Hemodialysis and Vascular Access

Introduction

Access to the vascular system in order to perform life-sustaining dialysis in the face of renal failure remains an important and challenging clinical scenario for vascular surgeons. The number of individuals requiring vascular access for hemodialysis continues to rise. Up to 16% of the world's population now suffers from chronic kidney disease (CKD), which is defined according to “the presence or absence of kidney damage and level of kidney function.” CKD most commonly occurs secondary to diabetes and hypertension. Many of those patients have advanced cardiovascular disease and live in low- or middle-income countries whose economies are ill equipped to shoulder the considerable financial burden of this vulnerable patient population. In 2008, there were 382,000 patients in the United States with end stage renal disease (ESRD), defined as a progression of CKD requiring the initiation of renal replacement therapy. Over 90% of those patients were hemodialysis-dependent. This chapter briefly discusses the history of dialysis access to supply perspective to the problem and then reviews catheter and permanent access in the form of an arteriovenous fistula constructed with an autogenous or prosthetic conduit. This discussion includes a review of configuration, results, and complications associated with the different methods of dialysis access.

Historical Perspective

The earliest recorded attempt at hemodialysis was made in 1913 by Abel, Rowntree, and Turner in Baltimore, Maryland. Abel and colleagues created the first “artificial kidney” while studying the physiologic consequences of partial plasma removal in animals. They developed a method of plasmapheresis, which they called vividiffusion , to advance this research. In 1924, Haas, in Germany, was credited with the first human use of hemodialysis to treat a uremic patient. The procedure was short and experimental, lasting about 15 minutes, and his avant-garde research was largely ignored by the medical community of the time. In 1943, Kolff, in Holland, developed the first clinically effective hemodialysis machine. He used cellophane tubing to build a rotating drum artificial kidney. Over the course of World War II, Kolff treated 17 patients, of whom only 1 survived. The subsequent success of early dialysis machines was dulled by their inefficiency, requiring up to 10 hours per session, as well as a lack of reliable vascular access options. Therefore treatment was limited to patients with acute kidney failure who did not require long-term therapy. In 1960, in Seattle, Washington, Dr. Belding Scribner and colleagues, including Wayne Quinton, developed an external arteriovenous (AV) polytetrafluoroethylene (PTFE) shunt that was successfully used to dialyze a machinist, who survived for 11 years after starting treatment. Scribner went on to found the Seattle Artificial Kidney Center, the first outpatient dialysis facility. At around the same time, Shaldon, a British nephrologist, created a home-made indwelling hemodialysis catheters using yellow plastic tubing. These catheters were introduced into the femoral vein using the Seldinger technique. The advent of these indwelling vascular access devices heralded the era of chronic dialysis therapy. The first AV fistula created for dialyzing patients with ESRD was described in 1966 by Brescia and colleagues from the Veterans Administration Hospital in the Bronx, New York. Appel, the group's surgeon, performed a side-to-side anastomosis between the radial artery and the cephalic vein using a continuous silk suture. Of the 14 procedures that were performed, 12 matured without complication. In 1976, Baker and colleagues in Phoenix, Arizona, described the first use of expanded polytetrafluoroethylene (ePTFE) AV grafts for dialysis access. The authors placed 8-mm ePTFE grafts in 72 patients. Their satisfactory short-term results encouraged the further development of prosthetic grafts for patients with ESRD.

Much progress has been made in the management of patients with ESRD since the early days of hemodialysis, including important guidelines from the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (NKF KDOQI) and the National Vascular Access Improvement Initiative known as the Fistula First Breakthrough Initiative (FFBI). This initiative has led to an increase in the creation of autogenous arteriovenous fistulas and a decrease in the use of chronic central venous catheters. However, the number and complexity of patients with CKD who require dialysis has also grown considerably over the past several decades. The best approach to addressing these challenges is with multidisciplinary teams that include internists, nephrologists, and access surgeons. This approach has been associated with superior clinical outcomes after the initiation of dialysis therapy.

