carbon dioxide tension. Respiratory acidosis or alkalosis in halot hane-anesthetized dogs may obscure or mimic electroencephalographic ab normalities caused by intracranial disease.