Platelet Function Analyzer Research Articles

Comparison of the effects of a balanced crystalloid-based and a saline-based tetrastarch solution on canine whole blood coagulation and platelet function.

To evaluate the effects of a 6% hydroxyethyl starch (130/0.42) solution in either a buffered, electrolyte-balanced (HES-BAL), or a saline (HES-SAL) carrier solution on canine platelet function and whole blood coagulation. Prospective, randomized study. University teaching hospital. Thirty-seven client-owned dogs undergoing general anesthesia for arthroscopy or imaging studies. Dogs received a 15 mL/kg intravenous bolus of HES-SAL (n = 13), HES-BAL (n = 14), or a modified Ringer's solution (n = 10) over 30-40 minutes. Coagulation was analyzed using a Platelet Function Analyzer-100 (closure time [CtPFA ]), and whole blood thromboelastometry (ROTEM) with extrinsically (ex-tem and fib-tem) and intrinsically (in-tem) activated assays, which assessed clotting time (CT), clot formation time (CFT), maximal clot firmness (MCF), and lysis index (LI). Coagulation samples were assayed prior to fluid administration (T0), and 5 minutes (T1), and 3 hours (T2) following fluid bolus administration, respectively. Both HES solutions resulted in impaired platelet function as indicated by a significant prolongation of CtPFA at T1 as compared to T0, but which resolved by T2. An IV bolus of Ringer's solution did not alter platelet function. In both HES groups, whole blood coagulation was significantly impaired at T1 as indicated by a significant increase in in-tem CFT, and a significant decrease in ex-tem, in-tem, and fib-tem MCF compared to T0. Furthermore, a significant increase in ex-tem CFT at T1 compared to T0 was found in the HES-SAL group. With the exception of in-tem MCF after HES-BAL, these effects were not present at T2. No significant differences were found in CtPFA or any ROTEM variable at any time point between HES-SAL and HES-BAL. Administration of a single bolus of 15 mL/kg 6% HES 130/0.42 results in significant but short-lived impairment of canine platelet function and whole blood coagulation, regardless of carrier solution.

Dynamics of Hemorragic Events and Primary Hemostasis Deffects during Treatment with Ibrutinib. Real-Life Experience

INTRODUCTIONIbrutinib is a first-in-class Bruton kinase inhibitor (BTK) registered for the treatment of Chronic Lymphocytic Leukemia (CLL), mantle cell linphoma (MCL) and Waldenström Macroglobulinemia (WM).Increased risk of bleeding events is asociated with ibrutinib, mostly grade ≤2. Alleged mechanism for this risk could be the role of BTK in platelet activation via GPIb, GPVI and FVW.We here present our experience regarding hemorragic events and hemostasis tests alterations in CLL patients (pts) treated with ibrutinib. PATIENTS AND METHODS15 pts with relapsed CLL were started on ibrutinib between december/2012 and july/2016. Median age was 69 years (range: 42-83 years). 12 of them were male. Median exposure to the drug was 17 month (range 1- 38).After 9 to 36 months from initiation of treatment (median 22 months) 6/15 were thouroughly interviewed about personal history of bleeding events and the following laboratory work was performed: factor VIII level, FVW antigen and activity, platelet function analysis (PFA-100TM) with ADP and epinephrine, and aggregation studies with colagen, ADP and arachidonic acid. Along these tests all patients had blood counts with platelets more than 100 x 10e9/L. RESULTS3 out of 15 pts had bleeding events (grade 1 or 2), 2 consisting in spontaneus bruising and 1 in upper grastrointestinal bleeding, in the first weeks of treatment. 4 pts underwent minor invasive procedures with no complications, witholding the drug at least 3 days before and after. 2 pts were on concomitant antiplatelet (1) or anticoagulant (1, LMWH, due to AF) and had no bleeding events.All pts tested (6/6) had normal or slightly elevated leves of F VIII, FVW:Ag and FVW:Ac. 2 pts had abnormal PFA-100TM and abnormal aggregations with any agonist. One case had normal PFA-100TM while aggregations with colagen and AA were mildly altered. COMMENTSOur limited experience shows a moderate risk of minor bleedings consisting with a platelet disfunction drug-driven effect. Despite the fact that we have no baseline tests done, alterations in primary hemostasis test, including PFA-100TM and specially aggregometry could be expected early on after exposure to ibrutinib. DisclosuresLoscertales:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Speakers Bureau. Alegre:Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees.

Aspirin-Platelet Sensitivity in Patients with Polycythemia Vera and Human Platelet Antigen Genotype: Which Are Assays Valid?

