Innovations in vascular access for hemodialysis.

Worldwide, hemodialysis remains the prevalent dialysis modality for more than 2 million patients who require well-functioning vascular access for this procedure. Creation of an arteriovenous fistula for long-term hemodialysis was the first innovation since the Scribner shunt and was followed by the development of an arteriovenous graft and catheter. Bioengineered vessels were developed during the last century, but this field has been energized by recent technology relating to the creation of human vessels. Novel endovascular techniques for creating an arteriovenous fistula may resolve some of the logistical issues involved in obtaining a timely arteriovenous fistula. Treatment of access stenosis, infection, and thrombosis has remained suboptimal, and innovative technologies are evolving. Many new approaches are now targeting the biological and mechanical aspects of vascular access, such as creation and maturation of arterial and venous anastomoses, development of a biological conduit for outflow, and negotiating the problems of central vein stenosis. Importantly, processes of access care that have long focused on arteriovenous fistulas are now recognizing the new paradigm, providing a complementary niche to arteriovenous grafts and dialysis catheters in the algorithm for individualized access placement. Cumulatively, to the credit of the multidisciplinary team approach, the long overdue focus on the very existential issue of vascular access for hemodialysis is being approached with newfound evidence-based enthusiasm as the vexing challenges related to regulations and reimbursement in hemodialysis persist. Patient choice and experience, often missed and ignored in the challenging management of an end-stage organ failure, need to stay central as we focus on patient-centered care of vascular access.

Complications of Vascular Access: Superior Vena Cava Syndrome.

Stenosis or occlusion of central veins in hemodialysis patients is common, especially with previous intravascular catheter or device use. Superior vena cava (SVC) obstruction is emerging as a frequent chronic complication of central vein cannulation that not only jeopardizes the availability of vascular access for hemodialysis, but can become a life-threatening emergency. Clinical features of SVC syndrome can be subtle or dramatic, including facial swelling and shortness of breath, which require expeditious attention and intervention. The approach to SVC syndrome involves judicious use of imaging techniques to define the cause and location. Early management with endovascular intervention with angioplasty and stent placement is the usual first choice. The occlusion can often be recanalized using new techniques such as radiofrequency wire and then salvaged with stents, providing prompt resolution of symptoms. Limitations to interventions include requirement of cutting-edge equipment, expertise, expense, and the usually temporary nature of the resolution. Surgery is considered the treatment of last resort for refractory cases. SVC syndrome can be prevented by minimizing catheter and intravascular device use through early recognition of patients with chronic kidney disease, early referral for education about all choices for kidney replacement modalities, and early placement of arteriovenous access prior to the onset of dialysis therapy.

Iatrogenic graft to vein fistula (GVF) formation associated with synthetic arteriovenous grafts.

The prevalence of fistulous connection between arteriovenous graft (AVG) and an adjacent vein resulting in graft-vein fistula (GVF) formation is not established. AVG venous outflow stenosis along with repeated and traumatic cannulation is likely major contributing factor of this complication. Detection and resolution of venous outflow stenosis may be the only needed intervention. We report a series of eight cases with GVF formation between AVG and adjacent veins. Awareness of this complication and intervention to relieve stenotic lesions may result in improved AVG survival.

Hemodialysis access monitoring and surveillance, how and why?

Hemodialysis access is the 'life line' for patients on renal replacement therapy. Vascular access failure and complications are the second leading cause for hospitalization of patients on hemodialysis. The concept of access monitoring is based on the basic tenet that identification of patients at risk of developing future access failure, coupled with elective intervention will decrease the incidence of hemodialysis access failure and improve patient outcomes. Clinical monitoring and surveillance techniques are very effective in detecting hemodialysis access lesions. However, the studies analyzing the impact of monitoring and surveillance have yielded a variety of controversial results, which is likely the result of the differences in methodology and use of a variety of parameters. Despite the controversy surrounding the value of monitoring and surveillance, the Conditions of Coverage for dialysis providers mandate monitoring with appropriate and timely referrals to achieve and sustain vascular access. This review discusses pros and cons of various monitoring and surveillance techniques and suggests a strategy based on current literature.

Central vein stenosis: a nephrologist's perspective.

Central vein stenosis is commonly associated with placement of central venous catheters and devices. Central vein stenosis can jeopardize the future of arteriovenous fistula and arteriovenous graft in the ipsilateral extremity. Occurrence of central vein stenosis in association with indwelling intravascular devices including short-term, small-diameter catheters such as peripherally inserted central catheters, long-term hemodialysis catheters, as well as pacemaker wires, has been recognized for over two decades. Placement of multiple catheters, longer duration, location in subclavian vein, and placement on the left-hand side of neck seem to predispose to the development of central vein stenosis. Endothelial injury with subsequent changes in the vessel wall results in development of microthrombi, smooth muscle proliferation, and central vein stenosis. Central vein stenosis is often asymptomatic in nondialysis patients, but can result in edema of ipsilateral extremity and breast when challenged by increased flow from an arteriovenous fistula or arteriovenous graft. Bilateral central vein stenosis or superior vena cava stenosis can produce a clinical picture of superior vena cava syndrome, associated with engorgement of face and neck. Endovascular interventions are the mainstay of management of central vein stenosis. Percutaneous angioplasty and stent placement for elastic and recurring lesions can restore the functionality of the vascular access, at least temporarily. Frequent or multiple interventions are usually required. In recalcitrant cases, surgical bypass of the obstruction is an option. In resistant cases with severe symptoms, occlusion of the functioning vascular access will usually provide relief of symptoms. Further study of mechanisms of development of central vein stenosis and search for a targeted therapy is likely to lead to better ways of managing central vein stenosis. Prevention of central vein stenosis is the key to avoid access failure and other complications from central vein stenosis and relies upon avoidance of central vein stenosis placement and timely placement of arteriovenous fistula in prospective dialysis patient.