Clinical Evaluation

History

Most patients with CKD have multiple medical comorbidities that place them at a higher perioperative surgical risk, so it is imperative for the surgeon to obtain a careful medical and surgical history that will guide the operative decision-making process. The surgeon should first assess the patient's dominant hand, history of treatment for CKD, and the projected dialysis starting date if the patient still has a functioning kidney. A thorough medical and surgical history should be obtained to determine the patient's other ongoing medical issues, such as diabetes, hypertension, hypercholesterolemia, and smoking status. A complete list of current medications and allergies should also be documented. As with all vascular reconstructions, it is most useful to plan for AV access procedures in terms of inflow, conduit, and outflow.

To evaluate inflow, the surgeon should inquire about any history of prior AV access creation and the artery or arteries that were used. Operative notes should be obtained, if possible, and any postoperative complications documented. Peripheral arterial disease (PAD) of the upper or lower extremities—as manifested by claudication, tissue loss, or rest pain—may need further assessment to ensure the appropriate choice of an artery as an AV access inflow vessel. Outflow should be evaluated by assessing the patient's venous anatomy and risk for central venous stenosis. Patients with a history of neck or chest radiation, upper extremity or chest trauma, pacemakers, defibrillators, and central venous line placements for hemodialysis, chemotherapy, or fluid resuscitation are at a higher risk of central venous stenosis and subsequent AV access failure. Finally, conduit options should be evaluated by determining which veins are available for AV access creation or to serve as potential targets for the venous outflow for an AV graft. Patients with a history of multiple access procedures may have fewer autogenous conduit choices compared with patients presenting for their first AV access procedure. The availability of competent superficial and deep veins in a lower extremity may also allow the surgeon to consider a lower-extremity site for dialysis access.

Physical Examination

The physical examination should evaluate the patient's overall physical status as well as the arterial and venous systems. A careful inspection should look for superficial veins in the upper extremities and surgical scars or skin marks indicative of previous surgical procedures, trauma, or radiation therapy. Evidence of central venous stenosis or occlusion includes uni- or bilateral neck or arm swelling and chest wall telangiectasia.

Vital signs should be obtained and blood pressures measured in both arms. A markedly lower blood pressure in one arm is concerning for proximal arterial disease and should be further investigated. Radial and ulnar pulses as well as femoral, popliteal, and pedal pulses should be palpated and diminished or absent pulses documented.

An Allen test can be performed in each hand to assess whether the palmar circulation is dependent on the radial or ulnar artery. First described in 1929 by Allen in Rochester, Minnesota, the test has since undergone numerous modifications to improve its clinical utility. First, the radial and ulnar arteries are palpated at the proximal skin crease of the wrist and then compressed with three fingertips. With both arteries compressed, the patient is instructed to clench and unclench the hand 10 times, after which the blanched hand is held open without any hyperextension or splaying of the fingers. The ulnar artery is then released and the capillary refill time measured. If the capillary refill time is greater than 6 seconds, the test is considered positive and the patient's palmar circulation deemed to be predominantly dependent on the radial artery. Kohonen and colleagues in Finland reported a sensitivity of 73% and specificity of 97%. Numerous reports, however, have questioned the accuracy and clinical utility of the Allen test for assessing the palmar circulation.

Investigations

Bilateral upper extremity vein mapping should be performed in an accredited vascular lab to determine venous patency and diameter. There is currently no consensus on the usefulness of arterial Duplex in the workup of AV access patients who do not demonstrate any clinical signs or symptoms of arterial insufficiency. However, Kim and colleagues in Los Angeles performed arterial Duplex ultrasound examinations on 163 patients undergoing upper extremity AV fistula creation and found that the addition of arterial Duplex to venous mapping resulted in a change in the operative plan in up to 12% of patients in the study, particularly when a radiocephalic fistula had been planned.

Patients with abnormal clinical findings suggestive of central arterial or venous disease should be further evaluated with computed tomography angiography (CTA) or digital subtraction arteriography or venography. The advantage of the last two modalities is that they are both diagnostic and therapeutic, allowing for the angioplasty or stenting of any obstructing arterial or venous lesions.

