Fig. 19.1
Needle gauge size for a hemodialysis treatment range from 17-gauge needles for slower blood flow rates (250 mL/min) and initiating dialysis with a new arteriovenous fistula, up to 14-gauge needles for blood flow rates in excess of 450 mL/min. Dialysis adequacy will dictate needle gauge size and blood flow rates. (Counterclockwise from the top) 17 gauge, 16 gauge, 15 gauge, and 14 gauge
In recent years, techniques have been developed by surgeons and interventionalists to salvage such vascular accesses. One technique is superficialization of the vascular access [2]. A second technique is lipectomy (liposuction), which involves removing the excess tissue between the surface of the skin and the fistula [3]. These techniques have preserved future vascular access sites and made cannulation and dialysis treatments safer for patients. It is important that the surgeon takes into account the anatomic location of the vascular access. The vascular access needs to be in a location such that the patient can sit in a comfortable position for approximately 3–4 h. Vascular access placed near the axilla (Fig. 19.2), for instance, makes it difficult to position the arm that is comfortable for the patient, and leads to joint stiffness from remaining motionless during treatment. Also, compression of the dialysis tubing as it exits the arm can set off machine alarms, interrupting dialysis. Additionally, this creates a challenge for the cannulation process as it is difficult for the staff to position themselves for the cannulation process without feeling like they are sitting in the patient’s lap. While this may not seem like a serious problem, this inconvenience can lead to shortened dialysis treatments. Shortening dialysis treatments by even 10 min a session due to discomfort equals 2 weeks of missed treatments in a year, which impacts morbidity and mortality.
Fig. 19.2
Vascular access placement close to the axilla area is not only difficult for staff to cannulate but is uncomfortable for the patient as the arm would be kept in this position for a 4-h dialysis treatment (Courtesy of B. Inman)
While location and depth are major issues, utilizing the correct cannulation technique can also impact the number of interventions required for an access, as well as the overall life of the access.
Cannulation Techniques
Three cannulation techniques have been described: site rotation called “rope ladder,” area puncture, and constant site also known as “buttonhole” [4, 5].
Site Rotation Cannulation “Rope Ladder”
This technique utilizes the entire length of the AVF leading to even dilation of the vessel and giving cannulators the most surface area available for needle insertion (Fig. 19.3). For each dialysis treatment, cannulators select two new sites for needle insertion, staying at least ¼ inch from the previous cannulation site and not returning to that area for approximately 2 weeks to allow healing of previous cannulation sites. Impediments to site rotation cannulation are areas that are associated with high infiltration risk: areas with curves, flat spots (stenotic areas), or a segment that is too deep to reach. Also, short-segment AV fistulas (≤3 in.) will be subjected to more damage and potential shorter use-life due to more frequent aneurysmal degeneration.
Fig. 19.3
Site rotation “rope ladder” cannulation involves finding a new site for each treatment for both the arterial and venous needle. Spacing out the needle sites over time will allow the arteriovenous fistula to evenly dilate and at the same time continue to thicken the wall to prevent infiltrations (Courtesy of B. Inman)
Area Puncture Cannulation
Needle insertion occurs in the same small area of the access with each cannulation. This technique is also known as “one-site-itis.” This technique leads to multiple puncture sites as shown in Fig. 19.4 resulting in the creation of “two mountains and a valley.” Surprisingly, while we do not teach this technique, it is evident that it is a major cannulation technique utilized across the USA.
Fig. 19.4
Aneurysm formation as a result of repeated cannulations in the same small areas. Notice the two mountains (thin black arrows) and a valley (block arrow). It is very difficult to utilize the portion of the arteriovenous fistula in the valley because the wings of the access needle hit the mountain. This aneurysmal degeneration leads to a decreased cannulation zone for further needle insertions
Constant Site or Buttonhole™ Cannulation
This technique involves creating a tunnel from the surface of the skin to the blood vessel wall and then making one entrance site into the AVF wall (Fig. 19.5). The vessel wall tissue reorganizes into a stoma-like configuration, and when the needle touches the tissue, it opens up and allows the needle to enter the AVF. When removing the needle, the tissue closes back up and a small thrombus plug forms at the vessel wall and a scab forms on the surface of the skin. The creation of the tunnel and entranceway into the AVF is done utilizing sharp needles, and once the needle slides right down the tunnel, a transition to blunt needles occurs (Fig. 19.6). This technique became very popular in the USA around 1999 when a buttonhole tunnel was needed to access the LifeSite™ device. As popularity for this technique has grown in the USA, there are now some significant complications (i.e., infection, endocarditis) that have become apparent. The buttonhole technique has two permanent exit sites, compared to no permanent sites with site rotation cannulation. This technique incorporates concepts that are not a factor with site rotation cannulation such as colonization of bacteria and scab removal. It is known that bacterial count around exit sites is higher than surrounding skin (lessons learned from peritoneal dialysis and central venous catheter sites regarding colonization of bacteria surrounding exit sites in the skin). Improper cleaning or damage to the tissue could lead to an exit site infection. Dialysis patients carry staph on their skin and their noses at higher rate than the general population [7], making cleaning sites before needle insertion one of the most important aspects of infection prevention. Over the last decade, best practices have been identified to reduce the infection rate and its associated complications [6]. Patients are instructed to wash their access just prior to sitting down, and then staff preps the skin twice, once before scab removal and again after scab removal to ensure the bacterial count is as low as possible before inserting needles. Performing this two-step cleaning protocol can decrease the amount of bacteria surrounding the exit sites [8, 9]. As a result, this is the gold standard for constant site access cleaning.
