Introduction
To perform hemodialysis, access to the circulatory system is essential, usually achieved by surgically creating an arteriovenous fistula (AVF) or using a prosthetic bridge graft (PBG).
Internal vascular accesses are generally preferred over external options like tunneled dialysis catheters (TDC) due to their lower risk of complications such as infection and clotting However, unlike external access, internal access requires a maturation period before it can be utilized for dialysis; typically, a native AV fistula needs three to four months to develop, while a graft requires at least three weeks.
When dialysis is necessary, an external access method, such as a tunneled dialysis catheter, can be utilized for immediate treatment, while an internal access method is recommended for future use Ideally, internal access should be established well in advance to ensure readiness when dialysis is required According to NKF-K/DOQI guidelines, patients should be referred for arteriovenous fistula (AVF) placement when serum creatinine exceeds 4 mg/dl, creatinine clearance drops below 25 cc/min, or within a year of expected dialysis need In cases where patients lack suitable blood vessels for AVF creation, a peritoneal dialysis catheter may be considered as an alternative.
Vascular access is essential for patients undergoing hemodialysis, often regarded as their "life line." Without this access, life-sustaining hemodialysis treatments cannot occur While alternatives like peritoneal dialysis and transplantation exist, not all patients qualify for these options, making vascular access crucial for effective hemodialysis.
Vascular access complications are the primary reason for hospitalizations among hemodialysis patients, with studies indicating an average hospital stay of 5.8 days and costs ranging from $6,228 to $7,871 per patient annually In 1996, projections suggested that the total annual cost of morbidity associated with vascular access could surpass one billion dollars.
Preventing the development of complications by providing conscientious, high quality care along with early problem identification can reduce morbidity, improve quality of life, and
What are the major types of vascular access?
What are the advantages of an internal vascular access?
How soon can an AVF be used for dialysis? How about a PBG?
Determining the appropriate time to refer a patient for arteriovenous fistula (AVF) placement is crucial for improving outcomes in the dialysis population and reducing healthcare costs Early detection of potential vascular access issues can be achieved through regular physical examinations, allowing for timely intervention and better management of patient care.
Internal access types
The primary objective of an arteriovenous fistula (AVF) or a prosthetic graft (PBG) is to provide reliable access to the circulatory system for hemodialysis This vascular access is established through a surgical procedure, and it is essential to conduct venous mapping for all patients prior to their first access placement This assessment evaluates the patient's blood vessels to identify the most suitable option—either a fistula or graft—and the optimal location for its placement Typically, the forearm of the non-dominant arm is preferred; however, the quality and location of the blood vessels are critical factors in determining the best site for the arteriovenous access.
• Radial artery and cephalic vein
• Brachial artery and cephalic vein
• Brachial artery and basilic vein
An AV fistula, which utilizes the patient's own natural blood vessels, is the preferred access method due to its reliance on high-quality, closely located arteries and veins In contrast, a graft can connect vessels that are farther apart or compensate for vessels of lower quality.
An AV fistula, also known as a native fistula, is a surgical connection created between a patient's own blood vessels, typically in the forearm This procedure involves joining the radial artery with the adjacent cephalic vein through either an end-to-side or end-to-end method The connection point of these vessels is referred to as the anastomosis.
Blood from the artery will flow through the anastomosis into the vein used for the arteriovenous fistula (AVF) The higher flow and pressure in the artery compared to the vein will lead to the enlargement of the vein and thickening of its walls This physiological adaptation is essential for the AVF's functionality.
What are the 3 most common sites for the creation of an AVF?
What are the major advantages of an AVF?
Anastomosis, also known as maturation, is the process by which a vein develops the capacity to accommodate large gauge needles for dialysis, delivering essential blood flow of 500 to 600 cc/mm for effective treatment During this maturation phase, branches of the access vein may also develop and can be cannulated for dialysis; however, some branches may hinder access development and require ligation Typically, an arteriovenous (AV) fistula takes about 1 to 4 months to mature, with recommendations to avoid usage for at least one month, and ideally 3 to 4 months, as per the NKF-K/DOQI Clinical Practice Guidelines for Vascular Access.
