Objectives: The aim of this study was to investigate whether ROTEM platelet can provide additional information to the traditional ROTEM analysis to guide treatment with platelet transfusions in cardiac surgery and to identify factors triggering platelet administration. Background: Platelets play a crucial role in coagulation and haemostasis after cardiac surgery. Excessive bleeding after cardiopulmonary bypass usually requires transfusions of blood products, including platelets. The ROTEM platelet is a novel point-ofcare analysis for whole blood. Materials and methods: We included 23 patients scheduled for complex cardiac surgery. ROTEM (in-tem, ex-tem), ROTEM platelet (ARA-tem, ADP-tem and TRAP-tem) and platelet count were analysed before induction of anaesthesia (T0), after cardiopulmonary bypass and protamine reversal (T1) and after platelet transfusion (T2, n = 10). Results: ROTEM and ROTEM platelet tests were all significantly reduced between T0 and T1. ROTEM parameters improved significantly after platelet transfusion. Regarding ROTEM platelet, only TRAP-tem increased between T1 and T2 (P = .008). Factors triggering platelet transfusion were long duration of surgery and time on cardiopulmonary bypass. Conclusion: ROTEM platelet with thrombin activation, TRAP-tem, improved significantly, indicating that platelet transfusion may reverse cardiopulmonary bypassinduced platelet dysfunction. Further studies are needed to evaluate whether TRAPtem can be a valuable analysis regarding indications for transfusion of platelets after extensive cardiac surgery.