Evaluation of platelet count and its association with plateletcrit, mean platelet volume, and platelet size distribution width in a canine model of endotoxemia

Background: Platelets are of great importance in the pathogenesis of endotoxemia. Although thrombocytopenia is used as a diagnostic sign of endotoxemia, changes in values for platelet indices (plateletcrit [PCT], mean platelet volume [MPV], and platelet size distribution width [PDW]) in response to endotoxin are still unknown. Objective: The aim of this study was to evaluate platelet count and its relations with platelet indices in a canine model of endotoxemia. Methods: Twenty dogs were divided into 2 groups of 10 each, and treated intravenously with Escherichia coli endotoxin (1 mg/kg) or vehicle. Venous blood samples were collected before treatment (0 hour) and 0.5, 1, 2, 4, 6, 8, 12, and 24 hours after treatment. Platelet counts and indices were determined on a CELL-DYN hematology analyzer. Results: The platelet count and PCT decreased by a mean of 73% and 93%, respectively (P <.001), at 0.5 hour, and remained 70% and 85% lower than baseline values (P <.001) for 24 hours after endotoxin injection. MPV and PDW increased by a mean of 28% and 45%, respectively (P <.01), at 0.5 hour, and remained increased by 7% and 16% over baseline values for 24 hours (P <.01-.001). Platelet count correlated positively with PCT (P <.001), but correlated negatively with MPV (P <.001) and PDW (P <.01). Conclusions: Changes in platelet count and its association with platelet indices may reflect changes in platelet production and reactivity. Platelet indices have potential value in the diagnosis and monitoring of dogs and humans with endotoxemia.