Thrombosis in end-stage renal disease

Serum Indoxyl Sulfate Associates with Postangioplasty Thrombosis of Dialysis Grafts

Hemodialysis vascular accesses are prone to recurrent stenosis and thrombosis after endovascular interventions.In vitro data suggest that indoxyl sulfate, a protein-bound uremic toxin, may induce vascular dysfunction and thrombosis. However, there is no clinical evidence regarding the role of indoxyl sulfate in hemodialysis vascular access. From January 2010 to June 2013, we prospectively enrolled patients undergoing angioplasty for dialysis access dysfunction. Patients were stratified into tertiles by baseline serum indoxyl sulfate levels. Study participants received clinical follow-up at 6-month intervals until June 2014. Primary end points were restenosis, thrombosis, and failure of vascular access. Median follow-up duration was 32 months. Of the 306 patients enrolled, 262 (86%) had symptomatic restenosis, 153 (50%) had access thrombosis, and 25 (8%) had access failure. In patients with graft access, free indoxyl sulfate tertiles showed a negative association with thrombosis-free patency (thrombosis-free patency rates of 54%, 38%, and 26% for low, middle, and high tertiles, respectively;P=0.001). Patients with graft thrombosis had higher free and total indoxyl sulfate levels. Using multivariate Cox regression analysis, graft thrombosis was independently predicted by absolute levels of free indoxyl sulfate (hazard ratio=1.14;P=0.01) and free indoxyl sulfate tertiles (high versus low, hazard ratio=2.41;P=0.001). Results of this study provide translational evidence that serum indoxyl sulfate is a novel risk factor for dialysis graft thrombosis after endovascular interventions.

Inflammation in venous thromboembolism: Cause or consequence?

Venous thromboembolism (VTE) which includes deep vein thrombosis (DVT) and pulmonary thromboembolism (PTE) is a moderately common disease especially in elderly population with high rate of recurrence and complications. Evidence is accumulating that VTE is not restricted to coagulation system and immune system appears to be involved in formation and resolution of thrombus. The present study was aimed at reviewing current evidences on immune system abnormalities such as alterations in cytokines, chemokines and immune cells. Also, current evidences suggest that; a, inflammation in general functions as a double-edged sword, b, inflammation can be both a cause and a consequence of VTE, and c, current anti-coagulation therapies are not well-equipped with the capacity to selectively inhibit inflammatory cells and pathways. Applying such inferences for selective pharmacological targeting of immune mediators in VTE and thereby for adoption of higher effective anti-thromboinflammatory strategies, either therapeutic or prophylactic, is henceforth to be considered as the line of research for future.

The Aryl Hydrocarbon Receptor is a Critical Regulator of Tissue Factor Stability and an Antithrombotic Target in Uremia

Patients with CKD suffer high rates of thrombosis, particularly after endovascular interventions, yet few options are available to improve management and reduce thrombotic risk. We recently demonstrated that indoxyl sulfate (IS) is a potent CKD-specific prothrombotic metabolite that induces tissue factor (TF) in vascular smooth muscle cells (vSMCs), although the precise mechanism and treatment implications remain unclear. Because IS is an agonist of the aryl hydrocarbon receptor (AHR), we first examined the relationship between IS levels and AHR-inducing activity in sera of patients with ESRD. IS levels correlated significantly with both vSMC AHR activity and TF activity. Mechanistically, we demonstrated that IS activates the AHR pathway in primary human aortic vSMCs, and further, that AHR interacts directly with and stabilizes functional TF. Antagonists directly targeting AHR enhanced TF ubiquitination and degradation and suppressed thrombosis in a postinterventional model of CKD and endovascular injury. Furthermore, AHR antagonists inhibited TF in a manner dependent on circulating IS levels. In conclusion, we demonstrated that IS regulates TF stability through AHR signaling and uncovered AHR as an antithrombotic target and AHR antagonists as a novel class of antithrombotics. Together, IS and AHR have potential as uremia-specific biomarkers and targets that may be leveraged as a promising theranostic platform to better manage the elevated thrombosis rates in patients with CKD.

Considerations for Systemic Anticoagulation in ESRD

In the setting of end-stage kidney disease, the incidence and risk for thrombotic events are increased and use of anticoagulants is common. The incidence of bleeding, however, is also a frequent issue and creates additional challenges in the management of anticoagulation therapy. Patients with end-stage renal disease are typically excluded from large clinical trials exploring the use of anticoagulants, which limits our knowledge of optimal management approaches. Furthermore, varying degrees of renal failure in addition to conditions that alter the pharmacokinetics of various anticoagulants or pharmacodynamic response may warrant alternative approaches to dosing. This review will explore systemic chronic anticoagulation therapy in the setting of chronic kidney disease where hemodialysis is required. Agents discussed include vitamin K antagonists, low-molecular-weight heparins, fondaparinux, oral factor Xa antagonists, and direct thrombin inhibitors. Clinical challenges, approaches to dosing regimens, and tools for measuring responses and reversal will be explored.

Trends of pulmonary embolism before and after kidney transplantation in black versus white patients

BACKGROUND

Pulmonary embolism (PE) is an important cause of in-hospital mortality and is common in renal transplantation and maintenance dialysis patients. PE incidence is higher among patients who are black; however, differences in trends of incidence and outcomes of PE by race among patients on dialysis and after renal transplantation is not well known.

METHODS

In this observational study, the incidences of PE hospitalizations and mortality were studied in those with renal transplant, on maintenance dialysis, and in general population. Incidences were compared across racial groups. Renal transplantation status as a predictor of mortality was also examined.

RESULTS

The incidences of PE in general population, dialysis, and renal transplant groups were 70.5, 518.8, and 158.8 per 100,000 population, respectively. Incidence was higher in blacks across all groups. The age-adjusted incidence of PE admissions increased over time in all groups with greater increase in blacks in non-transplant groups (the slope in dialysis for blacks was 112.1 versus that for whites at 49.4; P = .001; the slope in general population for blacks was 9.3 versus 3.4 for whites; P = .003). The mortality rate in general population was not significantly different than renal transplant group (3.4% versus 1.9%, P = .2); however, was lower than 6.8% seen in dialysis group (P < .001). The mortality rate was not different between whites and blacks. Maintenance dialysis was an independent predictor of mortality (odds ratio [OR] 1.94; 95% confidence interval [CI] 1.62-2.32).

CONCLUSIONS

PE in those with renal transplant is more common than in general population but less common than those on maintenance dialysis. The mortality rate for PE hospitalizations is equivocal between renal transplant and general population but higher for patients on dialysis. The incidence of PE hospitalizations is not only higher among blacks, but is increasing disproportionately in this group among those who are on maintenance dialysis and within general population.

