VSITE REIVEW: HD Access

March 28th, 2020

 

Script by Dr. Young Lee, Brooklyn Hospital Center, New York

 

Management of Dialysis access is an important topic of discussion, not only because it is a significant part of the VSITE, but also because healthcare costs continue to rise for ESRD patients, particularly during the transition from CKD to ESRD. This is attributed to use of dialysis catheters and frequent hospitalizations for arteriovenous access failures and related procedures.

 

The National Kidney Foundation-Dialysis Outcomes Quality Initiative (NKF-KDOQI) and SVS has provided guidelines in the follow areas:

-       Timing of referral to access surgeons

-       Operative strategies to maximize placement of autogenous AV accesses

-       First choice for autogenous access

-       Choice of AV access when a patient is not a suitable candidate for a forearm autogenous access

-       The role of monitoring and surveillance of AV access management

-       Conversion of a prosthetic AV access to a secondary autogenous AV access

-       Management of nonfunctional or failed AV access

 

 This brings us to the question, who needs dialysis access?

-       Patients should be referred to a vascular surgeon for access when their creatinine clearance is <25mL/min which is CKD stage 4. You want to provide adequate time for your autogenous access to mature, so the ideal time for access creation would be > 6 months for anticipated need of dialysis. This allows for time for any subsequent interventions if your access is not maturing.

 

Should prosthetic access also be placed several months before anticipated dialysis?

-       Prosthetic access patency is limited by duration of access placement, thus, if a patient requires prosthetic access, placement should be delayed until about 3-6 weeks before initiation of dialysis

 

For dialysis access creation, which site should be considered and used first?

-       Due to the easier accessibility and lower infection rates, upper extremity access sites are used first. Furthermore, you want to place your access as far distally in the extremity as possible to preserve the proximal arm for future accesses.

 

What are some important considerations in a patient’s history when planning a dialysis access?

-       It is important to find out recent history of peripheral IV lines, sites of any indwelling catheters including pacemakers and defibrillators, as well as placement of previous catheters. Any previous access procedures should be identified. In additions, any history of trauma or surgery to the upper extremities is important to identify. Moreover, you also want to consider the patient’s quality of life, thus, noting which extremity is dominant is important. If possible, you want to create your dialysis access in the nondominant arm so that when the patient is receiving dialysis multiple times a week, they are able to use their dominant arm during their dialysis sessions

 

As with any preoperative planning, physical examination is extremely important. Central venous stenosis can cause problems such as prolonged bleeding after dialysis sessions at the puncture site. What are some signs of central venous stenosis?

-       Unilateral arm swelling or edema and prominent venous collaterals are signs of central venous stenosis. Central venous stenosis can lead to venous hypertension which affects access patency and function, and also causes disabling edema.  Beyond signs of central venous stenosis, when examining a patient, an Allen’s test should always be performed to evaluate palmer arch patency.

 

Preoperative planning should also include arterial and venous assessments. What are your size requirements for the artery and the vein to be used in your dialysis access creation?

-       First, you want equal pressure gradients in bilateral upper extremities and the artery should be greater than or equal to 2mm. A venous duplex should also be done to evaluate for diameter, distensibility and continuity. A vein mapping is useful to determine the size of the patient’s superficial veins at various points in the forearm and upper arm. The vein should be at least 2.5mm.

 

Autogenous access should always be considered first due to higher patency rates, lower infection rates, and longer duration of access survival. What are the different configurations of autogenous accesses?

-       The first and best option would be direct arteriovenous anastomosis. However, if that is not possible, then venous transposition should be considered next follow by venous translocation. Venous transposition is for deeper veins such as the basilic vein, which is transposed so the vein lies just below the skin for easier access for puncture during dialysis sessions. Transpositions are generally a 2-stage procedure in which the direct arteriovenous anastomosis is created during the first stage and once the vein has arterialized 4-6 weeks later, the second stage of transposition is done when the vein is easier to mobilize. Translocation procedures include harvesting the femoral or saphenous vein and using it as a conduit for AV access creation in the upper extremity.

