Dialysis Fistula

Anatomy and Physiology

An arteriovenous fistula is a surgical connection between an artery and a vein. Dialysis fistula maturation is a dynamic process called venous arterialization in which structural and functional remodeling of the venous wall is facilitated by the release of nitrous oxide and the breakdown of elastin to permit enlargement of the outflow vein.[7] Clinically mature arteriovenous fistulas are easier to cannulate with repetitive needlesticks and provide high flow rates necessary to sustain hemodialysis.

The KDOQI’s “Rule of 6’s” is used to assess fistula maturation and states that 6 weeks after creation, an arteriovenous fistula should achieve a blood flow rate of at least 600 ml/min, a diameter of at least 6 mm, an access length of 6 cm for cannulation, and a depth of 6 mm or less from the skin surface.[7]

A thorough understanding of the upper extremity vascular anatomy is paramount to successful AVF creation.

• Brachial Artery: A continuation of the axillary artery that courses medially down the arm to the antecubital fossa, where it branches into the radial and ulnar arteries.
• Radial Artery: A branch of the brachial artery that runs laterally down the forearm to the wrist, and terminates in the hand anastomosing with the ulnar artery to form the deep palmar arch.
• Cephalic Vein: A superficial vein that arises from the venous network of the hand, courses up the lateral flexor side of the forearm and the anterolateral arm, and terminates in the deltopectoral groove joining the axillary vein.
• Basilic Vein: A deep vein that arises from the venous network of the hand, courses posteromedially up the arm deep to the brachial fascia, and empties into the brachial vein before joining the axillary vein.
• Central Veins: Large diameter vessels that empty directly into the superior vena cava. The cephalic vein joins the axillary vein to become the subclavian vein. The subclavian vein then joins the internal jugular vein to become the innominate vein (brachiocephalic).

Indications

According to the KDOQI clinical practice guidelines, patients should receive education about kidney failure if they reach chronic kidney disease stage 4 (a glomerular filtration rate of less than 30 ml/min) or have an imminent need for maintenance dialysis at the time of initial assessment. This includes a discussion about the options for treatment, such as kidney transplantation, peritoneal dialysis, hemodialysis, or conservative treatment.[2]

Patients with chronic kidney disease stage 5 (GFR 10 to 15 ml/min) require maintenance dialysis in order to regulate metabolic derangements such as hyperkalemia, metabolic acidosis, hypervolemia, and uremic symptoms.[2][8] The nephrologist plays a key role in determining the type of dialysis best suited for their patients. If hemodialysis is chosen, patients are referred to a vascular surgeon to determine if arteriovenous fistula creation is feasible.

Contraindications

Absolute contraindications to dialysis fistula creation include venous occlusion, amputation, or advanced peripheral artery disease with necrosis on the side of AV fistula creation.[3]

Relative contraindications include pacemaker placement, central venous stenosis, active infection, or prior axillary node dissection. Patients who are elderly, have advanced heart failure, or decreased life expectancy are considered high risk.[9]

Equipment

A standard vascular operative tray is essential to the surgeon’s success in performing this procedure. Surgical instruments required include scalpels, needle holders, tissue forceps, scissors, self-retaining retractors, vessel loops, bulldog clamps, and vascular clamps of the surgeon’s preference. A vascular anastomosis is typically performed using monofilament nonabsorbable sutures. Suction and electrocautery are also essential. A Doppler ultrasound should be available throughout the procedure to assess patency and flow.

Personnel

In order to perform a dialysis fistula creation, the surgeon should have adequate experience in vascular surgery. Essential personnel includes the standard surgical team members including the operating surgeon, first assistant, anesthesiologist, scrub technician, and circulating nurse. 

