Validation of a procedure to assess ASA-response in patients with decreased, initial TRAP induced aggregation

Reduced mucosal side-effects of acetylsalicylic acid after conjugation with tris-hydroxymethyl-aminomethane. Synthesis and biological evaluation of a new anti-inflammatory compound

Acetylsalicylic acid (ASA) causes adverse haemorrhagic reactions in the upper gastrointestinal (GI) tract, and previous results have suggested that combination therapy with 2-amino-2-(hydroxymethyl)-1,3-propanediol (Tris) could provide protection in this scenario. Based on this hypothesis, our aim was to develop a new compound from ASA and Tris precursors and to characterize the biological effects of ASA-Tris and the derivatives ASA-bis- and mono-hydroxymethyl-aminomethane (ASA-Bis, ASA-Mono, respectively) using in vivo and in vitro test systems. ASA or ASA conjugates (0.55mmol/kg, each) were administered intragastrically to Sprague-Dawley rats. Changes in the mucosal structure and in the serosal microcirculation were detected by in vivo imaging techniques, the plasma TNF-alpha, tissue xanthine oxidoreductase and myeloperoxidase activities, and liver cytochrome c changes were also determined. In two separate series, platelet aggregation and carrageenan arthritis-induced inflammatory pain were measured in control, ASA and ASA-Tris-treated groups. Severe mucosal injury and a significant decrease in serosal red blood cell velocity developed in the ASA-treated group and an ~2-fold elevation in proinflammatory mediator levels evolved. ASA-Tris did not cause bleeding, microcirculatory dysfunction, mucosal injury or an elevation in proinflammatory markers. The ASA-Mono and ASA-Bis conjugates did not cause macroscopic bleeding, but the inflammatory activation was apparent. ASA-Tris did not influence the cyclooxygenase-induced platelet aggregation significantly, but the inflammatory pain was reduced as effectively as in the case of equimolar ASA doses. ASA-Tris conjugation is an effective approach through which the GI side-effects of ASA are controlled by decreasing the cytokine-mediated progression of pro-inflammatory events.

Comparative efficacy of in vitro and in vivo metabolized aspirin in the DeBakey ventricular assist device

Ventricular assist devices (VADs) are implanted in patients with end-stage heart failure to provide both short- and long-term hemodynamic support. Unfortunately, bleeding and thromboembolic complications due to the severely disturbed, dynamic flow conditions generated within these devices require complex, long-term antiplatelet and anticoagulant therapy. While several studies have examined the effectiveness of one such agent, aspirin, under flow conditions, data comparing the efficacy of in vitro and in vivo metabolized aspirin is lacking. Two sets of studies were conducted in vitro with purified human platelets circulating for 30 min in a flow loop containing the DeBakey VAD (MicroMed Cardiovascular, Houston, TX, USA): (a) 20 μM aspirin was added exogenously in vitro to platelets isolated from aspirin-free subjects, and (b) platelets were obtained from donors 2 h (n = 14) and 20 h (n = 13) after ingestion of 1,000 mg aspirin. Near real-time platelet activation state (PAS) was measured with a modified prothrombinase-based assay. Platelets exposed to aspirin in vitro and in vivo (metabolized) showed 28.2 and 25.3 % reduction in platelet activation rate, respectively, compared to untreated controls. Our results demonstrate that in vitro treatment with antiplatelet drugs such as aspirin is as effective as in vivo metabolized aspirin in testing the effect of reducing shear-induced platelet activation in the VAD. Using the PAS assay provides a practical in vitro alternative to in vivo testing of antiplatelet efficacy, as well as for testing the thrombogenic performance of devices during their research and development.

Pneumatic tube transport affects platelet function measured by multiplate electrode aggregometry

Multiple electrode aggregometry (MEA) is used to measure platelet function. Pneumatic tube transport systems (PTS) for delivery of patient samples to a central laboratory are often used to reduce turnaround time for vital analyses. We evaluated the effects of PTS transport on platelet function as measured by MEA. Duplicate samples were collected from 58 individuals. One sample was sent using PTS and the other was carried by personnel to the lab. Platelet function was measured by means of a Multiplate® analyzer using the ADP test, ASPI test, COL test, RISTO test and TRAP test. Samples transported using PTS showed a reduction of AUC-values of up to a 100% of the average as compared to samples carried by personnel and a majority showed reductions of AUC-values greater than 20% of the average. Bias±95% limits of agreement for the ADP test were 26±56% of the average. Bias±95% limits of agreement for the ASPI test were 16±58% of the average. Bias±95% limits of agreement for the COL test were 20±54% of the average. Bias±95% limits of agreement for the RISTO were 14±79% of the average. Bias±95% limits of agreement for the TRAP test were 19±45% of the average. We conclude that PTS transport affect platelet activity as measured by MEA. We advise against clinical decisions regarding platelet function on the basis of samples sent by PTS in our hospital settings.