Exploring associations between anthropometric indices and graft function in patients receiving renal transplant

BACKGROUND

The aim of the present study was to identify indicators of malnutrition, as obtained by anthropometric measurements, that might be potential predictors of transplant outcomes.

METHODS

One hundred and three patients receiving a graft from a living or a deceased donor were included in this prospective study. Body mass index (BMI) based on pretransplant dry body weight, triceps skinfold, mid-arm muscle circumference and corrected mid-arm muscle area were measured. Post-transplant data on delayed graft function (DGF) and glomerular filtration rate (GFR) at discharge were collected until patient discharge.

RESULTS

Delayed graft function developed in 36.9% of the patients. BMI was the only anthropometric variable associated with a higher likelihood of DGF (odds ratio = 1.25, 95% confidence interval = 1.07-1.47) after adjusting for age, gender, donor group, donor age and years of dialysis before transplantation. Obesity was associated with a higher frequency of DGF (83.3% versus 31.1%, P = 0.001) compared to normal weight. GFR at discharge was negatively associated with BMI [β = -0.014 (0.005), P = 0.004], being overweight [β = -0.151 (0.041), P < 0.001] and obesity [β = -0.188 (0.053), P = 0.001], after adjusting for age, gender, donor group, donor age and years of dialysis, but was not associated with indices of muscle reserves.

CONCLUSIONS

The likelihood of DGF was higher among obese patients, whereas GFR at discharge was negatively associated with being overweight and obesity.

Chronic kidney disease and stroke

Chronic kidney disease (CKD) is associated with an increased risk of both ischemic and hemorrhagic stroke. In addition to shared risk factors, this higher cerebrovascular risk is mediated by several CKD-associated mechanisms including platelet dysfunction, coagulation disorders, endothelial dysfunction, inflammation, and increased risk of atrial fibrillation. CKD can also modify the effect of treatments used in acute stroke and in secondary stroke prevention. We review the epidemiology and pathophysiology that link CKD and stroke and the impact of CKD on stroke outcomes. Interdisciplinary collaboration between nephrologists, pharmacists, hematologists, nutrition therapists, primary care physicians, and neurologists in providing care to these subjects may potentially improve outcomes.

Effectiveness and Safety of Antiplatelet in Stroke Patients with End-Stage Renal Disease Undergoing Dialysis

Background

Antiplatelet therapy is known to decrease the risk of secondary ischemic stroke. However, the effectiveness and safety of antiplatelet therapy in patients with end-stage renal disease are uncertain, especially in dialysis.

Aims and/or hypothesis

We estimated the effectiveness and safety of antiplatelet drugs (aspirin and clopidogrel) for the prevention of recurrent ischemic stroke in end-stage renal disease patients undergoing dialysis during long-term follow-up after first-time ischemic stroke.

Methods

The cases were identified from the National Health Insurance Research Database. Antiplatelet therapy was administered for 11 years to patients experiencing a first ischemic stroke between 1998 and 2006. Primary outcomes, including death and readmission to hospital for stroke, and secondary outcomes, including death, stroke, and acute myocardial infarction or bleeding, were examined.

Results

In total, 1936 patients experienced a first ischemic stroke during the follow-up. In a time-dependent analysis, the hazard ratio for primary outcomes in patients treated with aspirin was 0·671 ( P < 0·001) and that for clopidogrel was 0·933 ( P = 0·497). At secondary outcomes, patients treated with aspirin, hazard ratio for readmission for stroke was 0·715 ( P = 0·002) and that for bleeding was 0·885 ( P = 0·291). Independent risk factors for mortality and readmission due to ischemic stroke included age, diabetes mellitus, and administration of proton pump inhibitors.

Conclusions

Antiplatelet therapy, especially aspirin, still offers safe and effective treatment for ischemic stroke prevention in patients with end-stage renal disease undergoing dialysis.

Haemostasis in chronic kidney disease

The coagulation system has gained much interest again as new anticoagulatory substances have been introduced into clinical practice. Especially patients with renal failure are likely candidates for such a therapy as they often experience significant comorbidity including cardiovascular diseases that require anticoagulation. Patients with renal failure on new anticoagulants have experienced excessive bleeding which can be related to a changed pharmacokinetic profile of the compounds. However, the coagulation system itself, even without any interference with coagulation modifying drugs, is already profoundly changed during renal failure. Coagulation disorders with either episodes of severe bleeding or thrombosis represent an important cause for the morbidity and mortality of such patients. The underlying reasons for these coagulation disorders involve the changed interaction of different components of the coagulation system such as the coagulation cascade, the platelets and the vessel wall in the metabolic conditions of renal failure. Recent work provides evidence that new factors such as microparticles (MPs) can influence the coagulation system in patients with renal insufficiency through their potent procoagulatory effects. Interestingly, MPs may also contain microRNAs thus inhibiting the function of platelets, resulting in bleeding episodes. This review comprises the findings on the complex pathophysiology of coagulation disorders including new factors such as MPs and microRNAs in patients with renal insufficiency.

Thrombin-anti-thrombin levels and patency of arterio-venous fistula in patients undergoing haemodialysis compared to healthy volunteers: a prospective analysis

Background

Patients on haemodialysis (HD) are at an increased risk of sustaining thrombotic events especially to their vascular access which is essential for maintenance of HD.

Objectives

To assess whether 1) markers of coagulation, fibrinolysis or endothelial activation are increased in patients on HD compared to controls and 2) if measurement of any of these factors could help to identify patients at increased risk of arteriovenous (AVF) access occlusion.

Patients/Methods

Venous blood samples were taken from 70 patients immediately before a session of HD and from 78 resting healthy volunteers. Thrombin-antithrombin (TAT), D-dimer, von Willebrand factor (vWF), plasminogen activator inhibitor-1 antigen (PAI-1) and soluble p-selectin were measured by ELISA. C-reactive protein (hsCRP) was measured by an immunonephelometric kinetic assay. Determination of the patency of the AVF was based upon international standards and was prospectively followed up for a minimum of four years or until the AVF was non-functioning.

Results

A total of 70 patients were studied with a median follow-up of 740 days (range 72-1788 days). TAT, D-dimer, vWF, p-selectin and hsCRP were elevated in patients on HD compared with controls. At one year follow-up, primary patency was 66% (46 patients). In multivariate analysis TAT was inversely associated with primary assisted patency (r= -0.250, p= 0.044) and secondary patency (r = -0.267, p= 0.031).

