Ivan D. Maya

Standardized Definitions for Hemodialysis Vascular Access

Vascular access dysfunction is one of the leading causes of morbidity and mortality among end‐stage renal disease patients. Vascular access dysfunction exists in all three types of available accesses: arteriovenous fistulas, arteriovenous grafts, and tunneled catheters. To improve clinical research and outcomes in hemodialysis (HD) access dysfunction, the development of a multidisciplinary network of collaborative investigators with various areas of expertise, and common standards for terminology and classification in all vascular access types, is required. The North American Vascular Access Consortium (NAVAC) is a newly formed multidisciplinary and multicenter network of experts in the area of HD vascular access, who include nephrologists and interventional nephrologists from the United States and Canada with: (1) a primary clinical and research focus in HD vascular access dysfunction, (2) national and internationally recognized experts in vascular access, and (3) a history of productivity measured by peer‐reviewed publications and funding among members of this consortium. The consortium’s mission is to improve the quality and efficiency in vascular access research, and impact the research in the area of HD vascular access by conducting observational studies and randomized controlled trials. The purpose of the consortium’s initial manuscript is to provide working and standard vascular access definitions relating to (1) epidemiology, (2) vascular access function, (3) vascular access patency, and (4) complications in vascular accesses relating to each of the vascular access types.

Outcomes of Brachiocephalic Fistulas, Transposed Brachiobasilic Fistulas, and Upper Arm Grafts

BACKGROUND AND OBJECTIVES An upper arm vascular access is often placed in patients with a failed forearm fistula or with vessels unsuitable for a forearm fistula. The aim of this study was to compare the outcomes of three upper arm access types: brachiocephalic fistulas, transposed brachiobasilic fistulas, and grafts. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A prospective, computerized access database was queried retrospectively to identify the clinical outcomes of upper arm accesses placed in 678 patients at a large dialysis center, including 322 brachiocephalic fistulas, 67 brachiobasilic fistulas, and 289 grafts. RESULTS Primary access failures were less common for brachiobasilic fistulas and grafts compared with brachiocephalic fistulas (18%, 15%, and 38%; hazard ratio of brachiocephalic fistulas versus brachiobasilic fistulas 2.76; 95% confidence interval 1.41 to 5.38; P < 0.003). For the subset of patients receiving a brachiocephalic fistula, a multiple variable logistic regression analysis including age, sex, race, diabetes, coronary artery disease, peripheral vascular disease, cerebrovascular disease, prior access, surgeon, arterial diameter, and venous diameter found that only vascular diameters predicted primary failure (P < 0.001). When primary failures were excluded, cumulative access survival was similar for brachiobasilic and brachiocephalic fistulas, but superior to that of grafts. Total access interventions per year were lower for brachiobasilic and brachiocephalic fistulas than for grafts (0.84, 0.82, and 1.87, respectively, P < 0.001). CONCLUSIONS Transposed brachiobasilic fistulas may be preferred, due to (1) a lower primary failure rate (similar to grafts), and (2) a lower intervention rate (similar to brachiocephalic fistulas). However, this advantage must be balanced against the more complex surgery.

Percutaneous Renal Biopsy: Comparison of Blind and Real-Time Ultrasound-Guided Technique

