Long‐term effects of daily hemodialysis on vascular access outcomes: A prospective controlled study

Daily hemodialysis has been associated with surrogate markers of improved survival among hemodialysis patients. A potential disadvantage of daily hemodialysis is that frequent vascular access cannulations may affect long‐term vascular access patency. The study design was a 4‐year, nonrandomized, contemporary control, prospective study of 77 subjects in either 3‐h daily hemodialysis (six 3‐h dialysis treatments weekly; n = 26) or conventional dialysis (three 4‐h dialysis treatments weekly; n = 51). Outcomes of interest were vascular access procedures (fistulagram, thrombectomy and access revision). Total access procedures (fistulagram, thrombectomy and access revision) were 543.2 (95% confidence interval [CI]: 432.9, 673.0) per 1000 person‐years in the conventional dialysis group vs. 400.8 (95% CI: 270.2, 572.4) per 1000 person‐years in the daily hemodialysis dialysis group (incidence rate ratio = 0.74 with 95% CI: from 0.40 to 1.36, P = 0.33), after adjusting for age, gender, diabetes status, serum phosphorus, hemoglobin level and erythropoietin dose, there was no significant differences in incidence rate of total access procedures (P‐value > 0.05). There was no difference in time to first access revision between the daily dialysis and the conventional dialysis groups after adjustment for covariates (hazard ratio = 0.99 95% CI: 0.42, 2.36, P = 0.96). Daily hemodialysis is not associated with increased vascular access complications, or increased vascular access failure rates.     

The flow field near a venous needle in hemodialysis: A computational study

The vascular access used in hemodialysis can suffer from numerous complications, which may lead to failure of the access, patient morbidity, and significant costs. The flow field in the region of the venous needle may be a source of damaging hemodynamics and hence adverse effects on the fistula. In this study, the venous needle flow has been considered, using three‐dimensional computational methods. Four scenarios where the venous needle flow could potentially influence dialysis treatment outcome were identified and examined: Variation of the needle placement angle (10°, 20°, 30°), variation of the blood flow rate settings (200, 300, 400 mL/min), variation of the needle depth (top, middle, bottom), and the inclusion of a back eye in the needle design. The presence of the needle has significant effect on the flow field, with different scenarios having varying influence. In general, wall shear stresses were elevated above normal physiological values, and increased presence of areas of low velocity and recirculation—indicating increased likelihood of intimal hyperplasia development—were found. Computational results showed that the presence of the venous needle in a hemodialysis fistula leads to abnormal and potentially damaging flow conditions and that optimization of needle parameters could aid in the reduction of vascular access complications. Results indicate shallow needle angles and lower blood flow rates may minimize vessel damage.     

A pilot study of genetic polymorphisms and hemodialysis vascular access thrombosis

Vascular access thrombosis (VAT) remains a significant problem worldwide. This study determined the association between VAT and 7 candidate gene polymorphisms (factor V Leiden 1691G>A, factor II 20210G>A, methylenetetrahydrofolate reductase 677C>T, angiotensin converting enzyme 287 base pair (bp) insertion/deletion, transforming growth factor-β1 869T>C and 915G>C, NOS3 −786T>C and intron 4 27 bp tandem repeat, and endotoxin receptor CD14 −159C>T). This was a retrospective case-control pilot study conducted in 101 hemodialysis patients at a large tertiary-care, University health-science center. Sixty cases that experienced frequent VAT and 41 controls that had not experienced VAT in at least 3 years were evaluated for demographics and genotyping. These data were summarized, and univariable and multivariable regression models were constructed. Univariate VAT predictors included the NOS3 420 bp allele (P=0.03) and the presence of a central venous dialysis catheter (P<0.01). Aspirin use was protective against VAT (P=0.02). In the multivariate analysis, the dialysis access type remained a significant predictor of thrombosis (P<0.01), while aspirin use retained its protective status (P=0.01). Statin use was associated with the cases (P=0.02); however, the NOS3 420 bp allele failed to improve the model. These data confirm that central venous dialysis catheter access is associated with thrombosis, while aspirin use appears protective. The NOS3 420 bp allele may have an association with thrombosis; however, further epidemiologic data evaluating large dialysis registries are needed to confirm our observation.     

