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Brain pH responses to acetazolamide and hypercapnia in cats
K Kohshi1, Y Kinoshita, K Fukata
1Department of Neurosurgery, School of Medicine, University of Occupational and Environmental Health, Fukuoka.
Neurologia Medico-Chirurgica
|April 1, 1997
Summary
Acetazolamide causes brain acidosis not by increasing brain tissue CO2, but through other mechanisms. This study in cats shows the brain pH response differs from hypercapnia, indicating a non-CO2 related cause for acidosis.
Area of Science:
- Neuroscience
- Physiology
- Pharmacology
Background:
- Acetazolamide is a carbonic anhydrase inhibitor used clinically.
- Its mechanism for inducing brain acidosis is not fully understood.
- Increased brain tissue CO2 tension is a potential, but unproven, cause.
Purpose of the Study:
- To investigate if elevated brain tissue CO2 tension causes acetazolamide-induced brain acidosis.
- To compare the brain pH response to acetazolamide with that to hypercapnia.
Main Methods:
- Cats (n=18) were used, divided into two groups.
- CO2 and pH sensors were implanted in cerebral white matter.
- Group 1 received acetazolamide; Group 2 underwent controlled hypercapnia with mechanical ventilation.
Main Results:
- Brain tissue PCO2 (PbCO2) changes were similar between acetazolamide and hypercapnia groups.
- Brain tissue pH (pHb) decrease was progressive with acetazolamide.
- Brain tissue pH (pHb) decrease was transient with hypercapnia.
Conclusions:
- Acetazolamide-induced brain acidosis is not caused by increased brain tissue CO2 tension.
- The acidosis mechanism involves factors other than CO2 accumulation.
- Findings differentiate acetazolamide's effect from direct hypercapnia.