Polycythemia vera (PV) is a myeloid neoplasm characterized by thrombotic risk related to high hematocrit (HCT) and to platelet hyperactivation. According to PVSG, the antithrombotic therapy include low dose aspirin (ASA). However, there are insensitive ASA PV patients. It is debated if enherited thrombophilia is responsible to affect platelet activation and, hence, to cause ASA insensitivity. Therefore, we evaluated gene polymorphism human platelet antigen-1 (HPA-1) as thrombophilic indicator associated with abnormal platelet activity, HCT, platelet count, b-TG and PF4, as markers of platelet activation, the platelet functional activity (PFA) and the maximum clot firmness (MCF), as direct and indirect indicators of ASA sensitivity. We studied 40 patients (28 men, 12 women; mean age 64 years, range 35-85 years) with PV according to WHO criteria. Fifty subjects served as controls. The mean duration of disease was 9 years. All patients were on phlebotomy and ASA (100 mg once daily). Platelets and HCT were measured by automated analyzer. b-TG and PF4 were determined by ELISA. PFA and MCF were measured by Platelet Function Analyzer (PFA-100) and by ROTEM delta. Of 40 patients, 24 were homozygous HPA-1a/a and 16 heterozigous HPA-1a/b. The mean HCT value was 47±3% and platelets were 428±180x109/L. All patients had high b-TG and PF4 (113±47 IU/ml vs 20±11 IU/ml and 45±21 IU/ml vs 6±2 IU/ml, respectively), prolonged C/EPI closure time (CT, unit: s, n.v. 84-160 s) (233±65 s) and normal MCF (MCF, unit: mm, n.v. 50-72 mm) (65±5 mm). These findings suggest that PFA-100 and Thromboelastometric assays may be an useful tool to detect ASA platelet sensitivity in PV patients. DisclosuresNo relevant conflicts of interest to declare.

Coagulation Abnormalities and Hemostatic Surgical Outcomes in 142 Patients with Noonan Syndrome

Background: Noonan syndrome, characterized by dysmorphic facies, webbed neck, short stature, chest deformity, developmental delay and congenital heart defects, occurs as a result of mutations affecting the RAS-MAPK signaling pathway. A wide range of coagulation abnormalities are observed in these patients including: thrombocytopenia, platelet dysfunction and coagulation factor deficiencies. Screening for coagulation defects is recommended in childhood and especially prior to surgical procedures. Data available is limited and the extent of the hemostatic evaluation needed is not clearly defined. We carried out this study to outline the spectrum of coagulation abnormalities seen in patients with Noonan syndrome and their impact on surgical outcomes.Methods: In this retrospective cohort study, the electronic medical record system was queried for patients with Noonan syndrome seen at Mayo Clinic between 2000 and 2016. A detailed chart review was undertaken.Resultsi) Phenotypic correlates: 142 patients (58% male) met our study criteria, median age 21 years (range 14 days to 68 years). The referral specialty for initial evaluation was: cardiology 69 (49%), endocrinology 10 (7%), urology 10 (7%), neurology 8 (6%), pulmonary 6 (4%), orthopedic surgery 3 (2%), gastroenterology 2 (1%), psychiatry 2 (1%) and other specialties 4 (3%). Ten patients (7%) were referred for developmental delay, 13 (9%) for dysmorphism and 4 (3%) after having a family member diagnosed with Noonan syndrome. One patient (1%) presented with hematochezia. Twenty-seven (52%) of the 52 patients screened with genetic testing had a Noonan-associated gene defect. Bleeding was reported by 22 patients (15%) with a median International Society on Thrombosis and Haemostasis Bleeding Assessment Tool (ISTH-BAT) score of 2 (range 1-8). Of those tested, 11/121 (9%) patients had thrombocytopenia (platelets < 150 x 10^9/L). Screening coagulation tests were done in 58 (41%) patients, and included PT/aPTT in 43 (74%) and extended coagulation panels (including platelet function studies) in 15 (26%). Of the 22 patients with history of bleeding, 20 (90%) had screening coagulation testing. Twenty-two (38%) of patients screened had one or more coagulation laboratory abnormality. Ten (66%) patients with clinically suspected platelet dysfunction had normal platelet function analyzer (PFA)-100 testing and normal light transmission aggregometry, while 5 (33%) had decreased platelet aggregation with epinephrine. Four patients (7%) (including 2 siblings) had low vWF levels consistent with type 1 vWD, 9 (16%) had mild clotting factor deficiencies ( FIX- 3, FXII-2 and multiple clotting factors-5) and 4 (7%) had a prolonged baseline PT and/or aPTT without additional coagulation factor assessment (Table 1). Thirteen patients (9%) had both a bleeding phenotype and abnormal coagulation laboratory results.ii) Surgical outcomes: A total of 274 surgical procedures were performed in 89 patients (63%). These included: cardiac 118 (43%), orthopedic 30 (11%), ENT 27 (10%), neurosurgical 26 (10%), abdominal 17 (6%), urologic 17 (6%), gynecologic 12 (4%) thoracic 8 (3%), ophthalmologic 7 (3%), plastic surgery 5 (2%), maxillofacial 4 (1%) and lymph node dissection 3 (1%). Platelets were utilized in 26 procedures (10%), fresh frozen plasma in 19 (7%) and cryoprecipitate in 7 (3%). Two procedures were performed in patients with type 1 vWD using vWF concentrates. Abnormal intra or postoperative bleeding was seen in 5/274 procedures (1.8%) performed in 4 patients. One patient had a known functional platelet disorder, one had normal PT and aPTT and two were not screened for coagulation defects. Bleeding was managed with transfusional supportive care in 3 (60%) surgical cases, while in 2 (40%) cases patients required re-intervention to achieve surgical hemostasis (bleeding from femoral access site and pacemaker pocket hematoma). There was no mortality related to the excess perioperative bleeding.Conclusion: Varying hemostatic abnormalities are seen in patients with Noonan syndrome, ranging from thrombocytopenia to multiple coagulation factor deficiencies. Frank bleeding manifestations however are uncommon and when present are usually mild. Clinical evaluation focused on the bleeding history and basic coagulation screening allows for successful perioperative hemostatic support and good surgical outcomes. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