 

When can a venous transposition be done in a one stage procedure?

-       When the vein is >4mm

 

It was mentioned earlier that the dialysis access should be created as distally as possible on the extremity. What are some of the most distal locations?

-       The snuffbox fistula, which is the posterior radial branch to cephalic direct access and Brescia-cimino-appel fistula which is the radial-cephalic wrist direct access are two of the most distal fistulas that can be created.

 

What are your arterial and venous options in the upper extremity?

-       In the forearm, you have your radial, ulnar, and brachial arteries and cephalic and basilic veins. In the upper arm, you have your brachial or proximal radial arteries and cephalic, basilic, brachial and axillary veins.

 

If you need to use a prosthetic graft, what would you use?

-       PTFE is the most common,  they make tapered 4-7mm grafts to ensure the size of your arterial anastomosis isn’t too large to minimize chances of steal.

 

The techniques of arteriovenous fistula creation are standard. Can you go through the techniques?

-       First the vein is identified and the distal end is transected and flushed with heparin. By flushing with the heparin, you are able to access the caliber and extent of the vein as well as identify any side branches

-       Then after distal and proximal control of your artery, a 4-6mm arteriotomy is made. The length is limited to decrease incidence of arterial steal. The artery is then flushed with heparin to avoid thrombosis during the anastomosis and an anastomosis is created between the side of the artery and the end of the vein. A 6-0 or 7-0 nonabsorbable continuous suture should be used to create the anastomosis to avoid future dilation of the anastomosis.

 

What are some other options if an access is not able to be created in the upper extremity?

-       Autogenous accesses can also be created in the lower extremity. Femoral artery to femoral vein or saphenous vein anastomosis can be created. Both veins have to be transposed. However, one must ensure that the ABI is normal because limb ischemia can be a devastating consequence. Furthermore, for morbidly obese patients, the excess pannus can hinder access in the groin region.

-       Access creation in the chest wall or cervical region is also possible with axillary artery to ipsilateral axillary vein loop access, axillary artery to contralateral axillary or jugular vein straight access (ie necklace access) and brachial artery to jugular vein straight access.

 

For patients with central venous stenosis or occlusion, what is another alternative upper extremity access creation?

-       For these patients, the hemodialysis reliable outflow (HeRO) device can come to the rescue. This device is composed of 2 components: a graft which is made of 6mm PTFE with a titanium coupler at one end, and a venous outflow component of a 19 Fr silicone catheter reinforced with a nitinol braid to prevent kinking. The graft portion is anastomosed to an artery, usually brachial, and is tunneled subcutaneously and the venous component is percutaneously placed into the right atrium via the IJ or subclavian vein. The two components are connected with a titanium coupler at the deltopectoral groove. If you need more immediate dialysis, the super HeRO comes to the rescue in which the graft portion is the early cannulation graft.

 

When is the newly created dialysis access ready for use?

-       A good way to remember this is the rule of 6’s. it’s ready to use when the Fistula is 6mm in Diameter, has a flow of 600ml/min, is 6mm from the surface of the skin and usually takes 6 weeks to mature.   Prosthetic AV accesses can be used as early as 2 weeks postoperatively. If you use the early cannulation grafts, the access can be used as early as 24 hours after access creation. This is great because it offers the potential for avoidance of dialysis catheters in patients who need dialysis immediately.

 

What are some reasons why an access may fail to mature?

-       Sometimes your access may have arterial inflow stenosis. This is difficult to detect clinically because there will be a palpable thrill, however, due to the stenosis, the flow is not sufficient enough for dialysis. In the absence of arterial inflow issues, collateral or large venous branches can divert blood away from the main access channel resulting in insufficient flow.

 

If the newly created AV fistula is not maturing, what are some secondary procedures to help with maturation?

-       Open procedures include vein patches, interposition vein grafts, vein transposition to proximal arteries, branch ligations, and vein superficialization. Endovascular procedures include arterial and venous angioplasties.

 

Once a dialysis access is created, maintenance of the access is extremely important. The flow disturbances and hemodynamic changes associated with AV access creation causes intimal hyperplasia leading to venous outflow stenosis. This can ultimately lead to access thrombosis and failure. What are some methods of detecting access failure?

