DISCUSSION
Data from this study seem to suggest that cardiopulmonary bypass induces a reduction in platelets and coagulation factors, mainly fibrinogen and factors II and X, associated with a consensual modification of laboratory parameters (both traditional and viscoelastic). Several reviews attempted to describe CPB related coagulopathy to provide suggestions and recommendations for the transfusion management during cardiac surgery. However, only Hofer (15) and colleagues reported on the reduction of different haemostasis components, traditional laboratory and viscoelastic parameters following CPB. We found an increase in INR of 38.5% and aPTT of 21.34%, close to 33.3% and 17.9% found by Hofer. We then found a reduction in platelet count of 44.33%, substantially in line with what has already been reported (44.5%), whereas for fibrinogen the reduction was 34.82% compared with 36.4% reported in the literature.
reduction in Fibtem of 16.6% at the end of CPB, while the MCF – MCF difference, indicative of platelet contribution to clot strength, was reduced by 7.69%. Hofer for these parameters found a decrease of 33% and 34%, respectively. data confirm the association between CPcoagulation factors consumptionCT showed an increase of 22.64%, confirming that the entire coagulation cascade and the mechanism of thrombin generation seem severely subverted during CPB. In the study population, 17 patients underwent cardiac surgery with sternotomy access (sternotomy group) and 12 with minimally invasive access (HP Group). The two groups did not show significant differences regarding anthropometric parameters, major comorbidities, CPB length and aortic clamping, baseline values of Hct, PLTS, INR, aPTT, Fibrinogen, AT III (Table 1). We analysed the two groups to identify those variables better explaining the modification induced by the surgical approach. At T1, Protein C content was reduced in the sternotomy group (p < 0.04) (Table 3) and the difference was amplified at T2 (p<0.01) (Table 4). In the absence of a baseline value, it cannot be excluded that the detected difference at T1 was already present at baseline. However, a trend towards a higher protein C consumption in the sternotomy group seems confirmed. To our knowledge, there are no previous study on the trend of protein C during CPB. Even with the limitations illustrated above and in the specific context of the present study, we do believe this observation interesting since it could support a rational approach to the diversified use of clotting factor concentrates: in patients who have undergone a sternotomy, the administration of products containing protein C, when available, may be more suitable than products that do not. This is also confirmed by the fact that the sternotomic access group received a higher number of PRBCs and FFP. As also confirmed by the literature (8,9), it seems that the sternotomy approach is associated with a greater alteration of haemostasis compared to the minimally invasive approach, as evidenced by the greater variations in viscoelastic parameters and the greater number of transfusions of blood products. However, it should be emphasized that the two surgical approaches differ from each other in many respects, including the practical management of CPB (use of negative pressure for venous drainage, relative volume and metabolic impact of the different types of cardioplegia, differences in the feasibility of retropriming). All these variables, which are difficult to standardize, can contribute to the development of coagulopathy, making it difficult to identify which factors are most related to transfusion needs. Overall, the data we collectedseem to support the trend towards an increased use, in cardiac surgery, of minimally invasive techniques that already proved their effectiveness in improving postoperative outcomes(16). This study has limitations: first, the lack of randomization, which obviously exposes the risk of bias. It is also underpowered but, due to the lack of previous studies, it was not possible to calculate, a priori, an adequate power. Finally, variables such as techniques and practical aspects of CPB circuit are difficult to standardize, with a possible impact on study