Conclusions

The novel finding of this study is that in patients on haemodialysis, TAT levels were increased and inversely correlated with primary assisted patency and secondary patency. Further evaluation is required into the possible role of TAT as a biomarker of AVF occlusion.

Biomarkers in atrial fibrillation: a clinical review

Assessment of atrial fibrillation (AF)-associated stroke risk is at present mainly based on clinical risk scores such as CHADS2 and CHA2DS2-VASc, although these scores provide only modest discrimination of risk for individual patients. Biomarkers derived from the blood may help refine risk assessment in AF for stroke outcomes and for mortality. Recent studies of biomarkers in AF have shown that they can substantially improve risk stratification. Cardiac biomarkers, such as troponin and natriuretic peptides, significantly improve risk stratification in addition to current clinical risk stratification models. Similar findings have recently been described for markers of renal function, coagulation, and inflammation in AF populations based on large randomized prospective clinical trials or large community-based cohorts. These new findings may enable development of novel tools to improve clinical risk assessment in AF. Biomarkers in AF may also improve the understanding of the pathophysiology of AF further as well as potentially elucidate novel treatment targets. This review will highlight novel associations of biomarkers and outcomes in AF as well as recent progress in the use of biomarkers for risk stratification.

Mortality due to pulmonary embolism, myocardial infarction, and stroke among incident dialysis patients

BACKGROUND

It is has been suggested that dialysis patients have lower mortality rates for pulmonary embolism than the general population, because of platelet dysfunction and bleeding tendency. However, there is limited information whether dialysis is indeed associated with a decreased mortality risk from pulmonary embolism.

OBJECTIVE

The aim of our study was to evaluate whether mortality rate ratios for pulmonary embolism were lower than for myocardial infarction and stroke in dialysis patients compared with the general population.

METHODS

Cardiovascular causes of death for 130,439 incident dialysis patients registered in the ERA-EDTA Registry were compared with the cardiovascular causes of death for the European general population.

RESULTS

The age- and sex-standardized mortality rate (SMR) from pulmonary embolism was 12.2 (95% CI 10.2-14.6) times higher in dialysis patients than in the general population. The SMRs in dialysis patients compared with the general population were 11.0 (95% CI 10.6-11.4) for myocardial infarction, 8.4 (95% CI 8.0-8.8) for stroke, and 8.3 (95% CI 8.0-8.5) for other cardiovascular diseases. In dialysis patients, primary kidney disease due to diabetes was associated with an increased mortality risk due to pulmonary embolism (HR 1.9; 95% CI 1.0-3.8), myocardial infarction (HR 4.1; 95% CI 3.4-4.9), stroke (HR 3.5; 95% CI 2.8-4.4), and other cardiovascular causes of death (HR 3.4; 95% CI 2.9-3.9) compared with patients with polycystic kidney disease.

CONCLUSIONS

Dialysis patients were found to have an unexpected highly increased mortality rate for pulmonary embolism and increased mortality rates for myocardial infarction and stroke.

Impaired thrombolysis: a novel cardiovascular risk factor in end-stage renal disease

AIMS

End-stage renal disease (ESRD) patients have an excess cardiovascular risk, above that predicted by traditional risk factor models. Prothrombotic status may contribute to this increased risk. Global thrombotic status assessment, including measurement of occlusion time (OT) and thrombolytic status, may identify vulnerable patients. Our aim was to assess overall thrombotic status in ESRD and relate this to cardiovascular risk.

METHODS AND RESULTS

Thrombotic and thrombolytic status of ESRD patients (n = 216) on haemodialysis was assessed using the Global Thrombosis Test. This novel, near-patient test measures the time required to form (OT) and time required to lyse (lysis time, LT) an occlusive platelet thrombus. Patients were followed-up for 276 ± 166 days for major adverse cardiovascular events (MACE, composite of cardiovascular death, non-fatal MI, or stroke). Peripheral arterial or arterio-venous fistula thrombosis was a secondary endpoint. Occlusion time was reduced (491 ± 177 vs. 378 ± 96 s, P < 0.001) and endogenous thrombolysis was impaired (LT median 1820 vs.1053 s, P < 0.001) in ESRD compared with normal subjects. LT ≥ 3000 s occurred in 42% of ESRD patients, and none of the controls. Impaired endogenous thrombolysis (LT ≥ 3000 s) was strongly associated MACE (HR = 4.25, 95% CI = 1.58-11.46, P = 0.004), non-fatal MI and stroke (HR = 14.28, 95% CI = 1.86-109.90, P = 0.01), and peripheral thrombosis (HR = 9.08, 95% CI = 2.08-39.75, P = 0.003). No association was found between OT and MACE.

CONCLUSION

Impaired endogenous thrombolysis is a novel risk factor in ESRD, strongly associated with cardiovascular events.

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.

Progressive Increase of Inflammatory Biomarkers in Chronic Kidney Disease and End-Stage Renal Disease

Chronic kidney disease (CKD) has reached epidemic levels. It is a multisystem disease associated with elevated systemic inflammatory and hypercoagulable states. Most concerning are the cardiovascular risks associated with all stages of kidney disease. It is difficult to assess kidney disease stage progression and cardiovascular risk with current indicators such as estimated glomerular filtration rate and conventional cardiovascular risk factors. However, the use of biomarkers to assess the underlying pathological disease state may bridge the gap. This study evaluated biomarkers of inflammation including C-reactive protein, d-dimer, neuron-specific enolase, neutrophil gelatinase–associated lipocalin, tumor necrosis factor receptor I, and thrombomodulin in 3 groups of patients: CKD stages 2-4, end-stage renal disease (ESRD), and age-matched controls. The study demonstrated a statistically significant progressive upregulation in mean concentration of all markers when comparing controls to CKD and ESRD. Therefore, biomarkers may be able to evaluate the inflammatory state in kidney disease and potentially predict the cardiovascular risk.

