Before placing dialysis needles, it is important for the nephrology nurse to understand the anatomy of the access and its affects on adequacy. The direction of the blood flow determines the placement of the needles. The venous needle must always be placed in the direction of the venous blood return. In clinical practice, the venous needle is placed in an upward direction towards the heart. The arterial needle can be placed upward or in antegrade direction or downward in the retrograde direction. Antegrade cannulation can result in recirculation of the blood if the needle hubs are less than three inches apart, ultimately decreasing the Kt/V and the quality of patient care delivered (Brouwer, 1995). Loop grafts promote proper needle cannulation as it is natural to place both needles facing away from nurse. Nurses learn early in their training to start IVs with the needles facing away from them. Thus, straight grafts and fistulas logically pose a challenge to the nephrology nurse when determining which direction the arterial needle should be placed. In practice, nurses assess their patients for edema and shortness of breath, but they spend very little time deciding how to best place the arterial needle for dialysis. It is time for nephrology nurses to change their thinking and place all arterial needles in the retrograde direction. Like most changes, this will not be easy to accomplish and will take time. Dedicated nurses must begin with the basics and teach their colleagues why it is important to change an accepted procedure. These changes will be awkward at first; however, with practice the procedure will be perfected and incorporated into their routine. As new nurses begin their careers in hemodialysis, they will reap the benefits of being taught to place needles in the optimal position and patients will benefit from the change as well. ||

The patients benefit in many ways from this change. The obvious benefit is that when their Kt/V improves, their mortality rate decreases (NKF, 2001). Another benefit is that placing the hubs of the needles only one inch apart allows for better use of the access. The cannulation sites will have longer periods of time between uses which promotes healing and better utilization of the access. Additionally, it is difficult to place needle hubs three inches apart in a short access. The patients will need to be educated in the reasoning behind the change and how it affects them. If the nephrology nurse can reduce or eliminate recirculation in the access and improve the Kt/V by positioning arterial needles in the retrograde direction, then high quality care has been delivered.

References
Brouwer, D. (1995). Cannulation camp: Basic needle cannulation training for dialysis staff.

Retrieved October 2, 2004 from National Kidney Foundation.(2001). Clinical practice guidelines. New York: National Kidney Foundation, Inc.

 
The Arterial Needle Can Be Placed in the Direction of Flow to Achieve Effective Treatment
Elisabeth Harman, RN, CNN
Facility Administrator, Central Valley Dialysis, Salt Lake City, UT
Past Chapter President, ANNA’s Intermountain Chapter.

Placement of arterial access needles in fistulas and grafts has been a subject of some controversy. Do we cannulate in direction of flow or against the flow? In my years of experience, I have determined that there is very little difference in outcomes dependent upon direction of the cannulated needle.

When working with a new arteriovenous fistula (AVF), I advocate cannulating in the direction of flow because it then becomes much easier to recannulate if there are problems. It is usually the venous needle that infiltrates on a new AVF and, when it becomes necessary to recannulate, you can then decide whether to actually place a new arterial needle under the one that is still in place or go above. When the venous needle infiltrates it is often impossible to do what be would ideal, that is, cannulate placement above the infiltration extremely difficult.

It is believed that we can achieve higher pump speeds if the needle is against the flow, but I have seen that this increases the risk of venous infiltration and the subsequent swelling and bruising of the access arm. It is better to run with slower pump speeds initially to prevent infiltration and assist in the maturation of the AVF.

In mature AVFs, as with loop or straight AVGs, the arterial needle can face either direction with no problems. In doing recirculation studies in AVFÕs with needles in either direction, there is no significant increase in recirculation by cannulating in the direction of flow. Ordered pump speeds can be easily achieved.

I have, on many occasions following a venous infiltration, been able to turn the existing arterial needle that has been pointed against the flow to direction of flow without any problems. It has then been possible to recannulate an arterial site and use the previous arterial site as the new venous return. This is very difficult to do and is not advocated, especially for inexperienced staff. The access must be evaluated before further dialysis is attempted.

We are all aware of the trauma to the access and the patient secondary to numerous needlesticks. It seems to me that until a new AVF is mature it is imperative to minimize the number of sticks required to achieve a treatment.