VWF Multimer Quantitation for Assessment of Cardiac Lesion Severity and Bleeding Risk

Introduction: Recent reports have utilized von Willebrand factor (VWF) multimerquantitation in the assessment of native cardiac lesions and prosthetic valve dysfunction. However there is no standardized method for quantitation. We compared 3 methods of assessment which utilized a normal plasma control.Methods: We analyzed 476 samples and their control plasma from 395 patients including normal subjects, patients with aortic stenosis, hypertrophic cardiomyopathy, mitral or aortic regurgitation, normal and abnormal left cardiac valve prostheses, and left ventricular assist device therapy (LVAD). VWF multimers were assessed as normal or abnormal, or as normalized (patient / normal plasma) VWF multimerratios of gel bands >15/2-15 (NMR 15) or gel bands > 10/2-10 (NMR 10). We tested whether one technique was more strongly associated with hemodynamic severity of the cardiac lesion, with a history of acquired bleeding, and compared the results to a separate test of VWF function, platelet function analyzer 15 00 (PFA).Results: Two hundred seventeen patient samples reflected normal or mildly abnormal hemodynamics, 111 moderate, and 113 severely abnormal hemodynamics. Abnormal multimers were present in only 19% of samples with normal or mildly abnormal hemodynamics compared to 79% abnormal in the presence of moderate to severe hemodynamic abnormality. The distinction between moderate and severe hemodynamic abnormality was less striking, 65% versus 88% (figure, left). Quantitative NMR values declined with increasing cardiac lesion severity (figure, middle). The two quantitative multimermethods showed similar relationships to lesion severity by ANOVA, r=0.40 (NMR 15) versus r=0.36 (NMR 10), and by Spearman correlation, r=0.68 for NMR 15, and r=0.66 for NMR 10, and PFA results were comparable (all p< 0.001). Bleeding rates were associated with NMR 15, 10 and PFA (Mann-Whitney p<0.001, figure, right).Conclusion: The dichotomous normal / abnormal VWF multimer method appears to distinguish ≥ moderate hemodynamic disruption, whereas there is a continuous relationship between hemodynamic severity and quantitative multimer methods, which may be clinically useful in circumstances in which clinical estimation of lesion severity is challenging, such as with dysfunctional prosthetic valves. Progressive loss of VWF multimersappears to be associated with bleeding, suggesting that quantitative measures may provide incremental value over the dichotomous normal / abnormal designation. [Display omitted] DisclosuresBlackshear:Baxalta, Inc: Consultancy, Research Funding.

A simple method for activating the platelets used in microfluidic platelet aggregation tests: Stirring-induced platelet activation.

High-shear stimulation is well known as one of the key factors affecting platelet activation and aggregation, which can lead to the formation of a thrombus. In one of our previous studies, we introduced migration distance-based platelet function analysis in a microfluidic system. In this study, we set out to examine the effects of stirring on shear-induced platelet activation and aggregation in a chamber system by using a rotating stirrer. We found that the rotating stirrer caused not only rotational shear flow but also a strong radial secondary flow. The latter flow led to efficient mixing in the chamber. Moreover, the rotational flow led to the generation of shear stress, the magnitude of which can be controlled to activate the platelets. Activated platelets tend to aggregate themselves. The maximum platelet aggregation was observed at a critical shear rate of 3100 s−1, regardless of the stirrer shape. Furthermore, the time taken to attain maximum aggregation was significantly shortened when using a wide stirrer (30 s) instead of a narrow one (180 s). When using a flat stirrer, the non-uniform shear field in the chamber system was resolved with the radial secondary flow-induced mixing; thus, most of the platelets were homogenously activated. The stirring-induced platelet activation mechanism was experimentally confirmed in a microfluidic system for a platelet aggregation test while monitoring the migration distance until the microfluidic channel is occluded. Our findings indicate that the present system, consisting of a rotating stirrer and a confined chamber, provides effective shear stimulation for activating platelets and inducing platelet aggregates.