Renal function and aspirin resistance in patients with coronary artery disease

Aspirin resistance and chronic renal failure are both potentially important clinical issues in coronary artery disease. To test the hypothesis of a relationship between the two, we recruited 169 stable outpatients with proven coronary artery disease (myocardial infarction, coronary artery bypass grafting, intra-coronary stents) taking 75 mg aspirin daily. Blood was taken for light transmission aggregometry to agonists arachidonic acid (0.5mg/mL) and adenosine diphosphate (10 μmol/L), for platelet marker soluble P selectin (enzyme linked immunosorbent assay), resting and stimulated expression of CD62P (flow cytometry) and for renal function (estimated glomerular filtration rate). The estimated glomerular filtration rate was lower when aspirin resistance was defined by response to arachidonic acid after 3, 5 and 7 minutes (approximately 30% of patients) (p<0.021), and when defined by response to adenosine diphosphate after 3 minutes (approximately 17% of patients)(p=0.015) compared to those who were sensitive to aspirin. Mean [standard deviation] soluble P selectin levels were 57 [23] ng/mL in 49 patients with aspirin resistance, and 50 [15] ng/mL in the 119 aspirin sensitive patients (p=0.02). Estimated glomerular filtration rate correlated inversely with platelet CD62P expression at rest (r=-0.22, p=0.004), and when stimulated by arachidonic acid (r=-0.21, p=0.007) and by adenosine diphosphate (r=-0.17, p=0.023). Aspirin resistance was more than twice as prevalent in those with the greatest renal disease (50% of patients) compared to those with the best renal function (21.4%). Our data point to a weak relationship between worsening glomerular filtration rate and aspirin resistance. Nevertheless, we suspect that failure of patients to be fully responsive to aspirin may be important in the pathophysiology of thrombosis in renal dysfunction.

A high red blood cell distribution width predicts failure of arteriovenous fistula

In hemodialysis patients, a native arteriovenous fistula (AVF) is the preferred form of permanent vascular access. Despite recent improvements, vascular access dysfunction remains an important cause of morbidity in these patients. In this prospective observational cohort study, we evaluated potential risk factors for native AVF dysfunction. We included 68 patients with chronic renal disease stage 5 eligible for AVF construction at the Department of General and Vascular Surgery, Central Clinical Hospital Ministry of Internal Affairs, Warsaw, Poland. Patient characteristics and biochemical parameters associated with increased risk for AVF failure were identified using Cox proportional hazards models. Vessel biopsies were analyzed for inflammatory cells and potential associations with biochemical parameters. In multivariable analysis, independent predictors of AVF dysfunction were the number of white blood cells (hazard ratio [HR] 1.67; 95% confidence interval [CI] 1.24 to 2.25; p<0.001), monocyte number (HR 0.02; 95% CI 0.00 to 0.21; p = 0.001), and red blood cell distribution width (RDW) (HR 1.44; 95% CI 1.17 to 1.78; p<0.001). RDW was the only significant factor in receiver operating characteristic curve analysis (area under the curve 0.644; CI 0.51 to 0.76; p = 0.046). RDW>16.2% was associated with a significantly reduced AVF patency frequency 24 months after surgery. Immunohistochemical analysis revealed CD45-positive cells in the artery/vein of 39% of patients and CD68-positive cells in 37%. Patients with CD68-positive cells in the vessels had significantly higher white blood cell count. We conclude that RDW, a readily available laboratory value, is a novel prognostic marker for AVF failure. Further studies are warranted to establish the mechanistic link between high RDW and AVF failure.

Venous and arterial thrombosis in dialysis patients

Whether the risk of both venous and arterial thrombosis is increased in dialysis patients as compared to the general population is unknown. In addition, it is unknown which subgroups are at highest risk. Furthermore, it is unknown whether having a history of venous thrombosis or arterial thrombosis prior to dialysis treatment increases mortality risk. A total of 455 dialysis patients were followed for objectively verified symptomatic thrombotic events between January 1997 and June 2009. The incidence rates in dialysis patients as compared to the general population was 5.6-fold (95% CI 3.1-8.9) increased for venous thrombosis, 11.9-fold (95% CI 9.3-14.9) increased for myocardial infarction, and 8.4-fold (95% CI 5.7-11.5) increased for ischaemic stroke. The combination of haemodialysis, lowest tertile of albumin, history of venous thrombosis, and malignancy was associated with subsequent venous thrombosis. Increased age, renal vascular disease, diabetes, high cholesterol levels, history of venous thrombosis, and history of arterial thrombosis were associated with subsequent arterial thrombosis. The all-cause mortality risk was 1.9-fold (95% CI 1.1-3.3) increased for patients with a history of venous thrombosis and 1.9-fold (95% CI 1.4-2.6) increased for patients with a history of arterial thrombosis. A potential limitation of this study was that in some risk categories associations with venous thrombosis did not reach statistical significance due to small numbers. In conclusion, dialysis patients have clearly elevated risks of venous thrombosis and arterial thrombosis and occurrence of venous thrombosis or arterial thrombosis prior to the start of dialysis is associated with an increased mortality risk.

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.

Higher recipient body mass index is associated with post-transplant delayed kidney graft function

To examine whether a higher body mass index (BMI) in kidney recipients is associated with delayed graft function (DGF), we analyzed data from 11,836 hemodialysis patients in the Scientific Registry of Transplant Recipients who underwent kidney transplantation. The patient cohort included women, blacks, and diabetics; the average age was 49 years; and the mean BMI was 26.8 kg/m(2). After adjusting for relevant covariates, multivariate logistic regression analyses found that one standard deviation increase in pretransplant BMI was associated with a higher risk of DGF (odds ratio (OR) 1.35). Compared with patients with a pretransplant BMI of 22-24.99 kg/m(2), overweight patients (BMI 25-29.99 kg/m(2)), mild obesity patients (BMI 30-34.99 kg/m(2)), and moderate-to-severe obesity patients (BMI 35 kg/m(2) and over) had a significantly higher risk of DGF, with ORs of 1.30, 1.42, and 2.18, respectively. Similar associations were found in all subgroups of patients. Hence, pretransplant overweight or obesity is associated with an incrementally higher risk of DGF.

Endovascular Intervention for Central Venous Cannulation in Patients with Vascular Occlusion after Previous Catheterization

Objectives

This study was designed to assess endovascular intervention for central venous cannulation in patients with vascular occlusion after previous catheterization.

Methods

Patients referred for endovascular management of central venous occlusion during a 42-month period were identified from a regional endovascular database, providing prospective information on techniques and clinical outcome. Corresponding patient records, angiograms, and radiographic reports were analyzed retrospectively.

Results

Sixteen patients aged 48 years (range 0.5–76), including 11 females, were included. All patients but 1 had had multiple central venous catheters with a median total indwelling time of 37 months. Eleven patients cannulated for hemodialysis had had significantly fewer individual catheters inserted compared with 5 patients cannulated for nutritional support (mean 3.6 vs. 10.2, p<0.001) before endovascular intervention. Preoperative imaging by magnetic resonance tomography (MRT) in 8 patients, computed tomography (CT) venography in 3, conventional angiography in 6, and/or ultrasonography in 8, verified 15 brachiocephalic, 13 internal jugular, 3 superior caval, and/or 3 subclavian venous occlusions. Patients were subjected to recanalization (n=2), recanalization and percutaneous transluminal angioplasty (n=5), or stenting for vena cava superior syndrome (n=1) prior to catheter insertion. The remaining 8 patients were cannulated by avoiding the occluded route.

