Platelet-dependent thrombography gives a distinct pattern of in vitro thrombin generation after surgery with cardio-pulmonary bypass: potential implications

Use of thrombin generation test for monitoring hemostasis in coronary bypass surgery

To evaluate the parameters of the thrombin generation test (TGT) in coronary artery disease (CAD) patients on prolonged aspirin therapy during on-pump coronary artery bypass grafting (CABG) after donor platelet concentrate transfusion. A total of 148 patients with CAD on prolonged aspirin therapy (75–100 mg/day) who have undergone elective on-pump CABG were consecutively included in the study. Patients were divided randomly into two groups. Group 1 (n = 76) received donor platelet transfusions after cardiopulmonary bypass, whereas Group 2 (n = 72) did not. TGT parameters were measured using an analyzer at pre-, intra-, and early postoperative periods. Activation of the endogenous thrombin potential was observed in patients on prolonged aspirin therapy in the pre- and intraoperative periods, as confirmed by high peak thrombin and increased velocity index. The activation time of the prothrombinase complex and thrombin generation time were greater than the control group. The blood hemostatic potential in patients who did not receive transfusions in the early postoperative period decreased up to the level of the control group in the extended time parameters. Hemostatic potential in plasma in patients on aspirin was preserved. Given the laboratory test results and clinical data, platelet concentrate transfusion is unnecessary for prevention.

[Evaluation of the hemostatic potential at coronary artery bypass surgery during long-term aspirin therapy]

AIM

To estimate thrombin generation test parameters in patients with coronary heart disease during coronary artery bypass surgery under extracorporeal circulation after transfusion of donor platelet concentrates during long-term therapy with acetylsalicylic acid (ASA).

SUBJECTS AND METHODS

A total of 148 patients with coronary heart disease who had undergone elective primary coronary artery bypass surgery under extracorporeal circulation during preserved therapy with ASA (75-100 mg/day) were examined. According to donor platelet concentrate transfusion, all the patients were divided into 2 groups: 1) 76 patients undergoing donor platelet transfusion and 2) 72 without this procedure. A control group consisted of 20 apparently healthy individuals. At the pre-, intra-, and early postoperative stages, the investigators evaluated the following thrombin generation test parameters: lag time (min); peak thrombin concentration (nM/l); time to peak (min); the area under the thrombin generation curve (nM), and thrombin generation rate (nM/min).

RESULTS

During long-term ASA therapy, the patients were found to have an activated endogenous thrombin potential in the pre- and intraoperative periods, as evidenced by the high peak concentration of thrombin and the increased rate of its generation. At the same time, the time of prothrombinase complex activation and that of thrombin generation were longer than those in the control group. In the early postoperative period, the patients who had not been transfused with platelet concentrates with a further increase in the temporal parameters, showed a decreased hemostatic potential, reaching the control level, whereas donor platelet transfusion stimulated endogenous thrombin generation: the time to initiate clotting and that to reach the peak were shorter; in this case, the thrombin generation rate and concentrations increased, but the preoperative level was not reached. No perioperative (hemorrhagic or thrombotic ischemic) events were noted in the examined groups.

CONCLUSION

The hemostatic potential was preserved in patients receiving long-term therapy for ASA. Taking into account laboratory and clinical findings, platelet concentrate transfusions are unnecessary for preventive purposes. The appropriateness of donor platelet transfusion should be strictly individually approached with regard to the laboratory parameters of the thrombin generation test, by minimizing the risk of perioperative ischemic and hemorrhagic events in each specific patient.

Heparin and Protamine Titration Does Not Improve Haemostasis after Cardiac Surgery: A Prospective Randomized Study

Background

Bleeding complications are common in cardiac surgery. Perioperative handling of heparin and protamine may influence the haemostasis. We hypothesized that heparin and protamine dosing based on individual titration curves would improve haemostasis in comparison to standard dosing.

Subjects and Methods

Sixty patients scheduled for first time elective coronary artery bypass grafting or valve surgery were included in a prospective randomized study. The patients were randomized to heparin and protamine dosing with Hepcon HMS Plus device or to standard weight and activated clotting time (ACT) based dosing. Blood samples were collected before and 10 minutes, 2 hours and 4 hours after cardiopulmonary bypass. Primary endpoint was endogenous thrombin potential in plasma 2 hours after surgery as assessed by calibrated automated thrombography. Secondary endpoints included total heparin and protamine doses, whole blood clot formation (thromboelastometry) and post-operative bleeding volume and transfusions. Heparin effect was assessed by measuring anti-Xa activity.

Results

Endogenous thrombin potential and clot formation deteriorated in both groups after surgery without statistically significant intergroup difference. There were no significant differences between the groups in total heparin and protamine doses, heparin effect, or postoperative bleeding and transfusions at any time point. Significant inverse correlations between anti-Xa activity and endogenous thrombin potential were observed 10 min (r = -0.43, p = 0.001), 2 hours (r = -0.66, p<0.001) and 4 hours after surgery (r = -0.58, p<0.001).

Conclusion

In conclusion, the results suggest that perioperative heparin and protamine dosing based on individual titration curves does not improve haemostasis after cardiac surgery. Postoperative thrombin generation capacity correlates to residual heparin effect.

Trial Registration

www.isrctn.comISRCTN14201041.