Effect of remote ischemic preconditioning on electrophysiological and biomolecular parameters in nonvalvular paroxysmal atrial fibrillation (RIPPAF study): Rationale and study design of a randomized, controlled clinical trial.

Remote ischemic preconditioning (RIPC) has been studied in models of different cardiovascular entities. Recently, a beneficial effect of RIPC on incidence of atrial fibrillation (AF) in postsurgical patients has been suggested. However, the potential impact of RIPC on electrophysiological- and thrombogenesis-related parameters in the setting of paroxysmal nonvalvular AF has not been investigated. The aim of the study is to answer the following questions: (1) Does RIPC have impact on inducibility of AF in patients with known paroxysmal AF? If yes, what are the direct electrophysiological mechanisms of this phenomenon, and could RIPC be implemented to reduce AF burden? (2) Does RIPC have the potential to minimize thrombogenic effects of simulated episodes of AF? If so, what are inhibited components of thrombogenesis and can this be used to reduce thromboembolic risk related to paroxysmal AF? The presented study is a 2-arm, randomized, placebo-controlled, double-blinded, single-center trial in a cohort of 146 patients with paroxysmal AF referred for AF ablation in sinus rhythm. The study will collect electrophysiological data such as variability of P-wave morphology, atrial refractory period, conduction times, and inducibility/sustainability of AF. Furthermore, AF-induced prothrombotic processes will be analyzed by quantification of platelet aggregates, analysis of platelet function, and measurement of thrombogenesis-related plasma markers. Moreover, the study will provide a unique bio-database for further analysis of molecular and genetic mechanisms responsible for observed results.

Effects of Firocoxib, Flunixin Meglumine, and Phenylbutazone on Platelet Function and Thromboxane Synthesis in Healthy Horses.

Determine the effects of nonsteroidal anti-inflammatory drugs (NSAID) on platelet function and thromboxane synthesis immediately after drug administration and following 5 days of NSAID administration in healthy horses. Randomized cross-over study. Healthy adult horses (n=9; 6 geldings and 3 mares). Horses received either flunixin meglumine (1.1 mg/kg IV every 12 hours), phenylbutazone (2.2 mg/kg IV every 12 hours), or firocoxib (loading dose of 0.27 mg/kg IV on day 1, then 0.09 mg/kg IV every 24 hours for 4 days) for a total of 5 days. Blood samples were collected prior to drug administration (day 0), 1 hour after initial NSAID administration (day 1), and then 1 hour post-NSAID administration on day 5. Platelet function was assessed using turbidimetric aggregometry and a platelet function analyzer. Serum thromboxane B2 concentrations were determined by commercial ELISA kit. A minimum 14 day washout period occurred between trials. At 1 hour and 5 days postadministration of firocoxib, flunixin meglumine, or phenylbutazone, there was no significant effect on platelet aggregation or function using turbidimetric aggregometry or a platelet function analyzer. There was, however, a significant decrease in thromboxane synthesis at 1 hour and 5 days postadministration of flunixin meglumine and phenylbutazone that was not seen with firocoxib. Preoperative administration of flunixin meglumine, phenylbutazone, or firocoxib should not inhibit platelet function based on our model. The clinical implications of decreased thromboxane B2 synthesis following flunixin meglumine and phenylbutazone administration are undetermined.

Practice patterns in the diagnosis of inherited platelet disorders within a single institution.

: The diagnosis of inherited platelet disorders (IPDs) is challenging with variable diagnostic practices existing between institutions. To determine patterns and utility of diagnostic testing practices for IPDs within a single institution, a retrospective cohort study was performed. Records of 50 patients (50% women), median age 32 years (1 day to 81 years) were analyzed. In total, 28 (53%) had a positive International Society of Thrombosis and Hemostasis Bleeding Assessment Tool score. Test-ordering patterns were highly variable. All patients had platelet morphology analysis by light microscopy. In total, 42 (84%) underwent light transmission aggregometry, 43 (86%) platelet function analyzer, 37 (74%) platelet electron microscopy, 25 (50%) flow cytometry, and 15 (30%) genetic testing. Platelet function analyzer and light transmission aggregometry were always used as first-order tests, followed by platelet transmission electron microscopy and flow cytometry (81 and 84%, respectively). Genetic testing was obtained up front in five cases (33% of orders), mostly in patients with syndromic thrombocytopenia or in the setting of a known genetic disorder. Test-ordering practices did not adhere to published algorithms. Even within a single institution, great heterogeneity exists in the testing approach to IPDs. Although, a large proportion of cases were studied with platelet transmission electron microscopy and flow cytometry, standard platelet assays established the diagnosis in a great majority. Standardization of testing practices, first beginning at the institutional level is a much needed step forward.

