Hemodialysis: Creating the AV fistula using catheters

Interview with Prof. Ralf-Thorsten Hoffmann, Institute and Outpatient Clinic of Diagnostic Radiology, University Hospital Carl Gustav Carus in Dresden

09/08/2016

For many patients, the start of hemodialysis marks the lifelong dependency on needing their blood purified. But before they can actually begin treatments, a blood vessel in the patient’s arm needs to be enlarged to where it can move enough blood and withstand being connected to the dialysis machine several times per week. To do this, an arteriovenous (AV) fistula, a connection between artery and vein, is surgically created.
Image: Smiling man with short, grey-black hair, glasses, tie and suit - Prof. Ralf-Thorsten Hoffmann; Copyright: fotografDD.de

Prof. Ralf-Thorsten Hoffmann; ©fotografDD.de

This surgery could be replaced by an endovascular procedure in the future for some patients. In this interview with MEDICA-tradefair.com, Prof. Ralf-Thorsten Hoffmann explains the new method where the dialysis fistula is created using two catheters.

Prof. Hoffmann, you are testing a minimally invasive endovascular procedure to create a dialysis fistula in a patient’s forearm. What happens during this intervention?

Prof. Ralf-Thorsten Hoffmann: The surgery takes place under sedation. The patient lies on the angiography table. Using ultrasound guidance, we first puncture two neighboring blood vessels on the upper arm, the arteria and vena brachialis (brachial artery and vein). We subsequently place guidewires into the blood vessels and a lock for the special catheters both in the vein and artery which we insert to set up the fistula.

Using X-ray guidance, the catheters are placed in the arteria (ulnar artery) and vena ulnaris (ulnar vein), in juxtaposition to each other. The ideal position is typically just below the crook of the arm. Using magnets, we join the catheters and with them also both of the blood vessels together. Low-power direct current energy flows through a small blade which subsequently opens the vascular walls and thus connects the artery and vein. Before we remove the catheter again, we close the deep vein in which our lock was located and thus force the blood to no longer drain into the deep but the superficial venous system instead. This can be the vena cephalica (cephalic vein) or the vena basilica (basilic vein). Ideally, a cephalic shunt develops through which we can conduct dialysis.

Why do you use two different imaging procedures for this?

Hoffmann: Ultrasound provides superior tissue contrast resolution. This allows us to detect the blood vessels very well and also lets us see where the nervus ulnaris (ulnar nerve) runs. In turn, angiography is ideal to illustrate the catheter and wires in the vascular system.

What happens after the intervention?

Hoffmann: The deep and the superficial venous system are connected by perforator veins; these are tiny shunts between the larger veins. Since we partially close the drain through the deep venous system, the blood flows through the perforator veins into the superficial veins. They become gradually thicker thanks to the increased blood flow. We call this "maturing"; they get ready for hemodialysis. That is the case if their diameter is more than five or six millimeters.

Image: Open surgery at the forearm of a patient; Copyright: panthermedia.net/Chanawit Sitthisombat

The AV fistula for hemodialysis is traditionally created during open surgery at the forearm of the patient; ©panthermedia.net/ Chanawit Sitthisombat

There is another surgical intervention to create a dialysis fistula. What happens in this case?

Hoffmann: When placing a Cimino fistula, the arteria radialis (radial artery) is joined with a vein in the forearm. This procedure is currently considered the gold standard. Those patients who are unable to undergo the surgical method are being considered for the endovascular procedure.

What factors determine who is suitable for open surgery?

Hoffmann: The hand is normally supplied with blood through the arteria radialis (radial artery) and the arteria ulnaris (ulnar artery). If one of these two is closed, you should not create a fistula. Otherwise, the hand might not be adequately supplied with blood. Another exclusion criterion is if the veins in the forearm are not appropriately developed. These patients are subsequently candidates for the endovascular procedure.

Are they any risks with the endovascular procedure?

Hoffmann: So far, literature primarily states injuries to the nervus ulnaris (ulnar nerve). The result may be numbness in the hand, either temporarily or persistent.

How will the procedure be further developed?

Hoffmann: So far, it is still in its infancy. It was originally developed in the U.S. and tested for the first time in Canada with 60-70 patients. There was a second study in South America. We have already treated approximately ten patients here in Dresden. This makes us the leading center in Europe.

One study with several participating centers from Great Britain, the Netherlands, and Germany, including us, is currently in the planning stage. It is designed to include 250 patients who are being monitored after the procedure.

Image: Man with glasses and beard - Timo Roth; Copyright: B. Frommann

© B. Frommann

The interview was conducted by Timo Roth and translated from German by Elena O'Meara.
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