Hemodialysis Catheters

Hemodialysis catheters are commonly inserted in patients with acute kidney failure who require short-term hemodialysis, or as a bridging tool before the patient undergoes an AV fistula or graft procedure or receives a kidney transplantation. Indwelling catheters are also used in patients with no other viable AV access options and in patients with a limited life expectancy.

Limitations of hemodialysis catheters include a higher incidence of thrombotic complications, vascular stenosis, and bacterial infections compared with AV fistulas and grafts. Despite their numerous disadvantages, however, the use of hemodialysis catheters has been increasing. In the United States, the number of patients receiving dialysis through central catheters between 1995 and 2002 increased from 13% to 26%. However, this has also been associated with an increase in the proportion of AV fistulas created and a decline in AV graft procedures.

Hemodialysis catheters can be acute, intended for short-term use, or chronic, in which case a Dacron-cuffed catheter is tunneled under a subcutaneous tissue bridge that anchors the catheter and decreases the incidence of line infections. Most are constructed with polyurethane, silicone, or the copolymer Carbothane, although there is no conclusive evidence that any of those materials is associated with superior clinical outcomes. Catheters may also be coated with antithrombotic or antimicrobial treatments such as antibiotics, silver, or heparin. Of those, heparin has demonstrated the best antimicrobial properties by reducing bacterial trapping within fibrin clots and sheaths and decreasing bacterial adhesion on catheter material.

Catheters can have two separate lumens, one for arterial and another for venous flow, or a single double lumen. Two randomized controlled trials comparing the two designs concluded that, although there were no significant differences in infection rates, double-lumen catheters were easier to use. Furthermore, although most hemodialysis catheters have a staggered tip design to prevent recirculation, there is no evidence of an advantage for any particular tip design. The most important factor to consider in choosing a catheter should be its long-term function and complication rate.

Acute Catheters

Acute hemodialysis catheters are used primarily in critically ill patients in need of hemodialysis, patients with temporary loss of permanent access as an “in and out” strategy, and, far less frequently, in ambulatory patients being treated at centers that do not use tunneled catheters. Acute catheters are preferentially placed in the internal jugular or common femoral veins. The subclavian vein should be avoided, if possible, to prevent catheter-related stenosis, which would adversely impact future AV fistula or graft patency rates.

The advantage of acute hemodialysis catheters is that they can be inserted at the bedside without requiring an operating room (OR) or fluoroscopic guidance. If possible, the right internal jugular vein should be used preferentially as it is associated with a better hemodynamic profile due to its short and direct path to the right atrium compared with the left internal jugular vein, and is associated with a lower incidence of complications. Furthermore, line insertion should be performed using ultrasound guidance to decrease the risk of procedural complications. Indeed, studies have shown that ultrasound guidance increases the success rate to 95% compared with placement based on anatomic landmarks, and is associated with a lower risk of catheter placement failure, failure to place the catheter on first attempt, arterial punctures, and hematoma formation. It is also associated with a significantly decreased time to cannulate the vein and a lower number of attempts per catheter insertion.

For an internal jugular vein placement, the patient's neck is prepped with an antiseptic skin cleansing solution and draped in a sterile fashion. The patient is then placed in the Trendelenburg (head down) position to dilate the neck veins and decrease the risk of accidental air embolization to the brain. An ultrasound probe is used to identify the internal jugular vein, and the skin puncture site is infiltrated with a local anesthetic solution. A blade is used to create an entry incision in the anesthetized skin, and the puncture needle supplied in the hemodialysis catheter kit is flushed with saline solution and used to puncture the vein using ultrasound guidance while maintaining suction using a syringe. Once the vein has been accessed, the Seldinger technique is used to introduce a wire, followed by a dilator; finally the hemodialysis catheter is placed into the vein. Generally a 15-cm catheter is inserted into the right internal jugular vein and a 20-cm catheter into the left internal jugular vein. The catheter should be flushed with heparinized solution and then locked with a cap. An anchoring stitch should be placed at the entry site to tether the catheter to the skin. Finally, an upright chest x-ray confirms adequate catheter placement and rules out any immediate complications such as a pneumothorax. Femoral catheters are placed similarly; however, they are more likely to become infected and occluded due to the groin location. Femoral catheters range from 20 to 24 cm in length.

