Biphasic effects of hemodialysis on platelet reactivity in patients with end-stage renal disease: a potential contributor to cardiovascular risk

The use of a low-flux hemo-dialyzer is associated with impaired platelet aggregation in patients undergoing chronic hemodialysis

In patients with chronic hemodialysis (HD), both abnormal thrombotic and bleeding events are commonly observed. Uremic platelet dysfunction is one of the important attributing factors. Moreover, HD may also result in aggregation dysfunction of platelets during the therapeutic procedure. However, how the HD process affects platelet and coagulation function is unknown and dialyzer membrane flux could have an impact on it. We aimed to compare the impacts of low-flux and high-flux HD on the platelet function of patients undergoing chronic HD. This was a cross-sectional study conducted in the HD unit of E-Da hospital in Taiwan. A total of 78 patients with maintenance HD three times per week for more than one year, including 40 with high- and 38 with low-flux hemodialysis, were recruited. Their platelet functions were evaluated using an in vitro platelet function analyzer (PFA-100) before and after the HD session. Of the 78 patients undergoing HD, 60 (76%) had prolonged pre-dialysis collagen/epinephrine (CEPI) and collagen/adenosine diphosphate closure times. Those receiving low-flux dialyzer had a significant increase in CEPI closure time (pre-dialysis 212.3 ± 62.1 seconds. post-dialysis 241.5 ± 64.3 seconds, P = .01), but not collagen/adenosine diphosphate closure time, after HD. After adjusting confounding factors, only the low-flux dialyzer demonstrated an independent association with the prolonged CEPI closure time after HD therapy (odds ratio = 23.31, 95% CI: 1.94-280.61, P = .01). We observed that impaired platelet aggregation is prevalent in patients undergoing chronic HD. Therefore, the use of low-flux dialyzers may further worsen platelet aggregation after dialysis. Patients with uremic bleeding diathesis should take precautions. We suggest that further studies using flow cytometry should be conducted to explore the mechanism of dialysis flux and platelet activity during HD.

Coagulation Abnormalities in Renal Pathology of Chronic Kidney Disease: The Interplay between Blood Cells and Soluble Factors

Coagulation abnormalities in renal pathology are associated with a high thrombotic and hemorrhagic risk. This study aims to investigate the hemostatic abnormalities that are related to the interaction between soluble coagulation factors and blood cells, and the effects of hemodialysis (HD) on it, in end stage renal disease (ESRD) patients. Thirty-two ESRD patients under HD treatment and fifteen healthy controls were included in the study. Whole blood samples from the healthy and ESRD subjects were collected before and after the HD session. Evaluation of coagulation included primary and secondary hemostasis screening tests, proteins of coagulation, fibrinolytic and inhibitory system, and ADAMTS-13 activity. Phosphatidylserine (PS) exposure and intracellular reactive oxygen species (iROS) levels were also examined in red blood cells and platelets, in addition to the platelet activation marker CD62P. Platelet function analysis showed pathological values in ESRD patients despite the increased levels of activation markers (PS, CD62P, iROS). Activities of most coagulation, fibrinolytic, and inhibitory system proteins were within the normal range, but HD triggered an increase in half of them. Additionally, the increased baseline levels of ADAMTS-13 inhibitor were further augmented by the dialysis session. Finally, pathological levels of PS and iROS were measured in red blood cells in close correlation with variations in several coagulation factors and platelet characteristics. This study provides evidence for a complex coagulation phenotype in ESRD. Signs of increased bleeding risk coexisted with prothrombotic features of soluble factors and blood cells in a general hyperfibrinolytic state. Hemodialysis seems to augment the prothrombotic potential, while the persisted platelet dysfunction might counteract the increased predisposition to thrombotic events post-dialysis. The interaction of red blood cells with platelets, the thrombus, the endothelium, the soluble components of the coagulation pathways, and the contribution of extracellular vesicles on hemostasis as well as the identification of the unknown origin ADAMTS-13 inhibitor deserve further investigation in uremia.

Comparison of effectiveness and safety between ticagrelor and clopidogrel in patients with acute coronary syndrome and on dialysis in Taiwan

AIMS

This study aimed to evaluate and compare the effectiveness and safety between clopidogrel and ticagrelor in acute coronary syndrome (ACS) with renal dysfunction.

METHODS

We conducted a retrospective cohort study on patients on chronic dialysis and whose admission diagnosis between 1 July 2013 and 31 December 2016 included ACS. The primary effectiveness endpoint was a major adverse cardiovascular event (MACE), and the primary safety endpoint was a major bleeding event. The application of propensity scores through the inverse probability of treatment weighting (IPTW) was applied to the study groups. Cox regression was used to estimate hazard ratios (aHRs) of study endpoints. In addition, the competing risk was adjusted using the Fine and Gray competing risk model.

RESULTS

There were 1915 patients in the clopidogrel group and 270 patients in the ticagrelor group. At 12 months, the ticagrelor group had higher risks for MACE (aHR with IPTW: 1.29; 95% CI 1.16-1.44); death (aHR with IPTW: 1.65; 95% CI 1.47-1.86) and cardiac death (subdistribution HR [SHR] with IPTW: 1.64; 95% CI 1.41-1.91), compared with those in the clopidogrel group. For major bleeding event, the risk was significantly higher with ticagrelor than with clopidogrel (SHR with IPTW: 1.49; 95% CI 1.34-1.65). In terms of the risk for any bleeding event, there was no significant difference between the two groups (SHR with IPTW: 1.05; 95% CI 0.95-1.17).

CONCLUSIONS

Compared with clopidogrel, ticagrelor was associated with higher MACE, death, cardiac death and major bleeding risk within 12 months in patients with ACS and on dialysis.

Suppression of platelet reactivity during dialysis by addition of a nitric oxide donor to the dialysis fluid

Background

Dialysis membranes that release nitric oxide (NO) from their surface, mimicking one of the functions of endothelial cells, may suppress platelet reactivity during hemodialysis treatment. The aim of the present study was to examine whether the addition of a NO donor to the dialysis fluid can suppress platelet reactivity during dialysis.

Methods

Porcine whole blood was circulated for 4 h through a polysulfone (PS) dialyzer or polymethylmethacrylate (PMMA) dialyzer. After the blood was circulated through the blood circuit and dialyzer, sodium nitroprusside was added to the dialysis fluid as a NO donor. The changes in the platelet reactivity, measured by the platelet aggregation activity by the addition of adenosine diphosphate or collagen in the blood sample, were evaluated during ex vivo dialysis experiments in the presence of a dialysis fluid containing or not containing a NO donor.

Results

The platelet aggregation activity was significantly decreased at 30 min after the start of the experiment in the case where nitroprusside was added to the dialysis fluid (the NO (+) condition) as compared to the case where no nitroprusside was added to the dialysis fluid (the NO (−) condition), for both the PS and PMMA membranes. The suppression of the platelet reactivity in the NO (+) condition was sustained until the end of the experimental period (240 min). The platelet cyclic guanosine monophosphate level was also significantly increased in the NO (+) condition as compared to the NO (−) condition.

Conclusions

NO in the dialysis fluid appears to be capable of suppressing the increase of the platelet reactivity observed during dialysis.

