Review of Hemodialysis for Nurses and Dialysis Personnel, 8th Edition

Chapter 12. Access to the bloodstream

Historical background

Effective hemodialysis became a reality in the 1940s. Each treatment required a surgical cutdown. Hollow tubes (cannulas) of glass or metal were inserted into an artery and a vein. The glass and metal tubes were later replaced with cannulas of polyvinyl chloride or other plastic materials. During the 1950s, attempts were made to leave the cannulas in place for more than one treatment. Different methods of maintaining patency were tried. These attempts, at best, lasted only a few treatments.

In 1960 Scribner, Quinton, and Dillard at the University of Washington devised a cannula that could be left in place much longer. It consisted of Teflon tubes, one placed in an artery and one placed in a vein. These tubes were connected externally, allowing for continuous rapid flow of blood through the device. This technique was improved in 1962 with the use of Silastic (silicone rubber) for the external shunt loop and Teflon for the vessel tips. This allowed for greater flexibility of the tubing and increased comfort for the patient. This innovation not only was effective for a single hemodialysis but also offered a method for repeat treatments.

Another major development came in 1966 when Cimino, Brescia, and co-workers developed the forearm internal arteriovenous fistula. This was created by performing a surgical anastomosis between a forearm artery and vein. The subsequent flow of arterial blood into the vein permitted percutaneous puncture of this vessel that offered adequate flow for hemodialysis.

Use of internal synthetic graft materials began in 1974. Today the most common type of synthetic graft is polytetrafluoroethylene (PTFE). A “button” needle-free form of vascular access was developed in 1980. The button needle-free form worked, but not as well as the other internal synthetic graft material. These new synthetic grafts and devices offered new possibilities for patients who did not have adequate vessels for a Cimino fistula.

Shaldon described temporary access for hemodialysis via cannulation of the femoral vein in 1961. Uldall, in 1979, devised a special catheter for temporary access in the subclavian or internal jugular vein. When the dual lumen catheters were introduced, this further enhanced a means of temporary access, by allowing one catheter to function as both the inlet and the outlet ports.

Vascular access, as used for hemodialysis in the early 1960s, has evolved considerably during the past 30 years or more. However, maintaining patent access with adequate blood flow remains one of the major problems in the chronically hemodialyzed patient (Fig. 12-1).

image

Figure 12-1 A, Quinton-Scribner shunt with connector in place between dialysis runs. B, Shunt arms separated and connected to dialyzer bloodlines.

(From Larson E, Lindbloom I, Davis KB: Development of the clinical nephrology practitioner, St. Louis, 1982, Mosby.)

Internal accesses

The percentage of prevalent hemodialysis patients in the U. S. with an arteriovenous fistula (AV fistula) as their primary vascular access was 32.4% (87,344 patients) at the beginning of 2003. By May 2009 this percentage had increased to 52.6% (179,113 patients) (Fistula First Breakthrough Initiative Strategic Plan, 2009).

The Centers for Medicare & Medicaid Services’ (CMS’s) goal, based upon achievable practice, is a prevalent AV fistula use rate of 66%. The National Kidney Foundation (NKF) Kidney Disease Outcomes Quality Initiative (KDOQI) has established guidelines for the selection of a permanent vascular access for chronic hemodialysis. Current guidelines recommend AV fistula use rates of 50% or greater for incident, and at least 40% for prevalent, patients undergoing hemodialysis.

The Fistula First Breakthrough Initiative (FFBI) was established in 2005 by CMS to increase AV fistula use in all appropriate hemodialysis patients and to decrease the placement of central venous catheters. A group consisting of CMS and End-Stage Renal Disease (ESRD) Networks has created a coalition that supports and promotes 13 “Change Concepts” that can give all hemodialysis patients the opportunity to receive an AV fistula. These Change Concepts are strategies to provide the patient and staff with the resources, tools, and best demonstrated practices to implement the KDOQI guidelines for vascular access placement.

The order of preference for a vascular access for patients undergoing chronic hemodialysis is: (1) a wrist (radial-cephalic) primary arteriovenous fistula (Fig. 12-2, A), (2) an elbow (brachiocephalic) primary arteriovenous fistula, (3) an arteriovenous graft of synthetic material (Fig. 12-2, B), or (4) a transposed brachiobasilic vein fistula. If an AV fistula cannot be placed, an arteriovenous graft (AV graft) is acceptable. Long-term catheters, such as a cuffed tunneled central venous catheter, should be discouraged as a permanent vascular access. Short-term catheters may be used for acute dialysis but only for a limited duration of time (NKF KDOQI Vascular Access Clinical Practice Guidelines Update, 2006).

image

Figure 12-2 Options for long-term vascular access for hemodialysis. A, A surgically created venous fistula. The increased pressure from the artery forces blood into the vein. This process causes the vein to dilate enough for fistula needles to be placed for hemodialysis. When the vein dilates in this matter, the fistula is said to be “developed.” B, A surgically placed straight vascular graft in the upper arm. The graft creates a shunt between arterial and venous blood.

