Effect of 6% hydroxyethyl starch 130/0.4 on kidney and haemostatic function in cardiac surgical patients: a randomised controlled trial.

Whether third-generation hydroxyethyl starch solutions provoke kidney injury or haemostatic abnormalities in patients having cardiac surgery remains unclear. We tested the hypotheses that intra-operative administration of a third-generation starch does not worsen postoperative kidney function or haemostasis in cardiac surgical patients compared with human albumin 5%. This triple-blind, non-inferiority, clinical trial randomly allocated patients aged 40-85 who underwent elective aortic valve replacement, with or without coronary artery bypass grafting, to plasma volume replacement with 6% starch 130/0.4 vs. 5% human albumin. Our primary outcome was postoperative urinary neutrophil gelatinase-associated lipocalin concentrations, a sensitive and early marker of postoperative kidney injury. Secondarily, we evaluated urinary interleukin-18; acute kidney injury using creatinine RIFLE criteria, coagulation measures, platelet count and function. Non-inferiority (delta 15%) was assessed with correction for multiple comparisons. We enrolled 141 patients (69 starch, 72 albumin) as planned. Results of the primary analysis demonstrated that postoperative urine neutrophil gelatinase-associated lipocalin (median (IQR [range])) was slightly lower with hydroxyethyl starch (5 (1-68 [0-996]) ng.ml-1 ) vs. albumin (5 (2-74 [0-1604]) ng.ml-1 ), although not non-inferior [ratio of geometric means (95%CI) 0.91 (0.57, 1.44); p = 0.15] due to higher than expected variability. Urine interleukin-18 concentrations were reduced, but interleukin-18 and kidney injury were again not non-inferior. Of 11 individual coagulation measures, platelet count and function, nine were non-inferior to albumin. Two remaining measures, thromboelastographic R value and arachidonic acid-induced platelet aggregation, were clinically similar but with wide confidence intervals. Starch administration during cardiac surgery produced similar observed effects on postoperative kidney function, coagulation, platelet count and platelet function compared with albumin, though greater than expected variability and wide confidence intervals precluded the conclusion of non-inferiority. Long-term mortality and kidney function appeared similar between starch and albumin.

Diagnostic approach to microangiopathic hemolytic disorders.

Thrombotic micro-angiopathies (TMA) are a group of related disorders that are characterized by thrombosis of the microvasculature and associated organ dysfunction, and encompass congenital, acquired, and infectious etiologies. A hall mark of TMAs is the fragmentation of erythrocytes by the microvascular thrombi, resulting in a hemolytic anemia. There are several distinct pathophysiologies leading to microangiopathic hemolysis, ranging from decreased degradation of von Willebrand factor as seen in thrombotic thrombocytopenic purpura (TTP) to endothelial damage facilitated by Escherichia coli shiga toxin or complement dysregulation, seen in shiga toxin-related hemolytic-uremic syndrome (Stx-HUS) and complement-mediated TMA (also called atypical hemolytic-uremic syndrome), respectively. Distinguishing these disorders is important, as many TMAs are life-threatening, the treatments are distinct and selecting appropriate therapy can improve patient prognosis. Laboratory testing, including measurement of ADAMTS13, ADAMTS13 inhibitor, shiga toxin, and complement factors, can help establish diagnoses and guide therapy.

Validation of a panel of ADAMTS13 assays for diagnosis of thrombotic thrombocytopenic purpura: activity, functional inhibitor, and autoantibody test.

