Risk Of Vascular Access Thrombosis Research Articles

Relation between Endothelial Protein C Receptor Gene Polymorphism 6936A/G and the Risk of Vascular Access Thrombosis in Patients with End Stage Renal Disease on Hemodialysis

Relation between Endothelial Protein C Receptor Gene Polymorphism 6936A/G and the Risk of Vascular Access Thrombosis in Patients with End Stage Renal Disease on Hemodialysis

An Analysis of Vascular Access Thrombosis Events From the Proactive IV irOn Therapy in hemodiALysis Patients Trial

IntroductionTreatment of anemia in dialysis patients has been associated with increased risk of vascular access thrombosis (VAT). Proactive IV irOn Therapy in hemodiALysis Patients (PIVOTAL) was a clinical trial of proactive compared with reactive i.v. iron therapy in patients requiring hemodialysis. We analyzed the trial data to determine whether randomized treatment arm, alongside other clinical and laboratory variables, independently associated with VAT.MethodsIn PIVOTAL, 2141 adult patients were randomized. The type of vascular access (arteriovenous fistula [AVF], arteriovenous graft [AVG], or central venous catheter [CVC]) was recorded at baseline and every month after randomization. The associations between clinical and laboratory data and first VAT were evaluated in a multivariate analysis.ResultsA total of 480 (22.4%) participants experienced VAT in a median of 2.1 years of follow-up. In multivariable analyses, treatment arm (proactive vs. reactive) was not an independent predictor of VAT (hazard ratio [HR] 1.13, P = 0.18). Diabetic kidney disease (HR 1.45, P < 0.001), AVG use (HR 2.29, P < 0.001), digoxin use (HR 2.48, P < 0.001), diuretic use (HR 1.25, P = 0.02), female sex (HR 1.33, P = 0.002), and previous/current smoker (HR 1.47, P = 0.004) were independently associated with a higher risk of VAT. Angiotensin receptor blocker (ARB) use (HR 0.66, P = 0.01) was independently associated with a lower risk of VAT.ConclusionIn PIVOTAL, VAT occurred in nearly 1 quarter of participants in a median of just >2 years. In this post hoc analysis, randomization to proactive i.v. iron treatment arms did not increase the risk of VAT.

Association of Frailty With Thrombosis of Hemodialysis Vascular Access: A Prospective Taiwanese Cohort Study

Frailty, a multidimensional construct, has been associated with poor outcomes in patients receiving maintenance dialysis. This study assessed the association of frailty with dialysis vascular access patency. Multicenter prospective cohort study. 761 prevalent patients receiving hemodialysis at 9 centers in Taiwan as of January2018. Performance-based frailty was defined as 3 of the following: unintentional weight loss, weakness, exhaustion, low physical activity, and slow gait speed. Patients were categorized as prefrail if they had 1 or 2 of these characteristics. Rate of and time to dialysis access thrombosis. Data regarding vascular access events were collected for 30 months after enrollment through December 31,2020. Logistic regression analysis was used to estimate the association of clinical characteristics with frailty. Cox proportional hazards regression analysis was used to estimate the association of frailty with vascular access thrombosis adjusted for known clinical risk factors. The patients' mean age was 66 years, 46% were female, 18% had synthetic graft accesses, and 82% arteriovenous fistulas. Overall, 31% were frail, 35% were prefrail, and 34% were not frail. The frailty phenotype was associated with age, female sex, low body mass index, diabetes mellitus, and prior stroke. During a median follow-up of 731 days, 161 patients (21%) had access thrombosis events (not frail, 14%; prefrail, 20%; frail, 30%; P < 0.001). Frail patients had a higher risk of vascular access thrombosis than nonfrail patients (HR, 2.31 [95% CI, 1.55-3.39], P< 0.001). After multivariable adjustment for age and comorbidities, frailty remained significantly associated with access thrombosis for both fistulas and grafts. Limited generalizability and potential residual confounding. Frailty is associated with an increased risk of vascular access thrombosis. These findings highlight the risks of access failure experienced by frail patients receiving hemodialysis.

