Endovascular treatment of hemodialysis arteriovenous fistulas: is immediate post-interventional blood flow a predictor of patency.

PURPOSE: The purpose of this study was to investigate if the immediate hemodynamic outcome of an endovascular intervention on a dysfunctional hemodialysis arteriovenous fistula is a prognostic factor for primary patency. METHODS: This was a prospective observational study including 61 consecutive patients with dysfunctional arteriovenous fistulas referred to our endovascular unit. Patients were treated in accordance with institutional standard protocol including immediate pre- and post-interventional blood flow measurements using an intravascular catheter system. The primary endpoint was primary patency at 12 months in patients with an immediate post-interventional blood flow above or below 600 ml/min. Primary patency was estimated using the Kaplan-Meier method with the standard error of the estimate. Multivariate Cox regression analysis was used to study the effect of blood flow and other potential predictor variables. RESULTS: Post interventional flow did not significantly influence primary patency (p = 0.76). Primary patency was found to be affected by having a history of previous intervention(s) (p = 0.008, hazard ratio 2.9) or low fistula age (P=.038, hazard ratio 0.97 [one-month increase]). Primary patency in group 1 (previous intervention(s)) was 34% ± 13% at 12 months. In group 2 (no previous intervention), primary patency at 12 months was 62% ± 9%. CONCLUSIONS: The results of this study do not provide scientific support for using the immediate hemodynamic outcome of an intervention as a prognostic factor for primary patency. Low fistula age and a history of previous intervention in particular were found to reduce primary patency significantly.

Catheter-based flow measurements in hemodialysis fistulas - bench testing and clinical performance.

PURPOSE: The purpose of this study was to perform bench and clinical testing of a catheter-based intravascular system capable of measuring blood flow in hemodialysis vascular accesses during endovascular procedures. METHODS: We tested the Transonic ReoCath Flow Catheter System which uses the thermodilution method. A simulated vascular access model was constructed for the bench test. In total, 1960 measurements were conducted and the results were used to determine the accuracy and precision of the catheters, the effects of external factors (e.g., catheter placement, injection duration), and to test for systematic bias. In the clinical study, two interventional radiologists conducted a total of 250 measurements in 14 patients with arteriovenous fistulas to determine clinical precision and enable testing for bias between measurers. RESULTS: Accuracy was excellent for both catheters with a high level of agreement between results from the ReoCath Flow Catheter System and the reference flowmeter. Clinical precision, expressed as the mean coefficient of variation, was 5.9% and 4.7% for the antegrade and retrograde catheters, respectively. Flow measurements were significantly affected by the distance between a stenosis and the tip of a retrograde catheter with the effect being proportional to the degree of stenosis. There was no systematic bias between measurers. CONCLUSIONS: The Reocath Flow Catheter System was found to be accurate and precise. Reliable results require careful attention to catheter placement. Blood flow measurements provide unique information on the hemodynamic status of a vascular access and have the potential to optimize results of interventions.

Blood flow measurements during hemodialysis vascular access interventions--catheter-based thermodilution or Doppler ultrasound?

PURPOSE: To test the clinical performance of catheter-based thermodilution and Doppler ultrasound of the feeding brachial artery for blood flow measurements during hemodialysis vascular access interventions. METHODS: Thirty patients with arteriovenous fistulas who underwent 46 interventions had access blood flow measured before and after every procedure. Two methods, catheter-based thermodilution and Doppler ultrasound, were compared to the reference method of ultrasound dilution. Catheter-based thermodilution and Doppler ultrasound were performed during the endovascular procedures while flow by ultrasound dilution was determined within three days of the procedure. The methods were compared using regression analysis and tested for systematic bias. RESULTS: Failure to position the thermodilutional catheter correctly was observed in 8 out of 46 (17%) pre-intervention measurements. Post-intervention measurements and ultrasound measurements were feasible in all patients. The average level of agreement was good when comparing catheter-based thermodilution to ultrasound dilution. However, blood flow by ultrasound dilution may differ by ±130 mL/min (±22%) at a flow level of 600 mL/min by thermodilution. Results from Doppler ultrasound displayed a moderate level of agreement on average when compared to ultrasound dilution. Blood flow by ultrasound dilution may differ by ±160 mL/min (±27%) at a flow level of 600 mL/min by Doppler ultrasound. No systematic bias was detected by either method. CONCLUSIONS: On average, results from catheter-based thermodilution were more in agreement with results from the ultrasound dilution technique compared to Doppler ultrasound. However, considering the cost and the high technical failure rate of the thermodilutional system, we recommend the use of ultrasound.

UVC fluencies for preventative treatment of Pseudomonas aeruginosa contaminated polymer tubes.

