Aspirin potentiates LPS-induced fibrin formation (FPA) and TNF-alpha-synthesis in whole blood.

The effect of aspirin on LPS-incubation of whole blood was investigated. Aspirin induced a concentration dependent increase (2.5-5-fold at 5 mM aspirin) in LPS-induced appearance of TNF-alpha and fibrinopeptide A (FPA) in plasma, despite the concomitant increase in the inhibitory cytokine IL-100. Aspirin substantially raised the levels of LPS-induced TF-mRNA and TNFalpha-mRNA in monocytes isolated from whole blood. The median ratio for TF-/beta-actin mRNA increased from 1.5 +/- 0.44 in the presence of LPS-alone, to 2.5 +/- 0.51 when 5 mM aspirin was added. The TNFalpha/beta-actin mRNA ratios were 1.8 +/- 0.4 and 5.5 +/- 2.7 respectively. Addition of exogenous PGE2 before incubation nearly abrogated the effect of aspirin on TNF-alpha, substantiating the role of PGE2 as a regulator of TNF-alpha synthesis, whereas the effect on FPA was small. Thus, in the presence of LPS in this whole blood model, aspirin apparently had a pro-inflammatory rather than an anti-inflammatory effect.

Inhibition of platelet aggregation with a glycoprotein IIb-IIIa antagonist does not prevent thrombin generation in patients undergoing thrombolysis for acute myocardial infarction.

Thrombin activity has been implicated as a mechanism for failed reperfusion and reocclusion following thrombolysis. Aggregating platelets provide a phospholipid surface on which prothrombin is cleaved to form thrombin. We examined markers of thrombin generation and activity in patients enrolled in a randomized, placebo-controlled, dose escalating trial of the platelet glycoprotein IIb-IIIa inhibitor eptifibatide (Integrilintrade mark) administered concomitantly with tissue plasminogen activator for the treatment of myocardial infarction. Measurements were obtained at baseline, at 90 minutes, and at 6, 12, and 24 hours after starting therapy. Eptifibatide inhibited platelet aggregation in response to 20 microM ADP. Levels of fibrinopeptide A (FPA), thrombin-antithrombin complexes (TAT), and prothrombin fragment 1.2 (F1.2) were not lower in patients treated with eptifibatide than in the control group. In the course of dose escalation, two groups of patients received the same 135 microg/kg bolus of eptifibatide, one with and one without a heparin bolus. FPA levels were dramatically lower in the heparin-treated patients. Levels of FPA, TAT, and F1.2 were not higher in patients with than in those without recurrent ischemia, or in patients without than in those with Thrombolysis in Myocardial Infarction (TIMI) grade 3 angiographic flow at 90 minutes. These data suggest that thrombin generation and activity persist following thrombolysis, despite inhibition of platelet aggregation, and that treatment with inhibitors of thrombin activity may be required even when glycoprotein IIb-IIIa inhibitors are used.

Heparin-coated cardiopulmonary bypass circuits: hemostatic alterations and postoperative blood loss.

This prospective, randomized study involving patients undergoing isolated coronary artery bypass grafting investigated whether the use of heparin-coated bypass circuits with an uncoated cardiotomy reservoir (n = 10) compared with standard uncoated bypass circuits (n = 10) resulted in differences in patient outcome and hemostatic alterations. There were no differences in postoperative blood loss, transfusion requirements, and routine coagulation test results between groups. Immunoassays for platelet alpha-granule constituents platelet factor 4 and beta-thromboglobulin, thrombin generation by-product F1.2, fibrinopeptide A, thrombin-antithrombin complex, and fibrinolysis by-product D-dimer also demonstrated no significant differences between groups, although trends for lower platelet secretion with heparin coating were noted. Increases were found in beta-thromboglobulin and platelet factor 4 concentrations at 10 (p < 0.03) and 30 minutes (p < 0.001) of CPB, respectively, and continuing throughout CPB (p < 0.001) for both groups versus values measured before incision. No significant differences were seen between levels 5 minutes prior to aortic cross-clamp release and those obtained 8 and 45 minutes after cross-clamp release. Conversely, no significant increases in F1.2, thrombin-antithrombin complex, and D-dimer were seen prior to release of the aortic cross-clamp, but afterward increases occurred that were highly significant (p < 0.001). The temporal data suggest that platelet activation occurs primarily as a result of contact with the cardiopulmonary bypass circuitry, whereas thrombin generation and fibrinolytic activity are not significant until reperfusion of the heart and lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Heparin and antithrombin III levels during cardiopulmonary bypass: correlation with subclinical plasma coagulation.

The anticoagulant effect of heparin in the milieu of altered antithrombin III levels was investigated in adult (n = 7) and pediatric (n = 14) patients undergoing open heart operations. The pediatric patients were subdivided into a control group (n = 8) and an antithrombin III group (n = 6), which received 1,000 units of antithrombin III. The reduction in antithrombin III levels during cardiopulmonary bypass was obvious in patients of all ages, showing a greater reduction (although not statistically significant) in the pediatric patients. However, the antithrombin III group patients maintained their preoperative levels of antithrombin III. The elevated fibrinopeptide A levels in pediatric and adult control group patients suggested that considerable subclinical plasma coagulation occurred during open heart operations, especially during the normothermic period of cardiopulmonary bypass and after the administration of protamine. Antithrombin III levels in the children were the most predictive (r = -0.58; p < 0.001) for production of fibrinopeptide A during moderate hypothermic cardiopulmonary bypass, but the heparin levels were most predictive (r = -0.57, p < 0.03) in the adults. This result may be related to the different actions of heparin when antithrombin III levels are reduced. Supplementation with antithrombin III succeeded in suppressing the activation of the coagulation cascade and resulted in no statistical change in fibrinopeptide A levels at any time. We conclude that heparin and (in some patients) antithrombin III levels are important variables for the inhibition of fibrin formation and the possible preservation of coagulation proteins.

Intra-arterial thrombin activity produced by percutaneous transluminal angioplasty eliminated by segmentally enclosed thrombolysis.

We determined the specific marker of thrombin activity, fibrinopeptide A (FPA), in the vicinity of dilated sites during percutaneous transluminal angioplasty (PTA) for femoro-popliteal obstructions in 24 patients. Blood samples were drawn proximal to dilated segments from a 4F catheter inserted retrogradely in the common femoral artery and distal to dilated segments from the balloon catheter tip. Median +/- S.E. FPA concentration was 21.5 +/- 4.4ng ml-1 before PTA. Immediately after dilatation, FPA concentrations were increased to 970.0 +/- 836.9 ng ml-1 distal to dilated segments (p less than 0.00005) and to 48.5 +/- 11.4 ng ml-1 proximally (p less than 0.003). Segmentally enclosed thrombolysis (SET) was undertaken immediately after PTA, when a double balloon catheter was positioned with a balloon at each end of dilated segments. Both balloons were inflated and 5 mg recombinant tissue plasminogen activator (rt-PA) and 1000 IU heparin were enclosed in the segments for 30 min. Immediately after SET, FPA concentration distal to dilated segments was 34.0 +/- 14.2 ng ml-1 and not different from proximal concentrations found after PTA (p = 0.57). Intense fibrinolysis was indicated by significantly increased levels of cross-linked fibrin degradation products (D-dimer) for hours after SET, but FPA concentrations in peripheral blood remained near baseline values. This finding differed from increased thrombin activity found by others during systemic thrombolytic therapy. Early rethrombosis did not occur after PTA in this study.(ABSTRACT TRUNCATED AT 250 WORDS)