Evaluation of acid-base disorders in dogs and cats presenting to an emergency room. Part 1: Comparison of three methods of acid-base analysis

Objective - To compare the diagnostic performance of the traditional approach to acid-base analysis with the Stewart approach and a semiquantitative approach. Design - Prospective cohort study. Setting - University teaching hospital. Animals - A total number of 84 dogs and 14 cats presenting to a university teaching hospital emergency room. Procedures - All dogs and cats in which venous blood samples for acid-base, lactate, and serum biochemical analysis were all collected within 60 minutes of each other, over a 5-month enrollment period. Acid-base analysis was performed using the traditional approach, Stewart approach, and a semiquantitative approach. Results - Traditional acid-base analysis identified respiratory acid-base abnormalities in 14/98 animals and metabolic acid-base abnormalities in 67/98. A mixed disorder of metabolic acidosis and respiratory alkalosis was most common occurring in 29/98 patients. The Stewart approach identified metabolic abnormalities in 82/98 patients; strong ion difference abnormalities were evident in 68/98 cases; an increased strong ion gap acidosis was identified in 49/98 cases; and changes in the quantity of weak acids in 25/98 cases. The semiquantitative approach identified abnormalities in all cases evaluated. Of the 14 patients with a primary respiratory acid-base abnormality, the Stewart approach identified metabolic abnormalities in 9 and the semiquantitative approach found abnormalities in all animals. Conclusions and Clinical Relevance - The physicochemical approaches diagnosed more acid-base abnormalities in this population than the traditional approach although many of the abnormalities identified were small and of unknown clinical relevance. The physicochemical approaches may provide greater insight as to the underlying etiology of abnormalities, which maybe of particular relevance to cases with changes in albumin and/or phosphorus concentration.