Preferred strategy for hemodialysis access creation in elderly patients.

BACKGROUND: Adequate functioning vascular access is the key to successful hemodialysis. The use of an autologous arteriovenous fistula (AVF) is advised because of good long-term patency and a low incidence of complications. However, the number of patients with AVFs is declining because of the change in the demography of the dialysis population, with increasing numbers of very old patients with multiple comorbidities. METHODS: In this vignette an elderly patient is described with calcified distal arteries and a small cephalic vein who is referred at a late stage for access creation. The results and performance of different types of vascular access (AVF; arteriovenous graft; central vein catheter), in relation to late referral and patient demographics, are described. In addition, patient morbidity and mortality versus the type of access are discussed. CONCLUSIONS: The patient described in this vignette appears to be unsuitable for the creation of a forearm AVF because of calcified distal arteries and a small cephalic vein. The risk of non-maturing autologous AVFs is high in elderly patients and this observation might justify the use of early stick grafts. High risk patients may benefit from permanent central vein catheters.

Cost-effectiveness of vascular access for haemodialysis: arteriovenous fistulas versus arteriovenous grafts.

BACKGROUND: The use of an arteriovenous fistula (AVF) for haemodialysis treatment may be associated with a high early failure rate, but usually good long-term patency, while using an arteriovenous graft (AVG) yields a lower early failure rate with worse long-term patency. The aim of this study was to calculate and compare the costs and outcome of AVF and AVG surgery in terms of early and long-term patencies. METHODS: A decision tree and a Markov model were constructed to calculate costs and performance of AVFs and AVGs. The model was populated with a retrospective cohort of HD patients receiving their first VA. The outcomes were determined probabilistically with a 5-year follow-up. RESULTS: AVFs were usable for a mean (95% CI) of 28.5 months (24.6-32.5 months), while AVGs showed a patency of 25.5 months (20.0-31.2 months). The use of AVFs was the dominant type of VA and € 631 could be saved per patient/per month patency compared to AVG use. Regardless of the willingness to pay, the use of AVFs yielded a higher probability of being cost-effective compared to AVGs. CONCLUSIONS: AVFs are more cost-effective than AVGs. Nonetheless, early failure rates significantly influence AVF performance and initiatives to reduce early failure can improve its cost-effectiveness.

Feasibility of non-contrast-enhanced magnetic resonance angiography for imaging upper extremity vasculature prior to vascular access creation.

OBJECTIVES: Preoperative mapping of arterial and venous anatomy helps to prevent postoperative complications after vascular access creation. The use of gadolinium in contrast-enhanced (CE) magnetic resonance angiography (MRA) has been linked to nephrogenic systemic fibrosis in patients with end-stage renal disease (ESRD). The purpose of this study was to evaluate non-contrast-enhanced (NCE) MRA for assessment of upper extremity and central vasculature and to compare it with CE-MRA. METHODS: NCE and CE-MRA images were acquired in 10 healthy volunteers and 15 patients with ESRD. In each data set, two observers analysed 11 arterial and 16 venous segments with regard to image quality (0-4), presence of artefacts (0-2) and vessel-to-background ratio. RESULTS: More arterial segments were depicted using CE-MRA compared to NCE-MRA (99% vs. 96%, p = 0.001) with mean image quality of 3.80 vs. 2.68, (p < 0.001) and mean vessel-to-background ratio of 6.47 vs. 4.14 (p < 0.001). Ninety-one percent of the venous segments were portrayed using NCE-MRA vs. 80% using CE-MRA (p < 0.001). Mean image quality and vessel-to-background ratio were 2.41 vs. 2.21 (p = 0.140) and 5.13 vs. 3.88 (p < 0.001), respectively. CONCLUSIONS: Although arterial image quality and vessel-to-background ratios were lower, NCE-MRA is considered a feasible alternative to CE-MRA in patients with ESRD who need imaging of the upper extremity and central vasculature prior to dialysis access creation.

Open repair for ruptured abdominal aortic aneurysm and the risk of spinal cord ischemia: review of the literature and risk-factor analysis.