(From Ignatavicius DD, Workman ML: Medical-surgical nursing: critical thinking for collaborative care, ed 6, St. Louis, 2010, Saunders.)

The time of vascular access placement should be well before the need for dialysis treatment. The 2006 NKF KDOQI Clinical Practice Guidelines for chronic kidney disease (CKD) recommend initiation of a vascular access when the glomerular filtration rate (GFR) is less than 30 mL/min/1.73 m2. The goal is for the patient to have permanent and functioning access at the time when hemodialysis therapy is initiated. Early referral and placement provide the time needed for the fistula to properly mature and develop. Duplex ultrasound is the preferred method for preoperative vascular mapping and should be performed on all patients prior to placement of the vascular access (NKF Clinical Practice Guidelines and Recommendations, 2006).

Arteriovenous fistulas

What is an arteriovenous fistula?

An AV fistula is an internal access surgically created by a vascular surgeon using the patient’s own blood vessels. In an internal AV fistula, a small (5 mm) opening is created surgically in an adjoining artery and vein, and the two vessels are joined at this opening, creating an AV fistula. The two blood vessels used are anastomosed in a side-to-side, end-to-side, or end-to-end connection (Fig. 12-3). The diversion of arterial blood into the vein causes the vein to become enlarged, distended, and prominent, allowing placement of large-gauge needles for the dialysis treatment. The blood flow rate (Qb) and diameter of the access will increase in response to the high pressure of the arterial blood entering the venous system. KDOQI has issued the rule of 6s as an objective measure used to assess access maturation. At six weeks after creation the fistula should have a diameter of at least 6 mm with discernable margins with a tourniquet in place and the depth should be no more than 0.6 mm below the skin surface. The FFBI defines a fully matured AV fistula as one that can sustain three consecutive two-needle cannulations with no infiltrations at the prescribed needle gauge and blood flow rate (NKF, 2006)(FFBI Coalition, Clinical Practice Workgroup, 2010).

image

Figure 12-3 A, Vessels for the creation of elbow AV fistula. B, Brachiocubital AV fistula. C, Brachiocephalic AV fistula.

(From Floege J, Johnson RJ, Feehally J: Comprehensive clinical nephrology, ed 4, St. Louis, 2011, Mosby.)

Eventually the access will be able to deliver a blood flow of 300 to 500 mL/min. Maturation occurs when there is dilation and thickening of the venous segment of the fistula. This is due to the increase in blood flow and pressure of arterial blood. The vein used to create the AV access will sometimes develop additional branches, which will also enlarge and mature enough to be cannulated for dialysis. This is called collateral circulation, and it increases the available surface area for cannulation. However, if the collateral circulation prevents the development of the main vein, ligation would be necessary.

The AV fistula can be placed in either the upper or the lower arm. The radial artery and cephalic vein (lower arm) (Fig. 12-4) and brachial artery and cephalic vein (upper arm) are commonly used. Proper evaluation of the patient’s vasculature and physical assessment plays a role in determining the access of choice for that patient. A major cause of early AV fistula failure is the selection of suboptimal vessels. Venography allows for identification of appropriate veins and helps to rule out sites that are not suitable for use. Doppler flow studies may also be used if venography is not available.

image

Figure 12-4 Mid-forearm radiocephalic fistula is used if the distal radial artery is not suitable.

(From Wilson SE: Vascular access: principles and practice, ed 4, St. Louis, 2002, Mosby.)

Every attempt is made to use the patient’s nondominant arm to help the patient maintain the present standard of living and to facilitate self-cannulation if the patient performs his or her own dialysis care. The patient must have sufficient arterial blood flow to maintain the access and to provide an adequate dialysis treatment. The AV fistula may take up to four months, or longer, to mature enough to allow for cannulation.

What is basilic vein transposition?

Basilic vein transposition is a technique used to create a vascular access in patients with inadequate vessels in the wrist. This transposed vessel technique involves dissecting the basilic vein and transposing it anteriorly and subcutaneously while anastomosing it to the brachial artery (Fig. 12-5). This transposed vessel provides a large surface area for cannulation and requires only one anastomosis. The incision for this access is rather large, with the start of the incision being at the midantecubital fossa and extending to the medial aspect of the arm to the axilla. The main advantage of this type of access placement is the avoidance of using a synthetic graft. As with other autologous grafts, you will see a longer patency rate and fewer risks of infection.

image

Figure 12-5 Transposed brachiobasilic AV fistula. A, Dissection of the basilic vein. B, Anterolateral transposition and brachial artery anastomosis.

(From Floege J, Johnson RJ, Feehally J: Comprehensive clinical nephrology, ed 4, St. Louis, 2011, Mosby.)

What is a proximal radial artery arteriovenous fistula?

