**2. Types of vascular access**

Permanent vascular access in the patient with ESRD on hemodialysis is provided through a central venous catheter (CVC), arteriovenous graft (AVG), or AVF. The central venous access is provided by a cuffed catheter placed subcutaneously in the internal jugular vein. The most frequent complications of CVC with significant clinical consequences include infection and thrombosis; therefore this access is not a recommended option for permanent vascular access. An AVG is placed if the venous or arterial supply is inadequate. It is created by insertion of a synthetic conduit usually polytetrafluororthylene between an artery and vein. AV grafts have a high rate of thrombosis and infection with an average survival of only 2-3 years ( KDQOL, 2006). An AV fistula is created by a surgical anastomosis between and artery and vein. When a fistula is created the vein and artery may be in their normal positions, or the distal end of the vein is moved to a position that is better located for cannulation (vein transposition). A translocation is done when the entire vein is moved from one anatomic location to another requiring an arterial and venous anastomosis.

The fistula with the best outcome is the lower arm radiocephalic (RCF); however this access often fails to mature in the elderly patient with underlying vascular disease, particularly in diabetics (Miller,1999; Rodriquez, 2000). The second recommended fistula is the upper arm brachiocephalic fistula (BCF). This type of fistula is being placed with increased frequency because of the high failure rate of RCF. The third recommended fistula is the brachiobasilic fistula (BBF), which usually involves a two step surgical procedure and may be difficult to cannulate given the medial location of the basilic vein.

#### **2.1 Radial-cephalic fistula**

The RCF was the first fistula designed in 1966 by Brescia (Brescia, 1966). The RCF is created by an anastomosis between a radial artery and a cephalic vein usually with a transverse

Fig. 1. Radial-cephalic fistula. Figure reprinted by permission from Macmillan Publishers Ltd: Kidney International, 62, 2002

Permanent vascular access in the patient with ESRD on hemodialysis is provided through a central venous catheter (CVC), arteriovenous graft (AVG), or AVF. The central venous access is provided by a cuffed catheter placed subcutaneously in the internal jugular vein. The most frequent complications of CVC with significant clinical consequences include infection and thrombosis; therefore this access is not a recommended option for permanent vascular access. An AVG is placed if the venous or arterial supply is inadequate. It is created by insertion of a synthetic conduit usually polytetrafluororthylene between an artery and vein. AV grafts have a high rate of thrombosis and infection with an average survival of only 2-3 years ( KDQOL, 2006). An AV fistula is created by a surgical anastomosis between and artery and vein. When a fistula is created the vein and artery may be in their normal positions, or the distal end of the vein is moved to a position that is better located for cannulation (vein transposition). A translocation is done when the entire vein is moved from

The fistula with the best outcome is the lower arm radiocephalic (RCF); however this access often fails to mature in the elderly patient with underlying vascular disease, particularly in diabetics (Miller,1999; Rodriquez, 2000). The second recommended fistula is the upper arm brachiocephalic fistula (BCF). This type of fistula is being placed with increased frequency because of the high failure rate of RCF. The third recommended fistula is the brachiobasilic fistula (BBF), which usually involves a two step surgical procedure and may be difficult to

The RCF was the first fistula designed in 1966 by Brescia (Brescia, 1966). The RCF is created by an anastomosis between a radial artery and a cephalic vein usually with a transverse

Fig. 1. Radial-cephalic fistula. Figure reprinted by permission from Macmillan Publishers

one anatomic location to another requiring an arterial and venous anastomosis.

cannulate given the medial location of the basilic vein.

**2.1 Radial-cephalic fistula** 

Ltd: Kidney International, 62, 2002

**2. Types of vascular access** 

incision at the wrist (Fig 1). This access is easy to place and once mature and used for dialysis has a low complication rate. The classic Cimino fistula is constructed with a side-to side anastomosis but this design may lead to venous hypertension. Therefore an end-to-side anastomosis is commonly used. The most frequent clinical problem is that this access has a higher primary failure rate when compared to BCF or BBF (Miller, 1999). However, if a RCF matures, the 5 to 10 year cumulative patency rate is 53 and 45 percent respectively (Bonalumi, 1982, Rodriguez, 2000). Placement of a lower arm fistula is desirable as it preserves the upper arm for future use.

#### **2.2 Brachial-cephalic fistula**

The BCF is a suitable second choice for access (Reubens, 1993). The cephalic vein in the upper arm is larger with increased flow as compared to the lower arm. The anastomosis for a BCF is usually in the antecubital fossa between the brachial artery and cephalic vein (Fig 2). The location of the BCF enables ease of cannulation with the benefit of a large surface area. The major complication with a BCF is the steal syndrome (see complications) as compared to RCF or BBF. In a retrospective review of 2,422 patients with vascular access, the BBF had a superior patency rate in diabetic pateints when compared to diabetic pateints who had a RCF (Papanikolaou, 2009). The authors even went so far as to argue that the BCF may be the best access option for the older diabetic patient on hemodialysis.

