PB0780 - Elucidation of the mechanism of intraoperative and postoperative bleeding tendency associated with prolonged extracorporeal circulation time.

Background: Prolonged extracorporeal circulation time is known to cause intraoperative and postoperative bleeding tendency, but the mechanism is unknown.

Aims: In this study, we focused on platelets and analyzed them using a simulated extracorporeal circulatory circuit incorporating an extracorporeal membrane membrane artificial lung (ECMO).

Methods: After blood was drawn using unfractionated heparin as the anticoagulant, the blood was filled into a simulated extracorporeal circuit. Then, platelet counts and platelet surface markers were measured by flow cytometry after circulation using a roller pump at a blood flow rate of 0.75 L/min and a circulation time of 180 minutes.

Results: When whole blood was circulated for 180 minutes with a roller pump, the platelet count decreased markedly after circulation. In addition, glycoprotein IIb (CD41) expression was unchanged before and after circulation, but GPIb (CD42b) expression was significantly decreased after circulation compared to before circulation. To analyze the effect of decreased CD42b expression on platelet function, we prepared platelets in which CD42b was cleaved from the platelet membrane surface by O-sialoglycoprotein endopeptidase (OSGEP) treatment and measured platelet aggregation ability. Ristocetin aggregation capacity was completely absent in OSGEP-treated platelets compared to untreated platelets. Finally, platelet counts and CD42b expression were maintained when simulated extracorporeal circulation was performed with ACD-A fluid as an anticoagulant.

Conclusion(s): Decreased platelet counts and cleavage of CD42b from the platelet membrane surface after extracorporeal circulation were suggested as possible causes of the bleeding tendency observed intraoperatively and postoperatively with prolonged extracorporeal circulation time.