Chronic Tunneled Catheters

Tunneled hemodialysis catheters are also commonly placed in the internal jugular and femoral veins. The procedure should be done under ultrasound and fluoroscopic guidance. For a tunneled internal jugular vein line, the ipsilateral neck and chest are washed with antiseptic solution before the patient is draped. The neck skin approximately 1 to 2 cm superior to the clavicle is infiltrated with local anesthetic solution, and access to the internal jugular vein is obtained using ultrasound guidance and the Seldinger technique. Unlike the acute catheter technique, however, the vein puncture site is deeper along the course of the vein. Wire access is obtained, but the catheter is not yet introduced into the vein. The chest wall is generously infiltrated with local anesthetic, and an incision is made for the catheter entry site. A subcutaneous tunnel is then fashioned bluntly along the projected course of the catheter, and the catheter is introduced through the chest incision and exteriorized through the previously created neck incision, taking care not to displace the wire that is resting in the jugular vein. The wire is used to place a peel-away sheath into the jugular vein, and this is subsequently used to advance the catheter tip, under fluoroscopic guidance, into the distal superior vena cava or junction with the right atrium. A similar approach is carried out for a tunneled femoral hemodialysis line, although the catheter tip is positioned in the inferior vena cava. Similar to nontunneled catheters, tunneled femoral vein catheters are also more likely to be infected and occluded compared with jugular catheters and should be avoided if possible.

More complex pathways for tunneled hemodialysis catheters include collateral and small veins that develop in the mediastinum and chest wall secondary to chronic jugular vein occlusion, the thyrocervical collaterals, the inferior vena cava via a translumbar approach, and the hepatic vein in patients with infrarenal inferior vena cava occlusion. The advantage of using collateral veins is that they preserve other veins for future use, but they can be technically difficult to access and are associated with significant anatomic variability. The translumbar approach to the inferior vena cava is less technically challenging but is associated with poor patency and is a better bridging modality than a reliable long-term option for hemodialysis. Finally, the transhepatic approach is associated with frequent catheter exchanges, likely because of the dynamic variation in the position of the liver with the respiratory cycle.

Catheter Patency and Function

Hemodialysis catheter malfunction is defined as “failure to attain and maintain an extracorporeal blood flow sufficient to perform hemodialysis without significantly lengthening the hemodialysis treatment.” The minimum blood flow to maintain sufficient extracorporeal function is 300 mL/min. Malfunction can be positional, due to kinking or poor positioning, or, more commonly, mechanical, due to thrombosis, fibrin sheaths, and infection.

Shingarev and colleagues examined the natural history of tunneled hemodialysis catheters and reported a median primary patency of 202 days. Of the catheters examined in the study, 69% were still in place at 3 months, 53% at 6 months, and 34% at 12 months. The most common reason for nonelective removal of the catheters was catheter failure in 44% of the cases. The only predictor of catheter malfunction was placement in the left internal jugular vein. The most common strategy to prevent catheter malfunction is to employ “catheter locks” with anticoagulant agents such as heparin, citrate, tissue plasminogen activator (tPA), and oral medications such as warfarin, aspirin, and ticlodipine. None of those strategies, however, has been demonstrated to be clearly superior, and future large studies are needed to adequately determine the best strategy.

Catheters that are not complicated by intraluminal thrombosis usually fail secondary to the development of fibrin sheaths. Such sheaths form at the point of contact between the catheter and vessel wall and may encapsulate the full length of the catheter within 7 days of its insertion. Oliver and colleagues reported a 70% incidence of fibrin sheath obstruction in patients with long-term tunneled hemodialysis catheters with refractory catheter dysfunction. The authors concluded that the disruption of sheaths by angioplasty results in durable patency and modestly improves blood flow and clearance over the duration of catheter use.