Preparation

The planning for dialysis fistula creation requires proper patient selection, starting with a thorough history and physical examination. Pertinent medical and surgical history includes the presence of an automatic implantable cardioverter-defibrillator (AICD) or pacemaker, prior mastectomy or axillary dissection, or previous central venous catheters that may compromise venous drainage. Physical examination should include inspection of the venous system, blood pressure measurements, assessment of pulse symmetry, and performing an Allen test to evaluate the patency of the palmar arch.[10]

The patient’s vascular anatomy is the key determinant in whether an AV fistula can be created successfully and maintain long-term patency. Preoperative vein mapping using duplex ultrasound is used to assess the structural and functional aspects of the vessels. The KDOQI guidelines suggest having a vein diameter of 2.0 mm to 2.5 mm, an access segment of 6 cm for cannulation, and patent central and draining veins for successful AVF creation.[6][10] The Society of Vascular Surgery recommends placing access as distal in the upper extremity as possible to preserve future central access while giving preference to the non-dominant arm.[5]

Dialysis fistula creation of choice is radiocephalic fistula, brachiocephalic fistula, transposed brachiobasilic fistula, and then loop arteriovenous graft.[11] While autogenous AV fistulas are the gold standard for hemodialysis patients, patients who are elderly (small-caliber vessels), have poor vasculature (presence of calcification or patients with diabetes), have slowly progressive chronic kidney disease or those with poor health and limited life expectancy are unlikely to benefit from AV fistula creation.[6] 

Overall, in addition to vascular anatomy, a patient-centered approach must be taken, including patient preferences, attributes, life expectancy, and quality of life when considering vascular dialysis access.

Technique or Treatment

There are several dialysis fistula creation sites that can be made depending on the patient’s vascular anatomy. The patient should be positioned in a supine position with the corresponding arm outstretched to 90 degrees, prepped, and draped in the usual sterile fashion. Principles of arteriovenous fistula creation include obtaining vessel control proximally and distally, and the anastomosis should be made without tension or kinking.

Radiocephalic Fistula (Brescia-Cimino)

The radiocephalic fistula is a distal forearm fistula created by anastomosing the cephalic vein to the radial artery. A transverse incision is made in the wrist. The radial artery and cephalic vein are dissected, mobilized, and secured using vessel loops. Any small tributaries can be ligated and divided. An anterolateral arteriotomy is made, and the artery is flushed with heparinized saline. An end-to-side anastomosis can be made by ligating and dividing the distal cephalic vein and spatulating the end to match the size of the arteriotomy. A side-to-side anastomosis can be made by creating a venotomy in the corresponding portion of the cephalic vein. The arteriovenous anastomosis is then performed using a running nonabsorbable monofilament suture. Vascular Doppler should be used to confirm the thrill through the fistula, as well as the distal radial artery signal. Hemostasis is achieved, subcutaneous tissues are approximated, and skin is closed using nonabsorbable sutures.

Brachiocephalic Fistula (Kaufmann)

The brachiocephalic fistula is an upper arm fistula created by anastomosing the cephalic vein to the brachial artery. A transverse incision is made over the antecubital fossa. The brachial artery and cephalic vein are dissected, mobilized, and secured using vessel loops. Any small tributaries can be ligated and divided. An arteriotomy is made, and the artery is flushed with heparinized saline. An end-to-side anastomosis is performed by ligating and dividing the distal cephalic vein and spatulating the end to match the size of the arteriotomy. The arteriovenous anastomosis is then performed using a running nonabsorbable monofilament suture. Vascular Doppler should be used to confirm the thrill through the fistula, as well as the distal radial artery signal. Hemostasis is achieved, subcutaneous tissues are approximated, and skin is closed using nonabsorbable sutures.