A randomized trial of albumin infusion to prevent intradialytic hypotension in hospitalized hypoalbuminemic patients

BackgroundIntradialytic hypotension (IDH) is a frequent complication of intermittent hemodialysis (IHD), occurring from 15 to 50% of ambulatory sessions, and is more frequent among hospitalized patients with hypoalbuminemia. IDH limits adequate fluid removal and increases the risk for vascular access thrombosis, early hemodialysis (HD) termination, and mortality. Albumin infusion before and during therapy has been used for treating IDH with the varying results. We evaluated the efficacy of albumin infusion in preventing IDH during IHD in hypoalbuminemic inpatients.MethodsA randomized, crossover trial was performed in 65 AKI or ESKD patients with hypoalbuminemia (albumin < 3 g/dl) who required HD during hospitalization. Patients were randomized to receive 100 ml of either 0.9%sodium chloride or 25% albumin intravenously at the initiation of each dialysis. These two solutions were alternated for up to six sessions. Patients' vital signs and ultrafiltration removal rate were recorded every 15 to 30 min during dialysis. IDH was assessed by different definitions reported in the literature. All symptoms associated with a noted hypotensive event as well as interventions during the dialysis were recorded.ResultsSixty-five patients were submitted to 249 sessions; the mean age was 58 (pm 12), and 46 (70%) were male with a mean weight of 76 (pm 18) kg. The presence of IDH was lower during albumin sessions based on all definitions. The hypotension risk was significantly decreased based on the Kidney Disease Outcomes Quality Initiative definition; (15% with NS vs. 7% with albumin, p = 0.002). The lowest intradialytic SBP was significantly worse in patients who received 0.9% sodium chloride than albumin (NS 83 vs. albumin 90 mmHg, p = 0.035). Overall ultrafiltration rate was significantly higher in the albumin therapies [NS − 8.25 ml/kg/h (− 11.18 5.80) vs. 8.27 ml/kg/h (− 12.22 to 5.53) with albumin, p = 0.011].ConclusionIn hypoalbuminemic patients who need HD, albumin administration before the dialysis results in fewer episodes of hypotension and improves fluid removal. Albumin infusion may be of benefit to improve the safety of HD and achievement of fluid balance in these high-risk patients.ClinicalTrials.gov Identifier: NCT04522635

MO015HAEMODIALYSIS VASCULAR ACCESS THROMBOSIS: AN ANALYSIS OF EVENTS FROM THE PROACTIVE IV IRON THERAPY IN HAEMODIALYSIS PATIENTS (PIVOTAL) TRIAL

Abstract Background and Aims Haemodialysis vascular access thrombosis (VAT) is a common occurrence that undermines the safe and effective delivery of haemodialysis (HD) and has been associated with anaemia therapy. In the Proactive IV Iron Therapy in Haemodialysis Patients trial (PIVOTAL), proactive high-dose intravenous iron dosing was compared with reactive low-dose intravenous iron dosing. VAT was a pre-specified secondary endpoint. Here we present data detailing the VAT events in PIVOTAL, alongside univariate and multivariate analyses of risk association, testing the hypothesis that VAT may be independently associated with a proactive iron dosing regimen. Method In PIVOTAL 2141 adults with end-stage kidney disease within 12 months of initiating regular HD were randomised 1:1 to either high-dose intravenous iron administered proactively, or low-dose intravenous iron administered reactively, on the basis of monthly Ferritin and Transferrin saturation levels. Erythropoiesis Stimulating Agents were dosed sufficiently to maintain a haemoglobin of 100 to 120g/L. Vascular access use was recorded at baseline and on a monthly basis. VAT was regarded as a safety event with investigators mandated to record such events. VAT was defined clinically, with investigators expected to report thrombotic occlusion of the access (either arteriovenous or catheter thrombosis) significant enough to prevent further effective use without intervention. Baseline demographic, blood pressure and laboratory data underwent univariate analysis with regard to first event of VAT. Primary patient demographics (age, gender, primary renal disease, randomised treatment arm) were put forward for inclusion in a multivariable cox proportional hazards model alongside variables that associated on univariate testing with α&amp;lt;0.05. Analyses were performed using SAS software, version 9.4 (SAS Institute). Results 2141 eligible patients were randomised, of whom 877/2141 (41.0%) were using a central venous catheter (CVC), 1209/2141 (56.5%) an arteriovenous fistula (AVF), and 55/2141 (2.6%) an arteriovenous graft (AVG) at baseline. Over a median follow up of 2.1 years, 480/2141 (22.4%) experienced a VAT event; 194/887 (21.9%) of CVC patients; 263/1209 (21.8%) of AVF patients; and 23/55 (41.8%) of AVG patients. On univariate testing VAT events associated with diabetes as a cause of kidney failure (HR 1.44, 95%CI 1.19 to 1.74, p&amp;lt;0.001), AVG use at baseline (HR 2.37, p&amp;lt;0.001), digoxin use (HR 2.35, p=0.002), and diuretic use (HR 1.24, p=0.02). Angiotensin receptor blocker (ARB) use associated with less VAT (HR 0.66, p=0.013), as did male gender (HR 0.74, p=0.002), and never having smoked (HR 0.68, p=0.008). No association was seen with age, AVF use, CVC use, blood pressure, history of cardiovascular (CV) disease, atrial fibrillation, other CV medications, C-reactive protein, haemoglobin, transferrin saturation, ferritin or randomised treatment group (Proactive 262/1093 (24.0%) v Reactive 218/1048 (20.8%), HR 1.15, p=0.12) . Multivariate analysis found diabetes as a cause of kidney failure (HR 1.45, p&amp;lt;0.001), AVG use (HR 2.29, p&amp;lt;0.001), digoxin exposure (HR 2.48, p&amp;lt;0.001) and diuretic exposure (HR 1.25, p=0.018) to independently associate with VAT. Male gender (HR 0.75, p=0.002), never smoked (HR 0.68, p=0.004) and ARB use (HR 0.66, p=0.011) were found to independently associate with lower risk of VAT. Investigation of interaction between significant predictors found diuretic use in AVF patients to reach nominal significance (p=0.033). No other significant interactions being demonstrated. Conclusion In PIVOTAL, VAT affected nearly one quarter of the cohort over a median of 2.1 years. Diabetes as a cause of kidney failure, active smoking, AVG use, female gender, exposure to digoxin, and exposure to diuretic were independently associated with VAT, but this was not the case with higher iron dosing. ARB use was independently associated with lower risk.