Conclusions

Central venous occlusion occurs particularly in patients under hemodialysis and with a history of multiple central venous catheterizations with large-diameter catheters and/or long total indwelling time periods. Patients with central venous occlusion verified by CT or MRT venography and need for central venous access should be referred for endovascular intervention.

Superior vena cava syndrome due to thrombotic occlusion in a thrombophilic renal transplant recipient: a case report

The case of a superior vena cava syndrome due to a central venous catheter thrombosis occurring in a second renal transplant patient is described. Imaging revealed thrombosis of the right internal jugular vein with extension along the confluence of the brachiocephalic veins and partial obstruction of the superior vena cava. Anticoagulant therapy with subcutaneous low-molecular-weight heparin was followed by warfarin administration. Despite adequate treatment, the symptomatology worsened because of thrombus organization. A workup revealed a complex prothrombotic underlying condition. Cardiothoracic surgeons were consulted, and an operative reconstruction of the superior vena cava using spiral vein bypass grafting was performed. In this report we describe the clinical presentation, diagnosis, and treatment of this case, with an emphasis on the role of thrombophilia.

High prevalence of sickle cell trait in African Americans with ESRD

Sickle cell trait (HbAS) associates with impaired urinary concentration, hematuria, and renal papillary necrosis, but its prevalence among African Americans with ESRD is unknown. We performed a cross-sectional study reviewing available hemoglobin phenotypes for 188 of 206 adult African-American patients receiving renal replacement therapy in four dialysis units. Results from the state newborn screening program in corresponding counties provided the local population prevalence of sickle trait among African Americans. Compared with the general African-American population, HbAS was twice as common among African Americans with ESRD (15% versus 7%, P < 0.001). Prevalence of hemoglobin C trait (HbAC) was similarly more common (5% versus 2%, P < 0.01). The higher prevalence of HbAS and HbAC in the ESRD population raises the possibility that these hemoglobinopathies contribute to a decline in kidney function, either alone or in conjunction with other known risk factors for renal disease. The potential effect of HbAS on the development and progression of CKD and its effect on the course and management of patients with ESRD deserve further study.

Two Cases of Silent Superior Vena Cava Syndrome associated with Vascular access and End-Stage Renal Disease

Due to the unavoidable use of indwelling devices and the magnitude of the operative problems encountered, Superior Vena Cava Syndrome (SVCS) has become a serious threat for patients with a history of multiple catheter placements. True diagnosis sometimes is not available due to paucity of symptoms or due to the inadequate considerations of the disease. Particularly in patients with chronic kidney disease, the evidence of central venous occlusion dictates the avoidance of placing peripheral dialysis access in this extremity. In this article, we report two patients (case 1- a patient with end stage renal disease and case 2 - a patient with chronic kidney disease) with silent SVCS related to stenosis resulting from indwelling pacemaker leads. Furthermore, the first patient had an extrinsic factor of compression, a brachial artery pseudoaneurysm - which although it was not causative - it may certainly have contributed to the development of SVCS. The brachial artery pseudoaneurysm restricted even more the flow to cephalic vein and consequently to superior vena cava. Though pacemaker leads have been well identified previously in the literature as a cause of the SVCS, the brachial artery pseudoaneurysm causing extrinsic compression constitutes a novel factor. Through the publication of this paper the awareness of SVCS in these patients shall be definitely enhanced. Moreover, physicians, nurses and patients shall be educated regarding the requirement for peripheral vein presentation in chronic kidney disease.

Pretreatment with darbepoetin attenuates renal injury in a rat model of cisplatin-induced nephrotoxicity

BACKGROUND/AIMS

Darbepoetin alpha (DPO) exhibits comparable renoprotective effects to erythropoietin (EPO) in several animal models of acute renal injury. We examined whether DPO also attenuated renal injury in a rat model of cisplatin nephrotoxicity.

METHODS

Male Sprague-Dawley rats were divided into four groups: untreated, DPO-treated, cisplatin-injected, and DPO-treated cisplatin-injected. DPO pretreatment was conducted 24 hours after and just before cisplatin administration. Ninety-six hours after cisplatin administration, animals in all experimental groups were sacrificed. We examined serology; real-time reverse transcription polymerase chain reaction (RT-PCR) for TNF-alpha, Bcl-2, and MCP-1 gene expression; and Western blots for caspase-3. We also conducted terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and light microscopy.

RESULTS

Pretreatment with DPO significantly reduced the levels of blood urea nitrogen and serum creatinine, the magnitude of renal tubular epithelial damage, and renal gene expression of TNF-alpha, Fas, and MCP-1 in kidneys injured by cisplatin. Pretreatment with DPO significantly increased Bcl-2 mRNA levels in kidneys injured by cisplatin, and significantly reduced activated caspase-3 and TUNEL-positive cells.

CONCLUSIONS

DPO exhibits a renoprotective effect in experimental cisplatin-induced renal injury, the mechanism of which may involve DPO antiinflammatory and antiapoptotic effects.

Oxidative stress mediates a reduced expression of the activating receptor NKG2D in NK cells from end-stage renal disease patients

To characterize the immune defect of patients with end-stage renal disease (ESRD), we performed NK cell subset analysis in 66 patients with ESRD treated by hemodialysis (n = 59) or peritoneal dialysis (n = 7). Compared with healthy blood donors, patients undergoing chronic dialysis showed a profound decrease in NKG2D(+) cells within both the CD8(+) T cell (58% vs 67%, p = 0.03) and NK cell (39% vs 56%, p = 0.002) populations. CD56(dim) cells, which comprise the majority of NK cells in the periphery, were more affected in this regard than were CD56(bright) cells. Uremic serum could decrease NKG2D expression on NK cells from healthy donors. Among factors that could contribute to the decrease in NKG2D expression in ESRD patients, reactive oxygen species (ROS) play a major role. We found that catalase could reverse the effects of uremic serum on NKG2D expression (p < 0.001) and that ROS down-regulated NKG2D at the mRNA level and at the NK cell surface. Additionally, ESRD patients had both increased membrane-bound MHC class I-related chain A (MICA) on monocytes (p = 0.04) and increased soluble MICA (203 pg/ml vs 110 pg/ml; p < 0.001). Both ROS and uremic serum could significantly increase in vitro the expression of the NKG2D ligand MICA on the renal epithelial cell line HK-2. Taken together, these studies suggest for the first time that both low NKG2D expression and up-regulation of its ligand MICA are related to ROS production and may be involved in the immune deficiency of ESRD patients.