Transposition Brachiobasilic Fistula (One-Stage vs Two-Stage) 

The brachiobasilic fistula is used when the techniques above are not feasible or have failed. The basilic vein is medial and deep; therefore, in order to be easily accessed, the vein must be transposed into a more superficial and lateral location. This can be done in one or two stages. The two-stage approach has a better maturation and patency rate but requires reintervention and additional time before use.[12] 

One-Stage: A longitudinal incision is made in the upper arm over the previously mapped basilic vein from the axilla to the antecubital fossa. The incision is deepened, and the brachial fascia is incised to expose the basilic vein. The brachial artery and basilic vein are dissected, mobilized, and secured using vessel loops. Care is taken to avoid injury to the median antebrachial cutaneous nerve. An arteriotomy is made in the proximal brachial artery and then flushed with heparinized saline. A curved tunneler is used to create a subcutaneous tunnel along the anterior aspect of the upper arm. The distal basilic vein is ligated and divided and then tunneled laterally and superficially in a curved fashion. The end of the basilic vein is spatulated to match the size of the arteriotomy, and an end-to-side anastomosis is performed using a running nonabsorbable monofilament suture. Vascular Doppler should be used to confirm the thrill through the fistula, as well as the distal radial artery signal. Hemostasis is achieved, subcutaneous tissues are approximated, and skin is closed using nonabsorbable sutures.

Two-Stage: The first stage starts with making a transverse incision just distal to the antecubital fossa. The brachial artery and basilic vein are dissected, mobilized, and secured using vessel loops. An arteriotomy is made in the distal brachial artery and then flushed with heparinized saline. The distal basilic vein is ligated and divided, and the end spatulated to match the arteriotomy. An end-to-side anastomosis is made using a running nonabsorbable monofilament suture. The fistula is then allowed to mature over the next 6-8 weeks. The patient is then brought back to the operating room for the second stage. A longitudinal incision is made in the upper arm from the axilla to the antecubital fossa. The arterialized basilic vein is dissected proximally in a similar fashion and transected proximal to the anastomosis. The vein is mobilized and tunneled laterally and superficially using a curved tunneler. A new proximal brachiobasilic end-to-end anastomosis is made using a nonabsorbable monofilament suture.

Complications

As with any surgical procedure, there is a risk of bleeding, infection, or damage to surrounding structures. High-risk patients may be at increased risk for complications that may result in significant morbidity. Complications can be divided into immediate, early (days to months), or late (after maturity).

• Immediate Complications: Hematoma, bleeding, edema, ischemic steal syndrome, or loss of thrill secondary to acute thrombosis or intra-arterial flap
• Early Complications: Stricture, thrombosis, infection, venous hypertension, central venous stenosis, ischemic steal syndrome, or failure to mature
• Late Complications: Aneurysm, stricture, late thrombosis, infection, or neuropathy

The most common dialysis fistula complications that may require intervention include aneurysm, infection, thrombosis, central venous stenosis, ischemic steal syndrome, and failure to mature.[9] 

• Aneurysm: Repeated needle punctures in a centralized area can weaken the vascular access wall and cause aneurysm formation. Aneurysmal dilation can also occur over time due to high blood flow and be accelerated by elevated pressures within the fistula. Aneurysms generally require surgical repair if there is a loss of skin integrity, ulceration, or limited puncture sites available. High-risk aneurysms that are left untreated can result in rupture and fatal exsanguination.[9] 

• Infection: Most AV fistula infections involve perivascular cellulitis presenting as erythema, edema, and possible systemic signs. Localized infections can be treated with appropriate antibiotics based on wound and blood cultures. More serious infections associated with aneurysm, hematoma, or abscess require surgical excision and drainage.[9]

• Thrombosis: Thrombosis is the most common fistula complication and occurs in areas of stenosis, either at the anastomosis or fistula vein. The risk of thrombosis increases with the degree of stenosis. Compared to AV grafts, fistulas have lower rates of thrombotic events.[9]

• Central Venous Stenosis: Venous hypertension can result from central venous stenosis and causes upper extremity swelling that may progress to decreased mobility. The most common cause of central venous stenosis is the placement of central venous catheters and devices. Central stenosis may present as reduced quality of dialysis, problems with cannulation, pain in the area of the fistula, or increased venous pressures.[3][9]

