Abstract

Methods: Twenty-eight patients (24 males, 4 females; mean age 62±12 years; range 41 to 84 years) who underwent elective CABG due to ischemic heart disease were enrolled in this single-blind prospective study with the odd-even number of randomization method. Phosphorylcholine-coated ECC systems were used in group 1 and non-coated ECC systems were used in group 2. The percentage of the coagulation factor activations [factor (F)-II, F-V, F-VII, F-VIII, F-X, F-XII, and von Willebrand factor], D-dimmer, and anti-thrombin III levels were measured preoperatively, intraoperatively and postoperatively.

Results: The percentage of activation of F-II and F-X in group 1 were significantly higher than group 2 before the cross-clamp removal (T1) (p<0.05). The percentage of activation of factor XII after surgery (six hours later-T3, postoperative first week-T4) increased in both groups, however, this increase was significantly higher in group 2 than group 1 (p<0.01). D-Dimer levels gradually increased in both groups and remained significantly higher (p<0.001), however, no difference was observed between the groups. The antithrombin III activity significantly reduced in both groups at T1 compared to the baseline values (T0) (p<0.01). The von Willebrand factor activity increased significantly in both groups at T1 and after termination of cardiopulmonary bypass (T2) (p<0.01), indicating no significant difference between the two groups (p>0.05).

Conclusion: Although the percentage of activation of the factors is higher in non-coated ECC systems compared to PC-coated ECC systems, it does not indicate significant clinical differences. In addition, both PC-coated or non-coated ECC systems exert similar biological effects during cardiopulmonary bypass.

Improvements in surface modification and coating techniques with phosphorylcholine (PC) have been used to stop fibrinogen and protein adsorption as well as platelet collection and to inhibit the first step of activation of coagulation, thereby increasing the hemocompatibility of materials such as polytetrafluoroethylene (PTFE), polyethylene, polyurethane, silicone, and polyvinyl chloride (PVC) that are used in ECC circuits.[5] Although the protection of shaped-blood elements, such as neutrophils, platelets, and red blood cells (RBCs) as well as various inflammatory mediators has been well documented with PC-coated ECC, clotting activity factors, which provide hemostasis and coagulation, have not been studied in conjunction with PC-coated ECC and have not been associated with antithrombin III (AT III) or von Willebrand factor (vWF) in the literature.[5-8]

The first aim of the present study was to describe the activity of individual coagulation factors during and after cardiac surgery with cardiopulmonary bypass (CPB) and determine whether they were related to the clotting factors, AT III, and vWF. The second goal was to investigate whether the activity of any other plasma coagulation factor was correlated with clinical implications such as bleeding volume or length of intensive care unit (ICU) stays after cardiac surgery.

Methods

Those who had an extremely reduced left ventricular function [ejection fraction (EF) <30%], those who had undergone emergency surgery, reoperations, additional procedures such as valve replacement, carotid endarterectomies, or a left ventricular aneurysmectomies that required hemodialysis during or after the ECC, or those over the age of 80 who did not consent were excluded from the study. In addition, after the study was terminated, five of the patients (three in group 1 and two in group 2) were also excluded because they had used an antiplatelet drug seven days before the operation, which left a total of 28 study participants (24 males, 4 females; mean age 62±12 years; range 41 to 84 years).

The demographic characteristics and postoperative clinical data of the patients is given in Table 1. For the purposes of this study, blood samples were taken at the preoperative (T₀), and perioperative stage just before cross-clamp removal (T₁) as well as after the termination of CPB (T₂) and at the postoperative sixth hour (T₃), and first week (T₄).

The patients were anesthetized by the same physician with midazolam, fentanyl, and vecuronium at appropriate levels for the patients’ weight via a standard protocol. No volatile anesthetics were used. Furthermore, the procedures were performed in a normal manner for all of the patients by the same team. Systemic heparin (300 IU/kg) was given at the beginning of the operation and again one hour later to maintain the activated clotting time (ACT) (Hemochron^® 801, ITC, Edison, NJ, USA) at above 480 seconds and 200 IU/kg. As in a previous study.[9] 100 IU/kg of additional heparin was administered on an hourly basis as needed.