Impedance aggregometric analysis of platelet function of apheresis platelet concentrates as a function of storage time

Multiple electrode (impedance) aggregometry (MEA) allows reliable monitoring of platelet function in whole blood. The aims of the present study were to implement MEA for analyzing aggregation in platelet concentrates and to correlate results with storage time and blood gas analysis (BGA). We investigated the influence of platelet counts, calcium concentrations and agonists on platelet aggregation. Samples of apheresis concentrates up to an age of 12 days were investigated by MEA and BGA. For ASPI- and TRAPtest MEA was reproducible for a platelet count of 400 per 10−9 L and a calcium concentration of 5 mmol L−1. Platelets at the age of 2–4 days yielded steady aggregation. Platelet concentrates exceeding the storage time for transfusion showed steady aggregation up to 10 days, but a significant decline on day 12. Weak correlation was found regarding pCO2 and MEA as well as regarding glucose concentration and MEA. Our results indicate that MEA is applicable for evaluation of aggregation in stored apheresis concentrates. Prolonged storage seems not to be prejudicial regarding platelet aggregation. Platelet concentrates showed acceptable BGA throughout storage time. Further studies are required to evaluate the application of MEA for quality controls in platelet concentrates.

Influence of a low dosage of clopidogrel on platelet function in cats as measured by the platelet function analyser PFA-100 and the multiplate analyser

The antiplatelet drug clopidogrel is widely used for prophylaxis of arterial thromboses in cats in a standard dosage of 18.75mg per cat once daily. The aim of the study was to verify if a reduced daily dose of 10mg clopidogrel per cat has a similar antiplatelet effect as the standard dosage. Platelet function was measured with the platelet function analyser PFA-100® and a novel impedance aggregometer.Suitability of the platelet function analyser was tested in citrated blood samples of 59 healthy cats and reference ranges were established. In addition, agonist concentrations for impedance aggregometry were optimised. In the main experiment two groups of 6 healthy cats received clopidogrel either in a dosage of 10 or 18.75mg per cat over a period of seven days. Analyses were performed on days 1, 2, 3, 5, and 7.In comparison to baseline both clopidogrel dosages showed an inhibitory effect on results of the platelet function analyser and velocity of ADP-induced platelet aggregation. Values at all times were different from baseline, with the exception of day 1 in cats receiving 10mg clopidogrel where the closure time of the platelet function analysis and part of ADP-induced aggregation did not show a significant difference. Significant differences were not found between the two doses.In conclusion, our study indicates that 10mg clopidogrel per day may be as effective as 18.75mg although the latter may be advantageous as an initial loading dosage to achieve effective levels more rapidly.

Comparing light transmission aggregometry and PFA100 for monitoring antiplatelet therapy in patients with coronary heart disease

Abstract Objectives Many patients undergoing antiplatelet therapy continue to experience thrombotic events and failure of therapy leading to so-called ‘resistance’ to antiplatelet therapy. Recently, there has been an increasing focus on in vitro laboratory monitoring of platelet functions, which has the promise of identifying these patients. This study aimed to document the prevalence of laboratory evidence of resistance to aspirin and clopidogrel therapy in Saudi patients with stable coronary heart disease (CHD). Methods Light transmission aggregometry in platelet-rich plasma was performed in response to adenosine diphosphate (ADP), arachidonic acid (AA), collagen and adrenaline. In addition, a platelet function analyser (PFA100) was employed using both collagen/ADP and collagen/epinephrine cartridges. Results Light transmission aggregometry (LTA) identified the resistance to aspirin and clopidogrel therapy, according to the persistence of the aggregation response to AA aggregation, to be 13% and 26%, respectively. By PFA100 testing, closure times within the limits of laboratory reference values indicated residual platelet reactivity, and the prevalence of resistance to anti-platelet therapy was reported to be 33% for collagen/ADP cartridges and 30.7% for collagen/epinephrine. A concordance between LTA and PFA100 CT was noted in only 22.6% of patients. Conclusion This study showed a wide prevalence of on-treatment platelet reactivity in patients with CHD on dual platelet therapy ( aspirin and clopidogrel ). In addition, the global whole blood test of platelet function by PFA100 estimated a much higher prevalence of resistance than LTA when compared to the gold standard and more specific LTA analysis.

Acquired von Willebrand syndrome in children with aortic and pulmonary stenosis.