INTRODUCTION: Quantitation of ADAMTS13 activity, functional inhibitors, and autoantibodies is crucial in diagnosis and management of thrombotic thrombocytopenic purpura. We compared and optimized commercial assay kits and validated a testing panel. METHODS: Citrated plasma specimens from healthy volunteers and residual samples submitted for clinical testing were used in the study. Commercially available ADAMTS13 activity assays including ACTIFLUOR(™) ADAMTS13 (Sekisui Diagnostics, Stamford, CT, USA), LIFECODES ATS-13 (Gen-Probe Inc., San Diego, CA, USA), and TECHNOZYM(®) ADAMTS-13 (Technoclone, Vienna, Austria) were evaluated. Functional inhibitor assays were performed using internally developed mixing protocols. Two autoantibody assays were also evaluated: IMUBIND(®) (Sekisui Diagnostics) and TECHNOZYM(®) ADAMTS-13 INH ELISA kits (Technoclone). RESULTS: A laboratory-developed assay using ACTIFLUOR(™) reagents showed best agreement with the reference method, and full validation showed a reportable range of 5% (LLOQ) to 114% with a reference interval of ≥68%. Both intra- and interassay coefficients of variation were <10%. Inhibitor assays performed with the kits showed 95% overall agreement with the reference method. A modification of the TECHNOZYM(®) autoantibody assay showed 85% overall agreement with the reference method with imprecision approximately 20%. CONCLUSION: ADAMTS13 activity and inhibitor tests using ACTIFLUOR(™) reagents and modified TECHNOZYM(®) autoantibody ELISA showed superior performance compared to the other kits for clinical use in this study.

P2RY1 and P2RY12 polymorphisms and on-aspirin platelet reactivity in patients with coronary artery disease.

INTRODUCTION: Association of P2RY1 and P2RY12 polymorphisms with on-aspirin platelet reactivity was investigated. MATERIALS AND METHODS: Platelet reactivity was assessed by the light transmission aggregometry and TxB(2) assay in 423 patients with coronary artery disease (CAD) on aspirin. High residual platelet reactivity (RPR) was defined by ≥20% and ≥70% maximal aggregation stimulated with 0.5 mg/mL arachidonic acid (AA) and 10 µm ADP, respectively. Moderate RPR was considered aggregation ≥20% with AA, ≥70% with ADP, or ≥1 ng/mL stimulated TxB(2) . Fourteen P2RY1 and 35 P2RY12 single nucleotide polymorphisms (SNPs) were genotyped. RESULTS: High RPR was detected in 24% of the patients. Moderate RPR was observed in 31% with AA, 57% with 5 µm ADP, and 82% with 10 µm ADP. Stimulated TxB(2) was ≥1 ng/mL in 23% of patients. P2RY12 SNP rs9859538 was associated with high RPR (OR = 2.16, 95% CI = 1.24-3.75, P-value = 0.004). Four P2RY12 SNPs, rs1491974, rs10513398, rs3732765, and rs10935841, showed association with moderate RPR (OR = 1.79-2.94, P-value = 0.04-0.028), while five, rs7615865, rs1388623, rs1388622, rs7634096, and rs7637803, were associated with low RPR (OR = 0.50-0.55, P-value = 0.008-0.026), following ADP stimulation. TxB(2) level <1 ng/mL was linked to five P2RY1 SNPs, rs1439010, rs1371097, rs701265, rs12497578, and rs2312265 (OR = 0.36-0.54, P-value = 0.003-0.039). CONCLUSIONS: Polymorphisms in P2RY1 and P2RY12 are associated with on-aspirin platelet reactivity in patients with CAD.

Glycocalyx-mimetic dextran-modified poly(vinyl amine) surfactant coating reduces platelet adhesion on medical-grade polycarbonate surface.

A dextran-modified poly(vinyl amine) comb-like surfactant polymer, poly(N-vinyl dextran aldonamide-co-N-vinyl hexanamide), that can surface-adsorb on hydrophobic polymeric substrates, was designed to improve the interfacial blood-compatibility of polymeric biomaterials. Medical-grade polycarbonate was selected as a model substrate because of its extensive use in blood-contacting biomedical devices like hemodialyzers, blood pumps and oxygenators. The surfactant polymer was physisorbed from aqueous solution onto the polycarbonate substrate. The surfactant coating was stable under dynamic shear conditions in whole blood, as confirmed by fluorescence microscopy and total internal reflection fluorescence (TIRF) experiments with fluorescein-labeled surfactant polymer. The coated disks and uncoated control disks were exposed to platelet-rich plasma (PRP) and whole human blood in a rotating disk system (RDS) to study platelet-adhesion under dynamic shear stress environments. Adhered platelets were stained with fluorescein isothiocyante (FITC)-tagged anti-CD41a monoclonal antibody and imaged by epifluorescence microscopy. Complimentary images were obtained by phase-contrast microscopy. Platelet adhesion on the surfactant-coated disks was reduced by approximately 90%, compared with uncoated disks. The images also showed a concomitant reduction in platelet-derived microparticles on surfactant-coated disks, compared with uncoated disks. The results suggest potential application of carbohydrate-modified surfactant polymers as a glycocalyx-mimetic non-thrombogenic interfacial coating for blood-contacting biomaterials.