Arteriovenous Fistulas

AV fistulas are the most durable modes of access for hemodialysis and are associated with the fewest complications ( Fig. 57.1 ). Despite the fact that most patients begin hemodialysis with a catheter, Huber and colleagues demonstrated that access surgeons who adopt an “all autogenous policy” can attain up to a 90% rate for constructing a native AV fistula. The key to successful AV fistula creation is careful patient selection and optimization. Indeed, up to 25% of AV fistulas fail secondary to thrombosis or failure to mature. Preoperative workup should determine whether the patient has adequate arterial inflow, venous outflow, and an adequate vein to act as a conduit.

FIG 57.1, Autogenous upper extremity arteriovenous fistula configurations. (A) Radiocephalic, (B) brachiocephalic, and (C) brachiobasilic vein transposition. AVF, Arteriovenous fistula.

Configuration of AV Anastomoses

Four possible AV anastomotic configurations have been described: side to side, vein end to arterial side, arterial end to vein side, and end to end. Our group consistently uses the vein end–to–arterial side configuration, which can provide adequate flow while reducing the risk for venous hypertension that has been described with the side-to-side and arterial end–to–vein side configurations. Although the end-to-end anastomosis was common in the past, it should be avoided, especially in elderly and diabetic patients, because it requires severing of the radial artery and is disadvantaged by AV size mismatch. There is no high-quality evidence to suggest that any particular fistula configuration is associated with better clinical outcomes. O'Banion and Moini both reported that a side-to-side anastomoses with distal cephalic vein ligation was associated with better patency rates compared with vein end–to–arterial side anastomoses, Mozaffar and colleagues performed a small randomized controlled trial that showed no difference in clinical outcomes between patients receiving an end-to-side and a side-to-side AV fistula.

Type of Anesthesia

The anesthetic techniques used in AV fistula creation include monitored anesthesia care (MAC), which combines local anesthesia with conscious sedation, as well as regional anesthesia and general anesthesia. The use of MAC is popular because it is quick and easy to administer, allowing for shorter operative times and less hospital resource utilization. However, it is challenging to maintain in long cases and difficult dissections. Furthermore, the administration of large doses of local anesthetic may lead to neurologic and cardiac toxicity and is associated with significant vasoconstriction. Conversely, general anesthesia is associated with vasodilation and is commonly used in complex AV fistula procedures where a prolonged procedural time is anticipated. It is also the most commonly used anesthetic option in the United States, as reported by Siracuse and colleagues, who reviewed the National Surgical Quality Improvement Project (NSQIP) data for the years 2007 to 2010 and found that 85% of patients undergoing new upper extremity AV fistula creation received a general anesthetic. However, in addition to the greater operative and recovery room resources required with general anesthesia, it may not be an ideal option in dialysis patients, who carry a greater burden of comorbid disease compared with the general population.

Regional anesthesia has gained favor for AV access surgery. It can be performed preoperatively in a designated “block room,” which does not interfere with OR work flow. Regional anesthesia is also associated with vasodilation of the basilic and cephalic veins, making the creation of the AV anastomosis less technically challenging. However, regional anesthetic techniques require more resources than MAC. Ultimately the type of anesthesia used does not seem to affect fistula maturation and complication rates. In the absence of randomized controlled trials comparing local, regional, and general anesthesia, practice continues to be guided by physician and patient preferences and institutional norms rather than high-quality evidence.

Intraoperative Anticoagulation

The use of intraoperative anticoagulation during AV fistula creation is controversial. Patients with ESRD are uremic and have an impaired coagulation system, likely due to the altered metabolic interactions of the components of the coagulation cascade, platelets, and the vessel wall. As such, some have reasoned that intraoperative anticoagulation is superfluous while placing the patient at an increased bleeding risk. In an attempt to address this issue, Smith and colleagues conducted a meta-analysis of four randomized controlled trials, demonstrating that systemic anticoagulation led to a significant improvement in AV fistula patency but a highly significant increase in the risk of bleeding-related complications. Interestingly, the AV access advantage was lost when studies of AV grafts were included in the analysis. In our practice, intraoperative anticoagulation is selectively administered to patients with a prior history of hypercoagulable state and those with intraoperative evidence of small and thus technically challenging arteries or veins. Furthermore, when systematic anticoagulation is not administered, we occasionally flush the arteries with heparinized saline solution prior to clamping.

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