SummaryIntroduction:This prospective study was planned to investigate the frequency and relationship of acquired von Willebrand syndrome (AVWS) with aortic and pulmonary stenosis in patients.Methods:A total of 84 children, ranging from two to 18 years of age, were enrolled in this study. Of these, 28 had isolated aortic stenosis, 32 had isolated pulmonary stenosis and 24 were healthy. Children with aortic and pulmonary stenosis associated with other congenital heart diseases were excluded. Children with hypothyroidism, renal or liver disease, malignancy or autoimmune disease were also excluded. Wholeblood count, blood group, factor VIII level, prothrombin time (PT), activated partial thromboplastin time (aPTT), von Willebrand factor antigen (VWF:Ag), ristocetin co-factor (VWF:RCo), and bleeding time using a platelet-function analyser (PFA-100) were performed in all patients. All of the children in the study underwent a detailed physical examination and echocardiographic evaluation.Results:A history of bleeding was positive in 18% of the aortic stenosis group, 9% of the pulmonary stenosis group, and 4% of the control group. Seven of 60 (12%) patients had laboratory findings that implied a diagnosis of AVWS, and two of these (28%) had a history of bleeding. The frequency of AVWS was 14% in patients with aortic stenosis and 9% in those with pulmonary stenosis.Conclusion:AVWS is not rare in stenotic obstructive cardiac diseases. A detailed history of bleeding should be taken from patients with valvular disease. Even if the history is negative, whole blood count, PT and aPTT should be performed. If necessary, PFA-100 closure time and further tests should be planned for the diagnosis of AVWS.

Platelet function and activation in Cavalier King Charles Spaniels with subclinical chronic valvular heart disease.

OBJECTIVE To assess platelet closure time (CT), mean platelet component (MPC) concentration, and platelet component distribution width (PCDW) in dogs with subclinical chronic valvular heart disease. ANIMALS 89 Cavalier King Charles Spaniels (CKCSs) and 39 control dogs (not CKCSs). PROCEDURES Platelet count, MPC concentration, PCDW, and Hct were measured by use of a hematology analyzer, and CT was measured by use of a platelet function analyzer. Murmur grade and echocardiographic variables (mitral valve regurgitant jet size relative to left atrial area, left atrial-to-aortic diameter ratio, and left ventricular internal dimensions) were recorded. Associations between explanatory variables (sex, age, murmur grade, echocardiographic variables, platelet count, and Hct) and outcomes (CT, MPC concentration, and PCDW) were examined by use of multivariate regression models. RESULTS A model with 5 variables best explained variation in CT (R(2), 0.74), with > 60% of the variance of CT explained by mitral valve regurgitant jet size. The model of best fit to explain variation in MPC concentration included only platelet count (R(2), 0.24). The model of best fit to explain variation in PCDW included platelet count and sex (R(2), 0.25). CONCLUSIONS AND CLINICAL RELEVANCE In this study, a significant effect of mitral valve regurgitant jet size on CT was consistent with platelet dysfunction. However, platelet activation, as assessed on the basis of the MPC concentration and PCDW, was not a feature of subclinical chronic valvular heart disease in CKCSs.

Risk of perioperative bleeding related to highly selective cyclooxygenase-2 inhibitors: A systematic review and meta-analysis.

Several literatures reported that highly selective cycloxygenase-2 inhibitors (COX-2 inhibitors) had no effect on platelet function. However, some experts suggested stopping all non-steroidal anti-inflammatory drugs (NSAIDs), including COX-2 inhibitors at least five elimination half-lives prior to surgery. We, therefore, systematically summarized the risk of clinical bleeding or platelet dysfunction in healthy or surgical subjects who received COX-2 inhibitors. Two electronic databases, MEDLINE and EMBASE, were searched for randomized, controlled studies published during 1980-December 2015. Additionally, manual search was performed to identify potential eligible studies. Intervention was perioperative use of any available COX-2 inhibitors in current practice (celecoxib, parecoxib, or etoricoxib), compared to non-selective NSAIDs, analgesics, or placebo. Two independent reviewers selected eligible studies, extracted the data, and assessed the quality of the included studies. The primary outcome was postoperative bleeding. All analyses were performed using RevMan-5.3. Of 3900 abstracts reviewed, 35 studies met the inclusion criteria. The data from 16 out of 35 studies were used in this meta-analysis, and outcomes of other 19 remaining studies were descriptively summarized. COX-2 inhibitors did not significantly increase the risk of postoperative bleeding events (relative risk or RR = 0.92; 95% confidence interval or CI: 0.63-1.33; p = 0.65), intraoperative blood loss (mL) (weighted mean difference or WMD = -4.38; 95% CI: -14.69 to 5.92; p = 0.4), postoperative blood loss (mL) (WMD = -13.89; 95% CI: -30.24 to 2.47; p = 0.10), and 24-h postoperative hemoglobin loss (g/dL) (WMD = 0.47; 95% CI: -0.14 to 1.09; p = 0.13). Platelet function analyzer closure time (second) significantly decreased with the use of COX-2 inhibitors (WMD = -22.22; 95% CI: -44.03 to -0.41; p < 0.00001). In the 19 remaining studies, COX-2 inhibitors did not significantly increase risk of bleeding in both clinical and laboratory outcomes. Highly selective COX-2 inhibitors did not significantly increase the risk of intraoperative, postoperative bleeding, or blood loss. They also had no significant effect on platelet function. Therefore, perioperative, single dose, or short course of COX-2 inhibitors can be safely used in individuals who are undergoing surgery.