Delivering Safe and Effective Hemodialysis in Patients with Suspected or Confirmed COVID-19 Infection: A Single-Center Perspective from Italy.

New “Severe Acute Respiratory Syndrome Coronavirus 2” (SARS-CoV-2) is responsible for a clinical entity named Coronavirus Disease 2109 (COVID-19) by the World Health Orgazination, which is now a pandemic (1). In Europe, Italy was the first, and so far the largest, epicenter of the epidemic. It is now clear that many asymptomatic and paucisymptomatic patients went undetected, causing significant diffusion of the disease. Asymptomatic infections are common: among 634 confirmed patients on board the “Diamond Princess” cruise ship, 306 were symptomatic and 328 asymptomatic at the time of testing (2). It is now clear that when a patient with atypical severe pneumonia was diagnosed as COVID-19 in a small city, Codogno, in a previously healthy 38-year-old man, on February 20, 2020, more patients with undetected COVID-19 were present in Northern Italy. In addition to the cluster around Codogno, about 50 km south of Milan, which was promptly put under strict lockdown, two additional relevant clusters emerged near the cities of Bergamo and Brescia. The delay in enforcing a lockdown in the latter areas is probably one of the leading causes of the more severe outbreak now affecting these provinces. Extensive testing in the initial phase of disease diffusion was adopted in the Italian Veneto area, resulting in better containment of new cases. A nationwide lockdown measure was passed by the Italian government when Northern Italy, which has the highest concentration of well organized hospitals in the country, started showing signs of difficulty handling the rapid increase of patients in need of treatment in intensive care units (ICUs). A comparison of Chinese and Italian data on COVID-19 may be of interest to other countries where the disease is now spreading. The Chinese Center for Disease Control and Prevention described the characteristics of a large cohort of COVID-19 patients (3), showing that …

Risk of vascular access thrombosis in patients with systemic lupus erythematosus on hemodialysis.

Anticardiolipin antibody is associated with increased risk of vascular access thrombosis (VAT) in hemodialysis (HD) patients. Systemic lupus erythematous (SLE) patients have a high prevalence of anticardiolipin antibodies, but it is not clear whether these patients are at high risk of developing vascular access thrombosis. Thirty six SLE patients on HD, who had either an arterio-venous (AV) graft or AV fistula as vascular access, and were not on anticoagulation treatment, were retrospectively identified at Henry Ford Hospital. A similar number of patients without SLE, matched for age, sex, race and type of vascular access were selected as a control population. Vascular access thrombosis rate at one year was compared between two groups. Mean age at dialysis was 36+/-10 years in 36 SLE patients (28 females, 8 males) and was 38+/-6.4 years in 36 non-SLE patients (29 females, 7 males). Of all patients, 29/36 (80.5%) SLE and 27/36 (75%) non-SLE patients had AV grafts, whereas the rest had AV fistulas as vascular access (19.5% SLE and 25% non-SLE patients). Out of 36 SLE patients, 24 (66.6%) patients developed VAT at one year as compared to 14 (38.9%) patients in non-SLE group (p<0.05). The odds ratio of VAT in SLE patients was 3.1 (95% CI 1.2-8.2). SLE patients on hemodialysis are more likely to develop vascular access thrombosis as compared to non-SLE patients.