Exposing Pseudomonas aeruginosa biofilm grown on the inner surface of Teflon and silicone tubes to UVC light (265 nm) from light emitting diodes (LED) has previously been shown to substantially reduce biofilm growth. Smaller UVC fluencies were required to disinfect Teflon tubes compared to silicone tubes. Light propagation enhancement in tubes can be obtained if the refractive index of the intra-luminal saline solution is higher than that of the polymer. This condition is achieved by using Teflon tubes with a low refractive index (1.34) instead of the polymers with a high refractive index (1.40-1.50) normally used for tubing in catheter production. Determining whether or not UVC light exposure can disinfect and maintain the intra-luminal number of colony forming units (CFUs) at an exceedingly low level and thus avoid the growth and establishment of biofilm is of interest. The use of UVC diodes is demonstrated to be a preventative disinfection treatment on tubes made of Teflon, which enhances the UVC light propagation, and on tubes made of a softer material, ethylene vinyl acetate (EVA), which is suitable for catheters but much less suitable for UVC light propagation. Simulating an aseptic breach (∼10(3)-10(4) CFU ml(-1)), the UVC disinfection set-up was demonstrated using tubes contaminated with planktonic P. aeruginosa. After the tubes (10-20 cm) were inoculated with the bacterial solution for 3 h, they were emptied and filled with saline solutions (0.9-20%). Next UVC fluencies (0-21 mJ cm(-2)) were applied to the tubes 3 h after inoculation. Colony counts were carried out on liquid samples drawn from the tubes the first day after UVC treatment and liquid and surface samples were collected and analyzed 3-4 days later. A fluence of approximately 1.0 mJ cm(-2) was noted as being sufficient for no growth for a period of 3-4 days for the Teflon tubes. Determining the fluence threshold for the EVA tubes was not possible. Almost all of the UVC-treated EVA tubes were disinfected simply by filling the tubes with a saline solution. Direct UVC treatment of the contaminated EVA tubes revealed, however, that a fluence of 21 mJ cm(-2) killed the bacteria present in the tubes and kept them disinfected for a period of 3-4 days.

Disinfection of Pseudomonas aeruginosa biofilm contaminated tube lumens with ultraviolet C light emitting diodes.

Bacterial biofilms on long-term catheters are a major source of infection. Exposure to ultraviolet C (UVC - 265 nm) light was shown in an earlier study to reduce the number of bacteria substantially on ex vivo treated urinary patient catheters. Very large doses (long treatment times) should, however, be applied to obtain 99.9% disinfection rates. The major reason was that besides cells the mature biofilm contained absorbing and scattering particulates, which made the biofilm opaque. The potential of UVC light emitting diodes (LED) for disinfection purposes in catheter-like tubes contaminated with biofilm was investigated. It was shown that UVC light propagation was possible through both Teflon and catheter tubes (silicone). The disinfection efficiency of the diodes was demonstrated on tubes contaminated artificially with a Pseudomonas aeruginosa biofilm. The tubes were connected to a flow system and biofilms were produced during a 3 day period. Tubes in lengths of 10 (Teflon, silicone) and 20 cm (Teflon) were contaminated. Tubes for control and for UVC treatment were contaminated in parallel. Biofilms were sampled from the total inner surface of the tubes. Colony counts on the control samples were in the range of 5 x 10(5)-1.3 x 10(9) CFU ml(-1), with disinfection rates in the range 96-100%. The applied UVC doses corresponded to treatment times between 15 and 300 min. Disinfection (100%) was obtained in 10 cm Teflon tubes exposed for 30 min (detection limit <5 CFU ml(-1)). The same result was obtained for a 20 cm Teflon tube exposed for 300 min. The disinfection rate was 96% for the 20 cm tube if the dose was reduced to 30 min. A disinfection rate of 99.99% was observed for a 10 cm peritoneal dialysis catheter tube (silicone) exposed for 300 min. Differences between the tubes were dependent on the differences in length and the type of the material. The UVC light was transmitted six times more efficiently in Teflon than in silicone tubes of equal length (10 cm). The germicidal effect to obtain a 99.99% killing rate for the biofilm ( approximately 78 J m(-2)) is comparable to that for the planktonic bacterium. It is concluded that there is potential for LED UVC light sources if they are used for disinfection of thin biofilms.

[Endovascular treatment of dysfunctional haemodialysis fistulas]. / Endovaskulaer behandling af dysfungerende haemodialysefistle.