Fig. 19.5
Buttonhole cannulation technique in an arteriovenous fistula. Notice there are only two cannulation sites, with adequate space in between to eliminate the risk of recirculation. These sites had been in use for 3 years at the time of the photograph
Fig. 19.6
Sharp versus blunt needles. Sharp needles are utilized for site rotation cannulation and for the creation of the buttonhole tunnels and entranceway to the fistula wall. Once the buttonhole tunnel and entranceway are created, there is a transition to blunt or dull needles for cannulation (Reprinted with permission of L. Ball and the American Nephrology Nurses’ Association, publisher, Nephrology Nursing Journal, June 2006, Volume 33/Number 3)
The other compounding issue is scab removal. By inserting the needle repeatedly in the same spot at the same angle over a 3- to 4-week period, the result is the creation of a tunnel from the surface of the skin to the outside of the blood vessel wall of the AVF. The scab serves to protect the tunnel from bacteria and potential tunnel infection. So before every cannulation, scabs need to be completely removed. While the patient is having their dialysis treatment, the staph from other parts of the arm migrate back to the exit sites, so that when the needles are removed, staph can become incorporated into the scab. That is why it is imperative that scabs be completely removed and why cleaning must occur after scab removal. All makers of blunt cannulation needles have scab-lifting devices, but care must be exercised to prevent digging (Fig. 19.7). Digging can cause three potential issues: making the exit site bigger, which can allow staff to utilize in incorrect angle of insertion allowing for multiple tunnel creation; breaking the tissue surrounding the exit site that could cause an exit site infection; and breaking off pieces of the scab and pushing it down into the tunnel causing a tunnel or blood stream infection. The appropriate way to utilize a scab-lifting device is to lift a corner of the scab with the tip, then turn it on its side and scrap across the scab. Soaking scabs with saline and gauze for 3–5 min makes scabs much easier to remove [6].
Fig. 19.7
Scab-lifting devices. With the buttonhole technique, a major concern to prevent infection is to completely remove the scabs from the exit sites. There are three manufacturers of blunt buttonhole needles in the USA: (left) JMS Harmony, (center) Medisystems Steri Pick, and (right) Nipro BioHole. On the end of each of these needles is the scab-lifting device
The buttonhole technique requires much diligence, and any break in the process could result in infection. It is critical that staff be observed for competency, at least annually, to ensure that they are performing the technique correctly utilizing the evidence-based practices that have been identified. Careful selection of patients is important in reducing the risk of infection. The buttonhole technique literature has identified distant infection including endocarditis, heart valve growth and replacement, and spinal abscesses. As a result of a repeated pattern of these distant infections, patients with a history of endocarditis, heart valve disease, or artificial implants could be at higher risk for infection based on research outcomes, and their nephrologist should speak about the infection risk prior to initiating the buttonhole technique (Kelly Sutherland & Linda Mills, Vascular Access Coordinators at St. Joseph’s Healthcare, Hamilton, Ontario, Canada). Patients who pick at their scabs are also at increased risk for infections and are not considered appropriate for this cannulation technique.
Assessment and Cannulation of a New Vascular Access
It is of the utmost importance to have good communication between the surgeon, nephrologist, and expert cannulator when determining if a fistula is sufficiently mature to cannulate. While surgeons can check the diameter and flow rates of a new access, they do not have experience with cannulation, in particular, cannulation with the pressure exerted within the fistula from the blood pump of the dialysis machine. A fistula may appear and feel ready to cannulate, but the vessel wall may still be fragile and unable to tolerate the needle puncture. It takes a lot of cannulation experience to identify if there might be problems with needle insertion (i.e., infiltration), and if there is any doubt, then leave the needles out. There is good evidence to support identifying expert cannulators for assessment and needle insertion on all new AVFs – someone who will tell a nephrologist or surgeon that the access is not ready to cannulate and that it should be reevaluated by the physician before anyone inserts a needle. Robbin and colleagues (2002) evaluated experienced dialysis nurses and found an 80 % success rate of accurately predicting eventual fistula maturity [10].
While evidence-based research surrounding cannulation is limited, there are evidence-based practice guidelines. The KDOQI Clinical Practice Guidelines and Recommendations (www.kidney.org/professionals/guidelines) and the Fistula First Breakthrough Initiative (FFBI), now known as Fistula First Catheter Last (www.esrdncc.org/ffcl/), are both excellent resources with regard to cannulation of AVFs. For the initial cannulation, it is strongly recommended to utilize a smaller-gauge needle (17-gauge needle) to decrease injury to the vessel and prevent a large infiltration, hematoma, compression of the vessel, and possible clotting of the AVF [11]. Patients should be prepared for the potential for infiltration prior to any cannulation attempt. First-time cannulation has one of the highest risks of infiltration mainly because it is the first time that the vessel will have increased blood flow with additional pressure exerted on the walls from the use of the blood pump. A list of best practices “Do’s and Don’ts” for cannulation of new AVFs (Fig. 19.8) should aid in decreasing infiltrations related to needle positioning and manipulation or increasing pressure within the cannulation zone [12].