Association Between Thrombophilic Gene Mutations and the Risk of Vascular Access Thrombosis in Hemodialysis Patients.

The cause of thrombosis in hemodialysis vascular access is considered to be of a multifactorial nature, including stenosis of the venous or arterial connection. Therefore, identification of relevant thrombotic risk factors could lead to an improved antithrombotic therapy. This case control study was performed to evaluate the relationship between Factor V (G1691A and A4070G) and Factor II polymorphisms and vascular access thrombosis in hemodialysis patients. One hundred and twenty-one patients undergoing dialysis were selected as subjects. This sample was divided into two groups; a case group of 60 patients who had sustained one or more thrombotic events that resulted in vascular access failure and a control group of 61 patients, who never had a thrombotic occlusion of a functioning permanent dialysis access. Our data demonstrated a significantly increased risk of vascular access thrombosis in carriers of the mutant FV (G1691A and A4070G) polymorphisms (P < 0.05).Further studies on a large-scale population and other genetic variants will be needed to find candidate genes for vascular access thrombosis in hemodialysis patients.

Hyperhomocysteinemia and vascular access thrombosis in hemodialysis patients: a retrospective study

BackgroundElevated total plasma homocysteine is an independent risk factor for arterial and venous thrombosis in patients with normal renal function. Patients on hemodialysis have a high prevalence of mild to moderate hyperhomocysteinemia. Conflicting retrospective analyses and prospective studies have been reported regarding the association between total homocysteine levels and hemodialysis vascular thrombosis. The purpose of this retrospective study was to investigate the relationship between hyperhomocysteinemia and vascular access thrombosis (VAT) in patients on hemodialysis.MethodsOne hundred and twenty-five patients undergoing dialysis were selected as subjects. The experimental group participants were identified as those having one or more VAT during the previous 13 months and the control group participants had no access thrombosis during the same period. Additional subgroup analysis included the presence of hypertension, diabetes, low-density lipoprotein levels, sex, and use of aspirin.ResultsNo statistically significant difference was found in total homocysteine levels between the two groups (P = 0.27). No association was found between VAT and sex (P = 0.09), VAT and hypertension (P = 0.96), VAT and diabetes (P = 0.49), nor VAT and low-density lipoprotein level (P = 0.04). A lower rate of VAT was associated with aspirin intake (P = 0.04).ConclusionThis study did not demonstrate a relationship between total homocysteine concentrations and risk of VAT in patients with end-stage renal disease on hemodialysis. There were no significant differences in the number of VAT across additional variables of sex and previous morbidity. Aspirin intake was associated with a lower incidence of VAT.

Treatment of Anaemia with Erythropoiesis-Stimulating Agents in Patients with Chronic Kidney Disease Does Not Lower Mortality and May Increase Cardiovascular Risk: A Meta-Analysis

Background/Aims: Interpretation of the results of earlier meta-analyses in chronic kidney disease (CKD) patients on the impact of anaemia treatment with erythropoiesis-stimulating agents (ESAs) on clinical outcomes has been hampered by the inclusion of small trials and trials of short duration. We re-evaluated the benefits and harms of treating anaemia, including only relevant clinical trials. Methods: We conducted a systematic review and meta-analysis of randomised controlled trials performed in adults with CKD which allocated patients to different doses of ESAs, and we compared the effect of these interventions on vascular access thrombosis, stroke, risk of end-stage renal disease (ESRD) and all-cause mortality. Additional inclusion criteria were studies with a duration of at least 1 year and enrolling more than 500 participants. Results: Five trials (7,902 participants) met the inclusion criteria and were included in the meta-analysis. The number of patients enrolled in each trial ranged from 596 to 4,038. The mean/median duration of follow-up ranged from 14 to 36 months. A higher haemoglobin target was associated with increased risk of vascular access thrombosis (RR 1.343; 95% CI 1.162–1.554; p = 0.0005) and stroke (RR 1.735; 95% CI 1.323–2.275; p = 0.0005), and no effect on risk of ESRD (RR 1.089; 95% CI 0.986–1.203; p = 0.094) or all-cause mortality (RR 1.148; 95% CI 0.977–1.350; p = 0.093). Conclusion: In CKD patients, treatment of anaemia with ESAs targeting a higher haemoglobin value does not lower mortality or reduce the risk of ESRD, and may increase cardiovascular risk.

