Investigation of diagnostic importance of platelet closure times measured by Platelet Function Analyzer-PFA 100 in dogs with endotoxemia

Abstract

This study was performed to evaluate the diagnostic importance of the platelet closure times measured by the Platelet Function Analyzer (PFA-100 (TM)) in dogs with endotoxemia. E.coli endotoxin was given intravenously once, at the dose of 0.02 mg/kg or I mg/kg in groups I (n=9) and 11 (n=8), respectively. Normal saline (0.1 ml/kg) was injected in group III (n=8).The dogs were monitored for 48 In, and venous blood samples were collected prior to (baseline) and at intervals of 0.5, 1, 2,4,6,8,12,24 and 48 h subsequent to the treatments. The white blood cell (WBC), platelet counts, and hematocrit (Hct) values were recorded. Platelet closure times were determined, using collagen/epinephrine (CEPI) and collagen/adenosine diphosphate (CADP) cartridges.

Within 0.5 h after the endotoxin application baseline WBC and platelet counts (mean +/- SD) decreased significantly (p < 0.001) to 2000 +/- 500 and 1850 +/- 200 cells/mu l or 69.000 +/- 12.500 and 27.000 +/- 6.400 cells/mu l in groups I and 11, respectively. Platelet counts remained low during the first 1-48 h, but the WBC count was high at the 8(th)-48(th) h, in groups I and II, compared with baselines (p < 0.001). After the application of the endotoxin, Hct values increased from baseline values of 37 +/- 3 or 39 +/- 2 % to 48 +/- 2 or 51 +/- 3 %,within I h (p < 0.001), in groups I and 11, respectively. Hct values in group 11 were notably higher (p < 0.001) than those of group I during the 2(nd)-48(th) h. Hematological parameters and closure times did not differ significantly throughout the study in group III.

Baseline closure time ranged from 79 +/- 5 seconds (s) to 86 +/- 5 s for CADP and 144 +/- 13 s to 159 +/- 14 s for CEPI in all dogs (n=25). At 0.5 h after the endotoxin, the closure times of CADP as well as CEPI declined to 62 +/- 6 s and 76 +/- 8 s in group I (p < 0.001) and 57 +/- 5 s and 75 +/- 6 s in group 11 (p < 0.001). Afterwards, closure time prolonged to the levels of 280 8 s (CADP) and 294 5 s (CEPI) by 48 h (p < 0.001) in group 11, but returned to the baseline limit in group I. In conclusion, our results show that the shortened closure times may serve as a very early diagnostic sign of endotoxemia, prolonged closure times however may be used as an index for the severity of endotoxemia.