#### **2.3 Brachial-basilic fistula**

The BBF is the third choice for fistula placement (Dagher, 1976). Because the basilic vein is less accessible to venipuncture it tends to be better preserved and less involved with

Hemodialysis Access: The Fistula 21

problems of the venous segment. Outflow problems may occur because of underlying fibrosis of the vein. Other factors which contribute to the primary failure of fistulas include demographic factors such as age, obesity, non-white ethic group, female sex , history of diabetes or peripheral vascular disease (Lok, 2006; Huijbregts, 2008) The size of the underlying vein may also influence the ability of a fistula to mature. A cephalic vein diameter of less than 2.0 mm on ultrasound in the forearm and less venous distensibility

A cause of poor maturation is the development of collateral circulation. Often times a fistula is placed and when developing, collateral vessels may form which decrease the amount of flow through the designated vein to be used for cannulation. The physical exam may often help diagnosis this problem as you may palpate extra accessory vessels with an apparent augmentation in the vein when it is occluded. Small assessory vessels less than one-forth the diameter of the main AVF are likely to be insignificant. If a fistula is not maturing by 6 weeks, many algorithms suggest a vengram by 6 weeks. If collateral vessels are identified they may be coiled by interventional radiology techniques or ligated by surgical techniques

Prevention of early fistula thrombosis with pharmacologic intervention has been the subject of several recent trials, which have shown only minimal effect. The Dialysis Outcomes –Practice Patterns Study (DOPPS) noted a lower risk of failure of established fistulas in patients who used aspirin consistently over a year (Hassegawa, 2008). The Dialysis Access Consortium Fistula Trial (DAC) was a multi-center trial which compared the effects of the anti-platlet agent Clopidrogrel with placebo on early fistula failure. The proposed sample size was 1284, but the study was terminated after enrollment of 877 patients as interim data analysis showed that Clopridrogel reduced the risk of fistula thrombosis by 37% (Dember, 2008). In the DAC study 61% of newly created fistulas failed. These findings and others have shown a primary failure rate of 31-61% (Schild,2004; Biuckians,2008; December 2008). This suggests that failure of the

Late failure of the fistula is defined as occurring greater than three months after creation and is often due to outflow stenosis. Venous stenosis occurs less frequently in AVF when compared to AVG, but nonetheless it is a common cause of AVF failure. Venous stenosis is usually detected clinically by symptoms of swelling of the extremity, prolonged bleeding post dialysis, difficulty cannulation or poor clearance. When these symptoms develop, the patient may be sent for an ultrasound for diagnosis or more commonly an interventional venogram. The venogram is desirable as a patient may have the venogram/angioplasty as a

The most common anatomic location for an outflow stenosis in a RCF is 3 cm from the arteriovenous anastomaosis (Rajan, 2004). Outflow stenosis in RCF may be treated successfully by angioplasty with favorable primary and secondary patency rates (Rajan, 2004). Inflow lesions from inadequate arterial flow are often detected by a negative arterial pressure during hemodialysis and by physical examination using pulse augmentation. An arterial lesion may be present in 15-30% of fistulas (Leon, 2008). This type of lesion also is

One of the leading causes of failure of BCF is due to stenosis in the cephalic arch, which is the final bend in the cephalic vein prior to entry into the axillary vein (Fig 4). Cephalic arch stenosis (CAS) is found to occur in up to 77% of patients with BCF compared to 30% of

successfully treated by angioplasty or surgical revision (Turmel-Rodrigues, 2000).

increases the risk of primary failure (Silva, 1998).

fistula to mature is the main obstacle to successful fistula use.

(Rodriguez, 2000).

**3.2 Late failure/complications** 

treatment option during the same procedure.

traumatic post-phlebitic changes when compared to the cephalic vein. When the BBF is placed more surgical skill is required with an initial anastomosis deep between the brachial artery and basilic vein (Fig 3). The BBF is left to mature for two months and then a second surgical procedure is preformed to "lift" the vein to allow ease of cannulation. The anatomic location of this fistula is often located in a position which is difficult to cannulate. Overall, the failure rate of the BBF is worse than BCF or RCF (Taghizadeh, 2003).

Fig. 3. Brachial-basilic fistula. Figure reprinted by permission from Macmillan Publishers Ltd: Kidney International, 62, 2002
