***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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    ***EXAMPLES*** 
    Input: Introduction Thrombosis of tunneled central venous catheters ( CVC ) in hemodialysis ( HD ) patients is common and it can lead to the elimination of vascular sites . To compare the efficacy of alteplase vs. urokinase in reestablishing adequate blood flow through completely occluded vascular catheters . Methods In this r and omized study , patients with completely occluded tunneled HD catheters received 40 minutes intracatheter dwell with alteplase ( 1 mg/mL ) or urokinase ( 5000 IU/mL ) . Primary endpoint was the proportion of patients with occluded catheters achieving post-thrombolytic blood flow of ≥250 mL/min . Safety endpoints included the incidence of hemorrhagic and infectious complications . Findings Eligible adult patients ( n = 100 ) were treated with alteplase ( n = 44 ) or urokinase ( n = 56 ) . The two groups were similar in gender ( male : 51.8 % vs. 56.8 % , P = 0.35 ) , age ( 60 ± 12 vs. 59 ± 13 years , P = 0.71 ) , time on dialysis ( 678 ± 203 vs. 548 ± 189 days , P = 0.77 ) , diabetes and cardiovascular disease ( 55.6 % vs. 70.4 % , P = 0.08 and 17.8 % vs. 22.7 % , P = 0.38 , respectively ) , jugular vein as main vascular access ( 54.8 % vs. 62.5 % , P = 0.57 ) , and time of CVC ( 278 ± 63 vs. 218 ± 59 days , P = 0.67 ) . Primary success with alteplase and urokinase occurred in 42/44 ( 95 % ) vs. 46/56 ( 82 % ) , P = 0.06 . Success was not achieved after the second dose of alteplase and urokinase in 1 and 7 cases , respectively ( 2 % vs. 12 % , P = 0.075 ) . Serious adverse effects were not observed in both groups . There was no difference between the two groups in infectious complications ( P = 0.94 ) . Discussion Alteplase and urokinase are effective thrombolytic agents for restoring HD catheter patency . Our study has revealed a likely slight superiority of alteplase over urokinase for unblocking central lines , but which has enrolled too few patients to be able to detect a difference of this size BACKGROUND The effectiveness of various solutions instilled into the central venous catheter lumens after each hemodialysis session ( catheter locking solutions ) to decrease the risk of catheter malfunction and bacteremia in patients undergoing hemodialysis is unknown . METHODS We r and omly assigned 225 patients undergoing long-term hemodialysis in whom a central venous catheter had been newly inserted to a catheter-locking regimen of heparin ( 5000 U per milliliter ) three times per week or recombinant tissue plasminogen activator ( rt-PA ) ( 1 mg in each lumen ) substituted for heparin at the midweek session ( with heparin used in the other two sessions ) . The primary outcome was catheter malfunction , and the secondary outcome was catheter-related bacteremia . The treatment period was 6 months ; treatment assignments were concealed from the patients , investigators , and trial personnel . RESULTS A catheter malfunction occurred in 40 of the 115 patients assigned to heparin only ( 34.8 % ) and 22 of the 110 patients assigned to rt-PA (20.0%)--an increase in the risk of catheter malfunction by a factor of almost 2 among patients treated with heparin only as compared with those treated with rt-PA once weekly ( hazard ratio , 1.91 ; 95 % confidence interval [ CI ] , 1.13 to 3.22 ; P = 0.02 ) . Catheter-related bacteremia occurred in 15 patients ( 13.0 % ) assigned to heparin only , as compared with 5 ( 4.5 % ) assigned to rt-PA ( corresponding to 1.37 and 0.40 episodes per 1000 patient-days in the heparin and rt-PA groups , respectively ; P = 0.02 ) . The risk of bacteremia from any cause was higher in the heparin group than in the rt-PA group by a factor of 3 ( hazard ratio , 3.30 ; 95 % CI , 1.18 to 9.22 ; P = 0.02 ) . The risk of adverse events , including bleeding , was similar in the two groups . CONCLUSIONS The use of rt-PA instead of heparin once weekly , as compared with the use of heparin three times a week , as a locking solution for central venous catheters significantly reduced the incidence of catheter malfunction and bacteremia . ( Current Controlled Trials number , IS RCT N35253449 . ) Objective : To compare dialysis catheter function according