Effects of altered arterial carbon dioxide tension on quantitative electroencephalography in halothane-anesthetized dogs

Lesley J Smith From the Department of Veterinary Clinical Medicine and Surgery, Washington State University, Pullman, WA 99164-6610.

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Stephen A. Greene From the Department of Veterinary Clinical Medicine and Surgery, Washington State University, Pullman, WA 99164-6610.

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Michael P. Moore From the Department of Veterinary Clinical Medicine and Surgery, Washington State University, Pullman, WA 99164-6610.

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Robert D. Keegan From the Department of Veterinary Clinical Medicine and Surgery, Washington State University, Pullman, WA 99164-6610.

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Summary

Quantitative electroencephalography was assessed in 6 dogs anesthetized with 1.8% end-tidal halothane, under conditions of eucapnia, hypocapnia, and hypercapnia. Ventilation was controlled in each condition. Heart rate, arterial blood pressure, core body temperature, arterial pH, blood gas tensions, end-tidal CO2 tension, and end-tidal halothane concentration were monitored throughout the study. A 21-lead linked-ear montage was used for recording the eeg. Quantitative electroencephalographic data were stored on an optical disk for analysis at a later date. Values for absolute power of the eeg were determined for δ, θ, α, and β frequencies. Hypocapnia was achieved by hyperventilation. Hypercapnia was achieved by titration of 5% CO2 to the inspired gas mixture. Hypercapnia was associated with an increase in the absolute power of the δ band. Hypocapnia caused an increase in the absolute power of δ, θ, and α. frequencies. Quantitative electroencephalographic data appear to be altered by abnormalities in arterial carbon dioxide tension. Respiratory acidosis or alkalosis in halothane-anesthetized dogs may obscure or mimic electroencephalographic abnormalities caused by intracranial disease.

Summary

Quantitative electroencephalography was assessed in 6 dogs anesthetized with 1.8% end-tidal halothane, under conditions of eucapnia, hypocapnia, and hypercapnia. Ventilation was controlled in each condition. Heart rate, arterial blood pressure, core body temperature, arterial pH, blood gas tensions, end-tidal CO2 tension, and end-tidal halothane concentration were monitored throughout the study. A 21-lead linked-ear montage was used for recording the eeg. Quantitative electroencephalographic data were stored on an optical disk for analysis at a later date. Values for absolute power of the eeg were determined for δ, θ, α, and β frequencies. Hypocapnia was achieved by hyperventilation. Hypercapnia was achieved by titration of 5% CO2 to the inspired gas mixture. Hypercapnia was associated with an increase in the absolute power of the δ band. Hypocapnia caused an increase in the absolute power of δ, θ, and α. frequencies. Quantitative electroencephalographic data appear to be altered by abnormalities in arterial carbon dioxide tension. Respiratory acidosis or alkalosis in halothane-anesthetized dogs may obscure or mimic electroencephalographic abnormalities caused by intracranial disease.

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