Effect of acute changes in the PaCO₂ on acid–base parameters in normal dogs and dogs with metabolic acidosis or alkalosis

Abstract

There is a linear relationship between the PaCO2 and blood hydrogen ion concentration in normal dogs, but for theoretical reasons to be discussed, we questioned whether this relationship would apply in animals with metabolic acidosis or alkalosis. To study this in more detail, animals were divided into three groups: normal, metabolically acidotic, and metabolically alkalotic. Following anesthesia and bilateral ureteral ligation, dogs were intubated and ventilated to produce acute steady state PaCO2 values corresponding to the range observed during disease states. Changes in the volume and electrolyte composition of the gastrointestinal fluid and urine as well as the concentration and distribution of lactate were evaluated in all experiments. We observed the previously described linear relationship between the PaCO2 and blood hydrogen ion concentration in normal dogs, but the slope of the regression line differed significantly from those of dogs with metabolic acidosis and metabolic alkalosis. On the other hand, there was a consistent relationship between the ratio of the PaCO2 values, but not the absolute PaCO2, and the change in the plasma bicarbonate concentration over a wide range of PaCO2 values in all groups of dogs. The chemical basis for these observations will be discussed.

Can insulin administration cause an acute metabolic acidosis in vivo?

“…Hence there must be an addi-tional mechanism to explain this fall in bicarbonate. In quantitative terms, the expected fail in bicarbonate when dogs were hyperventilated is close to 2.5 mmol/1 for each halving of the PaCO2 [15].…”

Fundamentals of Arterial Blood Gas Interpretation

“…Mixed acid-base disorders that transpire in parallel can be treated as two serial disorders, virtually recapitulating prior canine experiments of mixed metabolicrespiratory acid-base disorders. (43) If metabolic alkalosis were the only disorder and [HCO3 -] increased from 24 mM to 73.1 mM, the compensatory increase in PCO2 is approximately 76.8 mm Hg (Figure 5a). The pH would increase to 7.60 = 7.62 -LOG (76.8/73.1), a displacement of +0.20 pH units from normal.…”