Platelet activation in a population of critically ill dogs as measured with whole blood flow cytometry and thromboelastography.

Objective: To determine whether critically ill dogs had increased platelet activation and whether the proportion of activated platelets correlated with severity of illness.

Animals: 82 dogs in the intensive care unit of a veterinary teaching hospital and 24 healthy control dogs.

Procedures: Flow cytometry with monoclonal mouse anti-human CD61 and CD62 antibodies in resting and ADP-treated samples and kaolin-activated thromboelastography were used to compare platelet activation in blood samples of critically ill and control dogs. Serum antithrombin, von Willebrand factor, fibrinogen, and activated protein C concentrations; prothrombin time (PT); and activated partial thromboplastin time (aPTT) were measured. Revised survival prediction index, acute patient physiology and laboratory evaluation, systemic inflammatory response syndrome, and multiple organ dysfunction syndrome scores were used to estimate severity of illness. Severity of illness scores and platelet activation measurements were compared with survival time and duration and cost of hospitalization.

Results: Critically ill and control dogs had no differences in platelet activation for non-ADP-treated samples measured. Critically ill dogs had significantly increased platelet activation in response to 2, 6, and 10 μM ADP. Critically ill dogs had significantly increased maximum amplitude, α angle, and global clot strength and significantly decreased clot formation time. Critically ill dogs had significantly increased fibrinogen concentration, PT, and aPTT and significantly decreased antithrombin concentration. Survivors and nonsurvivors had similar flow cytometry and thromboelastography values. Three dogs developed macrothrombosis.

Conclusions And Clinical Relevance: In this study, critically ill dogs had hyperreactive platelets, which may have contributed to a high incidence of hypercoagulability in this patient population.