Assessment of platelet function in healthy cats in response to commonly prescribed antiplatelet drugs using three point-of-care platelet function tests.

Objectives The objective was to determine if decreased platelet function could be detected after treatment with aspirin and/or clopidogrel in healthy cats using three point-of-care platelet function tests that evaluate platelet function by different methods: Multiplate (by impedance), Platelet Function Analyzer 100 (by mechanical aperture closure) and Plateletworks (by platelet counting). Methods Thirty-six healthy cats were randomly assigned to receive one of three oral treatments over an 8 day period: (1) aspirin 5 mg q72h; (2) aspirin 20.25 mg q72h; or (3) clopidogrel 18.75 mg q24h. Cats treated with 5 and 20.25 mg aspirin also received clopidogrel on days 4-8. Platelet aggregation in response to adenosine diphosphate and collagen ± arachidonic acid was assessed on days 1 (baseline), 4 and 8. Aspirin and clopidogrel metabolites were measured by high-performance liquid chromatography. Platelet function in response to treatment was analyzed by ANCOVA, linear regression and Spearman correlation. Results The only solitary aspirin effect was detected using Plateletworks with collagen in cats treated with 20.25 mg. The only effect detected by Multiplate was using arachidonic acid in cats treated with both aspirin 20.25 mg and clopidogrel. All clopidogrel treatment effects were detected by Platelet Function Analyzer 100, Plateletworks (adenosine diphosphate) and Plateletworks (collagen). Drug metabolites were present in all cats, but concentrations were minimally correlated to platelet function test results. Conclusions and relevance Platelet Function Analyzer 100 and Plateletworks using adenosine diphosphate ± collagen agonists may be used to detect decreased platelet function in response to clopidogrel treatment. Either aspirin is not as effective an antiplatelet drug as clopidogrel, or the tests used were not optimal to measure aspirin effect. Cats with heart disease are commonly prescribed antiplatelet drugs to decrease the risk of aortic thromboembolism. Platelet Function Analyzer 100 and Plateletworks may be useful for confirming clopidogrel treatment in these cats.

Decreased maximum clot firmness in rotational thromboelastometry (ROTEM®) is associated with bleeding during extracorporeal mechanical circulatory support.

We aimed to characterize the coagulation disturbances which may increase the risk of bleeding, thrombosis or death shortly after implantation of an extracorporeal membrane oxygenation (ECMO) or ventricular assist (VAD) device. Antithrombotic treatment was started in 23 VAD and 24 ECMO patients according to the hospital protocol. Additionally, conventional laboratory testing, rotational thromboelastometry (ROTEM®) and platelet function analysis (Multiplate®) were performed at predetermined intervals. Four out of twenty-four (16.7%) of ECMO patients and 6/23 (26.1%) of VAD patients had severe bleeding after the procedure. When all the patients were analyzed together, low maximum clot firmness (MCF) in ExTEM and FibTEM analyses was associated with severe bleeding (p<0.05) and low MCF in FibTEM with 30-day mortality. Low platelet count and hematocrit levels were also associated with severe bleeding. When VAD and ECMO patients were separated into different groups, the association between ROTEM® parameters, bleeding and survival was found only in limited time points. Four patients with VAD had cerebral ischemia indicative of thromboembolism. However, this had no significant correlation with ROTEM® or Multiplate® parameters. Hypocoagulation shown by ROTEM® was associated with bleeding complications in patients with mechanical circulatory support. In contrast, hypercoagulation did not correlate with clinical thrombosis.

The Effects of Cyclosporine and Aspirin on Platelet Function in Normal Dogs.