Effect of hirudin vs heparin on haemostatic activity in patients with acute coronary syndromes; the GUSTO-IIb haemostasis substudy.

AIMS: We compared the effects of hirudin and heparin on thrombin generation and activity among 350 patients with acute coronary syndromes enrolled in the GUSTO-IIb trial. METHODS AND RESULTS: We obtained blood at baseline; at 4, 8, and 24h into infusion; at drug termination; and 6 and 24h after termination. We assayed for thrombin activity (fibrinopeptide A, activated protein C, thrombin-antithrombin complex), thrombin generation (prothrombin fragment 1.2), and platelet activation (platelet factor 4). Median baseline fibrinopeptide A and platelet factor 4 levels were elevated. Thrombin formation tended to increase with hirudin and decrease with heparin; by 8h into infusion, thrombin formation was significantly less for heparin (P<0.01). Most patients showed reduced thrombin activity and platelet activation during infusion of either agent. Hirudin-assigned patients had significantly lower fibrinopeptide A levels during infusion. Six h post-termination, both groups had increased thrombin activity. Thrombin formation was increased in heparin patients (P<0.0001), significantly more than with hirudin (P=0.005). Higher values of haemostasis markers tended to be associated with poorer 30-day outcomes. CONCLUSION: Although hirudin did not prevent generation of new thrombin, it appeared to inhibit thrombin activity more than did heparin and produced slower increases in thrombin formation after discontinuation. The reelevation of thrombotic markers after stopping intravenous antithrombin therapy and the tendency toward increased thrombotic events with post-treatment increases in marker levels suggest an ongoing, clinically significant prothrombotic state. These results raise the possibility of improving on current antithrombotics by preventing thrombin generation and thrombin activity and by sustained suppression of the prothrombotic state.

The platelet function dose-response to abciximab during percutaneous coronary revascularization is variable.

The platelet function dose-response to incremental abciximab (Reopro, Eli Lilly/Centocor, Indianapolis, IN) bolus dosing during percutaneous coronary intervention (PCI) was evaluated in 85 patients using a point-of-service platelet function assay. Patients received incremental bolus doses of abciximab at 10- to 20-min intervals; platelet function was measured at 10-min intervals during dosing. The percentage of patients achieving > or = 80% inhibition of platelet function after 50%, 75%, and 100% of a standard abciximab bolus was 40%, 87%, and 95%, respectively. There were no significant associations between the platelet function dose-response to abciximab and age, weight, platelet count, hematocrit, heparin dose, peak activated clotting time, thienopyridine use prior to PCI, gender, cigarette smoking, diabetes mellitus, or clinical syndrome. This study demonstrated significant interpatient variability in platelet function dose-response to abciximab with a substantial proportion (87%) of patients achieving high-level platelet function inhibition with less than the standard abciximab bolus dose.

Single nucleotide polymorphisms in multiple novel thrombospondin genes may be associated with familial premature myocardial infarction.

BACKGROUND: Recent advances in high-throughput genomics technology have expanded our ability to catalogue allelic variants in large sets of candidate genes related to premature coronary artery disease. METHODS AND RESULTS: A total of 398 families were identified in 15 participating medical centers; they fulfilled the criteria of myocardial infarction, revascularization, or a significant coronary artery lesion diagnosed before 45 years in men or 50 years in women. A total of 62 vascular biology genes and 72 single-nucleotide polymorphisms were assessed. Previously undescribed variants in 3 related members of the thrombospondin protein family were prominent among a small set of single-nucleotide polymorphisms that showed a statistical association with premature coronary artery disease. A missense variant of thrombospondin 4 (A387P) showed the strongest association, with an adjusted odds ratio for myocardial infarction of 1.89 (P=0.002 adjusted for covariates) for individuals carrying the P allele. A variant in the 3' untranslated region of thrombospondin-2 (change of thymidine to guanine) seemed to have a protective effect against myocardial in individuals homozygous for the variant (adjusted odds ratio of 0.31; P=0.0018). A missense variant in thrombospondin-1 (N700S) was associated with an adjusted odds ratio for coronary artery disease of 11.90 (P=0.041) in homozygous individuals, who also had the lowest level of thrombospondin-1 by plasma assay (P=0.0019). CONCLUSIONS: This large-scale genetic study has identified the potential of multiple novel variants in the thrombospondin gene family to be associated with familial premature myocardial infarction. Notwithstanding multiple caveats, thrombospondins specifically and high-throughput genomic technology in general deserve further study in familial ischemic heart disease.

