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Tissue factor as the main activator of the coagulation system during cardiopulmonary bypass
F De Somer1, Y Van Belleghem, F Caes
1Heart Centre, University Hospital Gent, Belgium.
Insights
Blood aspirated during cardiopulmonary bypass activates coagulation and causes hemolysis. Coating bypass surfaces with phosphorylcholine reduces platelet activation and blood loss, highlighting tissue contact as a key factor.
Area of Science:
- Cardiovascular Surgery
- Biomaterials Science
Background:
- Cardiopulmonary bypass (CPB) can activate the coagulation system and cause hemolysis.
- The sources of CPB-induced coagulopathy and hemolysis are not fully understood.
Purpose of the Study:
- To investigate the impact of aspirated blood from nonvascular structures on coagulation activation, hemolysis, and blood loss during CPB.
- To compare the effects of discarding aspirated blood versus returning it, and the effect of phosphorylcholine-coated surfaces.
Main Methods:
- Randomized trial with 3 groups (control, discarded aspirated blood, phosphorylcholine-coated surfaces) of 10 patients each undergoing coronary artery bypass grafting.
- Measured plasma beta-thromboglobulin, thrombin generation, haptoglobin, and free hemoglobin.
- Quantified blood loss.
Main Results:
- Increased free plasma hemoglobin and thrombin generation observed in the control group.
- Significant platelet activation in the control and discarded blood groups.
- Negligible platelet activation and a 30% reduction in blood loss in the phosphorylcholine-coated group.
Conclusions:
- Aspirated blood contaminated by tissue contact is a primary activator of coagulation and cause of hemolysis during CPB.
- Foreign surface contact is less critical to the procoagulant effect.
- Mimicking cell membrane structure with phosphorylcholine coating reduces platelet activation and blood loss.
Objective:
This study investigates the influence of foreign material and blood aspirated from nonvascular structures on activation of coagulation, hemolysis, and blood loss.
Methods:
The series comprises 3 randomized groups (groups C, S, and S+P) of 10 patients undergoing routine coronary artery bypass grafting with cardiopulmonary bypass. In group C, the control group, all aspirated blood was returned into the circulation. In group S suction blood was discarded, whereas group S+P was identical to group S, with surfaces coated with phosphorylcholine. Plasma concentrations of beta-thromboglobulin, thrombin generation, haptoglobin, and free hemoglobin, as well as blood loss, were measured.
Results:
A steady increase in free plasma hemoglobin, as well as an increased generation of thrombin, was noticed in group C. Moreover, a close correlation (r = 0.916) between the generation of thrombin and its inhibition (thrombin-antithrombin complexes) was observed. Platelets were clearly activated in group C and, to a lesser extent, in group S. In contrast, platelet activation in group S+P was negligible, resulting in a 30% decrease in blood loss (P =.05).
Conclusions:
Aspirated blood contaminated by tissue contact is the most important activator of the coagulation system and the principal cause of hemolysis during cardiopulmonary bypass. Contact with a foreign surface is not a main variable in the procoagulant effect of bypass. Mimicking the outer cell membrane structure resulted in decreased platelet activation and decreased blood loss.