Formation of Calcified Nodule as a Cause of Early In-Stent Restenosis in Patients Undergoing Dialysis

Background Dialysis is an independent risk factor for in-stent restenosis (ISR) after stent implantation in coronary arteries. However, the characteristics of ISR in patients undergoing dialysis remain unclear, as there are no histological studies evaluating the causes of this condition. The aim of the present study was to investigate the causes of ISR between patients who are undergoing dialysis and those who are not by evaluating tissues obtained from ISR lesions using directional coronary atherectomy. Methods and Results A total of 29 ISR lesions from 29 patients included in a multicenter directional coronary atherectomy registry of 128 patients were selected for analysis and divided into a dialysis group (n=8) and a nondialysis group (n=21). Histopathological evaluation demonstrated that an in-stent calcified nodule was a major histological characteristic of ISR lesions in the dialysis group and the prevalence of an in-stent calcified nodule was significantly higher in the dialysis group compared with the nondialysis group (75% versus 5%, respectively; P<0.01). On the other hand, the prevalence of an in-stent lipid-rich plaque was significantly lower in the dialysis group compared with the nondialysis group (0% versus 43%, respectively; P=0.03). In all cases with an in-stent calcified nodule, the underlying calcification before stent implantation was moderate to severe. When tissue characteristics were stratified according to duration post-stent implantation, an in-stent calcified nodule in the dialysis group was mainly observed within 1 year after stent implantation. Conclusions In-stent calcified nodules are a common cause of ISR in patients undergoing dialysis and are observed within 1 year after stent implantation, suggesting different causes of ISR between patients undergoing dialysis and those who are not.

Haemodialysis-associated thrombocytopenia: interactions among the immune system, membranes and sterilisation methods

We present a case of a 47-year-old man with severe thrombocytopenia. The differential diagnosis for thrombocytopenia is wide. The assessment includes an evaluation for falsely low platelet counts (pseudothrombocytopenia), immune-mediated platelet destruction, bone marrow dysfunction, or increased consumption and sequestration. After extensive and systematic workup, we found a relationship of his thrombocytopenia with haemodialysis. Although not widely recognised by clinicians, partly due to an incomplete understanding of its pathophysiology, haemodialysis is also a potential cause of thrombocytopenia. His platelet counts completely normalised after the substitution of his haemodialysis membrane. We concluded that our patient had haemodialysis-induced thrombocytopenia, most likely secondary to electron-beam sterilisation.

Anticoagulation in Patients With Advanced Chronic Kidney Disease: Walking the Fine Line Between Benefit and Harm

Chronic kidney disease affects more than 3 million Canadians and is highly associated with cardiovascular diseases that require anticoagulation, such as atrial fibrillation and venous thromboembolism. Patients with chronic kidney disease are at a problematic crossroads; they are at high risk of thrombotic conditions requiring anticoagulation and bleeding complications due to anticoagulation. The limited high-quality clinical evidence to guide decision-making in this area further compounds the dilemma. In this review, we discuss the physiology and epidemiology of bleeding and thrombosis in patients with kidney disease. We specifically focus on patients with advanced kidney disease (estimated glomerular filtration rate ≤ 30 mL/min) or who are receiving dialysis and focus on the nephrologist perspective regarding these issues. We summarize the existing evidence for anticoagulation use in the prevention of stroke with atrial fibrillation and provide practical clinical recommendations for considering anticoagulation use in this population. Last, we examine specific scenarios such as the use of a glomerular filtration rate estimating equation and dosing, the use of existing prediction tools for stroke and hemorrhage risk, current patterns of anticoagulation use (including during the dialysis procedure), and vascular calcification with vitamin K antagonist use in patients with chronic kidney disease.

The effect of high-flux hemodialysis and post-dilution hemodiafiltration on platelet closure time in patients with end stage renal disease

INTRODUCTION

We aimed to compare prospectively the effect of high-flux hemodialysis and post-dilution hemodiafiltration on platelets.

METHODS

Twenty-two hemodialysis patients were treated with one high-flux hemodialysis and one post-dilution hemodiafiltration procedure. PFA-100 closure times (collagen/epinephrine-CEPI and collagen/adenosine diphosphate-CADP) were measured before and after the procedure, as well as platelet count, hemoglobin, hematocrit, and red blood cell count. All pre-dialysis and post-dialysis samples were taken from the afferent line.

FINDINGS

The platelet count after vs. before hemodialysis did not change significantly (229.3 ± 55.0 x10⁹ /L vs. 233.6 ± 55.8 × 10⁹ /L; P = 0.269), but was significantly lower after post-dilution hemodiafiltration (215.5 ± 51.7 × 10⁹ /L vs. 245.3 ± 59.9 × 10⁹ /L; P < 0.0001). CEPI after vs. before hemodialysis was not significantly prolonged (192.9 ± 60.8 s vs. 173.4 ± 52.5 s; P = 0.147), and the same applied to CADP (143.6 ± 40.3 s vs. 142.6 ± 38.4 s; P = 0.897). CEPI after vs. before post-dilution hemodiafiltration was significantly prolonged (268.3 ± 41.3 s vs. 176.4 ± 54.0 s; P < 0.0001) as was CADP (221.0 ± 53.9 s vs.133.9 ± 31.1 s; P < 0.0001).

DISCUSSION

Only after post-dilution hemodiafiltration, we found a lower platelet count and prolonged platelet closure times.

Acetylsalicylic acid decreases clotting in combination with enoxaparin during haemodialysis in vitro

BACKGROUND

Anticoagulation is a cornerstone in haemodialysis (HD) therapy to avoid clotting of blood when it comes into contact with the dialysis membrane. Although heparins are usually administered as anticoagulants, they are not always sufficient to maintain adequate HD. We investigated the additional effect of acetylsalicylic acid compared with standard anticoagulation on maintaining adequate flow properties during HD in vitro.

METHODS

We collected blood from 42 healthy volunteers, between 18 and 60 years of age, into bags filled with 1, 1.5 or 2 mg enoxaparin, with (treatment group) or without (control group) 100 mg of aspirin. Blood was evaluated before, during and at the end of each experiment to determine coagulation parameters, whole blood aggregation and thromboelastogram measurements. Transmembrane pressure was recorded as indirect estimate of dialysis patency. The primary endpoint was time to filter clotting.

RESULTS

Addition of acetylsalicylic acid significantly prolonged the time to circuit clotting from 120 (105-150) min to >180 min (120-180) min (P = 0.047) and allowed lowering the enoxaparin concentration from 2 mg per circuit to 1 mg without an increase in clotting. Furthermore, it reduced the transmembrane pressure from 46 to 4 mmHg (P < 0.001) after 4 h of dialysis. Acetylsalicylic acid better preserved the platelet count (128 versus 116 × 10E9/L, P = 0.01) and improved platelet aggregation at the end of the dialysis procedure.

CONCLUSION

Adding acetylsalicylic acid to HD circuits lowered the transmembrane pressure, better preserved platelet function and prolonged the time to circuit clotting, which in sum increases haemodialyser performance and may facilitate a more effective HD.

Biomarkers of Endothelial, Renal, and Platelet Dysfunction in Stage 5 Chronic Kidney Disease Hemodialysis Patients With Heart Failure

The aim of this study was to determine the role of endothelial, renal, and inflammatory biomarkers in the pathogenesis of heart failure (HF) in patients with stage 5 chronic kidney disease (CKD5) undergoing maintenance hemodialysis (HD). Plasma levels of biomarkers-kidney injury molecule 1 (KIM-1), N-terminal pro brain natriuretic peptide (NT-proBNP), glycated hemoglobin, neutrophil gelatinase-associated lipocalin, interleukin-18,platelet-derived growth factor, platelet factor 4 (PF4), 25-OH vitamin D, parathyroid hormone (PTH), endothelin, and endocan-were measured in CKD5-HD patients at the Loyola University Ambulatory Dialysis facility. The HF (+) CKD5-HD patients, as compared to HF (-) CKD5-HD patients, exhibited significantly elevated NT-proBNP ( P = .0194) and KIM-1 ( P = .0485). The NT-proBNP in HF (+) CKD5-HD patients was found to correlate with the levels of serum potassium ( P = .023, R = -.39), calcium ( P = .029, R = -.38), and PF4 ( P = .045, R = -.35). The KIM-1 in HF (+) CKD5-HD patients was found to correlate with PTH ( P = .043, R = -.36) and 25-OH vitamin D ( P = .037, R = .36). Elevated plasma NT-proBNP and KIM-1 in CKD5-HD and HF (+) CKD5-HD patients suggest that natriuretic peptides and KIM-1 may contribute to the pathogenesis of HF in CKD5-HD patients.

