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