OBJECTIVES: Spinal cord ischemia after open surgical repair for rAAA is a rare event. We estimated the current incidence and tried to identify risk factors. We also report a new case. METHODS: Group A consisted of 10 reports on open repair for rAAA from 1980 until 2009. Only series of ≥100 patients were considered to estimate the incidence. Thirty three case reports from 1956 until 2009 were identified (group B). Case reports from group B were not encountered in group A. Group B patients were stratified according to the type of neurological deficit as described by Gloviczki (type I complete infarction and type II infarction of the anterior two third). RESULTS: Group A consisted of 1438 patients. In group A 86% were male with a mean age of 72.1 years. The incidence of post-operative paraplegia was 1.2% (range 0-2.8%). In-hospital mortality was 46.9%. Of the 33 patients of group B were 86% male with a mean age of 68.0 years. Most patients developed a type I (42%) or type II (33%) deficit. In-hospital mortality was 51.6%. No significant differences between different types were encountered. CONCLUSION: Spinal cord ischemia after ruptured AAA is a rare complication with an incidence of 1.2% (range 0-2.8%).

Surgical techniques to improve cannulation of hemodialysis vascular access.

OBJECTIVE: Successful access cannulation is of utmost importance for adequate hemodialysis treatment. Upper arm fistulae, obesity and deep or tortuous veins may impair needling and can cause significant complications and inconvenience for the patient. In the ultimate case, cannulation problems lead to temporary central vein catheter use for dialysis or even to irreversible access loss. Surgical access revision may enhance successful cannulation. METHODS: A systematic literature review of all publications related to hemodialysis vascular access, cannulation complications and treatment was performed. RESULTS: A total of 384 publications were identified, of which only 17 were related to treatment of cannulation complications in large patient populations. The clinical success rate of surgical intervention with vein elevation or transposition ranges from 85% to 91%. The 1-year primary and secondary patencies are 60% and 71%, respectively. Lipectomy results in an initial success rate of 100% with a primary and secondary patency of 71% and 98%, respectively, after 1 year of follow-up. CONCLUSION: Surgical revision to improve hemodialysis vascular access cannulation has a high clinical success rate with good long-term patency.

Prospective evaluation of ischemia in brachial-basilic and forearm prosthetic arteriovenous fistulas for hemodialysis.

UNLABELLED: Ischemia is a devastating complication after arteriovenous fistula (AVF) creation. When not timely corrected, it may lead to amputation. Symptomatic ischemia occurs in 3.7-5% of the hemodialysis population. Upper arm AVFs have a higher incidence of ischemia compared to forearm AVFs. As more patients may need upper arm AVFs in the growing and older hemodialysis population, occurrence of symptomatic ischemia may increase. The purpose of this study is to identify predictors for occurrence of ischemia. METHODS: A prospective evaluation of ischemia was performed in patients randomised for either a brachial-basilic (BB-) AVF or a prosthetic forearm loop AVF. Clinical parameters, preoperative vessel diameters, access flows, digital blood pressures, digit-to-brachial indices (DBI) and interventions for ischemia were recorded. RESULTS: Sixty-one patients (BB-AVF 28) were studied. Seventeen patients (BB-AVF 8) developed ischemic symptoms. Six patients (BB-AVF 3) needed interventions for severe symptoms. Age, history of peripheral arterial reconstruction and radial artery volume flow were significant predictors for the occurrence of ischemia. CONCLUSION: Symptomatic ischemia occurred in 28% of patients with brachial-basilic and prosthetic forearm AVFs. Age, history of peripheral arterial reconstruction and radial artery volume flow might be important for prediction of ischemia.

Multi-slice computed tomographic angiography for stenosis detection in forearm hemodialysis arteriovenous fistulas.

PURPOSE: A method of diagnosing the extent and severity of arteriovenous fistula (AVF) stenoses is multislice computed tomographic angiography (MS-CTA). The aim of this prospective study was to assess the accuracy of MS-CTA for the detection and grading of stenoses in AVF in comparison to digital subtraction angiography (DSA), which was used as the gold standard of reference. METHODS: Fifteen hemodialysis (HD) patients with dysfunctioning forearm AVF were included. These AVFs were evaluated by both DSA and MS-CTA and were read in a prospective, blinded manner by two radiologists experienced in vascular imaging. RESULTS: ROC analysis revealed areas under the curve of 0.90+/-0.07 for observer I and 0.87+/-0.08 for observer II at a stenosis cut-off level of >or=50% diameter reduction. The combined results for MS-CTA showed sensitivity, specificity and positive and negative predictive values of 82%, 98%, 82% and 98% for stenoses>or=50% and 71%, 99%, 77% and 98% for stenoses>or=75%. Inter-observer agreement for the detection of stenoses>or=50% diameter reduction was 0.70 and 1.0, for MS-CTA and DSA, respectively. CONCLUSION: MS-CTA can provide good visualization of forearm HD access AVF and has moderate sensitivity, but high specificity for the detection of flow-limiting stenoses.

