***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Medications affect many measures of hemodialysis patients ' well-being . METHODS The Dialysis Outcomes and Practice Patterns Study ( DOPPS ) has evaluated the use of hydroxymethyl glutaryl coenzyme A reductase inhibitors ( statins ) , analgesics , antidepressants , and multivitamins . Additionally , DOPPS has reported on the associations between vascular access outcomes and related medications . RESULTS Prescription of statins varied widely across countries , with the highest use in the United States . Patients prescribed statins had lower risk of cardiac and noncardiac causes of mortality than those who were not prescribed statins . DOPPS data also show that statins are underprescribed relative to recent Kidney Disease Outcomes Quality Initiative guidelines . No guidelines have been established for analgesic use , but high pain levels self-reported by hemodialysis patients suggest opportunities for improved pain management strategies . Guidelines for analgesic use in dialysis patients may help balance improved quality of life against potential side effects of analgesics . Medical and patient question naires show that depression in hemodialysis patients is common , frequently underdiagnosed , usually untreated , and associated with increased rates of mortality and hospitalization . Calcium channel blockers were associated with improved primary graft patency , aspirin with improved secondary graft patency , and angiotensin-converting enzyme inhibitors with improved secondary fistula patency . All 3 medications were associated with significantly decreased relative risk for access failure . There is large country variation in multivitamin use , with significantly higher use in the United States compared with Europe and Japan . Patients taking multivitamins  had lower mortality risk than patients not taking multivitamins .  CONCLUSION DOPPS findings on medications indicate that prospect i ve trials are needed before guidelines can be developed for appropriate medication use in these different therapeutic categories BACKGROUND Several drugs have been proposed to improve vascular access patency based on favorable anticoagulant , antiplatelet , or vascular-remodeling properties . However , there is little evidence to guide drug strategies . METHODS The association between vascular access patency and the use of specific drugs was studied in a large sample of US hemodialysis patients enrolled in the Dialysis Outcomes and Practice Patterns Study , an international , prospect i ve , observational study . In general , it was assumed that the drugs were prescribed for indications unrelated to vascular access preservation . Primary ( unassisted survival ) and secondary vascular access patency ( assisted survival ) were modeled using Cox regression ( time to failure ) adjusted for age , sex , race , body mass index , incidence to end-stage renal disease , diabetes mellitus , hypertension , valvular disease , chronic obstructive pulmonary disease , aortic aneurysm , deep-vein thrombosis , number of previous permanent accesses , and facility-clustering effects . Fistulae ( n = 900 ) and grafts ( n = 1,944 ) were evaluated separately . Technical failures within the first 30 days of surgical placement were excluded from the analysis . RESULTS Treatment with calcium channel blockers was associated with improved primary graft patency ( relative risk [ RR ] for failure , 0.86 ; P = 0.034 ) . Aspirin therapy was associated with better secondary graft patency ( RR , 0.70 ; P < 0.001 ) . Treatment with angiotensin-converting enzyme inhibitors was associated with significantly better secondary fistula patency ( RR , 0.56 ; P = 0.010 ) . Patients administered warfarin showed worse primary graft patency ( RR , 1.33 ; P = 0.037 ) . CONCLUSION These findings should help guide clinical trial priorities toward vascular access preservation using one or more of the agents that show significant risk reduction for access failure in this study The optimal vascular access for chronic maintenance hemodialysis is the arteriovenous fistula ( AVF ) . Several studies suggest a role for antiplatelet agents in the prevention of primary AVF failure . A double-blind , r and omized trial was conducted to assess the efficacy and safety of clopidogrel in hemodialysis patients . Ninety three patients were r and omized to receive 75 mg/daily of clopidogrel or placebo .  The treatment was initiated 7–10 days prior to scheduled access surgery and continued up to six weeks postoperatively , and then patients were monitored for six months . The primary outcome was AVF failure eight weeks after fistula creation . With a permuted block r and omization schedule , 46 patients received clopidogrel and 47 patients received control placebo .  