Vascular imaging for hemodialysis vascular access planning

Introduction: Central venous catheters (CVC) increase risks associated with hemodialysis (HD), but may be necessary until an arteriovenous fistula (AVF) or graft (AVG) is achieved. The impact of vascular imaging on achievement of working AVF and AVG has not been firmly established. Methods: Retrospective cohort of patients initiating HD with CVC in 2010–2011, classified by exposure to venography or Doppler vein mapping, and followed through December 31, 2012. Standard and time‐dependent Cox models were used to determine hazard ratios (HRs) of death, working AVF, and any AVF or AVG. Logistic regression was used to assess the association of preoperative imaging with successful AVF or AVG among 18,883 individuals who had surgery. Models were adjusted for clinical and demographic factors. Findings: Among 33,918 patients followed for a median of 404 days, 39.1% had imaging and 55.7% had surgery. Working AVF or AVG were achieved in 40.6%; 46.2% died. Compared to nonimaged patients, imaged patients were more likely to achieve working AVF (HR = 1.45 [95% confidence interval [CI] 1.36, 1.55], P < 0.001]), any AVF or AVG (HR = 1.63 [1.58, 1.69], P > 0.001), and less likely to die (HR = 0.88 [0.83‐0.94], P < 0.001). Among patients who had surgery, the odds ratio for any successful AVF or AVG was 1.09 (1.02–1.16, P = 0.008). Discussion: Fewer than half of patients who initiated HD with a CVC had vascular imaging. Imaged patients were more likely to have vascular surgery and had increased achievement of working AV fistulas and grafts. Outcomes of surgery were similar in patients who did and did not have imaging.     

HCO3 increment in arterial line can reveal significant vascular access recirculation in high-flux hemodialysis: a preliminary report

We report a new and simple way that can reveal the presence of vascular access recirculation (VAR) in patients undergoing hemodialysis (HD). Acid-base and blood gas parameters (pH, pO(2), pCO(2), and HCO(3)) were measured in blood samples drawn from an arterial fistula needle before the initiation of HD and from arterial and venous lines simultaneously 5 min later, in 31 patients (group A). Vascular access recirculation was measured using the glucose infusion test (GIT) immediately after the withdrawal of the 5-min samples. The same study was repeated in 30 patients in whom HD lines were reversed (group B). A comparison with baseline (predialysis) values of an analysis of the arterial line in group A at 5 min revealed that pCO(2) increased by 1.14+/-2.5 mmHg and HCO(3) by 0.6+/-0.6 mM/L (p<0.02 and p<0.00001, respectively). The corresponding pO(2) and pH values did not show significant differences. Glucose infusion test at 5 min (GITa) was -0.058+/-0.03%. A comparison with baseline (predialysis) values of an analysis of the arterial line in group B at 5 min revealed that pCO(2) increased by 7.7+/-3.5 mmHg and HCO(3) by 2.9+/-1.0 mM/L (p<0.000001 in each case). The pH level was significantly lower in comparison with baseline values (p<0.00001), while pO(2) did not show a significant difference. Glucose infusion test at 5 min (GITb) was 12.0+/-6.1% (p<0.000001 in comparison with GITa values). Clinically significant VAR was defined as HCO(3) increment >1.8 mM/L, based on the receiver-operating characteristics curve, which showed a threshold value of HCO(3) increment >1.8 mmol/L as a predictor of GIT recirculation. Five minutes after the initiation of high-flux HD with a 0 ultrafiltration rate, there is a small increment in arterial HCO(3) values relative to predialysis values. Clinically significant VAR is present when this increment is higher than 1.8 mM/L.     

Stent use for hemodialysis access: What a general nephrologist needs to know

Recurrent stenosis due to neo‐intimal hyperplasia leads to loss of patency in an established hemodialysis access. The current treatment strategy to maintain patency involves percutaneous transluminal angioplasty with or without stent placement. There are several key points that an interventionalist needs to weigh before deciding to place a stent. These include appropriateness of stent placement, the long term consequences, the type of stent to be deployed, the size of stent and finally the impact on cannulation during dialysis. A general nephrologist needs to be aware of the various benefits and pitfalls of stent placement. The current review provides basic information that will educate the dialysis provider about stents and its use in treating dysfunctional hemodialysis access using commonly encountered clinical scenarios.     