Impact of proteinuria and glomerular filtration rate on risk of thromboembolism in atrial fibrillation: the anticoagulation and risk factors in atrial fibrillation (ATRIA) study

BACKGROUND

Atrial fibrillation (AF) substantially increases the risk of ischemic stroke, but this risk varies among individual patients with AF. Existing risk stratification schemes have limited predictive ability. Chronic kidney disease is a major cardiovascular risk factor, but whether it independently increases the risk for ischemic stroke in persons with AF is unknown.

METHODS AND RESULTS

We examined how chronic kidney disease (reduced glomerular filtration rate or proteinuria) affects the risk of thromboembolism off anticoagulation in patients with AF. We estimated glomerular filtration rate using the Modification of Diet in Renal Disease equation and proteinuria from urine dipstick results found in laboratory databases. Patient characteristics, warfarin use, and thromboembolic events were ascertained from clinical databases, with validation of thromboembolism by chart review. During 33,165 person-years off anticoagulation among 10,908 patients with AF, we observed 676 incident thromboembolic events. After adjustment for known risk factors for stroke and other confounders, proteinuria increased the risk of thromboembolism by 54% (relative risk, 1.54; 95% CI, 1.29 to 1.85), and there was a graded, increased risk of stroke associated with a progressively lower level of estimated glomerular filtration rate compared with a rate > or =60 mL x min(-1) x 1.73 m(-2): relative risk of 1.16 (95% CI, 0.95 to 1.40) for estimated glomerular filtration rate of 45 to 59 mL x min(-1) x 1.73 m(-2) and 1.39 (95% CI, 1.13 to 1.71) for estimated glomerular filtration rate <45 mL x min(-1) x 1.73 m(-2) (P=0.0082 for trend).

CONCLUSIONS

Chronic kidney disease increases the risk of thromboembolism in AF independently of other risk factors. Knowing the level of kidney function and the presence of proteinuria may improve risk stratification for decision making about the use of antithrombotic therapy for stroke prevention in AF.

Superimposed coagulopathic conditions in cirrhosis: infection and endogenous heparinoids, renal failure, and endothelial dysfunction

In this article, the authors discuss three pathophysiologic mechanisms that influence the coagulation system in patients who have liver disease. First, bacterial infections may play an important role in the cause of variceal bleeding in patients who have liver cirrhosis, affecting coagulation through multiple pathways. One of the pathways through which this occurs is dependent on endogenous heparinoids, on which the authors focus in this article. Secondly, the authors discuss renal failure, a condition that is frequently encountered in patients who have liver cirrhosis. Finally, they review dysfunction of the endothelial system. The role of markers of endothelial function in cirrhotic patients, such as von Willebrand factor and endothelin-1, is discussed.

Current practice perspectives on the management of thrombosis in children with renal insufficiency: the results of a survey of pediatric hematologists in North America

BACKGROUND

No guidelines exist for the management of venous thromboembolic events (VTE) in children with renal insufficiency (RI).

OBJECTIVE

To define current practice patterns of VTE management in children with RI.

METHODS

An online multiple choice survey encompassing general questions/clinical scenarios related to thrombosis in RI.

STUDY PARTICIPANTS

Pediatric hematologists who were members of Hemophilia and Thrombosis Research Society (HTRS) of North America.

RESULTS

Response rate was 54% (39/75). VTE was perceived as the major hemostatic problem in children with RI by half (20/39) of respondents. All respondents used anticoagulation for treatment of VTE while 56% used it for prophylaxis of VTE in this population. Management practices varied with respect to choice of anticoagulants employed, consideration of prophylactic anticoagulation, and evaluation for hereditary thrombophilia. Low molecular weight heparin was perceived as a safe anticoagulation for VTE treatment by 77% of respondents given that anti-factor Xa monitoring was performed to assess bioaccumulation in RI. Thromboprophylaxis was considered for preventing thrombosis at central venous catheter, renal allo-graft and arterio-venous fistula in the context of previous history of thrombosis and congenital/acquired thrombophilia. The majority (>70%) would treat life-threatening emergencies such as superior vena cava syndrome with fibrinolytics despite RI.

CONCLUSIONS

This pediatric study documents that substantial variability existed among pediatric hemologists with respect to VTE management in children with RI. Larger studies are required to better define the epidemiology and management of VTE in children with RI including the value of screening for underlying hereditary thrombophilia.

A rare complication of hemodialysis catheters: superior vena cava syndrome

Central venous catheters in hemodialysis patients may result in superior vena cava (SVC) syndrome. With the increasing use of these catheters, the SVC syndrome will probably be more common among hemodialysis patients. This report describes 3 cases of SVC syndrome due to central venous catheters that developed in hemodialysis patients with previous multiple catheter placements.

Warfarin anticoagulation in hemodialysis patients: a systematic review of bleeding rates

BACKGROUND

Despite common use of warfarin, the bleeding risk associated with this treatment in hemodialysis (HD) patients is unknown.

STUDY DESIGN

Systematic review.

SELECTION CRITERIA FOR STUDIES

Inclusion criteria were case series, cohort studies, and randomized controlled trials in dialysis patients that examined the bleeding risk associated with warfarin use compared with no warfarin or subcutaneous heparin. Studies with fewer than 10 subjects, case reports, abstracts lacking complete data sets, review articles, and editorials were excluded.

PREDICTOR

Warfarin use compared with no warfarin or subcutaneous heparin.

OUTCOMES

Data for bleeding were reported as rates: number of bleeding episodes per number of patient-years of warfarin exposure or follow-up.

RESULTS

Of 79 articles and abstracts, 5 met inclusion criteria and 3 more could be added after investigators provided additional information. All studies were of HD patients, and 7 of 8 evaluated the use of warfarin for the prevention of HD access thrombosis. Intensity of anticoagulation varied. Meta-analysis was not possible because of study heterogeneity. Studies of full-intensity anticoagulation and the 1 randomized controlled trial of low-intensity anticoagulation showed major bleeding episode rates ranging from 0.1 to 0.54 events/patient-year of warfarin exposure. These rates are approximately twice as high as those of HD patients receiving either no warfarin or subcutaneous heparin.

LIMITATIONS

This review is based largely on data from observational studies in which bleeding rates may be confounded by comorbidity. Relatively small sample sizes may provide imprecise estimates of rates.