• Ischemic Steal Syndrome: Steal syndrome is the result of decreased blood flow to the distal extremity after AV fistula creation. Clinically significant implications include pain, decreased motor function or sensation, or neuropathy. The rate of ischemic steal syndrome is decreased in forearm fistulas when compared to upper extremity fistulas. Furthermore, when compared to AV grafts, fistulas have a two-fold lower risk of developing steal syndrome.[9]

• Failure to Mature: One of the most common causes of failed maturation is due to anastomotic stricture caused by neointimal hyperplasia. Stricture is defined as a greater than 50% decrease in the luminal diameter of the outflow vein.[9] Risk factors that compromise AV fistula maturation include age greater than 65 years, an elderly patient with decreased vascular compliance, and comorbidities including hypertension, diabetes, obesity, heart failure, and peripheral atherosclerosis.[10] Surgical correction may be warranted, such as ligation of vein branches or revision of the anastomosis.

Clinical Significance

Hemodialysis is a standard therapeutic option for patients with ESRD. Arteriovenous fistula creation is associated with longer maturation time but decreased risk of infection, hospitalizations, central venous stenosis, and mortality when compared to prosthetic grafts or dialysis catheters.[4]

Enhancing Healthcare Team Outcomes

An interprofessional team approach is crucial to the success of dialysis fistula in ESRD patients and should involve collaboration between primary care physicians, nephrologists, vascular access surgeons, interventionalists, dialysis nurses, and vascular access coordinators. 

The primary care physician must actively screen patients for chronic kidney disease and intervene with timely referral to a nephrologist for evaluation and treatment. The nephrologist oversees the care of the patient to ensure appropriate dialysis care. Vascular surgeons must decide the placement and type of vascular access that will yield the greatest success rate. Given the high rate of vascular access dysfunction, interventionalists can play a critical role in the maintenance and restoration of dialysis access using endovascular techniques. The dialysis nurse plays a critical role in patient care as they can examine and monitor access three times per week during dialysis. Lastly, the vascular access coordinator is essential for organizing patient hemodialysis care.[6]

Nursing, Allied Health, and Interprofessional Team Interventions

Communication and coordination between the interprofessional team are required to optimize vascular access outcomes as well as patient morbidity and mortality.

Nursing staff must communicate effectively during handoff to report a history of end-stage renal disease and arteriovenous dialysis fistula. Nurses can help preserve veins for dialysis fistula creation by avoiding peripheral venous access, blood draws, or blood pressure measurements on the side of fistula planning. For nurses taking care of patients on the floor, it is paramount to learn how to assess for fistula thrill, differentiate thrill from pulsating fistulas, and identify loss of thrill. Understanding complications such as ischemic steal syndrome and patients complaining of numbness or tingling after dialysis can prompt nurses to call surgical services sooner.

Dialysis nurses also play a critical role in evaluating and managing dialysis fistulas. Dialysis nurses can report arteriovenous fistula malfunction during dialysis, such as decreased flow rates (possible inflow or outflow obstruction), delayed hemostasis at needle puncture sites (possible outflow obstruction), or erythema and drainage overlying the fistula site (possible infection). Dialysis nurses can also convey difficult access due to fistula depth so that patients can undergo a procedure called superficialization if necessary.

Nursing, Allied Health, and Interprofessional Team Monitoring

Doppler Signal: Place the doppler probe over the fistula to obtain a signal. Doppler signals may be described as monophasic, biphasic, or triphasic.

Thrill: Place the tips of the fingers lightly over the fistula. A thrill is a vibration felt over the fistula and implies patency. 

Pulsation: Place the tips of the fingers lightly over the fistula. Pulsation is a strong heartbeat felt over the fistula, which may indicate possible outflow stenosis. 

Overlying Skin Changes: Erythema, warmth, edema, or drainage may all be signs of possible fistula infection and can lead to loss of vascular access. These findings should be promptly reported to a physician. 

Bleeding: Continuous oozing at the cannulation site may suggest outflow stenosis or may be the result of coagulopathy secondary to uremia.