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) in dogs with endotoxemia. E. coli endotoxin was given intravenously once, at the dose of 0.02 mg/kg or 1 mg/kg in groups I (n=9) and II (n=8), respectively. Normal saline (0.1 ml/kg) was injected in group III (n=8). The dogs were monitored for 48 h, 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/microl or 69.000 +/- 12.500 and 27.000 +/- 6.400 cells/microl in groups I and II, respectively. Platelet counts remained low during the first 1-48 h, but the WBC count was high at the 8th-48th 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 1 h (p<0.001), in groups I and II, respectively. Hct values in group II were notably higher (p<0.001) than those of group I, during the 2nd-48th 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 II (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 II, 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.