Haemodialysis impairs clopidogrel but not aspirin responsiveness in patients with end-stage renal disease

Dual antiplatelet therapy (DAPT) with aspirin (ASA) and clopidogrel (Clp) is the standard treatment to reduce ischaemic coronary events, but in patients with end-stage renal disease (ESRD) the efficacy of Clp remains unclear. Patients with ESRD are at higher risk for coronary artery disease (CAD) and also their post-interventional outcome is worse compared to patients with normal renal function. Little is known about the influence of haemodialysis (HD) on ASA and Clp responsiveness. To assess the effect of HD on ASA- and Clp-responsiveness in patients with documented CAD and ESRD, 31 patients with ESRD (mean age 66.5 ± 1.8 years, 23 male ) on DAPT were evaluated for their ASA and Clp responsiveness with the Verify Now System (Accumetrics Inc.) We measured the antiplatelet effect in all ESRD patients at three time points: T1: just before HD; T2: directly after HD; T3: steady state on a HD free day one week after T1. In our study at baseline 10 (32.3%) patients were ASA-low responder (ASA-LR) and 14 (45.2%) patients Clp-low responder (Clp-LR). There was a significant difference in the PRU values before ( T1) and immediately after HD (T2) [PRU T1=234 (169; 274) vs PRUT2= 247 (199; 278); pT1,2=0.036; ]. Results were shown as median ARU T1 (25th, 75th percentile) or median PRU T1 (25th, 75th percentile). Hence HD seems to impair responsiveness to Clp, resulting in an increase of 6.5 % Clp-LR. No significant differences in the ARU values at the different time-points were found.

Factors influencing platelet reactivity in patients undergoing coronary artery bypass surgery

OBJECTIVE

Because coronary artery bypass graft (CABG) surgery is associated with a high turnover of platelets, assessment of platelet function should enable assessment of the effect of young (RNA-containing) platelets on platelet reactivity. This study was designed to assess platelet reactivity 1 day after CABG in patients treated previously with clopidogrel or ticagrelor.

METHODS

Patients (n=18) with acute coronary syndrome who required urgent CABG and had been treated for up to 2 days before surgery with aspirin plus clopidogrel (n=13) or aspirin plus ticagrelor (n=5) were enrolled. Care was not altered by participation, which entailed review of medical records and taking one sample of blood 1 day after surgery. The percentage of RNA-containing platelets was quantified using thiazole orange, and platelet function was assessed by flow cytometry.

RESULTS

Young platelets constituted, on average, 24% of platelets (range 4-54%) and were more likely to be activated in the absence or presence of an agonist (P<0.001). Differences between RNA-containing (young) and non-RNA-containing platelets were evident in patients treated previously with clopidogrel (P<0.001), whereas a nonsignificant trend was apparent in patients treated previously with ticagrelor. A high but variable prevalence of young platelets was seen 1 day after CABG.

CONCLUSION

Young platelets were more reactive and, consistent with the irreversible binding of clopidogrel to P2Y12, this effect was more pronounced after treatment with clopidogrel. The reversible binding of ticagrelor to the platelet P2Y12 receptor may be advantageous in patients with a high platelet turnover.

Comparison of Drug-Eluting and Bare Metal Stents in Patients With Chronic Kidney Disease: An Updated Systematic Review and Meta-Analysis

BACKGROUND

Drug-eluting stents (DESs) and bare metal stents (BMSs) are both recommended to improve coronary revascularization and to treat coronary artery disease in patients with chronic kidney disease (CKD). However, the potential superiority of DESs over BMSs for reducing the incidence of long-term major adverse cardiovascular events and mortality in CKD patients has not been established, and the results remain controversial. We aimed to systematically assess and quantify the total weight of evidence regarding the use of DESs versus BMSs in CKD patients.

METHODS AND RESULTS

In this systematic review and conventional meta-analysis, electronic studies published in any language until May 20, 2016, were systematically searched through PubMed, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials. We included randomized controlled trials and observational studies comparing outcomes in CKD patients with DESs versus BMSs and extracted data in a standard form. Pooled odd ratios and 95% CIs were calculated using random- and fixed-effects models. Finally, 38 studies involving 123 396 patients were included. The use of DESs versus BMSs was associated with significant reductions in major adverse cardiovascular events (pooled odds ratio 0.75; 95% CI, 0.64-0.88; P<0.001), all-cause mortality (odds ratio 0.81; 95% CI, 0.73-0.90; P<0.001), myocardial infarction, target-lesion revascularization, and target-vessel revascularization. The superiority of DESs over BMSs for improving clinical outcomes was attenuated in randomized controlled trials.

CONCLUSIONS

The use of DESs significantly improves the above outcomes in CKD patients. Nevertheless, large-sized randomized controlled trials are necessary to determine the real effect on CKD patients and whether efficacy differs by type of DES.

Drug-Eluting Versus Bare-Metal Stents During PCI in Patients With End-Stage Renal Disease on Dialysis

BACKGROUND

In patients undergoing percutaneous coronary intervention (PCI), drug-eluting stents (DES) reduce repeat revascularizations compared with bare-metal stents (BMS), but their effects on death and myocardial infarction (MI) are mixed. Few studies have focused on patients with end-stage renal disease.

OBJECTIVES

This study compared mortality and cardiovascular morbidity during percutaneous coronary intervention with DES and with BMS in dialysis patients.

METHODS

We identified 36,117 dialysis patients from the USRDS (United States Renal Data System) who had coronary stenting in the United States between April 23, 2003, and December 31, 2010, and examined the association of DES versus BMS with 1-year outcomes: death; death or MI; and death, MI, or repeat revascularization. We also conducted a temporal analysis by dividing the study period into 3 DES eras: Transitional (April 23, 2003, to June 30, 2004); Liberal (July 1, 2004, to December 31, 2006); and Selective (January 1, 2007, to December 31, 2010).

RESULTS

One-year event rates were high, with 38 deaths; 55 death or MI events; and 71 death, MI, or repeat revascularization events per 100 person-years. DES, compared with BMS, were associated with a significant 18% lower risk of death; 16% lower risk of death or MI; and 13% lower risk of death, MI, or repeat revascularization. DES use varied, from 56% in the Transitional era to 85% in the Liberal era and 62% in the Selective era. DES outcomes in the Liberal era were significantly better than in the Transitional Era, but not significantly better than in the Selective Era.

CONCLUSIONS

DES for percutaneous coronary intervention appears to be safe for use in U.S. dialysis patients and is associated with lower rates of death, MI, and repeat revascularization.

Antiplatelet effects of aspirin in chronic kidney disease patients

ESSENTIALS: Chronic kidney disease (CKD) patients have a high risk of cardiovascular events. A pharmacodynamic evaluation of the effects of aspirin in 116 patients was carried out. The antiplatelet effects of aspirin are associated with impaired renal function. The optimal antithrombotic regimen in CKD patients must be investigated on a larger scale.

BACKGROUND

The pharmacodynamic response to aspirin varies significantly between individuals. Insufficient antiplatelet effects of aspirin are associated with increased risk of ischemic events. Chronic kidney disease (CKD) is suggested to affect the pharmacodynamic response to antiplatelet medication. High on-treatment platelet reactivity (HTPR) to clopidogrel has been reported to partially account for the enhanced risk of death and cardiovascular events in CKD patients. Objective To investigate the antiplatelet effects of aspirin in patients with CKD.