Shear-induced platelet activation and adhesion on human pulmonary artery endothelial cells seeded onto hydrophilic polymers.

We evaluated platelet activation and adhesion on two plasma polymerized surfaces, N-vinyl pyrrolidone (NVP) and gamma-butyro lactone (GBL), which have been shown previously to promote endothelial cell growth and adhesion as well as fibronectin-coated glass (1 microg/cm(2)) coverslips. Human pulmonary artery endothelial cells were seeded onto coverslips at a low density ( approximately 20,000 cells/cm(2)) and grown to confluence (3-5 days). The materials, both with and without ECs, were then exposed to a shear rate of 400 s(-1) in a closed loop recirculating flow system containing human platelet-rich plasma. Plasma samples were taken at 0, 5, 15, 30, and 60 min and analyzed for platelet and coagulation activation. The coverslips were examined for EC coverage and platelet adherence. EC retention over a 1-h period was approximately 75% for all three materials. All three materials without ECs were highly platelet activating having similar P-selectin expression, platelet factor 4 (PF4) release, mepacrine uptake, and microparticle production. Both microparticle production and platelet adhesion were significantly lower in EC-seeded materials. Dense granule and PF4 release were both slightly diminished in all three materials seeded with ECs. P-selectin expression was reduced slightly for GBL, but remained the same for the other two materials. The EC-seeded materials displayed favorable characteristics with respect to platelet activation and adhesion; however, they still demonstrated some thrombogenic tendencies due to EC loss and exposure of the underlying substrate. Therefore, both EC coverage and EC hemostatic function are important factors in determining the thromboresistance of an EC-seeded surface.

Phase I trial of simultaneously administered GM-CSF and IL-6 in patients with renal-cell carcinoma: clinical and laboratory effects.

BACKGROUND: Metastatic renal-cell carcinoma is a neoplasm that is minimally responsive to cytotoxic chemotherapy. Tumor regression following therapy with cytokines such as interferon alpha and or interleukin-2 is seen in selected subsets of patients. Investigations with other immunomodulatory cytokines, such as GM-CSF and IL-6 are therefore of interest. PATIENTS AND METHODS: A phase I trial of concomitantly administered granulocyte macrophage-colony stimulating factor (3.0 mcg/kg/day s.c. d1-14) and escalating doses of interleukin-6 (1.0, 5.0 or 10.0 microg/kg/day d1-14) was conducted in patients with metastatic renal-cell carcinoma to explore the toxicity of the combination and its hematologic effects. RESULTS: The most common side effects seen were fever, fatigue and arthralgias. Dose limiting toxicity included thrombocytosis and hyperbilirubinemia in patients receiving 10 microg/kg/day of IL-6. The hematologic effects of IL-6 and GM-CSF included leukocytoses and thrombocytosis, with increases in peripheral blood progenitors (BFU-E, CFU-GM, and CFU-GEMM). Evidence of platelet activation demonstrated by increased platelet expression of CD62 was found. No clinical responses were observed. CONCLUSIONS: The combination of IL-6 and GM-CSF has pleotropic hematologic effects. Further studies with this combination for the treatment of renal-cell carcinoma are not recommended.

Profile and prevalence of aspirin resistance in patients with cardiovascular disease.

