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Vascular Access
Introduction
It is well established that dialysis cannot be provided without access; while this should not be taken for granted, such access can be achieved in a majority of cases. In contrast, the attainment and maintenance of a single reliable , long-lasting dialysis access with minimal complications continue to be challenging. Achievement of such access is associated with optimal patient clinical outcomes, superior quality of life, minimal costs, and is aligned with current guidelines. As such, a paradigm shift in thinking is needed and requires a focus on understanding the individual patient’s short- and long-term needs as a person with end-stage kidney disease (ESKD). Such a focus requires a multidisciplinary team approach where all kidney replacement therapy (KRT) options are understood and considered, in order for the patient to attain the potentially multiple , optimal access(es) at appropriate junctures in their ESKD lifetime. Such an approach thoughtfully considers patient transitions from one KRT modality to another, including conservative and palliative care, depending on individual needs. Clearly, the goals and abilities of a young man with glomerulonephritis as his cause of ESKD may differ from that of an elderly woman with multiple comorbidities and diabetes mellitus as her cause of ESKD; as such, these differences may be reflected in their access needs. This approach in considering the patient’s ESKD Life-Plan contrasts with a prior, more static approach where the goal was to attain an “ideal vascular access (VA)” for all patients for all time. Theoretically, such an ideal dialysis access would improve outcomes and limit costs, yet a “one-size-fits-all” approach may inadvertently have unintended negative consequences to both patients and health care systems. Thus, this chapter will discuss hemodialysis VA selection and review, the pros and cons, and unique clinical applications of each key hemodialysis VA, the arteriovenous fistula (AVF), arteriovenous graft (AVG), and central venous catheter (CVC). In doing so, the reader will be better equipped to consider these accesses in the context of what is appropriate for each patient at different phases of their own unique ESKD lifetime and help the patient develop an appropriate P-L-A-N. An individual P-L-A-N considers the P atient’s L ife-Plan and corresponding A ccess N eeds. Newer VAs on the horizon should be considered within the P-L-A-N. Further, while peritoneal dialysis (PD) is a clearly important KRT modality with its own access considerations, this chapter will not discuss PD access but will emphasize hemodialysis VA issues as they relate to a patient who may need to transfer to or from PD. Similarly, the importance of hemodialysis VA planning, creation, and maintenance in a patient transitioning from transplantation will be briefly discussed.
History of Vascular Access
The history of VA types reflects the changes in the ESKD population demographics and needs over time ( Table 15.1 ).
Table 15.1
Key Highlights in the History of Vascular Access
| Year | Patient Demographics and Needs | Important Influences | Key Vascular Access Development | Impact |
|---|---|---|---|---|
| 1945 | Kidney failure fatal without hemodialysis | HD was the only KRT available | Single arterial and venous cut-down for single HD | HD truly limited by access sites; short-term benefit |
| 1960 | Young patient (< 55 years old) with limited comorbidity | Ethics committee reviewed hemodialysis eligibility—provided at home | Scribner shunt | Maintenance HD became possible; infection and clotting were predominant issues |
| 1961 | Similar to 1960 | Rapid access for dialysis required | First subclavian vein access for dialysis | Subclavian catheter approach became the preferred method for temporary access for the following 2 decades |
| 1966 | Young patient (< 55 years old) with limited comorbidity | Individuals with diabetes were not eligible for dialysis | Cimino-Brescia fistula | Longer patency and reduced complications; Primary failure rate < 15% in original fistulas |
| 1970 | Patients with lack of or exhaustion of peripheral vessels; pediatric hemodialysis population with small vessels | A new method of access besides a shunt was required | Prosthetic graft | Thrombosis, infection remained a problem (as in shunts); aneurysms were linked with repeated cannulation |
| 1973 | Patients with diabetes and/or with greater comorbidities | Patients of all ages and etiologies of ESKD became eligible for dialysis | Prosthetic graft | Search for synthetic and biological materials that would improve patency and reduce complications began and is ongoing |
| 1993 | As earlier | Need for repeated catheter insertions in the same patient | Chronic central venous catheter (CVC) | Long-term HD with indwelling CVC possible |
| 1994 | As earlier + more home nocturnal dialysis patients | Uldall-Cook central venous catheter | Patients were able to provide dialysis of long duration overnight at home | |
| 2013 | As earlier | Increasingly older patients with greater comorbidities and living longer; exhaustion of vascular access options and central venous occlusion | HeRO graft; a hybrid between synthetic graft (arterial component) and CVC (venous outflow) | Bypasses the central occlusion with the CVC portion and allows peripheral access via graft portion. Combined risks of graft and CVC exist, diligent care required. |
| 2014 | As earlier | Endovascular AVF created percutaneously | Two devices (WavelinQ and Ellipsys) using novel techniques (magnetic catheters with radiofrequency energy and thermal resistance devices, respectively) for AVF creation | |
| 2016 | As above | Bioengineered vessels for AVG |
AVF , Arteriovenous fistula; AVG , arteriovenous graft; ESKD , end-stage kidney disease; HD , hemodialysis; KRT , kidney replacement therapy.
Multidisciplinary Approach to Vascular Access
Strategy and Roles
Key members of the multidisciplinary VA team include the nephrologist, surgeon, endovascular interventionalist, VA coordinator, cannulator (typically nurse or technician), and the patient and his/her support system. The planning, creation, and maintenance phases of the VA have different emphases, and as such, a different team member may “lead” where needed and appropriate. This requires mutual respect and trust among team members where clear, timely, and effective communication between health team members, the patients, and their support team are critical for successful access care. Examples of team members and roles are in Table 15.2 .