to catheter site . Design : Multicenter , open , r and omized controlled trial . Setting : Nine university-affiliated hospitals and three general hospitals in France . Patients : Seven hundred thirty-six patients in intensive care units who required a first venous catheterization to perform either intermittent hemodialysis ( 470 patients with 1275 sessions ) or continuous renal replacement therapy ( 266 patients with 1003 days ) . Intervention : Patients r and omly received either femoral ( n = 370 ) or jugular ( n = 366 ) catheterization . For the jugular site , right-side position ( n = 252 ) was recommended . Measurements and Main Results : Time to catheter ablation for dysfunction , urea reduction ratio ( intermittent hemodialysis ) , and downtime ( continuous renal replacement therapy ) were assessed for all participants and evaluated by r and omly assigned catheterization site ( femoral or jugular ) . Baseline demography and dialysis prescriptions were similar between the site arms . In modified intent-to-treat , catheter dysfunction occurred in 36 of 348 ( 10.3 % ) and 38 of 342 ( 11.1 % ) patients in the femoral and jugular groups , respectively . The risk of catheter dysfunction did not significantly differ between r and omized groups ( hazard ratio , 1.06 ; 95 % confidence interval , 0.67–1.68 ; p = .80 ) . Compared to the femoral site , the observed risk of dysfunction decreased in the right jugular position ( 15 of 226 ; 6.6 % ; adjusted hazard ratio , 0.58 ; 95 % confidence interval , 0.31–1.07 ; p = .09 ) and significantly increased in the left jugular position ( 23 of 118 ; 19.5 % ; adjusted hazard ratio , 1.89 ; 95 % confidence interval , 1.12–3.21 ; p < .02 ) . The postintermittent hemodialysis mean urea reduction ratio per session was 50.8 % ( st and ard deviation , 16.1 ) for femoral vs. 52.8 % ( st and ard deviation , 15.8 ) for jugular ( p = .30 ) sites , and the median continuous renal replacement therapy downtime per patient-day was 1.17 hrs ( interquartile range , 0.75–1.50 ) for both sites ( p = .98 ) . Conclusions : In terms of catheter dysfunction and dialysis performance among critically ill adults requiring acute renal replacement therapy , jugular site did not significantly outperform femoral site placement . ( Crit Care Med 2010 ; 38:1118–1125 PURPOSE To compare the effectiveness of two treatments for tunneled hemodialysis catheter malfunction : percutaneous fibrin sheath stripping ( PFSS ) and over-the-wire catheter exchange ( EX ) . MATERIAL S AND METHODS Adult patients with poorly functioning tunneled hemodialysis catheters ( flow rates < 200 mL/min ) were r and omly assigned to receive either PFSS or EX . Over the course of 20 months , 30 patients ( 37 encounters ) referred to a single institution met the inclusion criteria and consented to participate . PFSS employed transcatheter snares via femoral vein puncture , whereas EX was performed over a guide wire with use of fluoroscopic guidance . Patients were followed up to determine the duration of continued adequate hemodialysis via manipulated catheters for up to 4 months ( primary outcome measure ) . RESULTS Overall technical success rate was 97 % . Mean catheter patency for the PFSS group was 24.5 + /- 29.3 days , and 52.2 + /- 43 days for the EX group ( P < .0001 ) . After EX , patency rates at 1 , 2 , 3 , and 4 months were 71 % , 33 % , 27 % , and 27 % , compared to 31 % , 16 % , 7 % , and 0 % after PFSS ( P = .04 , logrank test ) . Exchanged catheters were significantly more likely to be patent for as long as 4 months ( 23 % versus 0 % ; P < .05 , chi2 test ) . CONCLUSIONS Malfunctioning tunneled hemodialysis catheters treated by means of EX are significantly more likely to remain patent for up to 4 months than are those treated by means of PFSS . According to the results of this trial , PFSS should not be performed as a routine therapy for catheter malfunction Background . A well-functioning vascular access ( VA ) is essential to efficient dialysis therapy . Guidelines have been implemented improving care , yet access use varies widely across countries and VA complications remain a problem . This study took advantage of the unique opportunity to utilize data from the Dialysis Outcomes and Practice Patterns Study ( DOPPS ) to examine international trends in VA use and trends in patient characteristics and practice s associated with VA use from 1996 to 2007 . DOPPS is a prospect i ve , observational study of  haemodialysis ( HD )  practice s and patient outcomes at > 300 HD units from 12 countries and has collected data thus far from > 35 000 r and omly selected patients . Methods .  