Let’s Empower Patients with the Choice of Self-Cannulation!
Catherine(Cate) Lewis, BSN, RN, CNN
Education Manager for Moses Taylor Regional Dialysis System
Scranton, PA
Recipient of ANNA Rehabilitation Award May 2002
Member of CMS Fistula First Initiative
Immediate Past Chair of NKF Patient and Family Council Executive
Committee
Member of Network 4 Organ Procurement/Transplant Committee

A successful cannulation allows easy draw and return of the patientÕs blood from the vascular access and extracorporeal system. The arterial needle must provide good flow with safe pre-pump arterial pressure and the venous needle must have easy return with venous pressures.

Cannulation is as basic to hemodialysis as the hemodialyzer, but is much less understood. Unfortunately, clinical research for the best practices of cannulation has not been done. We have to practice cannulation based on best theory and practical experience. Clinical research on the best cannulation technique for arteriovenous grafts (AVG) and arteriovenous fistulae (AVF) must be spearheaded by nephrology nurses. Since cannulation is a nursing procedure, nephrologists will not choose cannulation as a research topic. I hope that in the near future we can discuss nursing research on the various topics of cannulation. Until that time, we can discuss the theory of the arterial needle positioning.

Since the publication of the NKF K/DOQI Vascular Access Guidelines in 1997 and now the CMS National Vascular Access Improvement Initiative or Fistula First, I have presented ÒCannulation CampÓ training all over the United States. Proper needle direction is one of the most common questions I get when providing cannulation training. The questions about cannulation are basic and have remained unchanged for the past 10-15 years. The focus has changed from AVFs to AVGs and back to AVFs. Needle direction is universal for AVG or AVF. The venous needle must always point toward the venous return. The venous return is the direction of the blood flow from within the vascular access and back to the central circulation of the heart. Most of the time, the venous return points from the distal portion of the extremity and back towards the heart. This seems to be an obvious, except in the case of an AVF with retrograde flow down the extremity and back to the heart. This is common in mid forearm or upper arm AVFs. A venous needle placed against the blood flow direction can result in elevated venous pressures and possibility of damage to the blood cells.

The arterial needle placed up or in the direction of the blood flow of a radical cephalic AVF is called Òantegrade.Ó A needle placed down or against the direction of the blood flow is called Òretrograde.Ó The arterial needle placed in the arterial portion (limb) of the AVG can point up (antegrade) or point down (retrograde). If the venous portion (limb) of the loop graft must be used for both the arterial and venous cannulation, then easiest needle placement is the arterial needle down with the venous needle up to keep the needles from touching inside the lumen of the graft. The opposite placement is used if the arterial portion of the AVG is used.

The needle selection will impact the arterial needle placement. In the early days of hemodialysis, non-backeye needles were used. The needle bevel was the only source of blood entering the needle. In an AVF, the needle bevel would ÒsuckÓ up against the wall of the vein. To restore blood flow, the needle would be rotated or ÒflippedÓ. This is where the whole issue of ÒflippingÓ hemodialysis needles originated. The modern day AVF needles have a backeye or small hole in the back of the needle opposite of the bevel. The backeye allows for blood to be drawn into the needle from both sides. This eliminates the need to ÒflipÓ or rotate needles. The needle flip (in the absence of a rotating hub AVF needle) can cause damage to the AVG or AVF by enlarging the vessel/ graft puncture site as the wings of the needle must be lifted to rotate the needle 180 degrees. The tip or cutting edge of the needle bevel can also puncture though the vessel/graft wall when the needle is lifted to Òflip.Ó This can lead to an infiltration and damage the vascular access. If poor blood flow is achieved with a needle cannulation, repositioning the needle without ÒflippingÓ is the safest option.