The proximal radial artery arteriovenous fistula (PRA-AVF), also known as a “reverse flow” fistula, is a newer advanced surgical procedure for native AV fistula placement. In this type of access, the proximal radial artery is used for the arterial inflow. The arterial anastomosis is made higher in the arm and the vein develops both above and below the anastomosis. With this configuration, blood will tend to flow in two directions at the same time, allowing cannulation in both the forearm and the upper arm. When cannulating, if both needles are to be placed in the forearm, the venous needle should be placed downstream (retrograde) with the needle top pointing toward the hand, which is the direction of blood flow. If the upper arm is used for the venous return, the flow goes toward the heart, so the needle would be placed upstream (antegrade) with the needle top pointing toward the shoulder (Jennings, Ball, & Duval, 2006) See Fig. 12-6.

image

Figure 12-6 What you “KNOW” about the “FLOW” is really important with reverse flow AV fistulas, such as proximal radial artery fistulas.

(Courtesy of William Jennings, MD, FACS; Lynda Ball, BS, BSN, RN, CNN; and Linda Duval, RN, BSN.)

What is an arteriovenous graft?

When a patient is not a candidate for a native AV fistula, a vascular graft is substituted. An AV graft can be of biologic or synthetic material; however, synthetic grafts are used most frequently. The graft material is implanted subcutaneously into either the forearm or the upper arm. In some circumstances when the arm cannot be used, the chest or leg area may be used. The graft bridges an artery on one end and a vein on the other end. Blood flow direction is from the artery to the vein. With the AV graft, the needles for cannulation are placed directly into the graft material.

The synthetic graft is used most often in patients who do not have adequate vessels to create an internal AV fistula. The graft may be placed in several configurations: straight, looped, or curved. NKF KDOQI guidelines recommend the use of PTFE over biologic or other synthetic materials. The AV graft may be used as early as two to six weeks after placement, with the surgeon’s approval. The tissue surrounding the graft will grow into and around the graft, helping to stabilize this vessel.

Why do you need to know the direction of blood flow in the arteriovenous graft?

It’s necessary to know the direction of blood flow in the access to properly place the needles for the hemodialysis treatment. The venous needle should always be placed in the direction of the blood flow (artery to vein). Placing the venous needle against the flow of blood will cause increased resistance to the blood returning to the patient. This will be signified by a high venous pressure reading on the machine.

How do you determine the flow of blood in a looped arteriovenous graft?

In a looped or horseshoe AV graft, after gently depressing the graft at midpoint you can listen for a bruit or feel for a thrill on each side of the graft. Because you have occluded the flow of blood at midpoint, you will still be able to feel a thrill or hear a bruit on the side where the blood is entering the access (arterial side). The side of the graft with little or no thrill or bruit would be the venous side. Another technique used to determine the flow of blood is to palpate the graft at midpoint after the needles are placed. The arterial needle will continue to have a flashback of blood when the graft is compressed at midpoint.

What types of arteriovenous grafts are available?

Synthetic grafts are the most common AV grafts currently in use. Many synthetic materials (Dacron, PTFE) are available in various diameters and lengths. A newer form of PTFE allows for needle insertion immediately after placement, although the manufacturer recommends waiting five to seven days. Fig. 12-7 shows two types of placement for synthetic grafts.

image

Figure 12-7 Polytetrafluorethylene (PTFE) grafts in the arm. A, Straight forearm PTFE graft. B, Loop forearm PTFE graft. C, Curved upper arm PTFE graft. D, Looped upper arm PTFE graft.

(From Floege J, Johnson RJ, Feehally J: Comprehensive clinical nephrology, ed 4, St. Louis, 2011, Mosby.)

What are the advantages of an arteriovenous graft?

AV grafts can be used sooner than AV fistulas, usually after two weeks. Maturation time for the vessel to enlarge is not required. The larger vessel size allows for easier cannulation. Table 12-1 lists the advantages and disadvantages of internal accesses.

Table 12-1 Advantages and Disadvantages of Internal Accesses

Arteriovenous fistula

Arteriovenous graft

Advantages

Excellent patency rate
Can last for decades
Highest blood flow rates
Lowest rate of complications (infection, steal syndrome, stenosis)
Improved performance over time as access develops
Development of collateral circulation, which creates additional branches for cannulation

Large surface area for cannulation
Ability to span large areas of the body
Easy to cannulate
Little time required for maturation
Variety of shapes and configurations
Ease of surgical implantation

Disadvantages

Failure of vein to enlarge
More difficult to cannulate than graft
Cosmetically unattractive
Must find healthy veins that are in proximity and not too tortuous
Requires time to mature before use

Higher rates of infection
May reject graft material
Higher rates of thrombosis
Stenosis at venous anastomosis from intimal hyperplasia
No development of collateral circulation

What are the special care needs and potential problems with use of the arteriovenous fistula for access to the bloodstream?

Needle insertions are necessary for each hemodialysis. With repetitive venipunctures, scar tissue forms over the fistula, making insertion of needles more difficult and painful. Furthermore, if a needle becomes accidentally dislodged and passes through a vessel wall (infiltration), bleeding into the tissues may result in the formation of a painful hematoma. If this occurs, use of the fistula may be difficult or impossible until swelling decreases. At the end of each hemodialysis treatment, after the needles are withdrawn, firm pressure must be applied over the puncture area for 12 to 20 minutes to prevent persistent bleeding.