Challenges of long-term vascular access in pediatric hemodialysis: Recommendations for practitioners

Kidney transplantation is the preferred treatment of end-stage renal disease in children. However, time to transplant varies, making a well-functioning long-term vascular access essential for performing hemodialysis efficiently and without disruption until a kidney becomes available. However, establishing long-term vascular access in pediatric patients can present distinct challenges due to this population's unique characteristics, such as smaller body size and lower-diameter blood vessels. There are three main pediatric long-term vascular access options, which include central venous catheters (CVC), arteriovenous fistula (AVF), and arteriovenous graft (AVG). CVC are currently the most widely used modality, although various studies and guidelines recommend AVF or AVG as the preferred option. Although AVF should be used whenever possible, it is crucial that clinicians consider factors such as patient size, physical exam findings, comorbidities, predicted duration of treatment to decide on the most optimal long-term vascular access modality. This article reviews the three long-term vascular access methods in children and the benefits and complications of each.     

Cephalic arch stenosis in patients with fistula access for hemodialysis: relationship to diabetes and thrombosis

Numerous studies have identified the fistula as the best access for hemodialysis with fewest complications. The radiocephalic fistula (RCF) is the first access of choice, but often results in poor maturation. Therefore, an increased number of brachiocephalic fistulas (BCF) have been placed. Cephalic arch stenosis (CAS) can occur in patients with fistula access. The current study was done to determine the incidence and associated comorbidities in patients with BCF or RCF who have CAS. A retrospective review of 450 hemodialysis patients in 3 outpatient hemodialysis units between July 1, 2000 and July 1, 2005 (60 months) was preformed. We reviewed demographics, medications, and indications for venograms. Interventional Radiologists reviewed the venograms for evidence of CAS. Radiology reports were screened to determine incidence of thrombosis, treatment with either angioplasty or stent placement and if a complication such as venous rupture occurred. One hundred and twenty-seven patients had fistula access with at least 1 venogram. Of these, 30 were RCF and 97 were BCF. Cephalic arch stenosis occurred in 77% of patients with BCF and in 20% of patients with RCF. Those with diabetes had a lower rate of occurrence than those without (p<0.01). Cephalic arch stenosis led to a high rate of thrombosis (p<0.01). The probability of having multiple radiology procedures was higher with CAS than without (p<0.01). Cephalic arch stenosis is an important problem in hemodialysis patients who have fistula access, and contributes to thrombosis. Diabetes was found to have a negative association with CAS for undefined reasons. Attempts to understand this relationship are important.     

Vascular access for hemodialysis: experience of a team of nephrologists

A survey conducted by Bonucchi et al. underlined the different types of doctors placing arteriovenous fistula (AVF) for hemodialysis in the United States and Europe (in particular Italy). In fact, nephrologists definitely prevail in Italy, where almost 48.8% of nephrologists place an AVF themselves or with the help of a vascular surgeon (26.4%). In Europe, only 35% do so, whereas 89% of AVF are performed by surgeons in the United States. In 98% of the cases occurring at our center, the AVF was placed and reviewed by the nephrologists. This paper reports surgery cases related to the period between January 1983 and September 2006. Over this time, 1386 operations for placing and reviewing vascular access were conducted. Among these, 47 (3.3%) were related to a cuffed central venous catheter (CVC); 1138 (80.2%) related to a distal AVF; 201 (10.6%) related to a proximal AVF; and 51 (3.6%) related to an arteriovenous graft (AVG). In addition, 33 (2.3%) operations performed before January 1983 relating to AV Scribner shunts were included. Arteriovenous fistulas or AVGs were provided to our patients (only 2.6% of them have a CVC), and AVF rescue operations were performed in the shortest possible time with advantages for the patient and his vascular access.     