We determined the prevalence and clinical predictors of aspirin resistance by prospectively studying 325 patients with stable cardiovascular disease who were receiving aspirin (325 mg/day for > or =7 days) but no other antiplatelet agents. We also compared the detection of aspirin resistance with optical platelet aggregation, a widely accepted method, with a newer, more rapid method, the platelet function analyzer (PFA)-100, a whole blood test that measures platelet adhesion and aggregation ex vivo. Blood samples were analyzed in a blinded fashion for aspirin resistance by optical aggregation using adenosine diphosphate (ADP) and arachidonic acid, and by PFA-100 using collagen and/or epinephrine and collagen and/or ADP cartridges to measure aperture closure time. Aspirin resistance was defined as a mean aggregation of > or =70% with 10 microM ADP and a mean aggregation of > or =20% with 0.5 mg/ml arachidonic acid. Aspirin semiresponders were defined as meeting one, but not both of the above criteria. Aspirin resistance by PFA-100 was defined as having a normal collagen and/or epinephrine closure time (< or =193 seconds). By optical aggregation, 5.5% of the patients were aspirin resistant and 23.8% were aspirin semiresponders. By PFA-100, 9.5% of patients were aspirin resistant. Of the 18 patients who were aspirin resistant by aggregation, 4 were also aspirin resistant by PFA-100. Patients who were either aspirin resistant or aspirin semiresponders were more likely to be women (34.4% vs 17.3%, p = 0.001) and less likely to be smokers (0% vs 8.3%, p = 0.004) compared with aspirin-sensitive patients. There was a trend toward increased age in patients with aspirin resistance or aspirin semiresponders (65.7 vs 61.3 years, p = 0.06). There were no differences in aspirin sensitivity by race, diabetes, platelet count, renal disease, or liver disease.

Surface dependent structures of von Willebrand factor observed by AFM under aqueous conditions.

von Willebrand factor (VWF) is a large multimeric plasma glycoprotein that adheres rapidly to biomaterial surfaces upon exposure to blood. The adsorbed structure influences subsequent functional interactions with other blood components that mediate surface induced thrombosis. To examine the surface-dependent properties of VWF, we compared the adsorbed structures of VWF molecules on two different surfaces: Mica, which is hydrophilic; and octadecyltrichlorosilane (OTS) modified glass, which is hydrophobic. Atomic force microscopy (AFM) was used to image adsorbed VWF under aqueous conditions at physiologic pH and ionic strength. Individual VWF molecules were clearly discernible on both surfaces. On the hydrophobic surface, VWF displayed compact tertiary structures with rare examples of extended molecules. In addition, these data revealed intramolecular structural arrangements of the repeat units within VWF multimers. On the hydrophilic mica surface, VWF displayed extended structures in which intramolecular repeat units were exposed. The lateral dimensions of VWF on mica (640+/-161x303+/-113 nm) were larger than on the hydrophobic OTS (256+/-74x152+/-62 nm, P<0.005). Our results demonstrate how surface properties mediate the molecular level structure and probable function of VWF, and provide some essential groundwork to develop a mechanistic understanding of surface-induced thrombosis.

Determining intramolecular binding sites on surface-bound von Willebrand factor under aqueous conditions.

The results described in this report demonstrate the feasibility of using AFM in combination with immuno-gold labeling to investigate the accessibility of various binding sites on vWF and to localize the binding site within a vWF multimer. With the aid of monoclonal antibodies [5, 11 and 23] it should be possible to use this approach to perform a quantitative assessment of the differential accessibility of various binding sites on vWF. This should allow localization and quantification of binding sites within the observed tertiary structure of the vWF, providing a measure of the accessibility, a point of reference with which the tertiary structure of vWF could be correlated to the primary sequence, and a means to determine the structural features of the antibody binding regions under physiologic buffer conditions. There are a number of obvious questions that are not addressed here: The role of different biologic and artificial surfaces; time-dependent effects; vWF orientation with respect to different thrombogenic surfaces; and the location of critical binding sites, such as for platelet GPIalpha and GPIIb-IIIa binding regions in the hydrated tertiary structure of vWF. Nevertheless, the work described in this report provides essential groundwork that should provide a novel basis on which to explore the molecular steps, both structural and functional, of vWF in thrombus development. In a wider sense, this experimental approach is applicable to structure-function studies on a wide variety of proteins in physiologic environments.

Endothelial cell expression of monocyte chemotactic protein-1, tissue factor, and thrombomodulin on hydrophilic plasma polymers.