INTRODUCTION: A native AV-fistula (AVF) is the first choice of access for haemodialysis. An important complication is thrombosis, which typically results from an underlying stenosis. In 2001, we introduced a surveillance program measuring the access flow (Qa). At the same time percutaneous transluminal angioplasty (PTA) was introduced as the first choice of treatment. MATERIAL AND METHODS: Qa was conducted in a routine monitoring programme. Flow rates below a preset value indicated patient referral for angiography, and if the angiography revealed a significant stenosis, PTA was performed. In the period from August 2001 to March 2004, 71 angioplasties were performed in 52 patients. RESULTS: The technical success rate was 66/71 (93%). Clinically significant complications occurred at a rate of 3/71 (4%). The 2-year primary patency rate was 36% and the primary assisted patency rate was 67%. CONCLUSION: PTA in native haemodialysis fistulas was implemented. The rates of technical success, complications and patency were comparable with those recorded in the literature.

Dose requirements for UVC disinfection of catheter biofilms.

Bacterial biofilms on permanent catheters are the major sources of infection. Exposure to ultraviolet-C (UVC) light has been proposed as a method for disinfecting the inner surface of catheters. Specification of a UVC-based device for in vivo disinfection is based on the knowledge of the required doses to kill catheter biofilm. Given these doses and the power of available UVC light sources, calculation of the necessary treatment times is then possible. To determine the required doses, contaminated urinary catheters were used as test samples and UVC treated in vitro. Patient catheters (n = 67) were collected and cut into segments of equal size and treated with various UVC doses. After treatment, the biofilm was removed by scraping and quantified by counting colony forming units. Percentage killing rates were determined by calculating ratios between UVC-treated samples and controls (no UVC treatment). Mean killing rates were 89.6% (0.5 min), 98% (2 min), and 99% (60 min). Approximately 99% killing was obtained with a UVC dose of 15 kJ m(-2). This dose, which is about 100 to 1000 times greater than the lethal dose for planktonic cells, is expected to be the maximum dose required to maintain newly inserted catheters free of contamination. The combination of high doses required to kill mature biofilm and the limited effect of current UVC light sources result in a relative long treatment time ( approximately 60 min). If a UVC-based method is to be of practical use for disinfection of catheters in the clinic, repeated preventive treatments should be carried out on newly inserted catheters.

Kappa-opioid system in uremic pruritus: multicenter, randomized, double-blind, placebo-controlled clinical studies.

Uremic pruritus is a very common and frustrating condition for both patients and clinicians because no treatment has been demonstrated to be effective in relieving the itch. In this report, nalfurafine, a new kappa-opioid receptor agonist, was used to treat uremic pruritus in patients who were undergoing routine hemodialysis. Two multicenter, randomized, double-blind, placebo-controlled studies enrolled 144 patients with uremic pruritus to postdialysis intravenous treatment with either nalfurafine or placebo for 2 to 4 wk. A meta-analysis approach was used to assess the efficacy of nalfurafine. Statistically significant reductions in worst itching (P = 0.0212), itching intensity (P = 0.0410), and sleep disturbances (P = 0.0003) were noted in the nalfurafine group as compared with placebo. Improvements in itching (P = 0.0025) and excoriations (P = 0.0060) were noted for the nalfurafine-treated patients. Nalfurafine showed similar types and incidences of drug-related adverse events as did placebo. Nalfurafine was shown to be an effective and safe compound for use in this severely ill patient population.

Presence and significance of TT virus in Danish patients on maintenance hemodialysis.

OBJECTIVES: To determine the prevalence of TT virus (TTV) in a population of Danish hemodialysis patients and evaluate possible relations between TTV infection and elevated levels of C-reactive protein (CRP) and hypo-response to treatment with erythropoietin (EPO). MATERIAL AND METHODS: Patients on maintenance hemodialysis at a single center were invited to participate. Demographic and clinical data were registered. Blood samples for virological and routine biochemical tests were drawn simultaneously. TTV DNA was detected using polymerase chain reaction (PCR). TTV viral load was estimated by means of semi-quantitative PCR. All patients were tested for hepatitis B, hepatitis C and GB virus C. RESULTS: Of 252 patients, 204 (80.9%) gave their written informed consent to participate in the study. The prevalence of TTV was 68% and 50% of TTV-positive patients had a high TTV viral load. TTV-positive patients were significantly older than TTV-negative patients (p = 0.011). No relations were found between TTV infection and elevated levels of alanine aminotransferase (ALT) or CRP or hypo-response to EPO treatment. The mean hemoglobin concentration was 11.24 +/- 1.48 g/dl. Patients with a high TTV viral load had a lower level of hemoglobin (10.86 +/- 1.47 g/dl) than the others (p = 0.01). This trend suggested a positive relation between TTV infection and the number of blood transfusions. A restriction fragment length polymorphism assay suggested that patients were infected with different TTV strains. CONCLUSIONS: TTV is common in patients on maintenance hemodialysis. The presence of TTV is associated with increasing age. Patients with a high TTV viral load had lower levels of hemoglobin than the others. TTV infection is not related to elevated levels of ALT or CRP or to hypo-response to EPO treatment.