Poor blood flow has many causes including a low blood flow within the vascular access (access flow). An AVF can remain patent with an access flow of 300 ml/min. The average hemodialysis machine blood pump speed is set above 300 ml/min. If the flow within the vascular access is below, equal or very close to the hemodialysis machine blood pump speed, the pre-pump arterial pressure will become excessively negative (more negative than -200 to -250 mm/Mg). Excessively negative prepump arterial pressures lead to collapse of the blood pump segment. The actual extracorporeal blood flow is lower than the blood pump setting. An example is the blood pump set at 350 ml/min and the pre-pump arterial pressure is -300 mm/Mg, the actual extracorporeal blood flow could be 300 mm/Mg (Depner, 1990). The blood pump segment that moves the blood through the blood pump is round and the segment collapses to an oval shape as the pre-pump pressure becomes more negative. This leads to a decrease in the effective or delivered blood flow rate and thus a decrease in the delivered URR or Kt/V. For this reason, pre-pump arterial pressure is mandatory for safe and efficient hemodialysis. It is a very useful tool for determining adequate blood inflow of the extracorporeal circuit as supplied by the vascular access and needles.

In AVFs, a common area of stenosis is the arterial inflow (within the artery that supply the blood to the AVF) and the Òjust-anastomosis-stenosis (the area of the vein just above the arterial anastomosis or the swing site of the vein when the fistula was surgically created). The artery stenosis leads to poor blood flow into the AVF and often leads to failure of the AVF to mature. The Òjust-anastomosisstenosisÓ is the narrowed area felt on physical exam 1-2 finger widths above the anastomosis site. The stenosis is palpated as a ÒdipÓ in the AVF. If the arterial needle is placed down (retrograde) into the area of stenosis, the blood flow is impaired. The same AVF may be cannulated with the needle placed up away from stenosis and function well. This observation is diagnostic of the stenosis. Anytime this stenosis is found, the patient should be referred to interventional radiology/nephrology to image the AVF and treat the stenotic lesion with angioplasty.

Site rotation also plays a key role in needle direction. Site rotation to prolong the life of or salvage an AV access should always be utilized. The ability to place an arterial needle in both directions can help promote maximal site rotation. The AVF alternative to site rotation is the AV fistula buttonhole technique that limits the cannulation sites and thus protects prevents damage to the fistula and prolongs the life of the fistula.

Simplification of cannulation policies and procedures has lead to much of the traditional practices involving vascular access cannulation. Just because that is the way cannulation has always been done at a specific dialysis unit does not make the procedure the best possible nursing practice. Careful review of and open discussion about cannulation policies and procedures should occur routinely. The review process should also include the Medical Director of the dialysis unit. Ultimately, the Medical Director is responsible for all care given in the dialysis unit and his/her signature should be in the front of every dialysis unitÕs policy and procedure book. A separate policy/ procedure should be used for new AVF and mature AVF cannulation as well as for new and mature AVG cannulation. If buttonhole cannulation is used, a separate policy/ procedure is needed for new and mature buttonhole cannulation for AVFÕs only.

We cannot deliver adequate hemodialysis to the all patients with AVFs or AVGs if we do not achieve proper cannulation of the vascular access. The time has come for research to answer the many basic questions about the best practices of cannulation so we can move cannulation from an ÒartÓ to a Òscience.Ó Nephrology nursing can greatly advance the quality of care of all current and future patients with CKD stage 5 through the use of sound evidence based research on AVG and AVF cannulation techniques. LetÕs just do it!

Suggested Readings
Beathard, G.A. (1998) Physical examination of the dialysis vascular
access. Seminars in Dialysis, 11, 231-236.

Beathard,G.A. (1992). Physical examination of AV Grafts.
Seminars in Dialysis, 5, 74.

Brouwer, D.J. (2003). The care and feeding of the AV fistula…
The road to improvement? Part 2 Nephrology News and
Issues 19(7),48-51.

Brouwer, D.J. & Peterson, P. (2002). Back to basics: The arteriovenous
graft: How to use it effectively in the dialysis unit.
Nephrology News and Issues, 16(12), 41-49.

Brouwer, D.(1995). Cannulation camp: Basic needle training for
dialysis staff. Dialysis and Transplantation, 24(11),: 606-612.

Depner, T.A., Rizwan, S., & Stasi, T.A, (1990). Pressure effects on
roller pump blood flow during hemodialysis. ASAIO
Transactions, 36(3),M456-9.

Hartigan, M.F. (1994). Vascular access and nephrology nursing
practice: Existing views and rationales for change. Advances
in Renal Replacement Therapies, 1, 155-162.