Retrospective Evaluation of Acid–Base Disorders in Dogs With Hyperlactatemia Using Traditional and Semiquantitative Analysis: 3866 Cases

OBJECTIVE: To characterize acid-base disorders in dogs with hyperlactatemia via traditional and semiquantitative approaches, and to investigate the mechanisms of hyperlactatemia and the prognostic significance of metabolic acidosis in these patients. DESIGN: Retrospective study. SETTING: University teaching hospital. ANIMALS: A total of 3866 dogs with various diseases and a plasma lactate concentration >2 mmol/L at any timepoint during hospitalization underwent traditional acid-base analysis. Among these patients, 1755 dogs had data available for semiquantitative acid-base evaluation. MEASUREMENTS AND MAIN RESULTS: The most common disease associated with hyperlactatemia was gastrointestinal disorders in 1232 of 3866 dogs (29.3%), and the most common mechanism of hyperlactatemia was circulatory shock in 741 (19.1%). The traditional approach identified acid-base abnormalities in 2586 dogs (66.9%), with the most common being primary respiratory acidosis in 609 (15.7%). When considering both primary and mixed disorders, metabolic acidosis was present in 1452 patients (37.5%). When excluding the lactate effect, the semiquantitative approach identified concurrent acidifying and alkalinizing effects in 1241 of 1755 dogs (70.7%). Unmeasured anions, determined via semiquantitative analysis, were the most frequent acidifying effect in 775 dogs (44.1%). Metabolic acidosis, whether primary or as part of a mixed disorder, was associated with increased mortality (682/1452 [46.9%]) compared with patients without metabolic acidosis (479/2414 [19.8%]) (p < 0.001). Similarly, type A hyperlactatemia was associated with higher mortality (374/717 [52.5%]) than type B (227/746 [30.4%]) (p < 0.001). CONCLUSIONS: Acid-base disorders in dogs with hyperlactatemia were frequent and complex, with both acidifying and alkalizing processes often occurring simultaneously. The semiquantitative approach might be a valuable tool to improve our understanding of the underlying mechanisms of metabolic acid-base disorders in these patients. The presence of metabolic acidosis was most frequent in dogs with type A hyperlactatemia and was associated with higher mortality.