Increase of arterial oxygen tension at altitude by carbonic anhydrase inhibition

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Abstract
Unanesthetized dogs were injected intravenously with 10 mg/kg per 12 hr of the carbonic anhydrase inhibitor, acetazolamide, 24 hr before exposure to a simulated altitude of 21,000 ft (PB = 335 mm Hg). Arterial blood samples were drawn frequently from a Teflon T cannula surgically placed in a carotid artery 1 or 2 days before the experiment. Arterial PO2. PCO2. pH, lactic. and pyruvic acid concentrations were measured. In comparison with untreated dogs, arterial PO2 at altitude was 9 mm Hg higher, on the average, in treated animals. No physiologically significant accumulation of excess lactate was found. The conclusion was made that carbonic anhydrase inhibition did offer measurable protection, with respect to arterial PO2, against altitude hypoxia and that this protection was achieved at much smaller doses of drug than had been used by other investigators.