Are there special problems with an internal arteriovenous fistula?

Size and location of arterialized veins are important. It is often a matter of weeks, and sometimes months, before the veins become sufficient in size that large-gauge needles may be inserted without difficulty. This process takes longer in women than in men. The veins of the forearm vary in their pattern and distribution. The location of easily accessible vessels may be limited, so that a few sites must be used repeatedly for insertion.

Occasionally the desired blood flow is difficult to obtain through the inlet needle. This problem may result from the size of the vein or from branches that divert the flow. Occasionally the needle must be placed very near the anastomosis to obtain sufficient flow (the needle tip should never be closer than 1.5-2˝ from the anastomosis). Sometimes, with side-to-side AV fistulas, most of the dilation of the veins occurs over the back of the hand, and the arm veins do not become prominent. Surgical revision may be required to correct the flow of the blood.

A third problem is spasm of the vessel, which is common. This usually occurs at the beginning of hemodialysis, causing decreased arterial blood flow. Spasms occur when attempting to maintain high blood flows in an immature fistula. The lumen of the needle sucking against the vessel wall can cause spasms. This is painful and is accompanied by a fluttering sensation at the needle. The use of back-eye needles may help.

On the return flow side, resistance may be high secondary to venous stenosis in the outflow vessel above the anastomosis. Other mechanical causes of return flow resistance include position of the extremity and placement of the needle against the vessel wall. Repositioning of the needle may be necessary.

A fourth problem is accidental tearing of the vessel during venipuncture. This may result in the formation of a large hematoma, making the vessel difficult or impossible to use for many days. The same type of accident may occur if the patient suddenly moves or thrashes about during dialysis.

In addition, the radial artery “steal syndrome” may develop. A few patients develop ischemic changes of the fingers. This is manifested by coldness, poor function, and even gangrene and necrosis of the tips of the fingers. The “steal” is caused by low arterial pressure at the fistula site, resulting from diversion of radial artery blood to the vein. Because the radial artery distal to the fistula normally connects with the ulnar artery, the pressure gradient causes ulnar blood to be diverted from the arteries to the fingers and flow instead toward the fistula. Hypoperfusion of the palm and fingers results, causing pain and coldness that worsens during the dialysis treatment. If recognized early, the syndrome may be corrected by surgically tying off the radial artery distal to the fistula.

Infections, thromboses, and aneurysms are three additional potential AV fistula problems. Infection of the fistula can occur secondary to poor personal hygiene or poor aseptic technique during cannulation. This local infection can lead to thrombosis or sepsis if not treated. Signs and symptoms include redness and swelling of the access and/or pain and fever. Diagnosis is confirmed by culturing the drainage and/or doing blood cultures. Antibiotic therapy is then employed.

Thrombosis is the most common complication of AV fistulas. In addition to infection, it can be caused by hypotension or stenosis of the fistula. Thrombosis can also be secondary to compression of blood flow, caused by the use of tight bandages or a fistula-needle-holding device, the patient sleeping on the fistula arm, or hematoma formation. The use of fistula–needle-holding devices is discouraged and should never be used on new and developing AV fistulas. The bruit should always be auscultated after placing a fistula–needle-holding device on a patient’s access.

Finally, aneurysms (outpouchings of the vessel wall) can occur from repeated cannulation of the same site and from infection. Large aneurysms limit the available cannulation sites.

How does one assess the internal access before needle insertion?

A thorough assessment is key to skillful cannulation and will help to increase the longevity of the access as well as minimize other complications. A complete assessment of the access must be done before cleaning the site or actual cannulation. Assessment of the internal access involves several steps:

• Visibly observe the access, noting any signs of infection. Look for signs of redness or inflammation. The access extremity should have a normal skin temperature and be neither too hot nor too cold. The skin should be of a normal temperature for the patient. A hot feeling may indicate an infection, and an access that is noticeably cool might be thrombosed. Observe previous needle insertion sites for proper healing and scab formation. Make note of any open areas or drainage. A registered nurse should be informed of any unusual findings. A culture of drainage may be indicated, and the nurse must make the determination of whether the access may be cannulated.

• The skin should not be discolored or bruised and the patient should not complain of any pain or numbness in the access or extremity. Swelling may be seen in an access that has recently been placed. Some patients have poor venous drainage in the access limb, causing swelling. Finally, swelling may be present because of a previous needle infiltration. Elevation of the affected limb is helpful to increase the venous return and decrease the swelling. Swelling should be monitored from treatment to treatment for improvements or worsening conditions. The circumference of the arm may be measured with a tape measure and compared for any increases or improvements. A registered nurse should be informed of any unusual findings before cannulation of the patient is attempted.

