Prediction of Arteriovenous Fistula Dysfunction: Can it be Taught?

Physical examination (PE) is an excellent means of predicting arteriovenous fistula (AVF) dysfunction. Although quick and inexpensive, PE is seldom used as a tool to assess stenosis by general nephrologists, dialysis nurses, and dialysis technicians. Previous studies have demonstrated that PE can be taught to interventional specialists, but the perception remains that it is too complex to be performed by other health care professionals. We hypothesized that the physical exam can be taught to a nonmedical professional, and that, with time, it would be comparable to the physical exam performed by a full-time interventional specialist. An undergraduate student and an interventional specialist (MD) examined AVF for dysfunction in a tertiary care hospital over a 6-month period. PE was performed on patients who were suspected of having dialysis access dysfunction and were referred for angiography and intervention (n = 49). Physical exam findings were categorized blindly by each examiner into four categories of lesion location: inflow, outflow, both, or neither. Data were privately recorded and compared to the gold standard of angiographic results. Potential confounding variables, including age, gender, diabetic status, and location of AVF were recorded. Weighted Cohen's kappa value was used as a measurement of the level of agreement beyond chance between the diagnoses made by physical exam and angiography. The full-time interventional specialist demonstrated correct prediction of lesion location of 89.8% (kappa = 0.850), while the undergraduate student had a correct prediction of 77.6% (kappa = 0.625). The student's performance, however, differed significantly over time. The student correctly predicted the location of the lesion in 6 (42.9%) of the first 14 patients (kappa = 0.082), compared to 32 (91.4%) of the last 35 patients (kappa = 0.855). We suggest that physical exam of AVF can be taught to a nonmedical professional in a short duration of time and the predictive value of the exam can be similar to that of an interventional specialist.

Tunneled dialysis catheter exchange with fibrin sheath disruption is not associated with increased rate of bacteremia.

PURPOSE: Tunneled dialysis catheters are the most common form of vascular access among incident dialysis patients in the United States. Fibrin sheath formation is a frequent cause of late catheter dysfunction requiring an exchange procedure with balloon disruption of the fibrin sheath. It is unknown whether fibrin sheath disruption is associated with increased incidence of bacteremia or catheter failure. METHODS: We reviewed all tunneled dialysis catheter exchange procedures at the University of Wisconsin between January 2008 and December 2011. The primary outcome was incidence of bacteremia, defined as positive blood cultures within 2 weeks of the procedure. Catheter failure, requiring intervention or replacement, was examined as a secondary outcome. Baseline characteristics examined included diabetic status, gender, race and age. RESULTS: A total of 163 procedures were reviewed; 67 (41.1%) had fibrin sheath disruption and 96 did not. Bacteremia occurred in 4.5% (3/67) of those with and 3.1% (3/97) of those without fibrin sheath disruption (p=0.65). Fibrin sheath disruption was not significantly associated with the risk of catheter failure (adjusted hazard ratio [aHR]=1.34; 95% confidence interval [CI]: 0.87-2.10; p=0.18). Diabetes was associated with greater risk of catheter failure (aHR=1.88; 95% CI: 1.19-2.95; p=0.006), whereas higher age was associated with a lower risk of catheter failure (aHR per 10 years=0.83; 95% CI: 0.72-0.96; p=0.01). CONCLUSIONS: This study demonstrates that there is no significant increase in bacteremia and subsequent catheter dysfunction rates after fibrin sheath disruption compared to simple over the wire exchange. These results are encouraging given the large numbers of patients utilizing tunneled catheters for initial hemodialysis access and the known rates of fibrin sheath formation leading to catheter failure.

Interventional nephrology: Novel devices that will one day change our practice.

There is increasing awareness of vascular access dysfunction as a significant contributor to the morbidity associated with chronic hemodialysis. Over the last several years, interventional nephrologists, in conjunction with our colleagues in vascular surgery, have led the way in the creation of novel devices that are designed to help solve the vascular access problem. The purpose of this review is to describe novel devices in the precommercial stage of development that have the potential to revolutionize the field of dialysis vascular access. These devices include bioengineered blood vessels, access monitoring technology, and advanced anastomotic connectors.