2006 Updates Clinical Practice Guidelines and Recommendations

premature cannulation of a fistula may result in a greater incidence of infiltration, with
associated compression of the vessel by hematoma and permanent loss of the fistula. In
general, allowing the fistula to mature for 6 to 8 weeks before investigating the reason for
failure to mature is appropriate (see CPG 2). For a fistula to be considered successful, it
must be usable. In general, a working fistula must have all the following characteristics:
blood flow adequate to support dialysis, which usually equates to a blood flow greater
than 600 mL/min; a diameter greater than 0.6 cm, with location accessible for cannulation
and discernible margins to allow for repetitive cannulation; and a depth of approximately
0.6 cm (ideally, between 0.5 to 1.0 cm from the skin surface). This combination
of characteristics can be remembered easily as the Rule of 6s.
Although there are no definitive data in the literature, any intervention that increases
blood flow to the extremity may improve the chances of successful fistula development.
Therefore, regular hand-arm exercises, with or without a lightly applied tourniquet, are
recommended until the fistula matures. Failure of a fistula to mature occasionally is
caused by venous side branches that drain critical flow from the primary vessel. Ligating
these side branches may result in successful maturation (see CPG 6).
Studies relating to preoperative venous imaging/mapping for AVF construction underwent
systematic review. Duplex ultrasound is the preferred method for preoperative
vascular mapping. Vascular mapping in preparation for the creation of a vascular access
refers to the evaluation of vessels, both arterial and venous, of patients with CKD who
have selected HD therapy, and it should be performed in all patients before placement of
an access. Preoperative vascular mapping was shown to substantially increase the total
proportion of patients dialyzing with fistulae. 36–39 Several studies support the 2.0- to 2.5mm
vein diameter threshold for successful creation of a fistula. 39,40 Radiocephalic fistulae
constructed in veins less than 2.0 mm in diameter had only a 16% primary patency at
3 months compared with 76% for those with veins greater than 2.0 mm. 40 In a pivotal
study, 39 a threshold of 2.5-mm vein diameter, assessed by using duplex ultrasound, was
used; this resulted in an increase in fistula creation to 63% compared with a retrospective
14% rate in the absence of vascular mapping. 22 A similar study using the same duplex ultrasound
criteria showed a fistula increase from 34% in historical controls to 64%. Importantly,
in this study, duplex ultrasound altered the surgical plan based entirely on the
surgeon’s clinical evaluation, resulting in increased placement of fistulae. 41
There is no generally accepted “standard” for what constitutes vascular mapping. The
arterial evaluation should include pulse examination, differential blood pressure measurement,
assessment of the palmar arch for patency, arterial diameter assessed by using
duplex ultrasound, and the presence of arterial calcification. A preoperative arterial diameter
less than 1.6 mm has been associated with a high failure rate in radiocephalic fistulae.
42,43 Other studies suggested that a minimum diameter of 2.0 mm is required for
successful fistula creation. 39 Venous evaluation should include a luminal diameter of 2.5
mm or greater, continuity with the proximal central veins, and absence of obstruction. 39
The central veins may be assessed indirectly by using duplex ultrasound. 44 Compared
with invasive venography, duplex ultrasound had a specificity of 97% and sensitivity of
81% for detecting central vein occlusion. 45 Alternatively, venography or magnetic
KDOQI National Kidney Foundation CPGs for Vascular Access 247