AbstractBackgroundAcidemia in sick dogs often results from the accumulation of lactic acid. The resulting decrease in blood pH can have many physiologic effects, including alteration of platelet function.ObjectivesWe aimed to evaluate the effect of hyperlactatemia and subsequent acidemia on platelet aggregation in canine blood using impedance aggregometry.MethodsPlatelet aggregation was measured in blood from 27 healthy dogs using the Multiplate analyzer at baseline and after in vitro addition of two different volumes of lactic acid to adjust the pH. The area under the curve (AUC), reported by the Multiplate analyzer, was used to assess the extent of platelet aggregation in each sample. A linear mixed effects model was used to test for the association between platelet aggregation and pH. The association of baseline platelet aggregation with HCTs, platelet counts, and WBC counts was assessed using Pearson's correlations.ResultsAcidemia was associated with a significant decrease in platelet aggregation. No significant correlations were detected between platelet aggregation and HCT, platelet count, or WBC count. Platelet aggregation measured using the Multiplate analyzer showed substantial individual variation.ConclusionsWorsening acidemia due to the addition of lactic acid caused a mild but significant decrease in platelet aggregation in canine blood. The clinical significance of this change is uncertain but could be important when combined with other abnormalities of hemostasis associated with illness.