Contrast-enhanced magnetic resonance angiography findings prior to hemodialysis vascular access creation: a prospective analysis.

PURPOSE: To determine prospectively the clinical value of contrast-enhanced magnetic resonance angiography (CE-MRA) for assessment of the arterial inflow and venous outflow prior to vascular access (VA) creation. METHODS: Seventy-three patients underwent duplex ultrasonography (DUS) and CE-MRA prior to VA creation for detection of stenoses and occlusions. Two observers read the CE-MRA images for determination of inter-observer agreement. A VA was considered functional if it could be used for successful two-needle hemodialysis therapy within 2 months after creation. RESULTS: CE-MRA detected 6 stenosed, 8 occluded arterial vessel segments and 12 stenosed and 41 occluded venous vessel segments in 70 patients. Inter-observer agreement for detection of upper extremity arterial and venous stenoses and occlusions with CE-MRA was substantial to almost perfect (kappa values 0.76-0.96). CE-MRA detected lesions, not detected by DUS, that were associated with VA early failure and non-maturation in 33% of patients (7/21). Accessory veins detected preoperatively were the cause of VA non-maturation in a substantial group of patients (47%: 7/15). CONCLUSION: CE-MRA enables accurate detection of upper extremity arterial and venous stenosis and occlusions prior to VA creation. Preoperative CE-MRA identified arterial and venous stenoses, not detected by DUS that were associated with VA early failure and non-maturation. However, the use of gadolinium containing contrast media is currently contraindicated due the reported incidence of nephrogenic systemic fibrosis.

Accessory veins and radial-cephalic arteriovenous fistula non-maturation: a prospective analysis using contrast-enhanced magnetic resonance angiography.

PURPOSE: To determine if large caliber accessory veins are associated with radial-cephalic arteriovenous fistula (RC-AVF) non-maturation. METHODS: RC-AVFs were created in 15 consecutive patients (radial artery and cephalic vein diameter > 2 mm, in the absence of arterial inflow or venous outflow stenoses or occlusions). Contrast-enhanced magnetic resonance angiography (CE-MRA) was performed preoperatively for the determination of vessel diameters, stenoses and occlusions. The location and caliber of accessory veins was determined. Vascular access (VA) function was monitored and all interventions required to obtain a functioning VA were recorded. Non-maturation was defined as a nonfunctional VA at 2 months after creation. The predictive value of accessory vein caliber for prediction of RC-AVF non-maturation was evaluated using receiver operating characteristic (ROC) analysis. RESULTS: Non-maturation occurred in 10 (67%) out of 15 RC-AVFs. Large caliber accessory veins (n = 4), venous stenosis (n = 3) or both (n = 2) were associated with RC-AVF non-maturation. The presence of large caliber accessory veins was the only significant predictor for RC-AVF non-maturation (p = 0.01). Preoperatively detected accessory veins with a diameter > 70% of the cephalic vein diameter, had a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 80, 100, 100 and 91% for prediction of RC-AVF non-maturation on patient level. Accessory vein ligation and dilatation of venous stenosis resulted in an overall salvage success rate of 89% (8/9). CONCLUSION: Large caliber accessory veins are associated with RC-AVF non-maturation. Ligation of large caliber accessory veins is a successful salvage procedure in a substantial group of patients. Furthermore, ligation of these accessory veins during initial RC-AVF creation can potentially reduce non-maturation rates; and therefore, preoperative assessment of accessory veins is recommended.

Effect of upper arm brachial basilic and prosthetic forearm arteriovenous fistula on left ventricular hypertrophy.