Endothelial cells (EC) from human aortas, microvessels, and pulmonary arteries were examined for their expression and activity of monocyte chemotactic protein-1 (MCP-1), tissue factor, and thrombomodulin in response to tumor necrosis factor-alpha (TNFalpha) on the hydrophilic plasma polymers gamma-butyrolactone (GBL) and N-vinyl-2-pyrrolidone (NVP), along with a fibronectin (FN) control. RNAs isolated from EC grown on these substrates were subjected to reverse transcription-polymerase chain reaction (RT-PCR) and dot-blot analysis. EC expression of MCP-1 and tissue factor was very low in the absence of TNFalpha but high for constitutively expressed thrombomodulin. TNFalpha induced EC expression and activity of MCP-1 and tissue factor and suppressed that of thrombomodulin on all substrates. Greater differences were seen with regard to cell origin, but little difference was seen among substrates. Basal secretion of MCP-1 was very low in aortic and pulmonary artery EC and even less in microvascular EC. TNFalpha increased MCP-1 secretion significantly in aortic and pulmonary artery EC but to a lesser extent in microvascular EC. In contrast, tissue factor expression was greater in pulmonary artery EC compared to microvascular and aortic EC. Basal expression of thrombomodulin was largely comparable for all three cell types grown on different surfaces, but TNFalpha suppressed thrombomodulin to different extents depending on the origin of the EC. The activity of tissue factor and thrombomodulin and the secretion of MCP-1 by EC were largely correlated with the expression of these genes. We conclude that EC origin may be an important determinant of cellular function on hydrophilic plasma polymer substrates. However, the differences in cellular function due to variations in substrate surface hydrophilicity could have been masked by the extracellular matrix remodeling that presumably occurred during EC growth to confluence.

Attainment and maintenance of platelet inhibition through standard dosing of abciximab in diabetic and nondiabetic patients undergoing percutaneous coronary intervention.

BACKGROUND: Although the effectiveness of abciximab (c7E3 Fab; ReoPro) in large populations of patients undergoing a percutaneous coronary intervention has been consistently proved in clinical trials, it is unknown whether all patients achieve and maintain target inhibition during treatment. Diabetic patients in particular are a subgroup of patients with known underlying platelet abnormalities whose long-term response to abciximab has been shown to vary from that of nondiabetic patients. METHODS AND RESULTS: Forty-nine diabetic and 51 nondiabetic patients who received adjunctive abciximab therapy during percutaneous coronary interventions were evaluated prospectively. The degree of platelet function inhibition was determined immediately after the abciximab bolus, 8 hours after the bolus (during the 12-hour abciximab infusion), and the next morning (13 to 26 hours after the bolus) with the use of a rapid platelet function assay (Accumetrics). After the abciximab bolus, platelet function was inhibited by 95+/-4% (mean+/-SD). By 8 hours, the average percent inhibition had decreased to 88+/-9%, with 13% of patients with <80% inhibition. The next morning (mean 19 hours after the bolus), mean inhibition was 71+/-14%. A difference was not found between diabetics and nondiabetics, nor was any physiological parameter found to be predictive of the response to abciximab. CONCLUSIONS: Although the majority of patients achieve and maintain >/= 80% platelet inhibition during the 12-hour infusion with standard-dose abciximab, there is substantial variability among patients. Diabetic status does not appear to influence this variability.

Platelet-derived microparticles on synthetic surfaces observed by atomic force microscopy and fluorescence microscopy.

Platelet activation on a thrombogenic surface includes the release of membrane-derived microparticles that provide catalytic sites for blood coagulation factors. Here, we describe a quantitative investigation on the production and dimensions of platelet-derived microparticles observed on glass and polyethylene under aqueous conditions, using atomic force microscopy (AFM) and complementary fluorescence microscopy. The results show that contact-activated platelet microparticles are not evenly distributed over a thrombogenic surface, but in clusters in close proximity to adherent platelets. The microparticles are localized near the platelet periphery, and in some cases appear to emanate from platelet pseudopodia, suggesting that formation may result from vesiculation of the pseudopodia. The microparticles measured 125 +/- 21 nm (n = 73) in the x-y dimensions and 5.2 +/- 3.6 nm in height. The results compared closely with 125 +/- 22 nm width and 4.1 +/- 1.6 nm height obtained for control preparations of thrombin activated microparticles, that were filtered and deposited on glass. Large differences between the measured widths and heights of adsorbed microparticles suggest that platelet microparticles may undergo spreading after attachment to a surface. The adsorbed microparticles expressed platelet membrane receptor GPIIb/IIIa, and many expressed the platelet activation marker P-selectin as determined by fluorescence microscopy. The high number distribution of procoagulant microparticles per unit area of surface compared with platelets suggests that platelet-derived microparticles provide a mechanistic route for amplifying thrombus formation on a thrombogenic surface.