CONCLUSION

Low- and full-intensity anticoagulation use in HD patients is associated with a significant bleeding risk, which has to be balanced against any potential benefit of therapy. This has to be considered carefully when prescribing warfarin to HD patients.

Venous thromboembolism prophylaxis in emergency department admissions

BACKGROUND

Guidelines for venous thromboembolism prophylaxis exist, yet prophylaxis is underutilized and inadequately studied in the context of emergency department admissions.

OBJECTIVE

This study aimed to measure the rate of venous thromboembolism prophylaxis in emergency department hospitalizations.

DESIGN

Prospective observational study.

SETTING

Urban, teaching hospital.

PATIENTS

Adult emergency department admissions

INTERVENTION

Alternating admissions through the emergency department over 1 month were reviewed. Exclusion criteria were: requiring full anticoagulation, hemodialysis, length of stay less than 2 days, psychiatric admission, and primary physician declined review. An established risk assessment tool classified thromboembolism risk. Appropriate prophylaxis was defined as currently accepted medical or mechanical prophylaxis if in need or no prophylaxis if not indicated.

MEASUREMENTS

Factors associated with prophylaxis were considered significant if P < .05.

RESULTS

Of 254 patients, 201 (79%) had indications for prophylaxis, of whom 65 (32%) received it. Seventy-eight percent of prophylaxis orders were written in the first day of hospitalization. Factors related to increased use of prophylaxis included use of standard order sets (OR = 3, P < .009) and increased risk of venous thromboembolism (P < .0001). Factors related to underuse included primary cardiovascular diagnosis (OR = 0.18, P < .0001) and age (OR = 0.97, P < .0001). Eighteen of 26 patients admitted for whom standard order sets were used (69%) received appropriate prophylaxis (P = .01).

CONCLUSIONS

Patients admitted through the emergency department are at high risk of venous thromboembolism. Despite this, venous thromboembolism prophylaxis is underutilized and rarely started after the first day of hospitalization. Use of admission standard order sets on admission from the emergency department may increase thromboembolic prophylaxis.

Vascular access thrombosis prophylaxis

Vascular access thrombosis in the hemodialysis patient leads to significant cost and morbidity. Fistula patency supersedes graft patency, therefore obtaining a mature functioning fistula in patients approaching end-stage renal disease (ESRD) by early patient education and referral needs to be practiced. Current methods to maintain vascular access patency rely on early detection and radiologic or surgical prevention of thrombosis. Study of thrombosis biology has elucidated other potential targets for the prophylaxis of vascular access thrombosis. The goal of this review is to examine the current available methods for vascular access thrombosis prophylaxis.

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.

Spontaneous leukocyte activation and oxygen-free radical generation in end-stage renal disease

Oxidative stress and inflammation are common features and major mediators of atherosclerosis in end-stage renal disease (ESRD). Available evidence for oxidative stress in ESRD is indirect and based on accumulation of byproducts of interactions of reactive oxygen species (ROS) with various molecules. Inflammation is a major cause of oxidative stress. To explore the direct link between oxidative stress and inflammation in ESRD, we studied leukocyte integrin expression and ROS production in 18 ESRD patients and 18 controls. ESRD patients showed elevated plasma malondialdehyde (MDA) and increased superoxide and hydrogen peroxide (H(2)O(2)) production by granulocytes and monocytes before dialysis. Hemodialysis resulted in a further rise in plasma MDA and H(2)O(2) production by granulocytes and monocytes. Surface expression of Mac-1 (CD11b and CD18) on granulocytes and monocytes was significantly increased (denoting cell activation) in ESRD patients. Granularity of granulocytes was significantly reduced before dialysis and declined further after dialysis. The magnitude of ROS production by granulocytes and monocytes was directly related with CD11b expression as well as plasma ferritin and parathyroid hormone levels and was inversely related to protein catabolic rate. Thus, this study provides direct evidence of spontaneous leukocyte activation and increased ROS generation (hence the link between oxidative stress and inflammation) in ESRD patients.

Care of the end-stage renal disease patient on dialysis in the ED

End-stage renal disease is a major public health problem. In the United States, more than 350,000 patients are being treated with either hemodialysis or continuous ambulatory peritoneal dialysis. Given the high burden of comorbidities in these patients, it is imperative that emergency physicians be aware of the complexities of caring for acute illnesses in this population. This article reviews the common medical problems that bring patients with end-stage renal disease to the emergency department, and their evaluation and management.

Does the oxidation of methionine in thrombomodulin contribute to the hypercoaguable state of smokers and diabetics?

The leading cause of premature death in smokers is cardiovascular disease. Diabetics also suffer from increased cardiovascular disease. This results, in part, from the hypercoagulable state associated with these conditions. However, the molecular cause(s) of the elevated risk of cardiovascular disease and the prothrombotic state of smokers and diabetics remain unknown. It is well known that oxidative stress is increased in both conditions. In smokers, it is established that oxidation of methionine residues takes place in alpha(1)-antitrypsin in lungs and that this leads to emphysema. Thrombomodulin is a key regulator of blood clotting and is found on the endothelium. Oxidation of methionine 388 in thrombomodulin is known to slow the rate at which the thrombomodulin-thrombin complex activates protein C, a protein which, in turn, degrades the factors which activate thrombin and lead to clot formation. In analogy to the cause of emphysema, it is hypothesized that oxidation of this methionine is elevated in smokers relative to non-smokers and, perhaps, in conditions such as diabetes that impose oxidative stress on the body. Evidence for the hypothesis that such an oxidation and concomitant reduction in activated protein C levels would lead to elevated cardiovascular risk is presented.

The treatment of venous thromboembolism in special populations

Anticoagulant therapy for the typical venous thromboembolism patient is straightforward with predictably favorable outcomes. However, for certain patients with venous thromboembolism, there remains uncertainty and controversy about optimal treatment. These controversial areas include venous thromboembolism patients with: heparin resistance, renal insufficiency, morbid obesity, cancer, antiphospholipid antibody syndrome, recurrent thrombosis despite appropriate anticoagulation, and patients with unprovoked VTE who may or may not benefit from thrombophilia testing. This review summarizes the current data for these special patient populations with venous thromboembolism and provides our recommendations for management.