The primary AVF failures at two months were 21.6 % in placebo group and 5.2 % in clopidogrel group ( P = 0.03 ) . The hazard ratio for the incidence of primary AVF failure was 0.72 ( CI 95 % , 0.41–1.01 ) . Analysis of covariables indicated that this effect occurred principally as a result of clopidogrel administration . First hemodialysis from newly created AVF in clopidogrel group was significantly more successful than placebo group ( P = 0.008 ) . No life-threatening adverse event or severe bleeding was recorded in both groups . Clopidogrel seems to be effective and safe for prevention of primary AVF failure in hemodialysis patients Background Haemodialysis ( HD ) is critically dependent on the availability of adequate access to the systemic circulation , ideally via a native arteriovenous fistula ( AVF ) . The Primary failure rate of an AVF ranges between 20–54 % , due to thrombosis or failure of maturation . There remains limited evidence for the use of anti-platelet agents and uncertainty as to choice of agent(s ) for the prevention of AVF thrombosis . We present the study protocol for a r and omised , double-blind , placebo-controlled , clinical trial examining whether the use of the anti-platelet agents , aspirin and omega-3 fatty acids , either alone or in combination , will effectively reduce the risk of early thrombosis in de novo AVF . Methods / Design The study population is adult patients with stage IV or V chronic kidney disease ( CKD ) currently on HD or where HD is planned to start within 6 months in whom a planned upper or lower arm AVF is to be the primary HD access . Using a factorial- design trial , patients will be r and omised to aspirin or matching placebo , and also to omega-3 fatty acids or matching placebo , result ing in four treatment groups ( aspirin placebo/omega-3 fatty acid placebo , aspirin/omega-3 fatty acid placebo , aspirin placebo/omega-3 fatty acid , aspirin/omega-3 fatty acid ) . R and omisation will be achieved using a dynamic balancing method over the two stratification factors of study site and upper versus lower arm AVF . The medication will be commenced pre-operatively and continued for 3 months post surgery . The primary outcome is patency of the AVF at three months after r and omisation . Secondary outcome measures will include functional patency at six and twelve months , primary patency time , secondary ( assisted ) patency time , and adverse events , particularly bleeding . Discussion This multicentre Australian and New Zeal and study has been design ed to determine whether the outcome of surgery to create de novo AVF can be improved by the use of aspirin and /or omega-3 fatty acids . Recently a placebo-controlled trial has shown that clopidogrel is effective in safely preventing primary AVF thrombosis , but ineffective at increasing functional patency . Our study presents significant differences in the anti-platelet agents used , the study design , and surgical and patient demographics that should contribute further evidence regarding the efficacy of anti-platelet agents . Trial Registration Australia & New Zeal and Clinical Trials Register ( ACTRN12607000569404 ) Vascular access failure causes 20 % of all hospitalizations of dialysis patients . Native arteriovenous fistulas , the best type of dialysis vascular access , have a 1-year primary patency rate that is extremely variable , ranging 40 - 80 % . Neointimal hyperplasia is the most important cause of arteriovenous fistula late primary dysfunction . In recent years the arteriovenous fistula late primary patency rate has not improved because of the increase of old uremic patients with a high number of comorbidities and the lack of new therapeutic interventions . Therefore , we performed a long-term case-control study to analyze which factors or drugs may affect native arteriovenous fistula late primary patency rate in 60 incident hemodialysis patients . The arteriovenous fistula late primary patency rate was 75.1 % after 12 months , 58.5 % after 24 months , and 50 % after 987 days . Homocysteine levels during follow-up had a significant direct association with vascular access failure ( event vs. event-free 28.5+/-1.9 vs. 22.3+/-1.2 micromol/L , p<0.01 ) . Folate values had a trend toward an inverse relationship with arteriovenous fistula failure ( event vs. event-free 11.5+/-1.2 vs. 14.6 vs. 1.1 ng/mL , p=0.06 ) . Patients treated with folic acid and /or statin had an arteriovenous fistula late primary patency rate significantly higher than patients without folic acid and statin therapy , respectively , 