During catheter ablation of cardiac tissue, the insulting stimulus may damage and activate the blood. Specifically activation of platelets and the clotting system is a potential risk by their formation of thrombi. In this study the effect of two different techniques, a radiofrequency and a cryo-application procedure, on the activation of platelets and clotting in an in vitro blood circulation model was investigated. The radio-frequency procedure induced significantly more blood cell damage, platelet activation and clotting than did the cryo-application procedure. Macroparticles were circulating in blood after the radiofrequency procedure. In the cryo procedure, blood damage was limited to the frozen blood spherule around the tip of the catheter. It is concluded that at least in those circumstances where blood is directly contacting the tip of the radiofrequency or cryo-application catheter, the latter is more safe with regard to thrombus formation.

We conclude that, with human albumin the golden standard, 2.5% hydroxyethyl starch is a suitable colloid plasma substitute to be used as priming solution in an extracorporeal circuit as well as peri- and postoperative infusion fluid, reasonably well maintaining hemostasis.

The conlribulion of plalelel dysfunclion to Ihe impaired hemostasis afler cardiac surgery remains to be established, because Ihere is no sensilive method to assess platelet funclion. Measurement of the shear-induced pathway of platelet function, an importanl mechanism in inducing hemostasis, became possible by a novel shear-inducing technique, the in-vitro bleeding test (Thrombostat 4000). By using this test, the changes in plalelet function during cardiopulmonary bypass and their conlribulion 10 hemostasis were investigated in patients undergoing cardiac surgery. Platelet function is quickly impaired shortly after Ihe slarl of cardiopulmonary bypass, and partly recovered al Ihe end of cardiopulmonary bypass. The function of aspirin-Ireated platelets is more severely affecled Ihan of nonaspirin platelets during cardiopulmonary bypass. Furthermore, Ihe degree of platelet dysfunclion at Ihe end of Ihe operation, but neither the platelet number nor Ihe activated clotting lime, was significantly correlated with hlood loss from the chest drain after cardiac surgery. These results indicate the significant and variable effects of cardiopulmonary bypass on Ihe shear-induced pathway of platelel function. Moreover, the impairment of Ihis function of platelets appears to be a major cause of excessive bleeding in patients after cardiac surgery. Therefore, Ihe routine use of Ihe shear-inducing lesl seems helpful to make a proper diagnosis and design Ihe Iherapy for bleeders after cardiac surgery.Plalelet dysfunction is considered to be a major cause of excessive bleeding in patients after cardiopulmonary bypass. 1-3 The problem of excessive bleeding becomes larger in cardiac surgery because most patients suffering from coronary artery disease are now treated with aspirin before operation" Despite many investigations on this topic, no useful method has been established to assess platelet dysfunction during and after cardiopulmonary bypass. 5.6 Therefore, no clear evidence has been collected about the contribution of platelet dysfunction to the impaired hemostasis after cardiac surgery. With recent techniques inducing shear-stress, a standard measurement of the shear-induced pathway of platelet function has become possible 7 -J 1 Although the role of the shear-induced pathway remains to be established among other platelet functions, it has to be concluded 12 that the shear-induced pathway of platelet function is an important mechanism of platelet function contributing to hemostasis. In the present study, we hypothesized that the shear-induced pathway of platelet function is a main function of platelets inducing hemostasis, and investigated the change of platelet function during cardiopulmonary bypass and its correlation to the hemostatic status of patients after cardiac surgery. A novel shear-inducing technique, the invitro bleeding test (Thrombostat 4000), was used. PATIENTS AND METHODS Patients and ProtocolPatients undergoing elective, primary coronary artery bypass grafting surgery were selected for the study. 66

The contact of blood with the artificial extracorporeal circuit causes a systemic inflammatory response due to blood activation. In this study, we compared two different paediatric membrane oxygenators used for extracorporeal circulation: a hollow fibre membrane oxygenator (Dideco Masterflo D-701, n = 10), and a flat sheet silicone membrane oxygenator (Avecor Kolobow 800-2A, n = 10). Blood compatibility was indicated by measuring complement activation as well as leukocyte and platelet activation. In patients perfused with a flat sheet membrane oxygenator, concentrations of complement split products C3a were significantly increased 30 minutes after the start of bypass (p < 0.01), whereas only a mild increase of C3a was found in patients perfused with a hollow fibre membrane oxygenator. Leukocyte and platelet counts dropped uniformly in both groups after the start of bypass mainly due to hemodilution. Activation of leukocytes and platelets identified by both plasma beta-glucuronidase and beta-thromboglobulin was similar in both groups. Infants perfused with a flat sheet membrane oxygenator received significantly more donor blood than those perfused with a hollow fibre oxygenator (p < 0.05). These results indicate that when used during paediatric cardiopulmonary bypass, a flat sheet membrane oxygenator has a higher complement activity than a hollow fibre membrane oxygenator, which is probably due to the relatively larger blood-surface contacting area of the oxygenator.