The number of platelets reportedly decreases by 30–50% during extracorporeal circulation [5, 6]. The suspected causes include dilution by CPB introduction, damage due to flow in a nonphysiological environment, and activation of platelet aggregation . Autologous platelet collection is a method for preservation of platelets before mechanical damage during CPB, which is returned to the patient after the CPB has been discontinued; it can avoid consumption due to platelet damage and activation [3, 8]. However, this method is limited in its usefulness, because it requires approximately 90 min for collection, after induction of anesthesia and prior to introduction of heparin.
Platelet function is reportedly inhibited by various antiplatelet drugs; however, inhibition of platelet function during administration of heparin has not been shown to occur other than in cases of heparin-induced thrombocytopenia (HIT) , in which antibodies promote the production of antiplatelet factor 4 heparin complex antibody, thereby promoting platelet aggregation .
There has been no study regarding the effects of heparin administration before CPB on platelet aggregation. We previously reported that there was no difference in autologous platelet aggregation between those collected before and after heparin administration in an animal model. We concluded that platelet count and platelet function in PRP are not affected by heparin administration . Based on this experimental result, we planned the present collection of autologous platelets from blood after administration of heparin at the early stage of CPB initiation. The present results indicate that it is clinically feasible to collect autologous platelets from CPB circuit. This is consistent with the observation study which demonstrated that plasma components, platelet count, and platelet aggregation can be restored when plasma and platelets are sequestered at the time of CPB and subsequently returned after the procedure . This autologous PRP collection from CPB circuit seems to be feasible and safe. Platelet count and aggregation ability had improved after the return of autologous PRP in this study. However, platelet count and aggregation ability significantly decreased after CPB including autologous PRP collection. It was unclear whether significant decrease of platelet count and aggregation ability is due to CPB, autologous PRP collection, or both. Autologous PRP collection may have the risk of bleeding tendency after CPB because of significant decrease of platelet count and aggregation ability. Further examination is necessary to clarify this concern.
The number of patients that anti-platelet drugs are given has increased because less invasive endovascular interventions are developed, and will increase in future. We have excluded the patients with preoperative antiplatelet drug use to evaluate accurate platelet aggregation ability in this study. Platelet aggregation ability had recovered after a certain period of cessation time. We have reported that the platelet aggregation ability had already recovered at 5 days after clopidogrel cessation .
Therefore, we think that autologous PRP collection is also useful for the patient with antiplatelet drug use.
Recently, a meta-analysis concerning the autologous PRP have been reported which mention its usefulness in surgery with CPB .
The present study was limited in that the subjects were not compared with a control group. Moreover, there was no indicator other than coagulation ability to accurately determine the extent of platelet damage by cardiopulmonary bypass; other indices are influenced by various factors. We will evaluate the usefulness of the autologous PRP collection from CPB circuit by means of comparison between the cases with autologous PRP collection and without autologous PRP collection in future.