Q:  I am seeking information about a reverse flow AVF known as the PRA-AVF. What are the implications for providing hemodialysis?
 
A: The National Kidney Foundation Kidney - Dialysis Outcome Quality Initiative (K/DOQI) Clinical Practice Guidelines recommend native AV fistulas as optimal hemodialysis vascular access. There is much evidence that native AVFs, compared to arteriovenous grafts (AVGs) or catheter-based hemodialysis accesses, provide longer patency rates, require fewer interventions, have less infections and ischemic complications, and subsequently lower mortality rates for the patient. Despite the evidence, the United States continues to lag behind AVF placement and utilization when compared to other countries. Fortunately, advances are being made in the surgical community to address co-morbid conditions known to exist within the current United States population with end stage renal disease (ESRD) who are on hemodialysis (e.g., increasingly having diabetes, older, obese, and/or having complex, multiple co-morbidities).

One relatively new advance is a surgical procedure for native AVF placement that uses the proximal radial artery (PRA) for arterial inflow. Surgically, the PRA is easily mobilized to an anterior position allowing a tension-free anastomosis. Arterial inflow is reliable, and a side-to-side anastomosis to the median antebrachial vein or an end-to-side anastomosis to the communicating vein allows dialysis access both in the upper arm and, in a retrograde fashion, in the forearm. Retrograde flow is established into the median antebrachial vein by disruption of the first valve with a small probe. Flow into both the upper arm and forearm venous segments offers the potential for continued and uninterrupted vascular access. Review of available literature reflects that this type of native AVF offers excellent patency rates, and for the most part, avoids steal and infectious complications (Jennings, 2006). As with all fistulae, the use and performance of vessel mapping pre-operatively in AVF placements has been crucial in the selection of optimal sites and strategies for successful AVF placement and utilization (Parmley, Broughan, & Jennings, 2002).

Reverse flow fistulae, such as the Proximal Radial Artery arteriovenous fistula (PRA-AVF), are relatively new to most patient care staff. The anastomosis is located just below the elbow area and if the surgeon disrupts adjacent valves in the forearm vein, the AVF’s venous return will flow toward the hand (retrograde) in the forearm. Thus, a PRA fistula with valve disruption permits use of the forearm as well as the upper arm for cannulation sites.

An important point to remember when teaching staff members to cannulate reverse flow fistulae (such as PRA-AVFs) is that blood flow will often develop in two different directions at the same time (see Figure 1).

• If both needles are to be placed in the forearm, the venous needle should be placed downstream (i.e., retrograde) with the needle top pointing toward the hand, because that is the direction of the venous blood flow.
• If the upper arm is used for venous return, the flow goes toward the heart, so the needle would be upstream (i.e., antegrade) with the needle top pointing toward the shoulder.

1. What TYPE of AVF has been placed;
2. The DIRECTION of blood flow for a specific access site; and
3. If a reverse flow AVF (such as a PRA-AVF) has been created, blood flow direction dictates PLACEMENT of the arterial and venous needles.
   

1. Identifying patients with reverse flow AVFs can be done using chart stickers or indications on flow sheet and/or care plans.
2. Pictures of the access and/or cannulation sites (with arrows indicating needle tip pointing toward hand and/or shoulder) should be available for reference at the chair side when patient’s AVF is being cannulated.
3. Patients with reverse flow AVFs should be taught to tell all cannulators that they have an AVF with different blood flow (i.e., “up & down”, “2-way” or “flow to hand and shoulder”).