VA data were collected for each patient at study entry ( 1996–2007 ) . Practice pattern data from the facility medical director , nurse manager and VA surgeon were also analysed . Results . Since 2005 , a native arteriovenous fistula ( AVF ) was used by 67–91 % of prevalent patients in Japan , Italy , Germany , France , Spain , the UK , Australia and New Zeal and , and 50–59 % in Belgium , Sweden and Canada . From 1996 to 2007 , AVF use rose from 24 % to 47 % in the USA but declined in Italy , Germany and Spain . Moreover , graft use fell by 50 % in the USA from 58 % use in 1996 to 28 % by 2007 . Across three phases of data collection , patients consistently were less likely to use an AVF versus other VA types if female , of older age , having greater body mass index , diabetes , peripheral vascular disease or recurrent cellulitis/gangrene . In addition , countries with a greater prevalence of diabetes in HD patients had a significantly lower percentage of patients using an AVF . Despite poorer outcomes for central vein catheters , catheter use rose 1.5- to 3-fold among prevalent patients in many countries from 1996 to 2007 , even among non-diabetic patients 18–70 years old . Furthermore , 58–73 % of patients new to end-stage renal disease ( ESRD )  used a catheter  for the initiation of HD in five countries despite 60–79 % of patients having been seen by a nephrologist > 4 months prior to ESRD . Patients were significantly ( P < 0.05 ) less likely to start dialysis with a permanent VA if treated in a faciity that ( 1 ) had a longer time from referral to access surgery evaluation or from evaluation to access creation and ( 2 ) had longer time from access creation until first AVF cannulation . The median time from referral until access creation varied from 5–6 days in Italy , Japan and Germany to 40–43 days in the UK and Canada . Compared to patients using an AVF , patients with a catheter displayed significantly lower mean Kt/V levels . Conclusions . Most countries meet the contemporary National Kidney Foundation 's Kidney Disease Outcomes Quality Initiative goal for AVF use ; however , there is still a wide variation in VA preference . Delays between the creation and cannulation must be improved to enhance the chances of a future permanent VA . Native arteriovenous fistula is the VA of choice ensuring dialysis adequacy and better patient outcomes . Graft is , however , a better alternative than catheter for patients where the creation of an attempted AVF failed or could not be created for different reasons BACKGROUND AND OBJECTIVES Hemodialysis catheters are frequently complicated by dysfunction from fibrin sheaths . Previous studies of sheath disruption have method ologic limitations but suggest that the patency after disruption is short . DESIGN , SETTING , PARTICIPANTS , & MEASUREMENTS A r and omized , controlled 
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Catheter exchange was reported to be superior to sheath disruption with respect to catheter survival ( 30 participants : MD 213.00 days , 95 % CI 205.70 to 220.30).There is insufficient evidence to suggest any specific intervention is superior in terms of ensuring either dialysis adequacy or reduced risk of adverse events .
AUTHORS ' CONCLUSIONS Thrombolysis , fibrin sheath disruption and over-the-wire catheter exchange are effective and appropriate therapies for immediately restoring catheter patency in dysfunctional cuffed and tunnelled HD catheters .
On current data there is no evidence to support physical intervention over the use of pharmaceutical agents in the acute setting .
Pharmacological interventions appear to have a bridging role and long-term catheter survival may be improved by fibrin sheath disruption and is probably superior following catheter exchange .
There is no evidence favouring any of these approaches with respect to dialysis adequacy or risk of adverse events .