Background and Goal of Study：Dexmedetomidine (DEX) is a highly selective alpha2-adrenoceptor (alpha2-AR) agonist. Recently, an in vitro study using platelet-rich plasma demonstrated that DEX affected adenosine diphosphate (ADP)-induced platelet aggregation via alpha2-AR (Eur J Pharmacol 2015). However, the effect of DEX on platelet function in whole blood remains unclear, because platelet aggregation is a complex reaction that is associated with other blood cell components. In the present study, the effect of DEX on platelet function in whole blood was evaluated using the TEG6s® PlateletMapping®ADP assay.
Materials and Methods：The study was approved by the institutional review board and registered in the UMIN clinical registry (UMIN000030233). Whole blood was obtained from healthy male volunteers (25-35 years old, n = 6) and the blood was dispensed into 3 collection tubes. The blood was incubated with DEX (0nM, 10 nM or 100 nM), and the TEG6s® PlateletMapping®ADP assay was performed. The primary outcome was MAADP (clot strength when platelets are activated only through the ADP receptor). Given a type I error of 0.017 and a power of 0.9, a sample size of 6 subjects was estimated to be needed for detection of a 15% change in MAADP. Variables were compared in the 3 groups by the paired t-test. Applying Bonferroni correction for multiple comparison, p < 0.017 was considered statistically significant.
Results and Discussion：The values of MAADP were comparable in the 3 groups (Figure A). MAHKH and MAActF, which reflect global platelet function and fibrin contribution to clot strength, respectively, were also comparable (Figure B, C). Additionally, there was no significant difference in %Aggregation ADP (Figure D). Variables associated with coagulation factors were also evaluated in the present study, and no significant difference was found in R (clotting time), K (clot kinetic time), or Angle (velocity of clot formation) between the 3 groups. 
Conclusion：DEX did not affect platelet function measured by the TEG6s® PlateletMapping® assay in whole blood. The findings of our study indicate that DEX can be safely used without modification of platelet function.

02 / Analysis of the effect of dexmedetomidine on platelet function with TEG6s® PlateletMapping® assay in whole blood