HEMATOLOGY: ISSUES IN THE DIALYSIS PATIENT: The Safety of Heparins in End-Stage Renal Disease

In patients on chronic dialysis, unfractionated heparin (UFH) is the most commonly used agent for anticoagulation of the hemodialysis extracorporeal circuit, for hemodialysis catheter "locking" between dialysis treatments, and for nondialysis indications such as venous thromboembolic disease, peripheral vascular disease, and acute coronary artery disease. Potentially serious complications of UFH, such as hemorrhage, osteoporosis, and thrombocytopenia, have led to consideration of other options for anticoagulation, including low molecular weight heparin (LMWH) and direct thrombin inhibitors (DTIs). LMWH can be used for anticoagulation of the hemodialysis circuit, but whether this has significant benefit compared to UFH remains to be proven. Because of the somewhat unpredictable risk of severe bleeding complications when LMWH is used for other indications in dialysis patients, UFH rather than LMWH is preferred for treatment of thromboembolic disease in these patients. DTIs have been used for anticoagulation in dialysis patients with heparin-induced thrombocytopenia (HIT), with argatroban being the preferred agent if heparin-free hemodialysis cannot be performed. UFH still remains the preferred anticoagulant in the vast majority of dialysis patients requiring systemic anticoagulation and for anticoagulation of the extracorporeal hemodialysis circuit.

[Thrombocytopathy and blood complications in uremia]

Bleeding diathesis and thrombotic tendencies are characteristic findings in patients with end-stage renal disease. The pathogenesis of uremic bleeding tendency is related to multiple dysfunctions of the platelets. The platelet numbers may be reduced slightly, while platelet turnover is increased. The reduced adhesion of platelets to the vascular subendothelial wall is due to reduction of GPIb and altered conformational changes of GPIIb/IIIa receptors. Alterations of platelet adhesion and aggregation are caused by uremic toxins, increased platelet production of NO, PGI(2), calcium and cAMP as well as renal anemia. Correction of uremic bleeding is caused by treatment of renal anemia with recombinant human erythropoietin or darbepoetin alpha, adequate dialysis, desmopressin, cryoprecipitate, tranexamic acid, or conjugated estrogens. Thrombotic complications in uremia are caused by increased platelet aggregation and hypercoagulability. Erythrocyte-platelet-aggregates, leukocyte-platelet-aggregates and platelet microparticles are found in higher percentage in uremic patients as compared to healthy individuals. The increased expression of platelet phosphatidylserine initiates phagocytosis and coagulation. Therapy with antiplatelet drugs does not reduce vascular access thrombosis but increases bleeding complications in endstage renal disease patients. Heparin-induced thrombocytopenia (HIT type II) may develop in 0-12 % of hemodialysis patients. HIT antibody positive uremic patients mostly develop only mild thrombocytopenia and only very few thrombotic complications. Substitution of heparin by hirudin, danaparoid or regional citrate anticoagulation should be decided based on each single case.

N-3 Fatty Acids as Secondary Prevention against Cardiovascular Events in Patients Who Undergo Chronic Hemodialysis: A Randomized, Placebo-Controlled Intervention Trial

Patients who are treated with chronic hemodialysis (HD) experience premature cardiovascular disease and an increased mortality. N-3 polyunsaturated fatty acids (PUFA) may be effective in the secondary prevention of cardiovascular disease, but the effects of n-3 PUFA has not previously been examined in HD patients. It was hypothesized that secondary prevention with n-3 PUFA would reduce the number of cardiovascular events and death in patients who are treated with chronic HD. A randomized, double-blind, placebo-controlled intervention trial compared the effect of n-3 PUFA and a control treatment as secondary prevention of cardiovascular events in HD patients. The primary outcome was a composite of total cardiovascular events and death. A total of 206 patients were randomly assigned to treatment with n-3 PUFA or control treatment and followed for 2 yr or until reaching a predefined end point. During the trial, 121 (59%) of 206 patients reached a primary end point. N-3 PUFA had no significant effect on the primary composite end point of cardiovascular events and death (62 versus 59; NS). In the n-3 PUFA group, a significant reduction was seen in the number of myocardial infarctions (four versus 13; P = 0.036). This trial was limited by a relatively small number of patients and a large number of withdrawals. However, it is concluded that treatment with n-3 PUFA did not reduce the total number of cardiovascular events and death in this high-risk population. N-3 PUFA significantly reduced the number of myocardial infarctions as a secondary outcome, a finding that might be of clinical interest.

A patient with an uncommon etiology of intradialytic hypotension

Hemodialysis is associated with various complications, the most common being intradialytic hypotension (IDH). In the majority of cases, IDH is easily corrected and does not represent a life-threatening condition. We present a patient in whom IDH was unresponsive to various corrective strategies. A new mitral valve regurgitant lesion was diagnosed that eventually led to the patient's demise. Unusual etiologies of IDH need to be considered, particularly in instances where routine therapeutic measures are ineffective.

Predictors of Vascular Access Thrombosis Among Patients on the Cadaveric Renal Transplantation Waiting List

Acute thrombotic complications remain a constant, proportionally increasing complication before and after renal transplantation. We sought to investigate predictors for a prothrombotic state that increased the risk of vascular access thrombosis, among chronic renal failure patients during the waiting period prior to cadaveric renal transplantation. Chronic renal failure patients awaiting cadaveric renal transplantation and followed between January 2002 and January 2005 were included in this study. The 109 subjects including, 61 females and 48 males of mean age: 47.4 +/- 12.9 years; There were 36 continuous ambulatory peritoneal dialysis and 73 hemodialysis patients. Serum albumin, prealbumin, CRP, d-dimer, fibrinogen, antithrombin III, anticardiolipin antibodies (immunoglobulins G and M), homocystein, vitamin B12, folic acid, total cholesterol, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total platelet count were measured in each patient. Factor V Leiden, prothrombin 20210, ACE and MTHFR gene mutations were studied in all patients. Vascular Access thrombosis was detected in 62 patients. During follow-up 31 of 109 patients died. Vascular access thrombosis occurred in 78 patients who survived and 31 who died. The patients who died showed a significantly higher rate of thrombosis than those who survived (P = .003, OR: 4.61, CI: 1.70 to 12.50). Among the above biochemical risk factors, multiple regression analysis and backward logistic analysis revealed that d-dimer was the strongest biochemical predictor of thrombosis (P = .013, RR: 17.8). Upon evaluation of genetic risk factors, only factor V Leiden mutation was related to vascular access thrombosis (P = .001). In conclusion, the presence of vascular access thrombosis is a risk factor for mortality during the waiting period for cadaveric renal transplantation. As patients with factor V Leiden mutation or high serum d-dimer levels are at high risk for vascular access thrombosis, we recommend close monitorizing of these patients and use of anticoagulant therapy during the waiting period prior to renal transplantation.