The PC-coated open ECC system was used for group 1 from the tip of the artery to the tip of the vein end (Compactflo Evo, Sorin Group Italia S.r.l., Milan, Italy) while the non-coated open ECC system (Bıçakçılar-Bıçakçılar Medical Devices Industry and Trade. Co, Istanbul, Turkey) was used applied at the same location for group 2. A cardiotomy return sucker was used for the shed blood in the operation field, and a Stöckert S3 roller pump Sorin Group Deutschland GmbH, München, Germany) was also employed for all of the patients. Mild systemic hypothermia was applied with a nasopharyngeal temperature of 32° C, and hemodilution was achieved with a hematocrit level of 26%. Priming was carried out on all patients using a standard prime volume (1602±202 mL crystalloid prime), and no additional techniques, such as retrograde autologous priming, were needed. The total flow rate was maintained at between 2.2 and 2.4 L/minute with a perfusion pressure of 50-70 mmHg. Myocardial protection was achieved via antegrade cold blood cardioplegia with potassium, and topical cooling with iced saline and antegrade cardioplegia was repeated every 20 minutes. The effect of the heparin was neutralized with 1 mg protamine for 100 IU.[9]

The patients were followed up by routine hemodynamic monitoring in the cardiovascular surgery intensive care unit (ICU) after the operation, and those with hemoglobin levels of below 10 g/dl along with significant clinical signs, for example hypotension and tachycardia, underwent a blood transfusion during that time.

The blood samples were kept in gel-buffered dry tube, 3.2% sodium citrate and K3 ethylenediaminetetraacetic acid (EDTA) containing tubes. Complete blood counts (CBCs) were analyzed using an fully automated hematology analyzer (ABX Pentra XL 80, Horiba ABX, Inc., Irvine, CA, USA). The blood in the sodium citrate tube was centrifuged for 10 minutes at 5000 rpm, and once plasma was obtained, it was put into 2 ml of Eppendorf cryo for coagulation tests. These were then labeled with the proper encodings and stored for protection in a refrigerator at -80 °C. After all of the samples were collected, heating processes were applied in stages to the frozen plasma samples, and they were measured with a Siemens BCS^® XP coagulation measuring device (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany). Next, the AT III plasma activity was measured quantitatively with a Berichrom antithrombin III (A) kit via a chromogenic method (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany), and the D-dimer levels were measured using an INNOVANCE^® D-Dimer test kit (Siemens Healthcare Diagnostics Products, GmbH, Marburg, Germany). Furthermore, the factor II (F-II), F-V deficient, F-VIII, F-XI, F-XII, F-VII, and F-X activity percentages were measured with in vitro diagnostic F-II, F-V deficient, F-VIII, F-XI, F-XII, F-VII, and F-X reagents (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany) while plasma vWF activity was determined using an in vitro platelet agglutination diagnostic Innovance vWF Ac Assay kit (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany).

All analyses were done with the IBM SPSS Statistics version 21.0 for Windows (IBM Corporation, Armonk, NY, USA). The results were expressed as mean and standard deviation (SD) or number and percentage. Comparisons were carried out using the Mann-Whitney U test for non-parametric data and a chi-square test or Fisher’s exact test for categorical variables. Group findings at various times were compared with repeated measures of analysis of variance (ANOVA), and in-group comparisons were carried out using the Bonferroni test. A two-sided p value of <0.05 was considered to be statistically significant.

Results

Table 1: Demographic and preoperative characteristics of the patients in the study

Table 2: Hemostatic parameters in the peri- and postoperative state of coronary artery bypass graft surgery

Table 3: The mean values of the activity percentage of the factors and the vWF, D-dimer, and AT III levels at specified times

The patients were extubated shortly after the completion of the operation, and no surgical complications, such as reoperations due to bleeding, thromboembolic events, myocardial infarction (MI), lengthened stays on the ICU or hospital, or mortality were reported during the study (Table 2). The administered doses of heparin and protamine are given in Table 2, and the ACT values are shown in Table 3, and no significant differences were noted between the two groups.

The analysis of the factors’ activation percentages is shown in Table 3. All of the measured parameters differed significantly from the T0 when the in-group comparison was conducted (p<0.0001). The F-II and F-X activity percentages were also significantly different, with the measured value being reported as “no coagulation” between the groups at T1 (0 vs. 6.5±5.8 and 0 vs. 13.7±6.5, respectively; p<0.05). Additionally, the F-XII activity percentage in group 2 was significantly higher than in group 1 at T3 and T4 (134.2±41.4 vs. 171.3±39.5 and 165.4±20.2 vs. 185.2±36.2, respectively; p<0.05).

However, the AT III values did not differ significantly between the two groups. There were decreased levels within the group comparison, and a statistically significant reduction of under 80 mg/dl was seen at T1 and T2 compared with the T0 levels (Table 3).

Although there was no marked difference in the D-dimer values between the groups, they were exponentially higher at T1, T2, T3, and T4 within the groups (Table 3).