Asymmetric breast enlargement minus central venous thrombosis in a hemodialysis patient

A 76-year-old woman hemodialysis patient was hospitalized for community-acquired pneumonia complicating chronic obstructive pulmonary disease. End-stage renal disease secondary to hypertension had been diagnosed at the age of 64 for which the patient was initiated on maintenance hemodialysis. Then, she received a deceased donor kidney transplant at the age of 68 that succumbed to chronic rejection 4 years later when she was restarted on hemodialysis. Hemodialysis was performed via a right subclavian vein double lumen catheter for 2 months when a right brachio-axillary graft was inserted. Severe venous congestion, swelling, and nipple tenderness of her right breast noted on admission had been increasing for 6 weeks before hospital admission. No arm swelling was evident. Initial management of the patient's pneumonia and chronic obstructive pulmonary disease consisted of intravenous ceftriaxone and albuterol inhaler to which intravenous oxacillin (1 g q 6 hr) was added for presumed right mastitis. Radiological work-up for masses and malignancies was negative. An angiogram of the right upper extremity detected stenosis of the dialysis access graft at its anastomosis with the axillary vein. Angioplasty of the stenosis was performed without incident or evidence of central vein stenosis. Rapid resolution over 10 days of the unilateral breast congestion followed without complication.     

Cannulation and vascular access-related complications in hemodialysis: Factors determining successful cannulation

Little is known about cannulation of the vascular access (VA), such as the number of successful cannulation procedures, frequency of complications caused by cannulation, and VA failure. Incident patients were followed for 6 months, from the first successful cannulation with 2 needles—both used for the hemodialysis treatment. Data included patient characteristics, comorbidities, and medication. Vascular access characteristics included: type of VA and location, vein diameter assessed by Duplex ultrasound, length of the cannulation route, and maturation period. Longitudinal data were collected by dialysis nurses, using identical questionnaires, and a standardized method to register data from each dialysis session. Among 10 Dutch dialysis facilities, clinical data from 120 patients were collected from June 2005 to March 2007. The use of autogenous arteriovenous fistulae (P<0.001) and limited length of the cannulation route (P<0.003) negatively affect the outcome of cannulation and complications such as use of single-needle (SN) dialysis and central vein catheters (CVC). Previous use of CVC and SN hemodialysis were significant predictors for VA failure (P<0.0001). The present study demonstrated that during the first 6 months of a newly placed VA, a huge number of cannulation-related complications such as miscannulation, use of CVC, and SN dialysis are encountered. Despite the fact that guidelines recommended the arteriovenous fistulae as the preferred VA, cannulation-related complications can lead to increased morbidity. The length of the cannulation route positively correlates with successful cannulation. Therefore, adjusted cannulation techniques might be indicated to improve VA outcome.     

Effect of ethnicity on erythropoietin therapy response for hemodialysis patients: A retrospective study

Anemia is a common feature in chronic kidney disease patients due to deficiency of erythropoietin (EPO). Diseased kidneys are unable to produce EPO, which enhances red blood cell production from the bone marrow. Recombinant human EPO in hemodialysis patients was introduced with perfect outcomes as a hormonal substitutive treatment. Some ethnic minority groups have high prevalence of anemia associated with chronic kidney diseases. The aim of this study is to evaluate the differences between African Caribbeans and Caucasians’ EPO therapy response with regard to hemoglobin (Hb), some factors affecting it and some comorbid conditions. A retrospective study for 6 months of 100 patients on hemodialysis was conducted on two ethnic minorities groups; 46 patients were African Caribbean and 54 patients were Caucasian, who received EPO therapy at once or three times weekly dose at the Hanbury Dialysis Unit of Royal London Hospital. There were three types of EPO therapy used: Aranesp, Mircera and Neorecormon. Forty‐six patients were African Caribbean and 54 patients were Caucasian. There were 63.4% of patients treated by Aranesp while 13% were given Mircera; 22.8% of the sample used Neorecorman. It was shown that the chosen comorbid conditions had higher percentage in the African Caribbeans than in Caucasians. Diabetic and/or hypertensive patients are almost double the patient numbers. In addition, sickle cell anemia is only present in African Caribbeans. There were 43.5% of African Caribbeans and 81.1% of Caucasians who met the standards of Hb level. There was no significant difference between African Caribbeans and Caucasians regarding parathyroid hormone, c‐reactive protein, B12, mean corpuscular volume, ferritin, and folate. In this study, there was a significant difference in the Hb levels between African Caribbean and Caucasian groups. Sixty percent of African Caribbeans had mean Hb less than normal levels. However, they received lower EPO dose than Caucasians. As a result, this may affect the whole treatment and therapy which may lead to anemic complications.