• Check for circulation or patency. Palpate the internal access for a “thrill,” which should be felt over the entire length and resembles a gentle vibration. A thrill is indicative of adequate blood flow throughout the vessel of 450 mL or greater. A pulse will indicate less than adequate blood flow through the access. Listen with the bell of a stethoscope for a bruit or a swooshing sound. This should be clearly audible over the entire length of the access. The bruit should be heard with greater intensity over the anastomosis. Intensification in the normal sound of the bruit may indicate a stenotic area in the access. The absence of a bruit or thrill indicates the access is clotted or no longer patent. A clotted access should never be cannulated. The patient should be taught to assess the access daily by palpating for a thrill.

What is the proper aseptic preparation for cannulation of an arteriovenous graft?

An antiseptic solution, such as povidone-iodine, should be used to cleanse the skin over and around the fistula. Apply the antiseptic in a circular motion away from the puncture site until a circle of two inches in diameter has been covered. Be sure to follow the antiseptic manufacturer’s directions for effective disinfection. The povidone-iodine must be allowed to dry on the epidermis before needle insertion. If the patient is allergic to povidone-iodine, isopropyl alcohol may be used, but needle insertion must be performed before the alcohol dries.

What types of needles are used for puncturing the arteriovenous fistula?

Large-gauge, thin-wall, back-eye needles are preferred. The larger-gauge needle is used for the high blood flows necessary for high-flux or high-efficiency dialysis. Blood flows of 400 to 500 mL/min may be attained with 14-gauge needles. Smaller, 17-gauge needles are used with children or infants to accommodate their small vessel size and decreased blood flow rate requirements. It is generally recommended practice to use at least a 15-gauge needle with blood flow rates of 350 mL/min or greater. Dialyzing a patient at a high blood flow rate with a small-gauge needle may cause hemolysis of the red blood cells because the cells pass through a small needle opening with such sheer force.

Are there particular points to be observed in placing the needles?

The flow of blood through the access determines needle placement because the venous needle must always be placed in the direction of blood flow. Blood flow is sometimes identified as antegrade and retrograde, with the former meaning in the direction of blood flow and the latter meaning against the flow of blood. The arterial needle should be placed nearest the anastomosis but at least 1.5-2˝ away from the site. A thorough assessment must be done to ensure that the needle is placed at least 1.5-2˝ away from the anastomotic connection to avoid cannulating this site. The arterial needle may point toward the hand or the heart, or either antegrade or retrograde. The venous needle should be located so that the point is at least 5 cm proximal to the arterial needle. It should always be directed toward the heart or in the direction of blood flow (antegrade).

The AV fistula and AV graft are cannulated at different angles. Angle of entry depends on the depth of the access: the deeper the access, the steeper the angle required. The angle of insertion ranges from 20 to 45 degrees.

Cannulation of a new AV fistula must be approached with extreme care. The vessel is very fragile in its early stages and prone to infiltrations. Preferably, only the most seasoned employees will initially access the fistula. Many facilities have adopted cannulation protocols in which the AV fistula is initially cannulated with only one needle (arterial outflow) and the venous return is through the central venous catheter for the first few treatments. Smaller-gauge needles as well as lower blood flow rates are also used for the first few treatments. The temporary catheter is usually removed when cannulation with two needles has been successfully performed over consecutive treatments.

Why is the positioning of the needles important?

The manner in which needles are placed will affect the long-term patency rate of the access. Care must be taken to avoid placing the needles in the same general area at each treatment. Over time, this will cause the wall of the vessels to thin and aneurysms will develop. Aneurysms are weakened areas of the vessel that actually dilate, enlarge, and balloon out. These areas are generally avoided as sites for cannulation. Needle sites should be rotated at each treatment and it is best to use the entire length of the access to get maximum surface area and development.

Placing the arterial needle near the anastomosis will achieve the best blood flow. The tip should not be closer than 1.5-2˝ from the anastomosis. Placement of the needle toward or away from the anastomosis depends on the optimal blood flow. Usual practice is to place the arterial needle point with the flow. Finally, spacing the needles at least 1˝ apart minimizes recirculation of blood that may result in an inadequate dialysis.

What conditions favor recirculation?

A fistula with a low blood flow rate leads to recirculation. The low flow can be caused by stenosis at the arterial end or, more commonly, by stenosis at the venous end. It is usually associated with an increase in venous pressure and, if the recirculation is sufficiently great, may result in the “black blood” syndrome.

What is the “black blood” syndrome?

When recirculation is severe, the blood becomes acidotic, and the red blood cells cannot carry oxygen. The pH of this blood is usually below 7, and the blood appears very dark.

How is occurrence of recirculation determined?