METHODS

We conducted a cross-sectional study in 116 patients on permanent aspirin medication. The pharmacodynamic response to aspirin was determined by arachidonic acid-induced thromboxane formation.

RESULTS

HTPR to aspirin was more frequent in patients with impaired renal function (47% vs. 22%; odds ratio, 3.16; 95% confidence interval [CI], 1.34-7.41; P = 0.008). The pharmacodynamic response to aspirin was impaired in patients with moderate/severe CKD (92; interquartile range [IQR], 282 ng mL(-1) ) as compared to patients with normal/mildly reduced renal function (36; IQR, 100 ng mL(-1) ; difference in medians, 57; CI, 5-110 ng mL(-1) ; P = 0.013). Bivariate Pearson analysis showed residual thromboxane formation to be correlated with glomerular filtration rate (R = -0.303; R(2) = 0.092; P = 0.001). Patients with CKD were older and more frequently female. Multivariate linear regression analysis revealed that the correlation was independent of age (R = -0.314; R(2) = 0.082; P = 0.002) and gender (R = -0.305; R(2) = 0.077; P = 0.006).

CONCLUSION

Renal function is correlated with pharmacodynamic response to aspirin. Patients with CKD have an increased risk of impaired antiplatelet effects of aspirin. Larger trials are needed to assess the clinical impact of this finding and investigate the optimal antithrombotic regimen in CKD patients.

Impact of residual platelet reactivity under clopidogrel treatment for lesions and the clinical outcome after drug-eluting stent implantation in patients with hemodialysis

BACKGROUND

Hemodialysis (HD) patients are at high risk for adverse clinical outcomes after drug-eluting stent (DES) implantation. However, the impact of residual platelet reactivity under dual anti-platelet therapy in this subset of patients remains unclear.

METHODS

We enrolled 142 stable angina patients (194 lesions) treated with DES, who were taking aspirin and 75mg clopidogrel and had undergone 8-month angiography with optical coherence tomography (OCT). OCT findings and major adverse cardiac events (MACEs) at 1 year (cardiac death, acute coronary syndrome, target lesion and vessel revascularization, and stent thrombosis) were compared between 28 HD patients and 114 non-HD patients. Responsiveness to clopidogrel was assessed by measuring P2Y12 reaction unit (PRU) at 8 months.

RESULTS

PRU was significantly higher in HD patients than in non-HD patients (p=0.006), even though proportion of cytochrome P450 2C19 genotype was equivalent. HD patients had a significantly higher rate of thrombi formation (assessed using OCT) and MACEs than non-HD patients (thrombi: p=0.001; MACEs: p=0.0001). The PRU value was independently associated with MACEs in both groups. The optimal cutoff values of PRU for predicting MACEs were 235 for HD patients and 259 for non-HD patients.

CONCLUSIONS

HD was associated with a high residual platelet reactivity, which may contribute to the higher incidence of MACEs after DES implantation in HD patients. HD may be a patient profile that merits a more potent anti-platelet regimen.

Thrombosis in the uremic milieu--emerging role of "thrombolome"

Chronic kidney disease (CKD) is characterized by retention of a number of toxins, which unleash cellular damage. CKD environment with these toxins and a host of metabolic abnormalities (collectively termed as uremic milieu) is highly thrombogenic. CKD represents a strong and independent risk factor for both spontaneous venous and arterial (postvascular injury) thrombosis. Emerging evidence points to a previously unrecognized role of some of the prothrombotic uremic toxins. Here, we provide an overview of thrombosis in CKD and an update on indolic uremic toxins, which robustly increase tissue factor, a potent procoagulant, in several vascular cell types enhancing thrombosis. This panel of uremic toxins, which we term "thrombolome" (thrombosis and metabolome), represents a novel risk factor for thrombosis and can be further explored as biomarker for postvascular interventional thrombosis in patients with CKD.

Platelet reactivity after receiving clopidogrel compared with ticagrelor in patients with kidney failure treated with hemodialysis: a randomized crossover study

BACKGROUND

Patients with kidney failure treated with maintenance hemodialysis (HD) are poor responders to clopidogrel. More beneficial platelet-inhibiting strategies in HD patients therefore are required.

STUDY DESIGN

Single-center, prospective, randomized, crossover study.

SETTING & PARTICIPANTS

25 HD patients in Seoul, Korea.

INTERVENTION

Patients were randomly assigned to receive clopidogrel (300mg loading, 75mg once daily for maintenance dose) or ticagrelor (180mg loading, 90mg twice daily for maintenance dose) for 14 days, and after a 14-day washout period, crossover treatment for another 14 days. All patients received aspirin (100mg/d).

OUTCOMES & MEASUREMENTS

Platelet function was evaluated predosing and at 1, 5, and 48 hours and 14 days after the first loading dose. During the offset phase, platelet function was assessed at 1 hour and 2, 4, and 14 days after the last dose by light transmittance aggregometry and the VerifyNow P2Y12 assay, and patients were genotyped for the CYP2C19*2 allele. Maximal extent of aggregation, inhibition of platelet aggregation (IPA), P2Y12 reaction units (PRUs), and percentage of inhibition were evaluated. We performed per-protocol analysis, excluding patients who did not complete the protocol.

RESULTS

9 patients did not complete the protocol (7 patients due to adverse events; 2, nonadherence). Higher IPA occurred with ticagrelor than with clopidogrel at 1, 5, and 48 hours and 14 days after loading. By 5 hours after loading, a greater proportion of patients in the ticagrelor group than in the clopidogrel group achieved IPA>50% (75% vs 12%, respectively; P<0.05) and IPA>70% (44% vs 0%, respectively; P<0.05). Rates (slope) of onset and offset of the antiplatelet effect were faster in patients receiving ticagrelor than for those receiving clopidogrel (P<0.05). Regardless of CYP2C19*2 allele, the ticagrelor group had significantly lower PRUs at all times than the clopidogrel group.

LIMITATIONS

Single-center study with a small number of patients, not a double-blind study, and not intention-to-treat analysis.

CONCLUSIONS

Ticagrelor may result in more rapid and greater platelet inhibition than clopidogrel in patients with kidney failure receiving HD.

Thienopyridine use after coronary stenting in low income patients enrolled in medicare part D receiving maintenance dialysis

BACKGROUND

Coronary stenting in patients on dialysis has increased by nearly 50% over the past decade, despite heightened risks of associated stent thrombosis and bleeding relative to the general population. We examined clopidogrel, prasugrel or ticlopidine use after percutaneous coronary intervention (PCI) with stenting in patients on dialysis. We conducted 3-, 6-, and 12-month landmark analyses to test the hypothesis that thienopyridine discontinuation prior to those time points would be associated with higher risks of death, myocardial infarction, or repeat revascularization, and a lower risk of major bleeding episodes compared with continued thienopyridine use.

METHODS AND RESULTS

Using the US Renal Data System, we identified 8458 patients on dialysis with Medicare Parts A+B+D undergoing PCI with stenting between July 2007 and December 2010. Ninety-nine percent of all thienopyridine prescriptions were for clopidogrel. At 3 months, 82% of patients who received drug-eluting stents (DES) had evidence of thienopyridine use. These proportions fell to 62% and 40% at 6 and 12 months, respectively. In patients who received a bare-metal stent (BMS), 70%, 34%, and 26% of patients had evidence of thienopyridine use at 3, 6, and 12 months, respectively. In patients who received a DES, there was a suggestion of higher risks of death or myocardial infarction associated with thienopyridine discontinuation in the 3-, 6-, and 12-months landmark analyses, but no higher risk of major bleeding episodes. In patients who received a BMS, there were no differences in death or cardiovascular events, and possibly lower risk of major bleeding with thienopyridine discontinuation in the 3- and 6-month landmark analyses.