Figure 1 - The vascular anatomy of the arm
What is the process of maturation as it relates to an AVF?
AVF be used for dialysis?
What are the major veins of the arm?
What are the major arteries?
Figure 2 – Radial-cephalic arteriovenous fistula, end to side anastomosis
Figure 3 – Brachial-cephalic fistula Figure 4 – Brachial-basilic fistula
For effective dialysis treatment, the internal blood flow through the access should exceed 500 to 600 cc/min Insufficient blood flow can lead to increased access complications, higher failure rates, recirculation issues, and inadequate dialysis therapy.
In venous access procedures, only the vein and its branches are cannulated at two distinct sites for the arterial and venous needles This approach avoids cannulating the artery, which carries a higher flow and pressure, thereby reducing the risk of complications and access failure.
Describe the configuration of the three major types of
The condition and location of a patient's natural blood vessels can sometimes hinder the creation of an arteriovenous (AV) fistula, particularly if the vessels are too deep, tortuous, or small due to underlying issues like peripheral vascular disease In cases where the native blood vessels are inadequate, a synthetic material can be used as a substitute, known as a prosthetic bridge graft.
Grafts are surgically implanted to create a conduit that connects an artery to a vein, allowing blood to flow from the artery through the graft and into the vein For dialysis, needles are inserted into the graft rather than directly into the blood vessel Typically, a prosthetic bridge graft (PBG) is placed in the forearm or upper arm, but if these areas are not viable due to prior surgeries or failed access attempts, grafts may be positioned in the thigh.
Grafts are placed in either a straight or loop configuration Possible locations include:
• Radial artery and cephalic or basilic vein (straight)
• Brachial artery and cephalic or basilic vein (loop)
• Brachial artery and axillary vein or subclavian vein
• Femoral artery and femoral or saphenous vein
Why do patients receive a PBG rather than an
What are the most commonly used locations for PBG’s?
Figure 8 – Upper arm graft Figure 9 – Thigh graft
The configuration of grafts relative to the arterial side is crucial for proper dialysis function, as standard configurations are essential for optimal blood flow When surgeons mistakenly reverse the graft, it creates confusion in dialysis facilities, making it vital for staff to understand the direction of blood flow Incorrect needle placement can result in significant recirculation issues, highlighting the importance of knowing which side of the access connects to the artery and which connects to the vein for effective treatment.
In an arteriovenous graft (AVG), the detection of flow direction reveals that when the graft is occluded, the upstream arterial section (A) maintains a pulsatile flow, while the downstream venous section (V) exhibits a non-pulsatile flow.
To determine the direction of blood flow in a graft, a physical examination can be performed by compressing the graft at its midpoint and assessing the pulse on either side A strong pulse indicates arterial flow, while a weak or absent pulse suggests venous flow This critical information should be documented in the patient's medical record and chart for future reference Additionally, it is essential for patients to be aware of the orientation of their access, marked by the thumb blue.
To ensure optimal healing, it is recommended to allow a graft, excluding Vectra® grafts, to stabilize for a minimum of two weeks, ideally three to six weeks, before use, as outlined in the NKF-K/DOQI Clinical Practice Guidelines for Vascular Access: Update 2000 This healing period is crucial for the surrounding tissue to integrate with the graft, ensuring stability, and for the sutured connections and incision sites to properly heal.
Describe the configurations of the 4 most commonly used PBG’s
What will happen if the position of the dialysis needles is reversed?
How early can a PGB be used for dialysis?
Describe the technique used to determine the direction of blood flow in a graft.
Pre Dialysis Assessment
Before each dialysis session, it is essential to conduct a brief physical examination of the patient's access site Additionally, healthcare providers should inquire about any unusual or abnormal occurrences related to the access that may have occurred since the last treatment.
