title: In situ arterial and brain tissue PCO2 responses to acetazolamide in cats.
abstract: We have studied how in situ arterial (PaCO2) and brain tissue PCO2 (PbCO2) responses to acetazolamide (AZ) are affected by respiratory patterns. Sixteen cats were anesthetized with ketamine. Group 1 cats (n = 7) breathed air spontaneously. Group 2 cats (n = 6) were paralyzed and ventilated mechanically to maintain PaCO2 at 37 +/- 1 Torr before AZ administration; the respiratory rate and depth did not change during the course of measurements. Two CO2 sensors to measure in situ PaCO2 and PbCO2 continuously were used. One was placed through a burr hole into the cerebral white matter 15 mm in depth, and another was inserted into the femoral artery. After intravenous administration of AZ (20 mg/kg), PaCO2 decreased, after a significant transient rise, and then returned gradually to the baseline in group 1, but it increased gradually and reached a new steady state in group 2. PbCO2 and the PbCO2-PaCO2 gradient increased remarkably in the two groups immediately after administration. We conclude that AZ resulted in a large increase in both PbCO2 and the PbCO2-PaCO2 gradient and that there are two distinct in situ PaCO2 responses to AZ in spontaneously breathing vs. mechanically ventilated animals. The mechanisms for these observations are discussed.
authors.affiliation: Department of Hyperbaric Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kohshi
authors.forename: N
authors.initials: N
authors.lastname: Konda
authors.forename: Y
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: E
authors.initials: E
authors.lastname: Tsuru
authors.forename: A
authors.initials: A
authors.lastname: Yokota
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology*; D000818:Animals; D001158:Arteries / Q000187:drug effects; D015374:Biosensing Techniques; D001923:Brain Chemistry / Q000187:drug effects*; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism*; D002415:Cats; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008297:Male; D012119:Respiration / Q000187:drug effects; D012121:Respiration, Artificial
chemical_list: D002245:Carbon Dioxide; D000086:Acetazolamide