RESULTS
During the study period, 36 patients were evaluated for eligibility. Seven patients were excluded: five because of inadequacy of the sample taken at T2 (hemolysis) and two because of need for re-entry into CPB for intraoperative issues. Twenty-nine patients were enrolled over a four-month period. Seventeen patients were assigned, based on the surgical approach performed, to the sternotomy group and 12 patients to the HP group. As shown in Table 1 the two groups were comparable both for demographic characteristics and type of antithrombotic or anticoagulant therapies used. Between the beginning (T1) and the end (T2) of cardiopulmonary bypass we observed an increase of 38.5% (from 1.14 to 1.58) of the INR and of 21.34% (from 0.89 to 1.08) of the aPTT, as shown in Table 2. At the same time, we observed a decrease in platelet count, fibrinogen, and AT III, with a median percentage decrease of 44.33%, 34.82%, and 30.10%, respectively. Between the beginning and the end of the bypass we also observed a significant decrease in coagulation factors II, X, XI, XII, protein C and S with an average percentage decrease of 32.58%, 34.11%, 36.69 %, 47.45%, 33.65% and 30.20%, respectively. We also observed a moderate reduction for factors V and VII (24.77% and 23.52%) and a modest reduction in factors VIII and IX (9.81% and 13.51%). Comparing the consumption of coagulation factors in the sternotomy group and in the HP group we observed how, at T1, patients belonging to the sternotomy group showed a statistically significant reduction in Protein C activity compared to the HP group (96.9 ± 18.9 vs 113.2 ± 21.8 respectively, p = 0.04) and a statistically insignificant reduction of factor XI activity (101.8 ± 29.6 vs. 122.7 ± 30.9, p = 0.08). (Table 3). Even at T2, the sternotomy group was characterized by a significant reduction in the activity of protein C (68.4 ± 12.4 vs. 83.4 ± 15.3, p <0.01) and factor XI (65, 5 ± 21.1 vs 85.8 ± 24.5, p = 0.024), as well as a higher consumption of factors V and XII (p = 0.049 and p = 0.07 respectively) compared to the HP group (Table 4). Table 5 shows the negative correlation between the duration of CPB and aortic clamping and the factors consumption. As the duration of CPB and aortic clamping increases we see a progressive and statistically significant reduction of factors II, X, XI, XII, Protein C, and Protein S activity. Regarding viscoelastic parameters, we recorded a median increase of 22.64% of CT in Intem during CPB (159.0 [146.0-172.0] to 195.50 [189.0 - 248.0] ), with a reduction in MCF in Fibtem of 16.66%, as well as platelet contribution (MCF Extem - Fibtem), which was reduced by 7.69% (Table 6). Comparing sternotomy group and HP group 2 (Table 7), CT elongation at T2 appeared to be more pronounced in patients undergoing sternotomy compared with those undergoing minithoracotomy (233.70 ± 59.9 vs. 200.3 ± 35.9, p= 0.046). The same was observed for platelet contribution (MCF Extem-Fibtem) at T2, although not statistically significant (p=0.052) Finally, we investigated differences in terms of post-CPB transfusion needs between sternotomy and HP group . We observed a greater need for transfusion of PRBCs and FFP in the sternotomy group compared with HP group (p =0.02 and 0.047, respectively) as shown in Table 8.