CONCLUSIONS

The majority of patients on dialysis who undergo PCI discontinue thienopyridines before 1 year regardless of stent type. While not definitive, these data suggest that longer-term thienopyridine use may be of benefit to patients on dialysis who undergo PCI with DES.

Platelet-Related Hemostasis before and after Hemodialysis with Five Different Anticoagulation Methods

Purpose

To evaluate platelet-related hemostasis during hemodialysis performed with five different anticoagulation methods.

Methods

31 chronic hemodialysis patients, 71% men, aged 57.5 ∓ 17.4 years, participated in our prospective study. Platelet function analyzer PFA -100 closure time (collagen/epinephrine -CEPI, collagen/adenosine diphosphate -CADP) was measured before and after hemodialysis, which was performed consecutively with five different anticoagulation methods: full-dose unfractionated heparin (UFH) and low-molecular weight heparin (LMWH): 31 patients, regional citrate anticoagulation (RCA): 28 patients, low-dose heparin: 25 patients and “heparin-free” dialysis: 9 patients. The degree of clotting in the dialysis system was graded on a 5 point scale.

Results

CEPI (mean ∓ SD, reference range 80-160 sec) before vs. after hemodialysis: UFH: 171.7 ∓ 62.1 vs. 170.8 ∓ 67.3; LMWH: 167.4 ∓ 56.9 vs. 159.4 ∓ 56.4; low-dose heparin: 175.3 ∓ 69.0 vs. 183.1 ∓ 60.5; RCA: 172.6 ∓ 57.4 vs. 161.6 ∓ 57.0; “heparin-free”: 181.7 ∓ 56.8 vs. 209.0 ∓ 66.5; all differences nonsignificant. CADP (mean ∓ SD, reference range: 68-121 sec) before vs. after hemodialysis: UFH: 132.0 ∓ 56.6 vs.146.3 ∓ 68.4; LMWH: 132.4 ∓ 57,0 vs. 123.1 ∓ 50.8; low-dose heparin: 137.2 ∓ 64.2 vs. 143.8 ∓ 55.5; RCA: 140.7 ∓ 48.2 vs. 132.9 ∓ 48.1; “heparin-free”: 137.1 ∓ 68.0 vs.139.2 ∓ 29.7; all differences nonsignificant. Before hemodialysis procedure CEPI was increased in 51.2% and CADP in 48.4% of the patients. The best dialysis system clotting score was found with UFH, LMWH and RCA.

Conclusions

Platelet dysfunction was demonstrated in approximately half of the chronic hemodialysis patients and was not improved after hemodialysis, regardless of the anticoagulation regimen used.

Elevated levels of procoagulant plasma microvesicles in dialysis patients

Cardiovascular (CV) death remains the largest cause of mortality in dialysis patients, unexplained by traditional risk factors. Endothelial microvesicles (EMVs) are elevated in patients with traditional CV risk factors and acute coronary syndromes while platelet MVs (PMVs) are associated with atherosclerotic disease states. This study compared relative concentrations of circulating MVs from endothelial cells and platelets in two groups of dialysis patients and matched controls and investigated their relative thromboembolic risk. MVs were isolated from the blood of 20 haemodialysis (HD), 17 peritoneal dialysis (PD) patients and 20 matched controls. Relative concentrations of EMVs (CD144(+ ve)) and PMVs (CD42b(+ ve)) were measured by Western blotting and total MV concentrations were measured using nanoparticle-tracking analysis. The ability to support thrombin generation was measured by reconstituting the MVs in normal plasma, using the Continuous Automated Thrombogram assay triggered with 1µM tissue factor. The total concentration of MVs as well as the measured sub-types was higher in both patient groups compared to controls (p<0.05). MVs from HD and PD patients were able to generate more thrombin than the controls, with higher peak thrombin, and endogenous thrombin potential levels (p<0.02). However there were no differences in either the relative quantity or activity of MVs between the two patient groups (p>0.3). Dialysis patients have higher levels of circulating procoagulant MVs than healthy controls. This may represent a novel and potentially modifiable mediator or predictor of occlusive cardiovascular events in these patients.

Aspirin resistance in patients undergoing hemodialysis and effect of hemodialysis on aspirin resistance

The aim of this study was to evaluate the prevalence of aspirin resistance (AR) in patients undergoing hemodialysis (HD) and to assess the effect of HD on the results of the Multiplate test. A total of 54 patients undergoing HD were included in this study. Blood samples were taken just before and after the HD session. To determine AR, we used Multiplate test. Platelet aggregation values of the study population were 363.01 ± 225.69 aggregation unit (AU) × minutes before and 375.33 ± 254.05 AU × minutes after the HD (P = .597). There was strong correlation between the values before and after HD (R = .755, P < .0001). The AR status was changed in 9 (16.6%) patients after HD. Agreement of AR status before and after HD was substantial (κ coefficient = .667, P < .0001). The prevalence of AR in patients undergoing HD seems higher than in most of the studied populations, and this study has shown that the AR statuses of a significant number of patients undergoing HD change after an HD session.

Activation of platelets upon contact with a vitamin E-coated/non-coated surface

The purpose of this study was to determine the effects of a vitamin E-coated surface on platelet activation, focusing on the interactions among the vitamin E-coated surface, platelets and leukocytes. Platelet-rich plasma (PRP) or PRP containing leukocytes (LPRP) was used. No difference was observed in platelet activation between PRP and LPRP for a vitamin E-coated membrane, meaning that platelet activation triggered by leukocytes was suppressed in plasma coming in contact with a vitamin E-coated membrane, while the membrane itself directly induced platelet activation. The antioxidant capacity of the vitamin E-coated membrane in contact with PRP or LPRP was partially reduced, but sufficient residual capacity remained. The in vitro experiments using an oxidized vitamin E-coated surface revealed that P-selectin expression and superoxide anion production in the platelets and platelet adhesion were induced by contact with the oxidized vitamin E-coated surface. We conclude that contact with a vitamin E-coated surface reduces platelet activation mediated by superoxide anions, probably by reducing superoxide anions, but during the process of the reduction, the vitamin E-coated surface itself becomes oxidized, which again causes platelet activation. The beneficial effects of a vitamin E-coated dialyzer in respect of platelet activation were counteracted by the formation of oxidized vitamin E.

Platelets of patients with chronic kidney disease demonstrate deficient platelet reactivity in vitro

Background

In patients with chronic kidney disease studies focusing on platelet function and properties often are non-conclusive whereas only few studies use functional platelet tests. In this study we evaluated a recently developed functional flow cytometry based assay for the analysis of platelet function in chronic kidney disease.

Methods

Platelet reactivity was measured using flow cytometric analysis. Platelets in whole blood were triggered with different concentrations of agonists (TRAP, ADP, CRP). Platelet activation was quantified with staining for P-selectin, measuring the mean fluorescence intensity. Area under the curve and the concentration of half-maximal response were determined.

Results

We studied 23 patients with chronic kidney disease (9 patients with cardiorenal failure and 14 patients with end stage renal disease) and 19 healthy controls. Expression of P-selectin on the platelet surface measured as mean fluorescence intensity was significantly less in chronic kidney disease patients compared to controls after maximal stimulation with TRAP (9.7 (7.9-10.8) vs. 11.4 (9.2-12.2), P = 0.032), ADP (1.6 (1.2-2.1) vs. 2.6 (1.9-3.5), P = 0.002) and CRP (9.2 (8.5-10.8) vs. 11.5 (9.5-12.9), P = 0.004). Also the area under the curve was significantly different. There was no significant difference in half-maximal response between both groups.

Conclusion

In this study we found that patients with chronic kidney disease show reduced platelet reactivity in response of ADP, TRAP and CRP compared to controls. These results contribute to our understanding of the aberrant platelet function observed in patients with chronic kidney disease and emphasize the significance of using functional whole blood platelet activation assays.