BACKGROUND: Creation of an arteriovenous fistula (AVF) may increase left ventricular hypertrophy in the hemodialysis population. Aim of this study was to compare the effects of a brachial-basilic (BB) AVF and the prosthetic brachial-antecubital forearm loop access (PTFE) on cardiac performance. METHODS: Patients were randomized to receive BB-AVF or prosthetic brachial-antecubital forearm loop access. Before and three months after AVF creation patients underwent an echocardiographic examination. Mann-Whitney U-test was used to compare relative increase between the measured cardiac parameters for the two groups. RESULTS: Twenty-seven patients participated in the study. The relative increase in left ventricular parameters was not significantly different between the two groups. Only left ventricular end-diastolic diameter tended to be of significance. Mean blood flow through the brachial artery was 1680+/-156 and 1450+/-221 mL/min three months after surgery for the PTFE and the BB-AVF group, respectively. CONCLUSION: After three months of follow-up, changes in cardiac structure were comparable between patients with BB and PTFE AVFs. Also access flow was comparable at this time. In general, the effects of creation of a fistula on LV structure were limited. Longer follow up time may be needed to explore the long term effects of different vascular accesses on cardiac function.

The effect of chronic flow changes on brachial artery diameter and shear stress in arteriovenous fistulas for hemodialysis.

BACKGROUND: Vessel wall adaptation to acute or chronic flow changes is regulated by shear stress (SS) at the endothelium. This hypothesis was tested in the brachial artery (BA) of patients receiving an arteriovenous fistula (AVF) for hemodialysis vascular access. METHODS: The acute and sustained effects were evaluated in 13 patients. Pre-operatively and postoperatively on predetermined time-points BA diameter and shear rate (SR) were measured. SS was calculated from whole blood viscosity and SR. Analysis was performed with Wilcoxon's test and ANCOVA multivariate analysis. RESULTS: Acutely, mean SS increased (475%, p<0.05), peak-to-peak SS decreased (37%, p<0.05) and peak SS remained constant. BA diameter increased (15%, p<0.05). After one year a further increase was observed (r=0.59, p<0.001), plus an increase in mean SS (r=0.78, p<0.001). Peak-to-peak SS remained constant. CONCLUSION: Our results indicate that after AVF placement an acute increase in SS results in an acute increase of vessel diameter. However, one year of sustained high blood flow does not result in restoration of mean SS.

Current topics on vascular access for hemodialysis.

Vascular access remains the lifeline for end-stage renal failure patients, which have been treated by chronic intermittent hemodialysis. Due to the steady increase in the number of patients with difficulties to create access, in particular in elderly with various comorbidities, the need for more insight and regulations have evolved into the publications of the American and European guidelines. From the latter it may be obvious that an adequate preoperative assessment followed by the creation of autogenous arteriovenous fistulas (AVFs) is far better and preferred to the implantation of grafts. Vascular access maintenance by monitoring and elective percutanuous or surgical revision is of utmost importance to keep the access site functional. Despite up-to-date measures for vascular access maintenance, various complications may treaten not only the access site but also quality and expectance of life. Thrombotic occlusion remains a major event, leading to permanent failure in 10% of AVFs and 20% of grafts each year. Interventional (percutaneous transluminal angioplasty and/or stent implantation) or surgical revision of thrombosed accesses have similar outcomes with a high rate of reinterventions. The elderly diabetic population with peripheral arteriosclerotic obstructive disease is in particular prone to angio-access induced handischemia. When not timely and properly treated this may lead to minor or major amputation, further hampering quality of life. Also, the enormous application in the past 2 decades of acute central venous lines has lead to a significant increase of central venous obstruction with concomittent morbidity and problems creating vascular access in the upper extremities. Radiological intervention in these cases is a primary option, leaving surgical reconstruction as a second best method. It may be obvious that creation and maintenance of hemodialysis vascular access has become an important and time-consuming speciality. Only an up-to-date multidisciplinary management with involvement of nurses, nephrologists, interventionalists and surgeons, will lead to the desired outcome.

A sensitivity analysis of a personalized pulse wave propagation model for arteriovenous fistula surgery. Part A: Identification of most influential model parameters.