The concentration of any substance (urea or creatinine) should be the same in the arterial bloodline going into the dialyzer as in the patient’s systemic circulation. If the arterial concentration is less, the substance may be diluted by venous blood returning from the dialyzer so that some blood is going through the dialyzer more than once without returning to the systemic circulation. To calculate the percentage recirculation, three blood samples are obtained simultaneously. One represents the systemic circulation (S), or peripheral blood. Also necessary are specimens from the inflow line just before it enters the dialyzer (arterial blood, or A) and from the outflow line just after it leaves the dialyzer (venous blood, or V). Calculate the estimated recirculation as follows:

image

Example: Where S = 100, A = 90, and V = 20

image

Given a good fistula and use of two well-placed needles, the percentage of recirculation should be less than 10%. With double lumen catheters, recirculation commonly may be as high as 15%. Recirculation greater than 15% is excessive and should be investigated and corrected.

How is the peripheral blood sample obtained?

Peripheral veins are no longer used. The peripheral sample is obtained from the arterial line before the dialyzer, using the slow-stop flow technique for measuring access recirculation (Box 12-1).

image

Box 12-1 Protocol for Urea-based Measurement of Recirculation

Perform test after approximately 30 minutes of treatment and after turning off ultrafiltration.

1. Draw arterial (A) and venous (V) line samples.

2. Immediately reduce blood flow rate (BFR) to 120 mL/min.

3. Turn blood pump off exactly 10 seconds after reducing BFR.

4. Clamp arterial line immediately above sampling port.

5. Draw systemic arterial sample (S) from arterial line port.

6. Unclamp line and resume dialysis.

7. Measure blood urea nitrogen (BUN) in A, V, and S samples and calculate percent recirculation (R).

Recirculation Formula:

R = (S – A) / (S – V) × 100

From National Kidney Foundation Guidelines for Vascular Access, 2001.

image

What other techniques are available to measure access recirculation?

Newer techniques allowing for real-time measurement of access recirculation include the HD01 hemodialysis monitoring system (Transonic Systems, Ithaca, NY) and the Crit-Line instrument (In-Line Diagnostics Corporation, Farmington, UT).

How do these devices measure recirculation?

The Transonic Systems device uses flow dilution sensors placed on the arterial and venous bloodlines. Saline is injected through the venous drip chamber or through a port in the venous tubing. A laptop computer preloaded with dilution measurement software measures the volume flow through the bloodlines and the changes in the ultrasound signal velocity and calculates the percentage of recirculation. The Transonic Systems device also measures cardiac output.

The In-Line Diagnostics device uses a disposable blood chamber placed between the end of the arterial blood tubing and the arterial port of the dialyzer. An optical sensor is placed on the blood chamber and is attached to the device. The device calculates the percentage of recirculation based on changes in hematocrit following microinfusions of saline. This In-Line Diagnostics device also measures hematocrit, oxygen saturation, and blood volume change (Fig. 12-8, A and B). (See Chapter 13 for further discussion of the Crit-Line instrument.)

image

Figure 12-8 A, Proper arterial bolus. The peak height should be at least 15%. B, Proper venous bolus. The screen now displays a smaller bolus. If recirculation occurs, Crit-Line will calculate the area under the curve.

(Crit-Line manufactured by In-Line Diagnostics Corporation, Farmington, UT.)

Does the patient require an anesthetic before needle placement?

Some patients, particularly those with newer or never used accesses, experience discomfort with needle insertion. An anesthetic, such as lidocaine 1% (Xylocaine), may be used intradermally. The lidocaine is administered at a 15-degree angle just under the top tissue of the skin. You must always aspirate before giving lidocaine to make sure that you are not in a blood vessel. If you do withdraw blood with aspiration, you must discard that syringe and begin again. With repeated cannulations, scar tissue develops and the patient experiences less pain with cannulation. EMLA cream, a topical anesthetic, is another option for patients who require some type of anesthetic before needle insertion. The patient applies this cream before arriving for treatment. The cream must be removed before the patient is cannulated.

Can anything be done to cause the veins of an arm with an arteriovenous fistula to enlarge more quickly?

Nothing should be attempted for four or five days after the fistula is created. After that period, the physician will recommend a variety of isometric exercises to help the AV fistula mature after placement. Hand exercises, such as squeezing a rubber ball, fingertip touches, and hammer and bicep curls may help. The physician may or may not recommend a light tourniquet be used with any of these exercise. Warm compresses or soaks several times a day may speed up the venous distention.

What care is required for the fistula arm between dialyses?

An arm with a new fistula should be elevated on a pillow between treatments to decrease swelling in the extremity. It is important to maintain adequate pressure, either by hand or with a light pressure dressing over the puncture sites, for 10 to 20 minutes after the needles are removed. Most patients still have some heparin effect at the end of dialysis, and bleeding can be a serious problem. Even oozing under the skin can cause hematoma and scar formation, which eventually make the vessel difficult to use. After the bleeding has stopped, bandages are sufficient to protect the puncture sites. If bleeding continues from the puncture site more than 20 minutes after removal of the needles, the heparin dose should be evaluated and readjusted. Daily cleaning of the fistula arm with soap is advised. Some people like to use an ointment to keep the skin soft.

What is the buttonhole technique of cannulation?

