Changes in Blood Acid-Base Equilibrium in Mice Exposed to Carbon Monoxide

Abstract

The changes in blood acid-base equilibrium in mouse during and after exposure to carbon monoxide (CO) were studied with special reference to the relationship to carboxyhemoglobin (HbCO) content in blood. Acid-base parameters investigated were pH, pCO2, HCO3- and base excess (BE).The results obtained were as follows:1. The changes in blood acid-base equilibrium during CO exposure took place in two phases depending strongly upon HbCO content in blood.2. The decrease in pCO2 and increase in pH, i. e., a respiratory alkalosis was observed in the first phase which appeared when HbCO content in blood reached 50-60%. Little change in HCO3- and BE was observed.3. The decrease in HCO3-, BE and pH, i. e., a metabolic acidosis was observed in the second phase which appeared when HbCO content in blood increased more than 60-70%. The decrease in pCO2 was also remarkable.4. The metabolic acidosis caused by CO exposure remained unchanged for a while after discontinuing the exposure, although rapid decrease in HbCO content in blood was observed.5. All the blood acid-base parameters began to improve when HbCO content in blood fell to 30-40%. Metabolic acidosis disappeared when HbCO content in blood became approximately 20%. On the other hand, at this time, pCO2 increased beyond the upper limit of normal value and a state of respiratory acidosis developed.6. The results so far obtained indicate that shift in blood acid-base equilibrium must be carefully taken into consideration in the diagnosis of CO poisoning and its treatments.