Effect of epinephrine on PO2 in anterior chamber

A polarographic oxygen electrode was inserted through the cornea into the middle of the anterior chamber, and the aqueous humor PO2 was continuously monitored. Epinephrine hydrochloride applied topically to the cornea (1% Epifrin: 0.05 to 0.1 mL) or injected into the anterior chamber (Adrenalin Chloride: 1 mg/mL, 0.05 mL) caused a marked decrease in the anterior chamber PO2. This drop in anterior chamber PO2 was not simply due to mydriasis, since atropine sulfate administered in a similar fashion did not cause a notable drop in anterior chamber PO2, and epinephrine applied to eyes with the pupils previously dilated with atropine still caused the typical drop in anterior chamber PO2. The hypoxic effects of epinephrine were reversed by injection of an alpha-adrenergic blocker, phentolamine mesylate (5 mg/mL, 0.05 mL), into the anterior chamber.