-       One way of detecting a well functioning access is a strong thrill at the arterial anastomosis which continues a few centimeters into the outflow vein. If you feel a pulsation near the venous outflow, then a stenosis or thrombosis is likely. If you feel a thrill distal to the area of pulsation, then you have likely localized your area of stenosis. It is important to note that you may feel a pulsation at a pseudoaneurysm independent of venous outflow issues.

-       Another way to detect stenosis is collateral veins or upper extremity edema. This is indicative of venous hypertension likely secondary to stenosis. You will typically see this in the shoulder area or anterior chest as a results of subclavian vein stenosis/thrombosis. Moreover, these high venous pressures as a result of the stenosis can result in excessive and prolonged bleeding after removal of needles from the dialysis puncture sites. This is often the first sign of elevated venous pressures.

 

What are some endovascular interventions for a failing access?

-       The most common intervention is a simple balloon angioplasty of the stenosed area. Insufflation times are generally up to 2-3 minutes. Treatment of stenosis 2/2 intimal hyperplasia often require high pressures of 20atm or more. However, this is a double edge sword because this can lead to trauma in the veins stimulating a further intimal hyperplasia process. Some advocate a cutting balloon before high pressure dilation. Stenting is also an option to treat residual stenosis or dissections after balloon angioplasty. Covered stents have shown good patency results.

 

If endovascular interventions fail, what are some open options for managing a failing access?

-       Generally an interposition graft or patch angioplasty is performed and the results of the two techniques are largely equivalent.

 

If an AV access has ultimately failed and thrombosed, what are your endovascular options at this point?

-       Some endovascular options are catheter directed thrombolysis with about 2-4mg of tPA injected into the clot, followed by balloon angioplasty (typically an 8mm by 8cm high pressure balloon). A mechanical thrombectomy device, such as angiojet, can also be used in combination to thrombolysis.

 

Alternatively, an open thrombectomy with a thromboembolectomy balloon and patch angioplasty of venous stenosis areas can also be used. Moreover, a hybrid approach of open thrombectomy with percutaneous interventions of venous stenosis areas has been described.

 

Earlier, you mentioned steal syndrome, can you explain to us what this is?

-       Steal syndrome is also known as Access Related Hand Ischemis = ARHI. It is an uncommon but devastating complication of access creation. All patients with arteriovenous fistulas have some degree of physiologic steal or reversal of flow in part of the artery distal to the fistula. However, this is not sufficient enough to cause ischemia. Rather, ischemia results from inadequate collateral circulation and inability of peripheral arteries to meet the increased demand. Diseased vessels do not dilate and stenosis of arteries leads to decreased distal perfusion pressure. Furthermore, hypotension during dialysis further decreases perfusion causing symptoms. Steal can be limb threatening and is graded from 0 – 3. Grade 0 is no symptoms, Grade 1 is mild ischemia with signs of cool extremity and flow augmentation with access occlusion. Grade 2 is moderate/intermittent ischemia that is experienced only during dialysis and patients feel claudication. Grade 3 is severe, ischemic pain at rest with tissue loss.

 

What are some symptoms and signs of Steal syndrome?

-       Symptoms include coolness, parasthesias, rest pain, and weakness. Signs of steal include cool to touch, pallor, cyanosis, delayed capillary refill, absent pulses/signals, diminished sensation, weak grip, and in severe cases ulceration or gangrene. If the patient shows improvement with access compression, diagnosis is confirmed.

 

When is an intervention necessary to treat steal syndrome?

-       You do not need to intervene for grade 0 and 1. For grade 3 an intervention is mandatory. The goal of treatment includes symptom resolution and access preservation, and this is achieved by reducing access flow and increasing distal arterial flow.

 

What are your intervention options for resolving steal syndrome?

-       One simple option is banding to reduce access flow. This is done by suture plication, placement of single narrowing tie or wrap by constrictive cuff to cause a stenosis in the AV access near the arterial anastomosis. A minimally invasive approach is used by the MILLER banding which uses an endoluminal 4 or 5mm balloon as a sizer and a suture is placed around the access with the balloon inflated. This procedure increases arterial inflow towards the hand.

