Increased platelet aggregation (over)compensates thrombocytopenia in patients undergoing orthotopic liver transplantation: 
Mohamed Soliman, Jürgen Peters, Matthias Hartmann
Klinik für Anästhesiologie und Intensivmedizin, Universität Duisburg-Essen & Universitätsklinikum Essen, Essen, Germany.
Introduction: Liver transplantation patients often present with thrombocytopenia, increased von Willebrand factor, and decreased ADAMTS13 concentrations (1-3) but the net effect on primary haemostasis is unknown. We hypothesized that platelet aggregation is increased in liver transplantation.
Methods: Following ethics committee approval, platelet aggregation was determined (impedance aggregometry; Multiplate ®) using the activators ristocetin, ADP, arachidonic acid, collagen, and thrombin receptor activating peptide (TRAP) in 37 liver transplantation patients (at 4 time points) and in 10 controls (patients scheduled for minor surgery without liver disease or previous liver surgery). Platelet count was assessed by using a Coulter counter. The correlation of platelet aggregation and count was also evaluated. Statistics: Student t-test for independent samples.
Results: In vitro (n=8), there is a strict correlation between platelet count and aggregation (r=0.91 ± 0.07, p= 0.0001). In liver transplant recipients, platelet count was decreased compared to controls (114 x 103 mm-3 vs. 225 x 103 mm-3, p=0.0001), but ristocetin induced aggregation was markedly increased (101.8 AU vs. 56.9, p=0.02). Correction of the assay for platelet count revealed a 3-fold increase in ristocetin-induced aggregation (0.95 AU/103 platelet mm-3 vs. 0.27; p=0.0001). ADP-, arachidonic acid-, collagen-, and TRAP induced platelet aggregation did not differ from the respective control values without correction for platelet count. After correction, however, evoked platelet aggregation was markedly increased with all these activators (by 67-156 %, p<0.05). Platelet aggregation normalized at the end of surgery.
Conclusion: Platelet aggregation is markedly increased in liver transplantation recipients but normalizes towards the end of surgery. While increased platelet aggregation in liver recipients can potentially compensate for thrombocytopenia, it might also favour thrombotic complication.
References: 1. Uemura M. Thromb Haemost. 2008, 99:1019, 2. Pereboom IT. Anesth Analg. 2009,108:1083, 3. Tsai HM. ASAIO J. 2012 58:163.