Any abnormal findings observed and/or reported by the patient should be documented on the treatment sheet and reported to the physician
A compromise in the skin's integrity can permit normally harmless bacteria, known as normal bacterial flora, to infiltrate deeper tissues or the bloodstream While these bacteria are safe when confined to the skin's surface, their entry into the body can lead to severe complications, including the risk of systemic infections that may be life-threatening.
Before needle insertion, it is essential to inspect the skin surrounding the access site Previous needle sites should be exposed to air, free of dressings, and showing signs of proper healing, which may include scabs that should not be disturbed Additionally, the skin must be clean and intact, free from lesions, rashes, or any drainage.
The presence of drainage generally indicates an infectious process
What questions should be asked of the patient concerning their access in the pre-dialysis assessment?
Can normal skin bacteria cause problems? If so what types of problems?
Describe the expected appearance of the skin overlying the patient’s access site?
Question the Patient About the Following:
• Change in thrill or pulse
Document the color and quantity of drainage on the treatment sheet and report it to the nurse, who should inquire about the onset of the drainage Prior to access preparation and needle insertion, the nurse must evaluate this finding and obtain a culture of the drainage before cleansing the access site, ensuring a medical order is in place for this test Additionally, the nurse should inform the physician about the drainage.
The access can only be cannulated in areas that are not in close proximity to the site of suspected infection
The skin over the access area of the extremity should match the condition of the opposite extremity, typically feeling warm due to increased blood flow However, if the area feels hot, it may signal inflammation or infection Conversely, cool or cold extremities, particularly in the fingers, could indicate ischemia, which is associated with reduced blood supply to that region.
Normal skin tones should be assessed by comparing them to the opposite extremity, ensuring there is no discoloration present The skin should neither exhibit redness nor appear overly pale, indicating a healthy and balanced complexion.
Observation of the Skin Includes:
• Skin is clean and intact - no evidence of cuts, scratches, excoriations, rashes
• Presence of drainage - note onset, color, and amount; nurse to culture and notify MD
• Healing of previous needle insertion sites - do not disturb scabs if present
• Presence of skin erosion over the vessel(s) of the access
List the important points to note in examining the skin in the pre-dialysis evaluation
Describe the normal temperature of the access area and extremity
Observation for Temperature and Color Includes:
• Skin over access is warm – not hot
• Fingers are same as opposite hand – not cool or cold
• Normal skin tones – no discoloration, bruising
What is the significance of drainage and what should be done when it is found?
The normal coloration of the access area and extremity should appear healthy and free from any discoloration Signs of bruising or ecchymosis, including purple, black, blue, yellow, or green hues, should not be present.
In the initial weeks after receiving a new prosthetic bridge graft, patients may notice a localized red flare over the graft site, which is not accompanied by swelling or infection This redness is likely a skin reaction to the graft and typically resolves on its own over time However, it is important for patients to report any persistent redness to their physician for further evaluation.
Figure 11 – Appearance of arm with red flare Note that flare corresponds to the course of the graft There is no other redness This occurs early after placement
When assessing a patient, it's crucial to ensure that there is no pain in the access site or the affected limb Patients should be asked about any pain they may experience If pain is reported, gather detailed information regarding its onset, type (sharp, dull, throbbing, etc.), frequency, duration, and any triggering events This information must be documented in the medical record and communicated to the physician for further evaluation.
Numbness should not be present It can indicate nerve damage or possibly decreased blood flow to the affected area The presence of
What is the significance of numbness associated with the access? numbness should be reported to the physician for further evaluation
Swelling associated with a new access is sometimes present This is secondary to the trauma of surgery Post-surgical swelling is temporary and can be decreased by
A patient with subclavian occlusion often presents with a significantly swollen arm To promote improved venous return, it is essential to elevate the affected limb above heart level Persistent swelling, particularly if it develops later, may indicate central venous occlusion in the limb Continuous swelling requires careful monitoring, and measuring the arm's circumference with a tape measure is recommended to track any changes.
What is the significance of early swelling of the access extremity? What about late or continuous swelling ?