The use of real‐time ultrasound‐guided renal biopsy is believed to be superior to blind biopsy, but there are few reports comparing the two techniques. The goal of the present study was to compare the outcomes of ultrasound‐guided and blind renal biopsies at a single teaching institution, in terms of adequacy of tissue yield and frequency of hemorrhagic complications. We reviewed retrospectively the outcomes of all patients undergoing a percutaneous native kidney biopsy during a 2‐year period (January 1, 2004 to December 31, 2005). Of 129 renal biopsies, 65 were ultrasound‐guided and 64 were performed by the blind technique. All biopsies were performed by nephrology fellows under direct faculty supervision. The two patient groups were comparable in terms of age, sex, race, diabetes, hypertension, serum creatinine, and hematocrit. The mean number of glomeruli per biopsy was higher in the ultrasound‐guided group than in the patients with a blind biopsy (18 ± 9 versus 11 ± 9, p = 0.0001). An inadequate tissue sample requiring repeat biopsy occurred in 0% of the ultrasound‐guided biopsies and 16% of the blind biopsies (p = 0.0006). Large hematomas requiring vascular intervention or transfusion were less frequent in the ultrasound‐guided biopsies (0% versus 11%, p = 0.006). The hematocrit 24 hours postbiopsy was higher in the ultrasound‐guided biopsies when compared with the blind biopsies (32 ± 5% versus 30 ± 4%, p = 0.04). When compared with blind renal biopsy, real‐time ultrasound‐guided percutaneous renal biopsy provides a superior yield of kidney tissue and results in fewer hemorrhagic complications. Real‐time ultrasound‐guided renal biopsy is the preferred technique.

Treatment of refractory central vein stenosis in hemodialysis patients with stents.

Central venous stenosis is a frequent complication in hemodialysis patients, which can manifest clinically with ipsilateral upper extremity edema. When symptomatic, it is usually treated by percutaneous transluminal angioplasty. When angioplasty is unsuccessful, stent deployment is a therapeutic option. The goal of the present study was to evaluate the primary and secondary patency of refractory central vein stenosis after treatment with a stent. Using a prospective vascular access database we retrospectively identified 23 patients presenting with unilateral upper extremity edema and a significant (> 50%) central vein stenosis, who underwent stent placement due to refractory stenosis following angioplasty. The primary (unassisted) central vein patency was determined from the initial intervention to the next angioplasty for recurrent central vein stenosis, and the secondary (assisted) patency from the initial intervention to permanent central vein occlusion. An immediate technical success was achieved in all patients after the stent deployment. However, the median primary central vein patency was only 138 days, with a 19% patency at 1 year. Recurrence of ipsilateral edema was always due to in‐stent restenosis. The median secondary central vein patency was 1036 days, with a 64% patency at 1 year. In patients with symptomatic central vein stenosis that is refractory to percutaneous transluminal angioplasty, stent deployment provides short‐term relief of the stenosis and ipsilateral upper extremity edema. However, long‐term symptomatic relief can be achieved with multiple subsequent interventions in many patients.

Who should be referred for a fistula? A survey of nephrologists

BACKGROUND There is marked variation in the use of the arteriovenous fistula (AVF) across programmes, regions and countries not explained by differences in patient demographics or comorbidities. The lack of clear criteria of who should or should not get a fistula may contribute to this, as well as barriers to creating AVFs. METHODS We conducted a survey of Canadian and American nephrologists to assess the patient variables considered to determine the timing and type of access requested. Perceived barriers and absolute contraindications to access were also collected. RESULTS An immediate referral for a fistula was more highly preferred when patients are <65 years old, have minimal comorbidities or have no history of failed accesses. In older patients, and in those with increased comorbidities or a previously failed fistula, US nephrologists selected arteriovenous grafts as an alternative to the fistula, while Canadian nephrologists selected primarily catheters. Referral for vascular mapping was more common in the USA than in Canada. Gender did not influence the timing or the type of access. Perceived barriers to establishing a mature fistula included patient refusal for creation (77%) or cannulation (58%), delay in decision regarding dialysis modality (71%), wait time for surgical creation (55%) and high failure-to-mature rate (52%). We found that 27% of Canadian and 43% of American nephrologists indicated no absolute contraindications for permanent vascular access. CONCLUSIONS This study demonstrated marked variability in timing and criteria used to select patients for referral for a vascular access between nephrologists practicing within Canada and the USA. Establishing minimal eligibility criteria for fistulae is an important area of future research.

Percutaneous renal biopsy: outpatient observation without hospitalization is safe.