-       Revision using distal inflow (RUDI) involves ligation of the fistula at the arterial anastomosis and reestablishment of flow via a more distal artery by bypass or vein translocation. This allows for decreased flow through the access by reducing the fistula diameter and by taking inflow form a smaller vessel. However, ultimately, the fistula is placed at risk

-       Proximalizaiton of arterial inflow (PAI) involves ligation of AV anastomosis, and the inflow is moved to a more proximal level with a prosthetic interposition. Dialysis can be continue via the vein. The main advantage is the native artery’s continuity.

-       Distal revascularization-interval ligation (DRIL) is ultimately considered the best option by many vascular surgeons due to the excellent results shown. There is an arterial bypass created originating proximal to the access and ending distal to the access, with ligation of the artery distal to the anastomosis. This prevents retrograde flow from distal vessels and allows for a low resistance pathway for arterial supply to the hand.

-       Lastly for palmar arch steal syndrome from radio-cephalic av accesses, distal radial artery ligation (DRAL) can be performed to prevent reversal of flow in the palmar arch. However, the ulnar artery patency needs to evaluated first.

 

Steal syndrome is not the only complication of AV access creation. What are some other nonthrombotic complications?

-       Other nonthrombotic complications include pseudoaneurysms which is a result of trauma due to repeated punctures or poor technique and true aneurysms which is a result of hemodynamically significant stenosis. Both can lead to cannulation difficulties, increased risk of thrombosis, pain, bleeding and cosmetic deformities.

-       Prosthetic grafts can results in seroma from ultrafiltration of the graft and most resolve without intervention.

-       Most interestingly, access creation can result in neuropathy. It is important to note that over 2/3s of the patients have preexisting peripheral neuropathy. Neuropathy is also graded from 0-3, with 0 as asymptomatic, 1 as mild intermittent changes (pain, paresthesia, numbness with sensory deficit), 2 as moderate persistent sensory changes, and 3 as severe sensory changes with progressive motor loss (motion, strength, muscle wasting). Ischemic monomelic neuropathy is rare but occurs acutely after AV access creation. Within hours of surgery, patients develop acute pain, weakness, or paralysis of hand and forearm muscles with prominent sensory loss. However, the hand is warm with palpable pulse or audible signal in distal radial and ulnar arteries. It is important to note that pain out of proportion is what differentiates IMN from ARHI. Treatment is access ligation or emergent augmentation of flow.

 

Since we’ve beaten to death arteriovenous accesses, we are ready to focus our attention to a different type of dialysis access. We cannot forget about dialysis catheters. What is the difference between an acute and chronic hemodialysis catheter?

-       Chronic catheters have a subcutaneous cuff at the exit site and tunneled to the vein. This decreased infection rates and is less likely to become dislodged. Tunneled hemodialysis catheters can be used up to 12 months.

 

If catheters cause so much problems such as infection and central venous stenosis, what would be an indication for them?

-       The most common indication would be for urgent hemodialysis. But other indications include patient who are not operative candidates due to advanced comorbidities, or patients who are unable to have an AVF or AVG due to anatomic feasibility.  Temporary dialysis access may also be needed in patients who have just had a peritoneal dialysis catheter placement or in chronic peritoneal dialysis catheter patients requiring abdominal or inguinal surgery.

 

Which site is the most ideal site for a hemodialysis catheter?

-       The right internal jugular vein is preferred because it has the best patency

 

Every procedure has potential complications. What are the immediate complications of catheter placement?

-       When placed in the internal jugular veins, there is always a chance of a pneumothorax or hemothorax. Wire embolism can occur is control of the wire is lost during the procedure. If the guidewire is placed too far, then there is always a chance of arrhythmia. Thus, the best place for the wire is through the IVC. With a left internal jugular vein approach, there is always a risk of thoracic duct laceration. If a leak is apparent, then the catheter needs to be removed immediately and a pressure dressing applied.