Alteration of the platelet transcriptome in chronic kidney disease

Bleeding and thrombotic disorders are major complications affecting patients with chronic kidney disease (CKD). Exposure of circulating platelets to uraemic toxins and contact with artificial surfaces during dialysis induce platelet abnormalities and alter the platelet proteome. We hypothesised that these changes may be subsequent to changes in the composition and/or regulation of the platelet transcriptome. In this study, we investigated the circulating platelets of 10 CKD patients (i.e. five chronic haemodialysis patients and five stage 4 CKD uraemic patients) and five age- and sex-matched healthy subjects. We observed an alteration of the platelet messenger RNA (mRNA) and microRNA transcriptome in CKD patients. Impaired in uraemic platelets, the levels of some mRNAs and of most microRNAs appeared to be corrected by dialysis, which is consistent with a beneficial effect of dialysis and a mRNA regulatory role of platelet microRNAs. Reduced in platelets of uraemic patients, phosphatidylcholine transfer protein (PCTP) and WD repeat-containing protein 1 (WDR1) were found to be regulated by microRNAs, the latter of which involving hsa-miR-19b, a microRNA increased in platelets of uraemic patients and involved in platelet reactivity. These results suggest that an alteration of microRNA-based mRNA regulatory mechanisms may underlie the platelet response to uremia and entail the development of platelet-related complications in CKD.

Effect of uremia and hemodialysis on proteome profile of blood platelets and plasma

The aim of the present research was to assess the differences in blood platelet and plasma proteome profiles of patients with uremia in comparison with healthy participants. It was found that 23 peptides in the platelet proteome profiles of hemodialyzed patients and only 6 peptides in nondialyzed patients were upregulated. On the other hand, 18 peptides with reduced expression in nondialyzed patients and only 1 peptide in hemodialyzed patients were found. For serum, only 6 upregulated peptides in patients undergoing hemodialysis and 15 peptides in nondialyzed patients were found, most of these were about 10 kDa. A decrease in serum peptide expression was not observed. In conclusion, it should be noted that the process of hemodialysis modifies the platelet proteome to a greater extent than uremia alone, however the sera of nondialyzed patients have much larger amounts of low-molecular-weight peptides than those of hemodialyzed patients.

Effect of uremia and hemodialysis on platelet apoptosis

The blood platelet proteome of hemodialyzed patients with uremia exhibits significant difference in comparison with the blood platelet proteome of healthy individuals. This alteration is manifested by the presence of high concentrations of low-molecular peptides within the whole range of isoelectric points. Increased platelet apoptosis has been put forward as a possible cause of this phenomenon. The aim of the present research was to assess whether blood platelet populations from hemodialyzed patients with uremia exhibit higher binding capacity of Annexin V than control samples from healthy donors. It was found that blood platelets of hemodialyzed patients, in the period between dialyses, bound significantly more Annexin V with no different incorporation of propidium iodide in comparison with platelets of control donors and conservatively treated patients with uremia. The results support the hypothesis that the process of hemodialysis may be at least partially responsible for triggering blood platelet apoptosis and result in increased risk of thrombosis.

Antiplatelet effects of prasugrel vs. double clopidogrel in patients on hemodialysis and with high on-treatment platelet reactivity

BACKGROUND

High on-treatment platelet reactivity (HTPR) is frequent in patients on hemodialysis (HD) receiving clopidrogel.

OBJECTIVES

The primary aim of this study was to determine the antiplatelet effects of prasugrel vs. high-dose clopidogrel in patients on HD with HTPR.

PATIENTS/METHODS

We performed a prospective, single-center, single-blind, investigator-initiated, randomized, crossover study to compare platelet inhibition by prasugrel 10 mg day(-1) with that by high-dose 150 mg day(-1) clopidogrel in 21 patients on chronic HD with HTPR. Platelet function was assessed with the VerifyNow assay, and genotyping was performed for CYP2C19*2 carriage.

RESULTS

The primary endpoint of platelet reactivity (PR, measured in P2Y12 reaction units [PRU]) was lower in patients receiving prasugrel (least squares [LS] estimate 156.6, 95% confidence interval [CI] 132.2-181.1) than in those receiving high-dose clopidogrel (LS 279.9, 95% CI 255.4-304.3), P < 0.001). The LS mean differences between the two treatments were - 113.4 PRU (95% CI - 152.9 to - 73.8, P < 0.001) and - 163.8 PRU (95% CI - 218.1 to - 109.2, P < 0.001) in non-carriers and carriers of at least one CYP2C19*2 allele, respectively. HTPR rates were lower for prasugrel than clopidogrel, in all patients (19% vs. 85.7%, P < 0.001) and in non-carriers (25.7% vs. 80%, P = 0.003). All carriers continued to show HTPR while receiving high-dose clopidogrel, but none showed it while receiving prasugrel.

CONCLUSIONS

In HD patients exhibiting HTPR following standard clopidogrel treatment, prasugrel 10 mg day(-1) is significantly more efficient than doubling the clopidogrel dosage in achieving adequate platelet inhibition. Neither effect seems to be influenced by carriage of the loss-of-function CYP2C19*2 allele.

Prothrombotic changes in platelet, endothelial and coagulation function following hemodialysis

PURPOSE

Patients on hemodialysis (HD) have an increased risk of thrombotic events, including myocardial infarction and vascular access thrombosis. The study hypothesis is that a single session of dialysis leads to platelet, endothelial and coagulation activation. Our aim is to determine the effect of a single HD session on prothrombotic vascular biomarkers before and after a single session of hemodialysis.

METHODS

Blood samples were taken from the vascular access of 55 patients immediately before and after a hemodialysis session. Platelet function was assessed by (1) flow cytometric measurement of P-selectin expression and fibrinogen binding +/- ADP stimulation, (2) Ultegra rapid platelet function assay (RPFA) using the agonists thrombin receptor activating peptide (TRAP) and arachidonic acid (AA), (3) soluble P-selectin, and (4) soluble CD40L. Coagulation (thrombin-antithrombin III [TAT] and D-dimer), endothelial von Willebrand factor (vWF) and high sensitivity C-Reactive protein (hsCRP) were assessed by ELISA.

RESULTS

Unfractionated heparin was given to all patients during dialysis and 30 patients (55%) were on antiplatelet agents. Post-hemodialysis there were significant increases in unstimulated platelet P-selectin (p=.037), stimulated P-selectin (p<.001), soluble P-selectin (p<.001) and soluble CD40L (p=.036). Stimulated platelet fibrinogen binding was increased post-hemodialysis (p<.001) but unstimulated fibrinogen binding was unchanged. TRAP- (p<.001] and AA-(p=.009) stimulated aggregation were reduced post-hemodialysis. There were increases post-hemodialysis in TAT (p<.001), D-dimer (p<.001), vWF (p<.001) and hsCRP (p=.011).

CONCLUSION

This study has shown that despite heparin therapy, a single session of HD induced increases in platelet, endothelial, and coagulation activation. More effective medical strategies to reduce the prothrombotic state of patients on hemodialysis should be investigated.

Platelet activation, coagulation activation and C-reactive protein in simultaneous samples from the vascular access and peripheral veins of haemodialysis patients

INTRODUCTION

Most studies of haemodialysis (HD) patients compare venous blood samples from controls with samples from the vascular access (VA) of HD patients. We hypothesised that VA samples may be more prothrombotic compared with venous samples.

METHODS

Samples were taken simultaneously from the VA and the contralateral antecubital vein, from 26 patients immediately before HD. Platelet function was assessed by (1) flow cytometric measurement of P-selectin expression and fibrinogen binding (±ADP) and 2) Ultegra rapid platelet function assay. Plasma soluble P-selectin, von Willebrand factor antigen, high sensitivity C-reactive Protein (hs-CRP), thrombin-antithrombin III complex and D-dimer measured by ELISA.

