INTRODUCTION
Bleeding, due to surgical or non-surgical causes, complicates 10% of(1-3) while up to 20-40% of elective procedures require blood products (4,5). These percentages increase during urgent/emergency surgery and more complex and long-lasting procedures bypass (CPB)a technique used in several surgical settings to obtain an adequate operating fieldrequires a profound modification of patient’s normal coagulation pattern, eventually leading to a multifactorial coagulopathy which is associated with an increased risk of non-surgical bleeding, both in the period immediately following weaning from CPB and in the first hours / days of hospitalization in the Intensive Care Unit (ICU) and, consequently, a longer hospital stay and a poorer long-term outcome. After the publication of the 2017 EACTS / EACTA guidelines on blood management in adult patients undergoing cardiac surgery procedures (6), several studies have addressed the topic of the pathophysiology of CPB-related coagulopathy and the management of blood products. Nevertheless, to date, there is no agreement in the literature on the optimal management to be applied in this specific context. Ternström and colleagues (7)described the coagulation factors activity following coronary artery bypass surgery and observed an inverse correlation between fibrinogen levels, platelets, FXIII and postoperative bleeding while no significant association was observed for other coagulation factors. Both Chandler and Ranucci (8,9) described the key role of haemodilution in reducing platelets, fibrinogen, and coagulation factors, but also in increasing blood products consumption in both operating room and ICU. Finally, Gielen and colleagues(10) emphasized the importance of haemodilution and hyperfibrinolysis in determining CPB coagulopathy. Nowadays, the coagulation status of the cardiac surgical patient is monitored using standard laboratory parameters, including prothrombin time (PT), activated partial thromboplastin time (aPTT), international normalized ratio (INR), activated clotted time (ACT), fibrinogen concentration, and platelet count. Although these tests are widely and routinely used, they involve long turnaround times, a critical limitation in settings where the patient’s coagulation status can change very quickly. Furthermore, PT and aPTT are generally described as useful to detect coagulation deficiencies (11,12) but, although they are normally used as guide for transfusion, they have been shown to be very poor predictors of bleeding. Viscoelastic methods are increasingly used in addition to standard laboratory tests. Conventional viscoelastic parameters recorded with TEG (Haemoscope Inc, Niles, Illinois) or ROTEM (Tem International GmbH, Munich, Germany) devices during CPB include ROTEM clotting time (CT), ROTEM maximum clot firmness (MCF), TEG reaction time (R), and TEG maximum amplitude (MA). Viscoelastic tests can be easily run at the point of care, decreasing the time required to obtain information about patients’ coagulation status. Sharma and colleagues (13) compared TEG results and conventional tests in predicting postoperative bleeding, stratifying patients into two groups ”bleeders” and ”non-bleeders” and TEG parameters were the only ones found to be able to effectively predictive postoperative bleeding. Notwithstanding, haemostatic alteration of patients undergoing cardiac surgery is still unclear and is therefore still subject of debate. The aim of the present study is to describe, through serial blood controls, traditional tests and Point Of Care (POC), the coagulation status of patients undergoing CPB for cardiac surgery and to identify specific coagulation ‘patterns’.