Intradialytic Hypotension Strikes Again

Intradialytic hypotension (IDH) has plagued hemodialysis (HD) patients and their caregivers since the early days of renal replacement therapy. Its persistence in the current era is evident from the results of the 1426-patient Hemodialysis (HEMO) study in this issue of JASN in which a median of 12.5

Role of Thrombophilia in Vascular Access Thrombosis Among Chronic Hemodialysis Patients in Tunisia

Vascular access thrombosis represents a serious and common problem in hemodialysis patients. Therefore, identification of relevant thrombotic risk factors could lead to an improved antithrombotic therapy. This case control study was performed to evaluate the relationship between some thrombophilias and vascular access thrombosis in hemodialysis patients. Seventy-eight patients undergoing dialysis (between May 2007 and September 2009) were selected as subjects. This sample was divided into two groups; a case group of 28 patients who had sustained one or more thrombotic events that resulted in vascular access failure and a control group of 50 patients, who had never had a thrombotic occlusion of a functioning permanent dialysis access. Antithrombin, protein C and protein S levels were measured. Also, both groups were tested for the factor V Leiden mutation, the prothrombin G20210A mutation, the methylene tetrahydrofolate reductase C677T and A1298C mutations. Among genetic mutations of factor V Leiden, prothrombin G20210A and methylene tetrahydrofolate reductase genes, the C677T methylene tetrahydrofolate reductase mutation was the only significant genetic cause of vascular access thrombosis (P=0.005). Our data demonstrated a significantly increased risk of vascular access thrombosis in carriers of the C677T methylene tetrahydrofolate reductase mutation.

Risk of Vascular access Thrombosis in Patients with Systemic Lupus Erythematosus on Hemodialysis

Introduction Anticardiolipin antibody is associated with increased risk of vascular access thrombosis (VAT) in hemodialysis (HD) patients. Systemic lupus erythematous (SLE) patients have a high prevalence of anticardiolipin antibodies, but it is not clear whether these patients are at high risk of developing vascular access thrombosis. Methods Thirty six SLE patients on HD, who had either an arterio-venous (AV) graft or AV fistula as vascular access, and were not on anticoagulation treatment, were retrospectively identified at Henry Ford Hospital. A similar number of patients without SLE, matched for age, sex, race and type of vascular access were selected as a control population. Vascular access thrombosis rate at one year was compared between two groups. Results Mean age at dialysis was 36±10 years in 36 SLE patients (28 females, 8 males) and was 38±6.4 years in 36 non-SLE patients (29 females, 7 males). Of all patients, 29/36 (80.5%) SLE and 27/36 (75%) non-SLE patients had AV grafts, whereas the rest had AV fistulas as vascular access (19.5% SLE and 25% non-SLE patients). Out of 36 SLE patients, 24 (66.6%) patients developed VAT at one year as compared to 14 (38.9%) patients in non-SLE group (p&lt;0.05). The odds ratio of VAT in SLE patients was 3.1 (95% CI 1.2–8.2). Conclusion SLE patients on hemodialysis are more likely to develop vascular access thrombosis as compared to non-SLE patients.

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 B 12, 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.

Association of Various Point Mutations as Risk Factors for Synthetic Graft Thrombosis in African American Hemodialysis Patients

Single-nucleotide polymorphisms in the genes that code for coagulation factor V (factor V (Leiden)) and II (prothrombin G20210A), as well as the methyltetrahydrofolate reductase (MTHFR) have been implicated in the majority of cases of hereditary thrombophilia. In our hemodialysis patient population, comprised mainly of African Americans, we have seen a high incidence of early vascular access thrombosis without any identifiable predisposing factors. In some instances, there is recurrent access thrombosis that may be related to an inherited condition. In this study we evaluated the presence of these gene mutations and their association with increased risk of recurrent vascular access thrombosis in our hemodialysis patient population. Our results show that factor V Leiden and factor II prothrombin point mutations did not appear to increase the risk of vascular access thrombosis in African Americans with end-stage renal disease on hemodialysis. Patients heterozygous for the MTHFR gene, also did not show a significant increased risk for synthetic graft thrombosis.