Previously, a pulse wave propagation model was developed that has potential in supporting decision-making in arteriovenous fistula (AVF) surgery for hemodialysis. To adapt the wave propagation model to personalized conditions, patient-specific input parameters should be available. In clinics, the number of measurable input parameters is limited which results in sparse datasets. In addition, patient data are compromised with uncertainty. These uncertain and incomplete input datasets will result in model output uncertainties. By means of a sensitivity analysis the propagation of input uncertainties into output uncertainty can be studied which can give directions for input measurement improvement. In this study, a computational framework has been developed to perform such a sensitivity analysis with a variance-based method and Monte Carlo simulations. The framework was used to determine the influential parameters of our pulse wave propagation model applied to AVF surgery, with respect to parameter prioritization and parameter fixing. With this we were able to determine the model parameters that have the largest influence on the predicted mean brachial flow and systolic radial artery pressure after AVF surgery. Of all 73 parameters 51 could be fixed within their measurement uncertainty interval without significantly influencing the output, while 16 parameters importantly influence the output uncertainty. Measurement accuracy improvement should thus focus on these 16 influential parameters. The most rewarding are measurement improvements of the following parameters: the mean aortic flow, the aortic windkessel resistance, the parameters associated with the smallest arterial or venous diameters of the AVF in- and outflow tract and the radial artery windkessel compliance.

A sensitivity analysis of a personalized pulse wave propagation model for arteriovenous fistula surgery. Part B: Identification of possible generic model parameters.

Decision-making in vascular access surgery for hemodialysis can be supported by a pulse wave propagation model that is able to simulate pressure and flow changes induced by the creation of a vascular access. To personalize such a model, patient-specific input parameters should be chosen. However, the number of input parameters that can be measured in clinical routine is limited. Besides, patient data are compromised with uncertainty. Incomplete and uncertain input data will result in uncertainties in model predictions. In part A, we analyzed how the measurement uncertainty in the input propagates to the model output by means of a sensitivity analysis. Of all 73 input parameters, 16 parameters were identified to be worthwhile to measure more accurately and 51 could be fixed within their measurement uncertainty range, but these latter parameters still needed to be measured. Here, we present a methodology for assessing the model input parameters that can be taken constant and therefore do not need to be measured. In addition, a method to determine the value of this parameter is presented. For the pulse wave propagation model applied to vascular access surgery, six patient-specific datasets were analyzed and it was found that 47 out of 73 parameters can be fixed on a generic value. These model parameters are not important for personalization of the wave propagation model. Furthermore, we were able to determine a generic value for 37 of the 47 fixable model parameters.

Assisting vascular access surgery planning for hemodialysis by using MR, image segmentation techniques, and computer simulations.

The surgical creation of a vascular access, used for hemodialysis treatment of renal patients, has considerable complication rates (30-50 %). Image-based computational modeling might assist the surgeon in planning by enhanced analysis of preoperative hemodynamics, and in the future might serve as platform for outcome prediction. The objective of this study is to investigate preoperative personalization of the computer model using magnetic resonance (MR). MR-angiography and MR-flow data were obtained for eight patients and eight volunteers. Blood vessels were extracted for model input by a segmentation algorithm. Windkessel elements were added at the ends to represent the peripheral beds. Monte Carlo-based calibration was used to estimate the most influential non-measurable parameters. The predicted flow waveforms were compared with the MR-flow measurements for framework evaluation. The vasculature of all subjects were segmented in on average <5 min. The Monte Carlo-calibrated simulations showed a deviation between measured and simulated flow waveforms of 9 and 10 % for volunteers and patients, respectively. The presented method accurately mimics the preoperative hemodynamic state. Furthermore, the surgeon can interactively explore the hemodynamics at any vascular tree position. This integration of measurements in a modeling approach can provide the surgeon with additional information for preoperative planning.

Traumatic dissection and thrombosis of the popliteal artery in a child.

Injuries of the popliteal artery have the highest rate of limb loss compared with other peripheral vascular injuries. Particularly, blunt popliteal artery trauma is known to be associated with a high rate of amputation. Traumatic vascular injuries are usually associated with dislocations and fractures. We describe the radiographic findings as well as the delayed presentation and management of a crush injury of the left leg in an 8-year-old girl resulting in dissection of the popliteal artery without a dislocation or fracture.