RESULTS

Thrombin receptor activating peptide-induced platelet aggregation (P < 0.001) and hs-CRP (P < 0.001) were higher in VA compared with venous samples. Unstimulated platelet fibrinogen binding (P = 0.016) and ADP-stimulated P-selectin expression (P = 0.008) were lower in VA compared with venous samples. The significant difference in hsCRP persisted when patients taking and not taking antiplatelet therapy were analysed separately, but platelet activation remained significantly different only in the nonantiplatelet group.

CONCLUSION

There are statistically significant differences between sampling sites, although samples from the VA do not appear to be more pro-thrombotic. Future studies comparing HD patients with controls should ensure uniformity of sampling sites to prevent inaccurate conclusions being drawn.

Intravenous recombinant tissue plasminogen activator therapy for stroke patients receiving maintenance hemodialysis: the Stroke Acute Management with Urgent Risk-Factor Assessment and Improvement (SAMURAI) rt-PA registry

BACKGROUND

To examine the therapeutic effect of intravenous recombinant tissue plasminogen activator (rt-PA) therapy for stroke patients receiving maintenance hemodialysis (HD). methods: Of 600 stroke patients receiving intravenous rt-PA using 0.6 mg/kg alteplase who were enrolled in a multicenter observational study in Japan, 4 patients (3 men, 64-77 years old) on maintenance HD were studied.

RESULTS

The primary kidney disease requiring HD was glomerulonephritis in 2 patients, diabetic nephropathy in 1, and undetermined in 1. The duration of HD ranged between 1.2 and 28 years. Three patients developed stroke on the day of HD, including 1 during HD and another just after HD. All patients had stroke in the carotid arterial territory. Pretreatment NIH Stroke Scale scores ranged between 4 and 20, and decreased by 2-5 points at 7 days. One patient needed intravenous antihypertensive therapy before rt-PA; he developed an ectopic cortical hematoma and intraventricular hemorrhage after rt-PA. The other 3 did not develop hemorrhagic complications. The modified Rankin Scale score at 3 months was 0 in 1 patient, 2 in 2 patients, and 4 in 1 patient.

CONCLUSIONS

rt-PA therapy for stroke patients receiving maintenance HD might improve the stroke outcome. Ectopic hematoma was a unique complication in our case series.

Gender differences in platelet aggregation in healthy individuals

This study evaluated gender variability in platelet aggregation in response to common agonists. Platelet aggregation was measured in 36 healthy men and women free of any antiplatelet medication, aged 22-36 years, of Caucasian (White not of Hispanic origin), Hispanic, and African-American not of Hispanic origin. In this ex-vivo study, we investigated platelet aggregation in response to adenosine-5'-diphosphate (ADP), epinephrine (EPI), arachidonic acid (AA) and collagen (COL), using a platelet ionized calcium aggregometer (Chrono-Log Co.). Platelet aggregation response to all tested agonists was higher in females than in males regardless of ethnicity. The most significant differences were observed with collagen (P < 0.01). Among the ethnic groups, Caucasian women were most prone to platelet aggregation. Gender is a determinant of agonist effects on platelet aggregability in healthy subjects.

The blood platelet proteome is changed in UREMIC patients

Comparative analysis of the protein profile of blood platelets isolated from nondialyzed and hemodialyzed uremic patients and healthy controls has been performed. These preliminary results indicate markedly changed expression of several proteins in blood platelets from both groups of patients compared with controls, with dramatic changes in hemodialyzed patients in the over-expression of low molecular peptides with a very wide range of pI values.

Differential effects of dialysis and ultrafiltrate from individuals with CKD, with or without diabetes, on platelet phosphatidylserine externalization

Individuals with chronic kidney disease (CKD) and/or diabetes mellitus (DM) are at increased risk of cardiovascular events and have elevated externalization of phosphatidylserine (PS; which propagates thrombus formation) in a small subpopulation of platelets. The purpose of this study was to examine the effect of 1) removing uremic toxins by hemodialysis on PS externalization in patients with either CKD or CKD and DM and 2) ultrafiltrate (UF) from these individuals on PS externalization in healthy platelets. PS externalization was quantified by a fluorescence-activated cell sorter using annexin V in platelet-rich plasma. PS externalization was elevated threefold in CKD patients and returned to basal values during 3-h hemodialysis. In contrast, it was elevated fivefold in individuals with CKD and DM and was still threefold above control after 3-h treatment. UF significantly increased PS externalization in a small subpopulation of platelets from healthy controls. The effect of UF from individuals with CKD and DM was significantly greater than that from patients with CKD alone, and the responses were partially inhibited by the protein kinase Cδ (PKCδ) inhibitor rottlerin and the 5-hydroxytryptamine (5-HT)2A/2Creceptor antagonist ritanserin. The data suggest that uremic toxins present in UF mediate PS externalization in a small subpopulation of platelets, at least in part, via the 5-HT2A/2Creceptor and PKCδ and demonstrate that DM further enhances platelet PS externalization in CKD patients undergoing hemodialysis. This may explain, at least in part, the additional increase in vascular damage observed in CKD patients when DM is present.

Increased platelet expression of FcGammaRIIa and its potential impact on platelet reactivity in patients with end stage renal disease

BACKGROUND

Increased platelet reactivity has been implicated in cardiovascular disease - the major cause of death in patients with end stage renal disease (ESRD). FcGammaRIIA is a component of glycoprotein VI and Ib-IX-V that mediate activation of platelets by collagen and von Willebrand factor. To determine whether expression of FcGammaRIIA impacts platelet reactivity we quantified its expression and platelet reactivity in 33 patients with ESRD who were undergoing hemodialysis.

METHODS

Blood samples were obtained from patients immediately before hemodialysis and before administration of heparin. Platelet expression of FcGammaRIIA and the activation of platelets in response to low concentrations of convulxin (1 ng/ml, selected to mimic effects of collagen), thrombin (1 nM), adenosine diphosphate (ADP, 0.2 microM), or platelet activating factor (PAF, 1 nM) were determined with the use of flow cytometry in samples of whole blood anticoagulated with corn trypsin inhibitor (a specific inhibitor of Factor XIIa).

RESULTS

Patients were stratified with respect to the median expression of FcGammaRIIA. Patients with high platelet expression of FcGammaRIIA exhibited 3-fold greater platelet reactivity compared with that in those with low expression in response to convulxin (p < 0.01) and 2-fold greater activation in response to thrombin, ADP, and PAF (p < 0.05 for each). For each agonist, expression of FcGammaRIIA correlated modestly but positively with platelet reactivity. The strongest correlation was with thrombin-induced activation (r = 0.6, p < 0.001).

CONCLUSION

Increased platelet reactivity in response to low concentrations of diverse agonists is associated with high expression of FcGammaRIIA and may contribute to an increased risk of thrombosis in patients with ESRD.

Platelet dysfunction and end-stage renal disease

Patients with end-stage renal disease (ESRD) develop hemostatic disorders mainly in the form of bleeding diatheses. Hemorrhage can occur at cutaneous, mucosal, or serosal sites. Retroperitoneal or intracranial hemorrhages also occur. Platelet dysfunction is the main factor responsible for hemorrhagic tendencies in advanced kidney disease. Anemia, dialysis, the accumulation of medications due to poor clearance, and anticoagulation used during dialysis have some role in causing impaired hemostasis in ESRD patients. Platelet dysfunction occurs both as a result of intrinsic platelet abnormalities and impaired platelet-vessel wall interaction. The normal platelet response to vessel wall injury with platelet activation, recruitment, adhesion, and aggregation is defective in advanced renal failure. Dialysis may partially correct these defects, but cannot totally eliminate them. The hemodialysis process itself may in fact contribute to bleeding. Hemodialysis is also associated with thrombosis as a result of chronic platelet activation due to contact with artificial surfaces during dialysis. Desmopressin acetate and conjugated estrogen are treatment modalities that can be used for uremic bleeding. Achieving a hematocrit of 30% improves bleeding time in ESRD patients.

