Summary Little is known about the role of platelets in relation to ischemia/reperfusion injury (IRI) of the liver graft especially in children. Thrombocyte function was prospectively analysed in 21 consecutive pediatric liver transplantation (pLT) patients by platelet aggregometry secondary to adenosine diphosphate (ADP), collagen, and the von Willebrand factor activator ristocetin (VWF:rco). Post‐OP serum levels of ALT were used to divide patients into groups with high (highHD, n = 8) and low (lowHD, n = 13) hepatocellular damage. Clinically, highHD‐patients showed impaired plasmatic coagulation and elevated serum bilirubin levels early after pLT when compared with lowHD‐patients. Further, platelet counts markedly decreased between pre‐OP and postreperfusion (postrep.) in the highHD group (P = 0.003) and did not recuperate by POD6. In lowHD individuals thrombocytopenia improved from both pre‐OP (P < 0.05) and postrep. (P < 0.001) respectively towards POD6. Experimental thrombocyte testing revealed that before graft reperfusion only ADP‐dependent platelet aggregation correlated with reperfusion injury, thrombocytopenia and early graft function. During the  first 48 h after graft reperfusion, all inducers tested demonstrated elevated platelet aggregation levels in the highHD group. Our data suggest a possible role of platelets and their aggregative status in liver IRI subsequent to clinical pLT. Reperfusion‐independent ADP‐triggered platelet function may be a determinant for IRI in the pediatric hepatic graft recipient.

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Summary Von Willebrand factor (vWF) is a major platelet adhesion molecule at sites of vascular injury, such as observed in ischemia/reperfusion injury following orthotopic liver transplantation (OLT). Thirty‐three OLT patients were divided into groups with elevated or low markers of hepatocellular damage (high and low‐HD). Whole‐blood aggregometry was performed to evaluate platelet function. Multimeric analysis was utilized to evaluate functional vWF levels in the course of OLT. Donor and recipient demographics were comparable among groups. Low‐HD patients demonstrated better preserved coagulation parameters on POD 1–6 if contrasted to high‐HD patients. One year graft survival for the high‐HD group was lower than low‐HD patients (P = 0.037). Preoperative vWF‐dependent platelet aggregation and functional vWF plasma levels correlated directly with alanine transaminase levels early after OLT as did the decrease of functional vWF to reperfusion. In summary, these data suggest that vWF may serve as a significant mediator of platelet recruitment and hepatocellular injury in the graft following reperfusion.

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