The buttonhole technique, or constant site technique, used to cannulate AV fistulas has been used on a limited basis for approximately 25 years but has now grown in popularity, particularly for self-care patients. In the buttonhole technique of cannulation, the access is cannulated in exactly the same spot and angle of insertion from treatment to treatment. A tunnel tract of scar tissue eventually develops, which then allows the needle to be easily inserted into the same channel with each cannulation. This type of cannulation is associated with less pain and fewer incidents of infiltrations. This method is a useful alternative for the patient who self-cannulates or for the patient dialyzing at home. Medisystems offers a buttonhole needle set with antistick dull bevels. This blunt needle can be used after the buttonhole develops. The antistick dull bevel prevents cutting of the tissue surrounding the scar tissue tunnel track. The 2006 KDOQI Clinical Practice Guidelines and Recommendations suggest that patients who are capable and who have a well-positioned access be encouraged to self-cannulate with the preferred method of buttonhole technique.

What is the hero vascular access device?

The HeRO Vascular Access Device is a vascular access option for patients who have limited peripheral access sites to use for fistulas or grafts due to central venous stenosis or superior vena cava occlusion and who have become catheter dependent. The HeRO access is a subcutaneous graft with central outflow requiring no venous anastomosis, thus able to bypass any stenosis of the central veins. The device is implanted surgically and can be used as a long-term vascular access. The HeRO device consists of two components: a venous outflow component and an arterial graft component. The venous outflow component is inserted directly into the internal jugular vein with the tip positioned in the right atrium. The arterial graft component consists of a 6-mm PTFE upper arm graft that has a titanium connector on its end. The arm graft is then joined to the outflow component with the titanium connector. Blood will begin flowing from the artery through the graft and outflow component and to the heart.

Are there special techniques to cannulate the hero device?

The HeRO device is approved by the Food and Drug Administration as a graft and can be treated as such. KDOQI guidelines for cannulation should be followed. The HeRO device is cannulated like a conventional upper arm graft. Cannulation should be deferred until any swelling has subsided. Standard fistula needles should be used and your facility algorithm protocol may be followed. Cannulation should take place at a 45-degree angle and cannulation sites should be rotated. The thrill may be less prominent than with a conventional graft due to the absence of a venous anatomosis.

Single-needle technique

Kopp developed the single-needle device in 1970 for use with the internal AV fistula and the single lumen catheter. Single-needle dialysis has not been practiced in the U. S. for many years.

What is the principle of operation of single-needle dialysis?

A Y-type hub is connected to a single needle or catheter. As blood is drawn into the dialyzer, a clamp simultaneously occludes the outflow line. Then the inflow line is occluded while the outflow is released to return blood from the dialyzer to the patient. In Europe, two blood pumps are used: one for the arterial bloodline and one for the venous bloodline. High-flux dialysis, with its need for high blood flow rates, and the popularity of double lumen catheters has minimized the use of single-needle devices outside of Europe.

Are temporary vascular accesses used in dialysis?

Dialysis catheters are used in the management of the hemodialysis patient in certain situations: (1) as an access for acute dialysis, (2) in the patient who is imminently awaiting a kidney transplant, (3) when allowing for maturation of the AV access, (4) as a permanent access when the availability of vessels is limited for a permanent internal access, (5) for patients undergoing plasmapheresis, (6) for patients receiving continuous venovenous renal replacement therapy, and (7) for patients on peritoneal dialysis requiring temporary hemodialysis because of peritonitis. It should be noted that prolonged use of subclavian vein catheters would result in subclavian vein stenosis.

The NKF KDOQI guidelines suggest that only 10% of chronic maintenance hemodialysis patients should have catheters as their permanent vascular access. The use of central venous catheters as a permanent access for hemodialysis is not the best choice, but is an alternative in access selection. Patients with CKD stage 4 should be informed of the risks and benefits associated with catheters and strongly encouraged to opt for the placement of a permanent vascular access, such as a fistula, well before the need to initiate dialysis.

Which veins are used for temporary access?

The subclavian, internal jugular, and femoral veins are used for temporary access (Fig. 12-9, A). Vessels are accessed using double lumen catheters (Fig. 12-9, B).

image

Figure 12-9 A, Temporary vascular access using subclavian double lumen venous catheter. B, Double lumen temporary catheter.

(Courtesy MEDCOMP Corp., Harleysville, PA)

What are the contraindications for using subclavian or jugular catheters?

Subclavian or jugular catheters should not be used on the following patients:

• Patients with acute respiratory distress who cannot be positioned either supine or in the Trendelenburg position

• Patients with known subclavian vein stenosis

How is the subclavian or jugular catheter placed?

The physician uses strict aseptic technique. The patient lies supine in the Trendelenburg position with the head turned to the opposite side. The skin around the area is cleaned and covered with sterile drapes. With local anesthesia, the catheter is inserted and sutured into place. Verification of correct placement by chest x-ray examination is required before the catheter may be used.

What complications can occur with subclavian or jugular catheters?

Immediately after the insertion of the catheter, pneumothorax, hemothorax, or air embolism may occur. Bleeding is another complication if the artery is inadvertently punctured during insertion.