Observations for Pain / Numbness / Swelling include:
• Presence of pain - note onset, type, frequency, duration, precipitating events
• Presence of numbness - indicates nerve involvement and/or disturbance to blood flow
Swelling may occur due to recent surgery or central venous occlusion and requires careful monitoring It is essential to measure the circumference of the affected area periodically, ideally weekly or more frequently if changes are observed, and document these measurements in the patient’s chart Any increase in circumference should be reported to the physician, as severe cases may necessitate the closure of the patient’s graft.
Detection of complications in grafts
PBGs are associated with a higher frequency of complications compared to fistulae, with major issues including venous stenosis, thrombosis, infection, pseudo-aneurysm formation, and ischemia A thorough physical examination can provide significant insights into these complications.
Stenosis refers to the narrowing or constriction of an orifice or passage, which can occur in dialysis access vessels over time As the lumen of a blood vessel or graft becomes narrowed due to the thickening of its inner lining, a condition known as neointimal hyperplasia develops This phenomenon is commonly referred to as venous stenosis.
Graft stenosis typically occurs at the venous anastomosis at the graft's venous end, leading to issues with venous outflow This condition can also develop within the graft itself and in the veins that drain the graft.
• Arterial inlet stenosis is much less common It can be identified by the inability to achieve the targeted flow rate and an elevated negative pre pump arterial pressure
Progressive stenosis results in a gradual reduction of blood flow through the access point, ultimately causing clot formation within the vessel or graft This condition is the leading cause of access failure in dialysis, highlighting stenosis as the main functional defect affecting dialysis access.
Before inserting a needle, it's essential to palpate and auscultate the access site with a stethoscope to assess blood flow Palpation provides key insights into two critical characteristics of the access site's blood flow.
What are the three characteristics of the access that are examined when evaluating blood flow in an access?
Define the pulse, thrill and bruit
What are the major complications associated with a PBG?
What is the most common site for stenosis to occur with a PBG?
What are the consequences of venous stenosis?
Palpation – Pulse - beat of the heart
Thrill refers to the "buzzing" sensation experienced due to turbulence in blood flow, while auscultation reveals a bruit, which is a "swooshing" sound also caused by this turbulence The pulse represents the sudden pressure change or shock wave generated by the heart's beat Together, the thrill and bruit are key indicators in the physical examination of vascular access, highlighting the importance of these sensations and sounds in assessing blood flow dynamics.
Changes in pulse, thrill, or bruit can signal alterations in blood flow through the access site A prevalent issue affecting the PBG is venous stenosis, often resulting from narrowing at the venous anastomosis or within the veins draining the PBG This condition can lead to serious complications, with recurrent thrombosis of the PBG being the most significant concern.
Figure 13 – A is the cephalic vein, B is the basilic vein, D is the access graft and C is a stenosis at the anastomosis
A strong pulse or vigorous thrill is frequently mistaken for a sign of good access and excellent flow, rather than indicating a pathological lesion In contrast, a properly functioning PBG features a soft, easily compressible pulse, with a continuous thrill that is only palpable at the arterial anastomosis without compression Additionally, it produces a low-pitched bruit that is continuous and includes both systolic and diastolic components.
The progression of significant venous stenosis leads to increased upstream resistance, resulting in heightened pulse force within the graft located below the stenosis As this resistance escalates, the pulse may develop a pounding quality, commonly known as a "water-hammer" pulse.
Narrowing within the blood-flow channel causes turbulence Turbulent blood flow results in a palpable thrill The greater the turbulence, the stronger the thrill A stenotic lesion results in
What does a change in the pulse, thrill or bruit suggest?
Describe the character of the pulse, thrill and bruit of a normal access graft
The character of the pulse, thrill, and bruit in a graft with venous stenosis is marked by localized turbulence and a distinct thrill By palpating the venous anastomosis and the veins draining the graft, clinicians can identify a stenotic site through the presence of a thrill These abnormal thrills are typically not continuous and are observed during systole only.
