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Abstract #13181 Published in IGR 7-3
Effect of carbogen breathing and acetazolamide on optic disc PO2.
Petropoulos IK; Pournaras JA; Munoz JL; Pournaras CJInvestigative Ophthalmology and Visual Science 2005; 46: 4139-4146
PURPOSE: Acetazolamide was previously shown to increase optic disc partial pressure of oxygen (PO2 ). The study was conducted to evaluate optic disc PO2 variations during normoxia, hyperoxia (100% O2 ), and carbogen breathing (95% O2 , 5% CO2 ), before and after intravenous administration of acetazolamide. METHODS: PO2 measurements were obtained at intervascular areas of the optic disc in nine anesthetized minipigs using oxygen-sensitive microelectrodes (10-μm tip diameter) placed at < 50 μm from the optic disc. PO2 was measured continuously during 10 minutes under normoxia, hyperoxia, or carbogen breathing. Oxygen measurements were repeated under these conditions after intravenous injection of acetazolamide (500-mg bolus). RESULTS: In hyperoxia, optic disc PO2 increased moderately (ΔPO2 = 4.81 ± 1.16 mmHg (mean ± SD; 24%; P < 0.001) after a much larger increase in systemic PaO2 . Carbogen breathing induced a significant increase in both systemic PaO2 and PaCO2 , which resulted in a large increase in optic disc PO2 (ΔPO2 = 13.17 ± 2.18 mmHg; 67%; P < 0.001). Acetazolamide induced a slow and progressive increase in both systemic PaCO2 and optic disc PO2 (30 minutes ΔPO2 = 4.24 ± 2.45 mmHg; 24%; P < 0.04). However, it was when carbogen was simultaneously administered that optic disc PO2 increased most substantially (ΔPO2 = 18.91 ± 5.23 mmHg; 90%; P < 0.002). CONCLUSIONS: Carbogen breathing increases optic disc Po2 significantly in minipigs, more than hyperoxia. The association of acetazolamide injection with carbogen breathing could induce an additional increase in optic disc PO2 through the effect of higher systemic PaCO2 .
Dr. I.K. Petropoulos, Department of Ophthalmology, University Hospitals of Geneva, Switzerland
Classification:
2.14 Optic disc (Part of: 2 Anatomical structures in glaucoma)
6.11 Bloodflow measurements (Part of: 6 Clinical examination methods)
3.8 Pharmacology (Part of: 3 Laboratory methods)