81.7 % vs. 66 % after 1 year and 71.5 % vs. 39.1 % after 2 years ( p=0.02 ) . Many other factors were not associated with vascular access failure . Statin and homocysteine-lowering folic acid therapy is associated with prolonged arteriovenous fistula survival . It is important to perform r and omized trials to verify our observation Diets enriched with fish oil may favorably affect the vascular perturbations underlying synthetic graft thrombosis . Therefore , these studies were design ed to test the hypothesis that diets enriched with fish oil would decrease the incidence of thrombosis in newly constructed polytetrafluorethylene grafts . A double-blind , r and omized trial was conducted . Twenty-four patients were r and omized to receive 4000 mg of fish oil or 4000 mg of control oil . Both preparations were enriched with antioxidants and deodorized with peppermint . Patients began therapy within 2 wk after graft placement and were monitored for 12 mo or until thrombosis developed . With a permuted-block r and omization schedule , 12 patients received fish oil and 12 patients received control oil . The primary patency rates at 365 d were 14.9 % for the control group and 75.6 % for the fish oil-treated group . Survival analysis revealed a significant difference between fish oil-treated and untreated patients ( P < 0.03 , Mantel-Cox test ) , with a power of 90 % . Moreover , analysis of covariables , including age of > or = 50 yr , gender , race , body weight , diabetes mellitus , bleeding times , and lipid profiles , indicated that this effect occurred principally as a result of fish oil administration . Importantly , fish oil treatment also decreased venous outflow resistance and systemic BP , compared with control values . Fish oils possess unique biologic properties that favorably affect the incidence of polytetrafluorethylene graft thrombosis , and they thus represent a potential treatment strategy for the prevention of access thrombosis Thrombosis of hemodialysis vascular access grafts represents a major medical and economic burden . Experimental and clinical models suggest a role for antiplatelet agents in the prevention of thrombosis . The study was design ed to determine the efficacy of the combination of aspirin and clopidogrel in the prevention of graft thrombosis . The study was a r and omized , double-blind trial conducted at 30 hemodialysis units at Veterans Affairs medical centers . Participants undergoing hemodialysis with a polytetrafluoroethylene graft in the arm were r and omized to receive either double placebos or aspirin ( 325 mg ) and clopidogrel ( 75 mg ) daily . Participants were to be monitored while receiving study medications for a minimum of 2 yr . The study was stopped after r and omization of 200 participants , as recommended by the Data Safety and Monitoring Board because of a significantly increased risk of bleeding among the participants receiving aspirin and clopidogrel therapy . The cumulative incidence of bleeding events was significantly greater for those participants , compared with participants receiving placebos [ hazard ratio , 1.98 ; 95 % confidence interval ( CI ) , 1.19 to 3.28 ; P = 0.007 ] . Twenty-three participants in the placebo group and 44 participants in the active treatment group experienced a bleeding event ( P = 0.006 ) . There was no significant benefit of active treatment in the prevention of thrombosis ( hazard ratio , 0.81 ; 95 % CI , 0.47 to 1.40 ; P = 0.45 ) , although there was a trend toward a benefit among participants who had not experienced previous graft thrombosis ( hazard ratio , 0.52 ; 95 % CI , 0.22 to 1.26 ; P = 0.14 ) . In the hemodialysis population , therapy with aspirin and clopidogrel was associated with a significantly increased risk of bleeding and probably would not result in a reduced frequency of graft thrombosis BACKGROUND AND OBJECTIVES Neointimal hyperplasia is the major cause of vascular access failure in hemodialysis patients .  Statins reduce neointimal hyperplasia in experimental models , which may 
    Output:
    
Treatment with the antiplatelet agents ticlopidine and dipyridamole ( hazard ratio [ HR ] , 3.54 ; 95 % CI , 1.07 - 11.76 ; P 1⁄4 .04 ) , or aspirin ( HR , 2.49 ; 95 % CI , 1.31 - 4.73 ; P 1⁄4 .005 ) was associated with worse AV fistula patency rates compared with nonuse in this retrospective cohort study .
The presence of oxidative stress and inflammation accelerates neointima formation and thrombosis .
Aspirin not only acts as an antiplatelet agent but also reduces oxidative stress and inflammation .
Importantly double antiplatelet treatment with clopidogrel plus aspirin is not indicated due to an increased risk of bleeding .