Background
We previously reported that dexmedetomidine (DEX) enhances the function of human platelets (Eur J Pharmacol 2015;766:122-8) and that propofol (PRO) has bidirectional effects on platelet function (Anesthesiology 1999;91:361-9). DEX and PRO are often administered in postsurgical patients in an intensive care unit (ICU), but the effects of these drugs on postoperative platelet function are unclear. In this study, we examined the effects of DEX and PRO on expression of P-selectin, an adhesion molecule on the surface of activated platelets, in an in vitro study of samples from postsurgical ICU patients.
Methods
Venous blood was taken with a 10% volume of 3.8% trisodium citrate from 8 patients at the time of ICU admission after elective abdominal surgery under general anaesthesia. Patients with coagulopathy and those who took medication before and during surgery that might affect platelet function were excluded. Platelet-rich plasma was stimulated by adenosine diphosphate (ADP) with DEX or PRO for 30 min and then coincubated with PerCP-labeled anti-CD61 antibody and PE-labeled anti-CD62P (P-selectin) antibody for 1 h. P-selectin expression was assessed by flow cytometry. 
Results
DEX (10-100 ng/ml) dose-dependently enhanced P-selectin expression on ADP-stimulated platelet surfaces. PRO (40 μM) enhanced P-selectin expression, whereas PRO (70, 100 μM) had no effect (Fig. 1).
Discussion
In our previous study in healthy volunteers, DEX (100 ng/ml) enhanced P-selectin expression, and PRO (40 μM) enhanced and PRO (>70 μM) suppressed platelet aggregation, consistent with the results of this study. P-selectin stabilizes initial platelet aggregates in vitro and increases and stabilizes arterial thrombi. To confirm whether the effects of DEX and PRO on platelet function increase in the postoperative period, the perioperative time-course of P-selectin expression must be examined, and in vivo studies are needed to clarify effects on platelet functions and hemostasis in a clinical setting.
Conclusion
DEX enhanced in vitro P-selectin expression dose-dependently, while PRO enhanced P-selectin expression only at a low concentration in postsurgical ICU patients.

07 / Effects of dexmedetomidine and propofol on in vitro platelet P-selectin expression in postsurgical patients in an intensive care unit