What are indications for using a femoral catheter?

A femoral catheter is used in the following types of cases:

• The acutely ill patient confined to bed

• The CKD patient whose access is clotted but who requires urgent dialysis

• Patients receiving continuous renal replacement therapy

• Patients who may have subclavian vein stenosis

What complications can occur with femoral catheters?

Although femoral catheters are not widely used, some complications that might occur as a result of their placement are retroperitoneal hemorrhage from puncture of the vein during insertion, bleeding at the insertion site, hematoma, and infection.

Is special nursing management necessary with these catheters?

The use of aseptic technique when initiating and terminating dialysis is of utmost importance. All catheters are prone to infection. The caps and ports should be wrapped in a 4 × 4 dressing soaked in an approved disinfectant before initiating or terminating dialysis. It is of the utmost importance that the caregiver be aware of the type of catheter the patient has to provide the appropriate site care. The manufacturer’s recommendations for disinfectant must be followed to maintain the integrity of the catheter. The exit site should be cleaned with the facility’s recommended disinfectant after every treatment, and a sterile dressing should be applied. The appearance of the exit site, especially if there is redness or drainage, must be documented.

Heparin is instilled into the port(s) of the catheter following dialysis. This heparin must be removed before the next dialysis to avoid the patient’s receiving a bolus. Do not attempt to instill saline into a clotted catheter; this might force the clot into the vascular system.

What technical problems can occur with these catheters, and how are they best combated?

The main problem experienced with catheters, poor blood flow, can be corrected with the following measures:

• Lowering the patient’s head or turning the patient’s head to the side opposite the catheter, if using a subclavian or jugular vein

• Keeping sterile dressing intact until the end of the treatment

• Applying external pressure to the exit site

• Rotating the catheter shaft 180 degrees if the catheter has wings and with a physician order

• Reversing the lines, using the arterial port for venous return (as a last resort)

The other difficulty that commonly occurs is clotting. Proper heparinization of the catheter after dialysis, according to the manufacturer’s directions, will help to alleviate this problem. Fibrinolytic agents may be prescribed if the catheter is clotted or to prevent clotting.

Are double lumen catheters available for permanent use?

The permanent catheter is becoming more widely used. A silicone rubber catheter is inserted intraoperatively. The catheter has a subcutaneous Dacron graft that impedes infection. These catheters are usually placed in the internal jugular vein and a subcutaneous tunnel is created that allows the catheter to exit through the chest wall (Fig. 12-10, A). Permanent catheters are also placed in the subclavian, mammary, and femoral veins. Another type of permanent catheter is a Tesio catheter (Fig. 12-10, B), which uses two single lumen catheters placed side by side in the same vein. This allows for customized catheter placement with increased blood flow rate. Permanent catheters are useful in pediatric patients whose small arteries and veins prohibit placement of an AV graft.

image

Figure 12-10 A, Internal jugular permanent vascular access using the Tesio catheter. B, Permanent catheter modified by Tesio. (

Courtesy MEDCOMP Corp., Harleysville, PA)

What continuous quality improvement issues are important with vascular access?

The greatest concern surrounds issues of assessment, clotting, and venous pressure. In assessment, documentation on the treatment record should include absence or presence of a bruit and thrill with fistulas and grafts. A decrease in thrill may denote graft stenosis and impending graft clotting. Note the appearance of the access, including redness, swelling, and any drainage. It is important to document the ease or difficulty of cannulation.

Second, adequate blood flow is important to prevent clotting of the lines and dialyzer, resulting in unnecessary loss of blood. Clotting occurs most often with catheters. Increased bleeding from the needle sites after dialysis may indicate venous stenosis.

Finally, increasing venous pressure is often a sign of stenosis. Venous pressure is measured immediately after initiation of hemodialysis at a blood flow rate of 200 mL/min. With 16-gauge needles, the venous pressure should be <150 mm Hg. With 15-gauge needles, the venous pressure should be <100 mm Hg.

What are the kdoqi guidelines for vascular access?

The KDOQI guidelines, formulated by the NKF in 1997, advocate both early placement of an AV fistula predialysis and avoidance of temporary catheters. The guidelines also emphasize that the AV fistula should be the first access attempt. KDOQI guidelines also suggest that the percentage of AV fistulas should be increased. To follow these guidelines, each dialysis unit should have an aggressive continuous quality improvement access program. Copies of the KDOQI vascular access guidelines can be obtained from the NKF. (See page 365 for additional information on NKF KDOQI.)

In summary, when the Scribner shunt was developed in 1960, the impact it would have on prolonging the life of the patient with CKD was unforeseen. More than 326,000 patients in the U.S. are on maintenance hemodialysis, and there are many in acute renal failure whose care is facilitated by technologic advances in vascular access. Experimentation with new devices is ongoing. The future portends innovations that will enhance both the care and the quality of life of the patient with renal failure.



If you find an error or have any questions, please email us at admin@doctorlib.org. Thank you!