The influence of the haemodialysis procedure on platelets, coagulation and fibrinolysis

In end-stage renal disease, in particularly when treated with haemodialysis, the function of platelets, coagulation and fibrinolytic systems can be disturbed, thus contributing to either thrombotic or bleeding complications. It is important to know whether the currently used haemodialysis procedure itself (by biocompatible membranes and better anticoagulation with nandroparin) affects platelets, coagulation or fibrinolysis. In 15 patients who had been treated with chronic haemodialysis, we measured and compared platelet aggregation (induced by adenosine diphosphate, collagen and epinephrine), the markers of coagulation and fibrinolysis activation (thrombin-antithrombin complexes, thrombin fragments F1+2, D-dimer), and fibrinolytic parameters, i.e. fibrinogen, plasminogen, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 antigen and activity, before and immediately after the regular haemodialysis sessions. We did not find differences between pre- and post-haemodialysis platelet aggregation induced with all agents. Markers of coagulation and fibrinolysis activation remained unchanged during the process of haemodialysis. However, in post-haemodialysis samples, t-PA activity was significantly increased. Other fibrinolytic parameters remained unchanged. In conclusion, our results showed that the current technique of haemodialysis procedure does not affect platelet aggregation or activate coagulation, and therefore, does not contribute to a thrombotic tendency. However, it does directly affect fibrinolysis through activation of t-PA, which might be clinically relevant since this could increase the bleeding tendency in some haemodialysis patients.

Platelet surface receptor activation in patients with chronic renal failure on hemodialysis, peritoneal dialysis and those with successful kidney transplantation

Hemostatic disorders associated with chronic renal failure (CRF) include hemorrhagic and/or thrombotic manifestations, which were ascribed, in part, to uremic platelet dysfunction including abnormalities of expression of platelet glycoprotein receptors. There is, however, still no general agreement on the exact characterization of these platelet abnormalities. This study aims at characterizing the platelet glycoprotein abnormalities associated with CRF, by recording the effect of the three renal replacement therapies, hemodialysis (HD), chronic ambulatory peritoneal dialysis (CAPD), and renal transplantation, on these receptors. The study, which was mainly cross-sectional, included two groups: (i) Patient groups (n = 50): HD patients (n = 20), CAPD patients (n = 10) and successful renal transplant patients (n = 20); (ii) Healthy Controls (n = 34): 23 were men and 11 were women who were age- and sex-matched with the patients. Flow cytometric quantitation of CD41, CD42a, CD42b and CD61 was carried out using a Becton-Dickinson FACScan. The expression of CD41 levels showed a highly significant increase in HD and CAPD patients when compared with the normal control levels. However, levels in transplant patients were comparable to the normal control levels. On the other hand, the expression of CD42a, CD42b, and CD61 showed no significant change in HD and CAPD patients when compared with normal control levels, but there was a significant decrease in transplant patients when compared to the normal control levels. In conclusion, there was evidence of increased expression of one glycoprotein receptor (GpIIb-IIIa) pre-dialysis whether HD or CAPD. In transplant patients, no evidence of platelet activation could be demonstrated.

Attenuation of platelet reactivity by enoxaparin compared with unfractionated heparin in patients undergoing haemodialysis

BACKGROUND

Increased platelet reactivity presages adverse cardiac events. Because both haemodialysis and unfractionated heparin (UFH) can increase platelet reactivity, we compared platelet reactivity during haemodialysis when patients were anticoagulated with UFH or enoxaparin.

METHODS

Patients (n = 20) underwent consecutive haemodialysis sessions with either UFH or enoxaparin in a random order. Blood was taken from the arterial end of the haemodialysis circuit at the initiation of haemodialysis before anticoagulation. Subsequently, blood was taken during dialysis from the venous end of the circuit 10 min after treatment with UFH or enoxaparin. Platelet reactivity was assessed with the use of flow cytometry by determining the capacity of platelets to bind fibrinogen and the surface expression of P-selectin in response to adenosine diphosphate (ADP, 0 and 0.2 microM). Results were compared with the use of two-way repeated measure ANOVA.

RESULTS

Platelet reactivity in arterial blood obtained at the beginning of dialysis prior to patients being treated with either UFH [0.2 microM ADP-induced capacity to bind fibrinogen = 28+/-15% (SD)] or enoxaparin (30+/-18%) was similar (P = 0.15). In contrast, platelet reactivity was less after treatment with enoxaparin compared with UFH (P = 0.006). The 0.2 microM ADP-induced capacity to bind fibrinogen in venous blood obtained 10 min after anticoagulation was 34+/-11% after treatment with UFH and 22+/-11% after treatment with enoxaparin.

CONCLUSIONS

Anticoagulation with enoxaparin during haemodialysis is associated with less platelet reactivity compared with UFH. Accordingly, enoxaparin use may contribute to a lesser risk of cardiac events in patients with end-stage renal disease treated with haemodialysis.

Review of antithrombotic agents used for acute coronary syndromes in renal patients

Management issues in acute coronary syndromes (ACSs) with regard to patients with renal insufficiency or failure are complex. Renal patients have a greater risk for bleeding compared with those with normal renal function because of prolonged bleeding time and platelet dysfunction. Some of the drugs used have significant renal excretion, such as the glycoprotein IIb/IIIa receptor antagonists. Additionally, thrombolytics are underused, which contributes to the delay in instituting immediate treatment of acute myocardial infarction. Clinical data regarding the optimum management of ACSs in renal patients are still lacking. In this article, we review the available data on the use of antithrombotic agents, particularly in patients with renal impairment.

Decreased platelet reactivity in blood anticoagulated with bivalirudin or enoxaparin compared with unfractionated heparin: implications for coronary intervention

BACKGROUND

Platelet reactivity predicts complications after percutaneous coronary intervention (PCI). Accordingly, agents that suppress platelet reactivity should decrease adverse events after PCI. This study was designed to determine the effects of therapeutic concentrations of unfractionated heparin (UFH), bivalirudin, or enoxaparin alone or in combination with tirofiban on platelet reactivity.

METHODS

Blood taken from 13 patients with coronary artery disease was exposed to each anticoagulant alone or in combination with tirofiban ex vivo. Platelet reactivity was characterized with flow cytometry to quantify the percentage of platelets capable of binding fibrinogen (activation of glycoprotein IIb-IIIa) and expressing P-selectin in response to adenosine diphosphate (ADP, 0, 0.2, and 1 microM).

RESULTS

Platelet reactivity was greater in blood treated with UFH than in blood anticoagulated with bivalirudin with respect to both the capacity to bind fibrinogen (by 4 +/- 1.8%, p = 0.01) and P-selectin expression (by 7.7 +/- 0.7%, p, < 0.0001) in response to 1 microM ADP. Platelet reactivity was greater in blood treated with UFH than in blood exposed to enoxaparin with respect to P-selectin expression (by 7 +/- 1.1%, p, < 0.0001) in response to 1 microM ADP. Platelet reactivity was similar in blood treated with bivalirudin or enoxaparin. Addition of tirofiban suppressed the capacity to bind fibrinogen in the presence of each anticoagulant to a similar extent.

CONCLUSIONS

As platelet reactivity is greater in blood anticoagulated with UFH in comparison with blood anticoagulated with enoxaparin or bivalirudin, the use of bivalirudin or enoxaparin rather than UFH during PCI should contribute to a reduced incidence of adverse cardiac events after PCI.