Abnormalities can range from completely normal to severe stenosis, with intermediate changes observed in lesser degrees of stenosis Notably, significant stenosis exhibits characteristics similar to those of a severe lesion.
Venous stenosis alters the characteristics of the bruit heard over a graft, with increasing stenosis leading to a higher pitch and shorter duration of the diastolic component In cases of severe stenosis, the bruit becomes high-pitched and predominantly features a brief systolic component.
Assessing the PBG and draining veins helps identify pulse characteristics, thrill intensity, and bruit duration, which are crucial for detecting grafts at risk of thrombosis due to venous stenosis The severity of the stenotic lesion influences these changes, making regular examination of access during each dialysis session essential for recognizing subtle alterations This proactive approach facilitates early detection of potential complications.
Physical Findings Of Venous Stenosis
Thrill Only at the arterial anastomosis At site of stenotic
Pulse Soft, easily compressible Water-hammer
Bruit Low pitch High pitched
Continuous Discontinuous Diastolic and systolic Systolic only
Graft occlusion is a crucial technique used to detect recirculation When the recirculating graft is occluded, venous pressure rapidly increases, triggering an alarm and halting the blood pump In this scenario, there may be a slight decrease in arterial pressure.
Venous stenosis can lead to recirculation, which occurs when the blood flow in an arteriovenous graft (AVG) falls below the pump's requirements, causing varying degrees of flow reversal between the needles This issue can often be identified through a physical examination by occluding the graft between the two needles during dialysis and monitoring the venous and arterial pressure gauges A closed hemostat is more effective than a finger for this occlusion In a normal AVG, pressure readings remain stable; however, if recirculation is due to venous stenosis, venous pressure will rise as the occlusion limits the lower resistance pathway This may trigger an alarm as pressure limits are exceeded Conversely, if recirculation stems from arterial stenosis, a significant drop in arterial pressure occurs, indicating insufficient blood flow Proper needle placement is crucial for this examination, as needles positioned too closely may hinder accurate assessment, and incorrect needle placement can lead to significant recirculation.
What happens to the pressure monitors when the graft is occluded between the two needles normally? When there is recirculation due to outflow obstruction?
When it is due to poor inflow?
Detection of complications in fistulae
Complications related to arteriovenous fistulae (AVF) are less frequent than those associated with prosthetic blood grafts (PBGs), but they can still arise Physical examinations play a crucial role in detecting these complications and identifying their underlying causes While there is significant overlap in the types of issues that can occur, complications of fistulas can be effectively categorized into those leading to early failure and those resulting in late failure.
Early failures of fistulae, defined as those that do not develop properly or fail within the first three months of use, can often be attributed to two primary causes: juxta-anastomotic venous stenosis and the presence of accessory veins, which are side branches of the cephalic vein These issues can typically be diagnosed through a thorough physical examination, provided that patients have been adequately evaluated prior to the placement of the fistula.
Figure 16 – Juxta-anastomotic stenosis A – radial artery, B – stenotic lesion, C – Cephalic vein fistula
What are the primary causes of early fistula failure?
Venous stenosis frequently occurs at the segment of the vein adjacent to the anastomosis in arteriovenous fistulas (AVFs), primarily due to surgical manipulation during fistula creation This manipulation can lead to stretching, torsion, or other trauma to the vein, resulting in an obstruction of fistula inflow Consequently, this early lesion can lead to early access failure, impacting the effectiveness of the AVF.
The diagnosis of juxta-anastomotic stenosis can be effectively made through palpation of the anastomosis and distal vein, where a prominent thrill is typically felt at the anastomosis In normal conditions, the pulse is soft and easily compressible; however, stenosis presents a water-hammer pulse at the anastomosis, with the thrill being present only during systole As one palpates the vein upward from the anastomosis, the pulse abruptly diminishes upon encountering the stenosis, revealing a weak pulse and poorly developed vein above this point The stenosis is often characterized by a noticeable reduction in the vein's size, resembling a shelf, making the underlying cause of inadequate fistula development clear once these physical signs are identified.