Moreover, the vWF activity percentage was significantly high at T1 c ompared w ith T 0, but the difference was not significant between the groups (Table 3).

Discussion

Coating the ECC with PC promises a reduction in thrombogenicity. Ishihara et al.[6] defined this antithrombogenicity as a reduction in adhesion molecules on the surfaces coated with PC which provides a natural zwetterionic structure as well as red blood cells and forms a biomembrane-like (biomimicry) layer of the material’ surface. This layer interacts with the blood cell components and proteins minimally. In our study, the F-II and F-X activation percentages were elevated in group 2 at T1 in spite of the presence of heparinization. This suggests that F-II, a key player in the coagulation process, and F-X, which is commonly seen on the pathway of clotting, were overactivated. De Somer et al.[5] s howed t hat i mmediately a fter the start of CPB, the thromboxane B2 (TXB-2) (a potent thrombocyte activator and aggregator) blood concentration fell quickly, after temporarily rising in the beginning, with the use of PC-coated ECC systems. In contrast, they found that the TXB-2 blood concentration began to rise and remained at a high plateau until the end of CPB with the non-coated ECC group. One possible interpretation of their findings is that the bio-compatible PC-coated surface that causes the activation of platelets was rapidly made passive. [11] In our study, the difference in the F -II a nd F -X activation percentages between the groups at T1 were consistent with the findings of the De Somer et al.[5] study. Similarly, the adsorption of fibrinogen and platelets was shown to be inhibited by PCC in an in vitro study by Campbell et al.[8] We determined that despite the quick rise in F-XII activation percentage, it was almost the same in both of our groups at the time of CPB output. Furthermore, the rising curve in F-XII activation percentage in group 2 that we discovered may have been due to the differences in the surface. Li et al.[7] showed that the surface of PC-coated systems resisted adsorption of F-XII and delayed the initiation of coagulation by the intrinsic pathway, and their results were similar to ours.

We also determined that the plasma activity of AT III decreased below the 80% level. Heparin activity occurs by connecting heparin to the AT III on a specific pentasaccharide sequence, which primarily leads to the inactivation of coagulation factors such as F-IIa and F-Xa.[12] Although we found that the ACT values were adequate for CPB, the AT III levels were under 80 U/dl in the blood samples at T1 and T2, and these low levels might have caused the continuous subclinical coagulation in our study. In fact, Despotis et al.[13] highlighted that low AT III levels, particularly when they are under 80 U/dL, may be inadequate for anticoagulation.[13]

Finally, we identified a marked increase in the vWF levels during CPB as well as a gradual increase in the D-dimer levels during CPB and after the surgery. Cardiopulmonary bypass-associated fibrinolysis frequently emerges after a rapid rise in D-dimer levels after neutralizing the effect of heparin.[14] Like the study by Páramo et al.[15] the D-dimer levels in our groups increased significantly during CPB and reached their peak after the administration of protamine.

Successful hemacompability during CPB offers increased protection in the hemostasis process via a reduction in consumption, less coagulation and the activation of coagulation factors, and expected low D-dimer values.[16] We determined that the D-dimer levels were the same in both of our groups, and after the surgery, they showed similar gradually increasing rising curve until postoperative week one. This similarity may indicate that the patients’ burden of fibrinolysis may also have been similar. As Nisanoğlu et al.[17] pointed out in their study, when increased hemacompability, subclinical thrombosis and fibrinolysis continue a rise in D-dimer levels usually occurs. The primary source of vWF is the vascular endothelium, which produces it without stimuli and also provides the rapid release of intracellular stores in response to other stimuli like thrombin, fibrin, and vasopressin. Wittwer et al.[18] have found that increase plasma vWF levels after surgery involving CPB. During CPB, many different variables, particularly vascular endothelial injuries, can influence vWF levels. In addition, endothelial cells can be damaged by both particles of reactive oxygen species (ROS) during CPB and free radicals during reperfusion caused by the effect of activated platelets.[19] Holdright et al.[20] mentioned that the vWF antigen (vWF:Ag) levels during the induction of anesthesia decrease before the introduction of crossclamping due to hemodilution secondary to a decrease in hematocrit levels. However, they found that after the cross-clamping, the levels continued to climb to the levels seen at induction, and they reached their highest levels when the CPB was terminated. They also determined that the rise in the vWF levels after the removal of the aortic cross-clamp were associated with vascular endothelial damage and the reperfusion of coronary arteries. Their findings were consistent with ours, and we did not identify any significant differences in the vWF levels between the groups.

Conclusion

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding
This work was supported by the Research Office of Istanbul University (5201).

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