Association of Various Point Mutations as Risk Factors for Synthetic Graft Thrombosis in African American Hemodialysis Patients

Single-nucleotide polymorphisms in the genes that code for coagulation factor V (factor V (Leiden)) and II (prothrombin G20210A), as well as the methyltetrahydrofolate reductase (MTHFR) have been implicated in the majority of cases of hereditary thrombophilia. In our hemodialysis patient population, comprised mainly of African Americans, we have seen a high incidence of early vascular access thrombosis without any identifiable predisposing factors. In some instances, there is recurrent access thrombosis that may be related to an inherited condition. In this study we evaluated the presence of these gene mutations and their association with increased risk of recurrent vascular access thrombosis in our hemodialysis patient population. Our results show that factor V Leiden and factor II prothrombin point mutations did not appear to increase the risk of vascular access thrombosis in African Americans with end-stage renal disease on hemodialysis. Patients heterozygous for the MTHFR gene, also did not show a significant increased risk for synthetic graft thrombosis.

Hyperhomocysteinemia, anticardiolipin antibody status, and risk for vascular access thrombosis in hemodialysis patients

Vascular access failure is an important cause of morbidity in end-stage renal failure patients on hemodialysis. Currently, little is known about risk factors that predispose certain hemodialysis patients to recurrent access thrombosis. Hyperhomocysteinemia (common in patients with renal failure) predisposes people with normal renal function to recurrent and early-onset venous thrombosis, although the effect on vascular access thrombosis is currently unknown. Previous studies have suggested that high titers of IgG anticardiolipin antibody (IgG-ACA) predispose hemodialysis patients to access thrombosis. This cross sectional study was designed to assess for an association between two predictive variables, hyperhomocysteinemia and elevated titers of IgG-ACA, and vascular access thrombosis in patients undergoing chronic hemodialysis. Risk factors for vascular access thrombosis were documented, and the number of episodes of access thrombosis was recorded for the previous three years in patients undergoing hemodialysis. Midweek predialysis total homocysteine and IgG-ACA levels were measured in all subjects. Of the 118 patients who were enrolled, 75.4% had a native arteriovenous fistula. Episodes of vascular access thrombosis were recorded for the previous three years; 34 (28.8%, 95% CI 20.9 to 37.9%) patients had 72 episodes of access thrombosis over the period of risk. Mean homocysteine levels were not significantly different between these 34 patients (28.6 micromol/liter, 95% CI 24.5 to 32.7) and the patients who had no episodes of graft thrombosis (29.8 micromol/liter, 95% CI 26.7 to 32.9). Sixty-seven unselected patients had IgG-ACA levels drawn for analysis, and all assays were negative. The only variable that was associated with a higher risk for graft thrombosis was the type of vascular access placed (odds ratio 4.0, 95% CI 1.6 to 9.6 for patients with a synthetic graft compared with those with an arteriovenous fistula). No association was found between homocysteine levels or anticardiolipin antibody and vascular access thrombosis in our patient population.

Effect of nifedipine on changes in fibrinogen and von Willebrand factor in haemodialysis patients treated with recombinant human erythropoietin

Erythropoietin (EPO) therapy in haemodialysis patients may be associated with the development of hypertension and vascular access thrombosis. Raised levels of fibrinogen and von Willebrand factor have been implicated in the pathophysiology of thrombosis under these circumstances. The effect of nifedipine, used to treat EPO therapy-related hypertension, on levels of fibrinogen and von Willebrand factor antigen (vWf) was studied in a group of 21 EPO-treated haemodialysis patients. Significant increments in both fibrinogen and vWf following EPO therapy were observed in the 13 patients who did not receive nifedipine (fibrinogen (median range), pre-EPO: 3.73 (2.41-6.38) mg/ml, post-EPO: 4.59 (3.03-8.80) mg/ml, P < 0.05; vWf pre-EPO: 183 (118-374)% normal, post-EPO: 253 (124-392)% normal, P < 0.01). Similar changes were not seen in the eight nifedipine-treated patients (fibrinogen, pre-EPO: 3.35 (2.58-6.32) mg/ml, post-EPO: 3.36 (2.69-7.20) mg/ml, P = NS; vWf, pre-EPO: 176 (104-298)% normal, post-EPO: 175 (82-371)% normal, P = NS). These effects were independent of blood pressure control. The use of nifedipine to treat EPO therapy-related hypertension may therefore potentially help to reduce the risk of vascular access thrombosis.