The physical examination of juxta-anastomotic stenosis reveals a strong pulse and thrill at the anastomosis site, indicated in Figure 17A and B However, this pulsation diminishes as one moves away from the fistula towards the lesion, as shown in Figure 17C.
As previously stated, the optimum venous anatomy for AVF development is a single cephalic vein stretching from the wrist to the antecubital space
The cephalic vein often has one or more accessory branches that divert blood flow from the main channel, which can reduce the blood flow to the section of the vein above these branches While this diversion can sometimes pose challenges for fistula maturation, it can also be beneficial by allowing the development of multiple venous access sites for cannulation.
What is meant by juxta- anastomotic stenosis?
Describe the examination procedure used to diagnose juxta- anastomotic stenosis
How do accessory veins cause problems leading less than optimum, the accessory vein(s) can result in early fistula failure
An upstream stenosis always aggravates the effects of an accessory vein
Figure 18 – Accessory vein A – Accessory branch coming off of the cephalic vein, B – cephalic vein
Accessory veins can often be identified through physical examination, either by their visibility or by palpating the fistula A palpable thrill over the arterial anastomosis typically disappears when the upstream fistula is manually occluded; if it persists, an accessory vein exists below the occlusion point By palpating the fistula beneath the occlusion, the location of the accessory vein can usually be determined by the thrill felt over its trunk As long as the main channel is identifiable for occlusion, the entire vein length can be assessed by progressively moving the occlusion point upward Ligation of these accessory veins redirects blood flow to the main channel, facilitating the development of a usable arteriovenous fistula (AVF).
Describe the technique used to detect the presence of an accessory vein by physical examination
During the physical examination of the accessory vein, it is observed that occlusion of the fistula at point A leads to the disappearance of the thrill at the anastomosis However, as the occlusion is shifted upward beyond the accessory vein to point B, the thrill persists even when the fistula is blocked.
Creating an arteriovenous fistula (AVF) through a side-to-side anastomosis can lead to abnormal venous flow patterns beyond the fistula, particularly over the back of the hand, which may contribute to early access failure This retrograde flow into the hand's veins can result in pain, swelling, and restricted movement.
Figure 20 - Venous hypertension in hand secondary to side-to-side anastomosis
A functional arteriovenous fistula (AVF) is linked to fewer complications compared to arteriovenous grafts, but issues can still arise Physical examinations are crucial for assessing these complications, which commonly include venous stenosis, thrombosis, ischemia, aneurysm formation, and infection.
Venous stenosis of the AVF:
The physical diagnosis of venous stenosis shares similarities with the assessment of arteriovenous fistulas (AVFs), with a few distinct differences A mature AVF typically presents a soft pulse and is easily compressible, collapsing partially when the extremity is elevated However, in cases of upstream stenosis, the AVF exhibits a more forceful pulsation and increased firmness, often enlarging to aneurysmal sizes When the extremity is elevated, the distal portion of the fistula remains distended while the proximal section collapses, aiding in the localization of the obstruction Additionally, there is a noticeable decrease in pulse strength and vessel caliber, along with changes in the characteristics of thrills and bruits, as previously noted in relation to the PBG.
Figure 21 - Physical examination of venous stenosis affecting an AVF
Aneurysms can develop in association with arteriovenous fistulas (AVFs), which tend to enlarge over time, sometimes reaching aneurysmal sizes A true aneurysm represents a localized bulging of the fistula, primarily caused by "one-site-itis," and can generally be prevented through site rotation This localized ballooning of the vein in an AVF is similar to a pseudoaneurysm seen with prosthetic bypass grafts (PBG), but unlike pseudoaneurysms, true aneurysms involve the vessel wall As blood flow in a normal AVF increases, the vein may continue to enlarge, becoming larger and more tortuous, potentially reaching aneurysmal proportions.
Describe the physical examination findings of a normal AVF; of one with stenosis
What is the difference between an aneurysm and a pseudoaneurysm?