BackgroundCyclosporine increases thromboxane synthesis in dogs, potentially increasing the thrombogenic properties of platelets.Hypothesis/ObjectivesOur hypothesis was that the concurrent administration of low‐dose aspirin and cyclosporine would inhibit cyclosporine‐associated thromboxane synthesis without altering the antiplatelet effects of aspirin. The objective was to determine the effects of cyclosporine and aspirin on primary hemostasis.AnimalsSeven healthy dogs.MethodsA randomized, crossover study utilized turbidimetric aggregometry and a platelet function analyzer to evaluate platelet function during the administration of low‐dose aspirin (1 mg/kg PO q24h), high‐dose aspirin (10 mg/kg PO q12h), cyclosporine (10 mg/kg PO q12h), and combined low‐dose aspirin and cyclosporine. The urine 11‐dehydro‐thromboxane‐B2 (11‐dTXB 2)‐to‐creatinine ratio also was determined.ResultsOn days 3 and 7 of administration, there was no difference in the aggregometry amplitude or the platelet function analyzer closure time between the low‐dose aspirin group and the combined low‐dose aspirin and cyclosporine group. On day 7, there was a significant difference in amplitude and closure time between the cyclosporine group and the combined low‐dose aspirin and cyclosporine group. High‐dose aspirin consistently inhibited platelet function. On both days, there was a significant difference in the urinary 11‐dTXB 2‐to‐creatinine ratio between the cyclosporine group and the combined low‐dose aspirin and cyclosporine group. There was no difference in the urinary 11‐dTXB 2‐to‐creatinine ratio among the low‐dose aspirin, high‐dose aspirin, and combined low‐dose aspirin and cyclosporine groups.Conclusions and Clinical ImportanceLow‐dose aspirin inhibits cyclosporine‐induced thromboxane synthesis, and concurrent use of these medications does not alter the antiplatelet effects of aspirin.

Evaluation of platelet function using PFA-100® in patients treated with Acetylsalicylic acid and qualified for Trauma and Orthopedic surgery procedures

The phenomenon of high on-acetylsalicylic acid (ASA) treatment platelet (PLT) reactivity – HATPR – and its clinical implications have not been fully understood. Little data is available on assessing PLT activity based on the severity of intra- and postoperative bleeding in a population of orthopedic patients with normal closure time (CT) measured by a PLT function analyzer PFA-100®, despite being given long-term ASA therapy. The aim is to assess PLT function using PFA-100® in patients with ASA therapy and qualified for trauma and orthopedic surgery procedures. The retrospective analysis covered 384 patients whose PLT reactivity was assessed using PFA-100®. Out of those, 198 had been taking ASA with a 75 mg dose until hospital admission. In addition, a group of 70 patients with a proximal femoral fracture surgically treated using the dynamic hip screw (DHS) was selected, in whom severity of bleeding was assessed by HIP ASA (+). The reference group comprised 52 patients (without ASA therapy) who were operated on due to the same indications. Normal CT was found in 37% of ASA-receiving patients. Patients with normal CT, despite ASA therapy, exhibited significantly more intense bleeding after DHS surgery. A similar number of patients required red blood cells (RBCs) transfusion in HIP ASA (+) and HIP ASA (-). Increased risk of complications in HIP ASA (+) group was not found.Conclusions: Normal PLT function assessed using PFA-100® is a common phenomenon in patients with long-term ASA treatment and who are qualified for trauma and orthopedic surgery procedures. In many cases, it seems that inadequate response to ASA is only a laboratory phenomenon.

0053 : Naproxen as an alternative to aspirin for platelet inhibition in patients with cardiovascular disease requiring nonsteroidal anti-inflammatory drug?

Concomitant prescription of non-steroidal anti-inflammatory drugs (NSAIDs) and low dose aspirin is not recommended due to competitive interaction with cyclooxygenase-1 and higher risk of gastrotoxicity. To assess the efficacy of naproxen over time as antiplatelet agent. We included 14 healthy volunteers. We first evaluated naproxen effiacy by performing aggregation tests: light transmission aggregometry with arachidonic acid (LTA-AA), platelet function analyzer-100 with epinephrine cartridge (PFA-EPI) and serum thromboxane B2 (TXB2) measurement at baseline (T0), 2 hours (T2), 12 hours (T12), 24 hours (T24) and 48 hours (T48) after receiving one single dose of naproxen 550mg and then at T24 and T48 after a twice daily dose of naproxen 550mg for three days. We then compared the peak of efficacy two hours after naproxen with ibuprofen 400mg and aspirin 75mg and tested the switch back from NSAIDs to aspirin. Platelet aggregation (LTA-AA) after one dose of naproxen was inhibited at T2 and T12 and 50% of volunteers recovered at T24 and 93% at T48. Similar results were found with serum TXB2 concentration and PFA-EPI and multiple doses of naproxen. After naproxen at T2, maximal aggregation intensity (MAI) was 4% [1%-16%], PFA EPI 260s [88s-300s], TXB2 inhibition 98% [89-99%]. After aspirin, MAI was 5% [0%-69%], PFA-EPI was 214s [103s-300s] and TXB2 inhibition 98% [91%-98%]. After ibuprofen, MAI was 2% [1%-4%], PFA EPI 211s [111s-300s] and TXB2 inhibition 94% [92-94%]. After a 48h interruption of NSAIDs with a verified recovery of platelet aggregation, aspirin did not inhibit platelet aggregation for 83% and 50% of subjects who took naproxen and ibuprofen. Naproxen has a stable biological antiplatelet effect similar to aspirin. However, after naproxen or ibuprofen, aspirin was unable to inhibit platelet aggregation. These results suggest than NSAIDs could block the action of aspirin on platelets for several days. The author hereby declares no conflict of interest