Vitamin K reduces bleeding in left ventricular assist device recipients.

BACKGROUND: Despite advances in left ventricular assist device (LVAD) design that permit support without anticoagulation, LVAD recipients often suffer profound bleeding complications. This bleeding diathesis may be attributable to pre-operative right-ventricular failure with concomitant hepatic dysfunction. The purpose of this study was to characterize coagulation abnormalities in LVAD recipients and determine the impact of pre-operative vitamin K administration on the incidence of postoperative bleeding. METHODS: Hemostatic and liver function profiles were obtained in 66 recipients of the Heartmate LVAD; 39 of these patients received perioperative vitamin K. RESULTS: During LVAD support, hepatic synthetic function improved as evidenced by increases in clotting factors II, V, VII, XI. There was ongoing fibrinolysis with elevation of fibrinopeptide A and D-dimers and diminution of fibrinogen; however, plasminogen levels did not decline suggesting that systemic disseminated intravascular coagulation (DIC) did not occur. Bleeding requiring re-exploration more than 48 hours postimplantation occurred in 9 of 66 patients (13.6%). Prior to implantation, patients that bled had decreased levels of factor II (52.2 +/- 27.1% vs 69.7 +/- 26.6%; p = 0.048) and prolonged prothrombin times (16.5 +/- 2.4 seconds vs 13.8 +/- 3.1 seconds; p = 0.005) compared to patients that did not bleed. Seven of 27 patients (25.9%) not treated with vitamin K bled, while only 2 of 39 (5.1%) patients treated with vitamin K required re-exploration for bleeding (p = 0.026). CONCLUSIONS: We conclude that: (1) Liver synthetic function improves during LVAD support resulting in increased levels of circulating coagulation factors; (2) ongoing fibrinolysis occurs but likely only represents remodeling of fibrin on the LVAD surface; (3) perioperative vitamin K reduces nonsurgical bleeding in LVAD recipients.

The effect of antiplatelet drugs, heparin, and preanalytical variables on platelet function detected by the platelet function analyzer (PFA-100).

The platelet function analyzer (PFA)-100 is a newly developed instrument that provides a rapid, in vitro, quantitative measurement of platelet adhesion and aggregation in whole blood flowing through a small aperture under high shear conditions. Thirty patients undergoing percutaneous transluminal coronary angioplasty (PTCA) and ten normal individuals were included in this study. In vitro and in vivo studies were conducted to discern the effect of combinations of antiplatelet drugs (aspirin, ticlopidine, abciximab) and heparin on the performance of the device as well as the effects of preanalytical variables, such as method of sample collection and ex vivo anticoagulants. Studies were also conducted examining the effect of aperture size (standard 150 microns vs. smaller 120 microns) on the ability of the device to detect the effect of antiplatelet drugs. There was no difference in mean PFA-100 closure time with citrate versus PPACK anticoagulants or with venipuncture vs. sheath sampling. Closure times did not vary with heparin administration. Closure times were slightly longer for patients taking aspirin plus ticlopidine compared to aspirin alone (p = NS). In contrast adenosine disphosphate (ADP) induced platelet aggregation was significantly less in patients that took aspirin plus ticlopidine vs. aspirin alone (p = .0005). In vitro, there was a dose-dependent increase in closure time for both aperture sizes with increasing abciximab concentration. Although both cartridges showed infinite closure times at an abciximab concentration of 2.25 micrograms/mL, there was a slight benefit to using the 120 microns aperture cartridges at abciximab concentrations of 1.75 to 2.0 micrograms/mL. In ten patients who were followed during abciximab therapy to assess the effect of aperture size, the PFA-100 was able to detect in vivo platelet inhibition by abciximab, but detection of recovery from abciximab-induced platelet dysfunction was slightly better for the PFA-100 with the 120 microns aperture compared to the standard 150 microns aperture collagen/ADP cartridge.