Background
Acidemia in sick or injured horses is often due to lactic acid accumulation. Alterations in platelet function and hemostasis are among numerous deleterious effects caused by decreased physiologic pH.
Objectives
We aimed to evaluate the effect of hyperlactatemia and resultant acidemia on platelet aggregation in equine whole blood using impedance aggregometry.
Methods
Platelet aggregation was measured using the Multiplate analyzer in whole blood from 34 healthy horses at baseline and after in vitro addition of lactic acid to adjust the pH. Platelet aggregation of each sample was quantified by the area under the curve measurement reported by the Multiplate system. The association between platelet aggregation and pH was analyzed using a linear mixed‐effects model. The association of baseline platelet aggregation with hematocrits (Hcts), white blood cell (WBC) counts, and platelet counts was evaluated using Pearson's correlations.
Results
There was a significant association between acidemia and decreased platelet aggregation. No significant correlations were detected between platelet aggregation and Hct, WBC count, or platelet count. Platelet aggregation measured in healthy horses using the Multiplate analyzer showed substantial variation between animals.
Conclusions
Acidemia caused by the addition of lactic acid to equine whole blood was associated with a mild though statistically significant decrease in platelet aggregation. In conjunction with other factors, this change may contribute to morbidity‐related disorders of hemostasis, although its precise clinical relevance is uncertain.
Objectives It can be challenging to collect sufficient blood from feline patients for both a biochemical profile and a complete blood count (CBC). The ability to generate accurate hematologic and biochemical data from a single, small (<2 ml) sample could reduce patient stress and improve clinical efficiency. The objective of this study was to determine the impact of preheparinization and/or sample size on routine hematology findings in cats. Methods Blood was collected from 20 healthy cats; measured aliquots were placed directly into tubes containing either EDTA or lithium–heparin (Hep). Within 2 mins, specific volumes were removed from the Hep tubes and placed in additional EDTA tubes. Four distinct sample sizes/types were created from each cat: (1) 1.3 ml EDTA (criterion standard); (2) 0.5 ml EDTA; (3) 1.3 ml Hep + EDTA; and (4) 0.5 ml Hep + EDTA. Three CBCs were performed on each sample using an automated bench-top hematology analyzer. Drops of blood were contemporaneously used to create three air-dried stained slides from each tube. Triplicate results were averaged for statistical analysis; results were compared across all sample types and against the criterion standard. Significance was set at P <0.05. Results Preheparinization did not significantly impact determinations of erythrocyte number, hematocrit, hemoglobin concentration, mean cell volume and neutrophil count. Platelet counts for the non-traditional samples correlated poorly with the criterion standard, although numbers could be effectively estimated using stained slides. Cell morphology was well preserved across all sample types. Conclusions and relevance These results indicate that a 0.5 ml preheparinized EDTA blood sample can generate clinically useful hematologic data (excluding platelet count) in cats, using a bench-top analyzer. Our findings support the collection of a single small (<2 ml) sample that can be used for both biochemical and hematologic analyses. Further studies are needed to verify these findings using other hematology machines and in diseased cats.
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