Percutaneous renal biopsy may be complicated by hemorrhage. Patients are frequently hospitalized for overnight observation. We evaluated prospectively the feasibility and safety of an outpatient renal biopsy protocol. During a 20‐month period, 100 consecutive patients underwent outpatient renal biopsy using a standardized protocol. The biopsy was performed by Nephrology Fellows, under direct faculty supervision. All biopsies were carried out under real‐time ultrasound guidance with a 16‐gauge spring‐loaded biopsy gun, and followed immediately by color Doppler ultrasound to exclude active bleeding. Blood pressure, heart rate, hemoglobin, and hematocrit were monitored for 8 hours postbiopsy. If there were no complications, the patients were discharged home after the observation period. A total of 91 patients required one or two needle passes, and nine needed three or four passes. A mean of 12.7 ± 9.7 glomeruli were obtained per patient. No major complications were encountered. A small (<2 × 2 cm) perinephric hematoma was observed postbiopsy in 13 patients. Four patients were hospitalized for overnight observation due to a >4% decrease in their hematocrit, but none required a transfusion or intervention. No patient experienced a delayed biopsy‐related complication. Outpatient, real‐time, ultrasound‐guided percutaneous renal biopsy is safe and effective, and minimizes the need for postbiopsy hospitalization. It can result in significant cost savings without exposing the patients to an increased risk of complications.

Patency rates for angioplasty in the treatment of pacemaker-induced central venous stenosis in hemodialysis patients: results of a multi-center study.

While hemodialysis access ligation has been used to manage pacemaker (PM) and implantable cardioverter‐defibrillator (ICD) lead‐induced central venous stenosis (CVS), percutaneous transluminal balloon angioplasty (PTA) has also been employed to manage this complication. The advantages of PTA include minimal invasiveness and preservation of arteriovenous access for hemodialysis therapy. In this multi‐center study we report the patency rates for PTA to manage lead‐induced CVS. Consecutive PM/ICD chronic hemodialysis patients with an arteriovenous access referred for signs and symptoms of CVS due to lead‐induced CVS were included in this analysis. PTA was performed using the standard technique. Technical and clinical success was examined. Technical success was defined as the ability to successfully perform the procedure. Clinical success was defined as the ability to achieve amelioration of the signs and symptoms of CVS. Both primary and secondary patency rates were also analyzed. Twenty‐eight consecutive patients underwent PTA procedure. Technical success was 95%. Postprocedure clinical success was achieved in 100% of the cases where the procedure was successful. The primary patency rates were 18% and 9% at 6 and 12 months, respectively. The secondary patency rates were 95%, 86%, and 73% at 6, 12, and 24 months, respectively. On average, 2.1 procedures/year were required to maintain secondary patency. There were no procedure‐related complications. This study finds PTA to be a viable option in the management of PM/ICD lead‐induced CVS. Additional studies with appropriate design and sample size are required to conclusively establish the role of PTA in the management of this problem.

Ultrasound/fluoroscopy-assisted placement of peritoneal dialysis catheters.

Peritoneal dialysis (PD) catheters may be inserted blindly, surgically, and either by laparoscopic, peritoneoscopic, or fluoroscopic approach. A modified fluoroscopic technique by adding ultrasound‐assistance was performed in the present study to ensure entry into the abdominal cavity under direct ultrasound visualization. From March 2005 to May 2007, ultrasound‐fluoroscopic guided placement of PD catheters was attempted in 32 end‐stage renal disease (ESRD) patients. Preoperative evaluation was performed on all patients prior to the procedure. After initial dissection of the subcutaneous tissue anterior to the anterior rectus sheath, the needle was inserted into the abdominal cavity under the guidance of ultrasound. The position of the epigastric artery was also examined using ultrasonography to avoid the risk of arterial injury. PD catheters were successfully placed in 31 of the 32 ESRD patients using this technique. In all of these patients, the needle could be seen entering the abdominal cavity using an ultrasound. In one patient the procedure was abandoned because of bowel puncture by the micro‐puncture needle that was inadvertently advanced into a loop of bowel. This patient did not develop acute abdomen nor needed any intervention. One patient died 4 days after placement of the catheter of unrelated causes. One patient was started on acute peritoneal dialysis the same day of catheter placement without any complications. The rest of the patients started peritoneal dialysis within 2–6 weeks of catheter placement. None of the patients had bleeding related to arterial injury as ultrasound was able to visualize the epigastric artery. Our experience shows that ultrasound‐fluoroscopic technique is minimally invasive and allows for accurate assessment of the entry into the abdominal cavity. This technique can avoid the risk of vascular injury altogether.

Outcomes of Percutaneous Mechanical Thrombectomy of Arteriovenous Fistulas in Hemodialysis Patients

Thrombosis of arteriovenous fistulas is usually superimposed on underlying stenosis in the arterial anastomosis, draining vein, or central vein. Restoring the patency of thrombosed fistulas requires mechanical thrombectomy, in conjunction with angioplasty of the underlying lesion. We evaluated the success rate of percutaneous thrombectomy of fistulas at our medical center. We retrospectively queried a prospective, computerized vascular access database to identify 41 patients with thrombosed fistulas treated percutaneously. Technical success was defined as the ability to use the fistula for at least one dialysis session. Primary patency was defined as time to the next intervention, and secondary failure as the time to permanent fistula failure. Of the 41 thrombosed fistulas, 21 were in the forearm and 20 in the upper arm. Percutaneous thrombectomy was technically successful in 31 of 41 patients (76%). The technical success rate was similar for upper arm and forearm fistulas (85% vs. 66%, p = 0.43). An underlying stenotic lesion was present at the arterial anastomosis in 13 patients (31%), in the draining vein in 37 (90%), and in the central vein in 3 patients (7%). Twelve patients (29%) had concurrent stenoses at two locations. At 6 months, the primary patency was 20%, and the secondary patency was 54%. In conclusion, percutaneous treatment of thrombosed fistulas can restore fistula patency about three‐fourths of patients. However, the primary fistula patency is fairly short‐lived, and the fistulas require repeated interventions to achieve long‐term survival.

Treatment of Dialysis Catheter–Related Enterococcus Bacteremia With an Antibiotic Lock: A Quality Improvement Report

BACKGROUND Catheter-related bacteremia (CRB) is a frequent complication of tunneled dialysis catheters, and Enterococcus is a common infecting organism. CRB may be treated by instilling an antibiotic lock into the catheter lumen in conjunction with systemic antibiotics. The efficacy of this approach in Enterococcus bacteremia is unknown. DESIGN Quality improvement report. SETTING & PARTICIPANTS 64 catheter-dependent hemodialysis outpatients with vancomycin-sensitive Enterococcus bacteremia treated with a uniform antibiotic lock protocol. Clinical outcomes were tracked prospectively. QUALITY IMPROVEMENT PLANS: Patients received intravenous vancomycin for 3 weeks in conjunction with a vancomycin lock instilled into both catheter lumens after each dialysis session. MEASURES Treatment failure was defined as persistent fever 48 hours after initiation of antibiotic therapy or recurrent Enterococcus bacteremia within 90 days. A clinical cure was defined as fever resolution without recurrent bacteremia. Major infection-related complications within 6 months were documented. RESULTS Treatment failure occurred in 25 patients (39%) because of persistent fever in 10 and recurrent bacteremia in 15. Treatment success occurred in 39 patients (61%). A serious complication of Enterococcus CRB occurred in 4 of 64 patients (6%); endocarditis in 1 and osteomyelitis in 3. The frequency of serious complications was 16% (4 of 25 patients) in those with treatment failure compared with 0% (0 of 39 patients) in those with treatment success (P = 0.01). LIMITATIONS This was a single-center study. We did not measure serum vancomycin. CONCLUSIONS An antibiotic lock protocol permits catheter salvage in 61% of hemodialysis patients with Enterococcus CRB. Serious complications occur in 6% of patients and are more common in those with treatment failure.