Table 15.2
Hemodialysis Vascular Access Team Members and Primary Roles
| Lead Team Member | Phase | Role | ||
|---|---|---|---|---|
| Vascular Access Coordinator | Nephrologist | Before VA created | Medical eligibility and timing of KRT modality and vascular access: evaluates comorbidities, functional status, life circumstances and goals; establishes ESKD Life-Plan with the patient | Patient and support system |
| Surgeon | Before VA created | Surgical eligibility of vascular access: vessel assessment +/- mapping | ||
| Surgeon or interventionalist | VA creation/ insertion |
Creates AV access ⁎ (fistula or graft) or inserts catheter | ||
| Nephrologist surgeon |
After VA creation | Assesses for development, complications, and readiness for use | ||
| Surgeon or interventionalist |
After VA creation | Facilitates or rectifies access issues in order to attain and/or maintain patency (e.g., AVF revision, AVG angioplasty, CVC exchange) | ||
| Cannulator nephrologist |
After VA creation | Assesses for readiness of cannulation Monitors for dialysis related complications |
AV , Arteriovenous; AVF , arteriovenous fistula; AVG , arteriovenous graft; CVC , central venous catheter; ESKD , end-stage kidney disease; HD , hemodialysis; KRT , kidney replacement therapy; VA , vascular access.
The VA coordinator facilitates communication and activities across all phases. The patient and his or her support system should be engaged to participate in informed decision making during all phases.
Education
Each member of the multidisciplinary team must coordinate educational efforts so that the patient receives nonconflicting and clear information about their chronic kidney disease (CKD), modality options, and the associated access. When patients and their family members are active participants in the decision-making process, adherence greatly improves. Optimal outcomes, such as initiating hemodialysis with a functioning access, are more likely when patients and their families receive high-quality, individualized CKD education. For example, in a nationwide study of > 3000 patients, patients who received education about VA had a twofold higher odds of having an AVF or AVG placed compared with a CVC. Patients who receive education about VA also had lower anxiety about receiving their AVF.
A key element to emphasize in the education of hemodialysis VA is to preserve veins by protecting them against venipunctures, intravenous lines, central venous catheterizations, and pacemaker insertions on the side of the planned future hemodialysis VA. For example, when venous access is required, only the dorsal aspect of the hand should be used. Peripherally inserted central catheters (“PICC lines”) should be avoided in patients with a potential future hemodialysis need and should be considered absolutely contraindicated in patients with stage 4–5 CKD. Patients already undergoing hemodialysis can have blood draws done during their hemodialysis session to preserve veins. Importantly, adequate arterial inflow is necessary for AVF maturation and prolonged patency. There has been a recent increase in the use of radial arteries as wrist access for cardiac interventions; such interventions may cause complications and damage arteries, limiting future lifelines for CKD patients. Alternate access, such as via femoral catheterization, should be used in CKD patients who may need VA in the future. Regardless of the CKD stage, each patient should have a vessel preservation plan. This emphasis on vessel preservation, as well as other important VA education, must be supported by health care workers and administration within the hospital or dialysis facility in order for it to be effective. Optimal patient outcomes and lowered costs will reinforce the effectiveness of comprehensive modality and access education.
Planning and Choice of Vascular Access
Dialysis access planning should start in CKD stage G4 (glomerular filtration rate [GFR] 15–30 mL/min) or in the “red” area of the risk map of CKD prognosis (Kidney Disease: Improving Global Outcomes [KDIGO] staging system ), when education about CKD and modalities of KRT should be discussed. The rate of decline of GFR over time is perhaps the best predictive guide to timely referral and access placement. Recently, a CKD progression prediction model was developed and validated ; this model and the patient’s degree of proteinuria may help estimate the progression of CKD to ESKD and planning for dialysis access. The components required for patient-focused access planning are:
- 1)
Timely and appropriate referral;
- 2)
Education (above);
- 3)
Patient history and physical exam; and
- 4)
Supportive investigations.
Timely and Appropriate Referral
Timely referral to a nephrologist and access surgeon or interventionalist (herein referred to as access “operator”) for CKD management and evaluation by an operator, respectively, increases the likelihood for placing a native vein AVF and reduces the likelihood of temporary CVC placement. Therefore, when GFR approaches 30 mL/min (CKD Stage G4), patient education about CKD, its potential progression to require KRT and dialysis access must begin. In terms of the GFR, “sweet spot” for arteriovenous (AV) access creation, this will depend on the patient’s age, rate of CKD progression, and prognosis. For example, elderly patients have a slower rate of GFR decline, lower incidence of ESKD, and higher mortality rate and may suffer from an unnecessarily high ratio of unnecessary to necessary AV access surgeries and interventions. Clinicians should aim to reduce the number of unneeded procedures to attain functioning necessary AV accesses. An approach to access creation is illustrated in Fig. 15.1 .
Patient and Vascular Access History
A “hemodialysis access–focused” history is unique and required in planning dialysis access. Such a history will shed light on potential complications that may occur, such as failure of an AVF to mature, potential for high cardiac output failure or AVG-associated steal syndrome, and will navigate the access operator to either preemptive intervention or consideration of an alternate access. This “vessel-focused” history includes determining the type and nature of past access procedures (especially CVCs, PICC lines, and pacemakers), past accesses (interventions required to facilitate or maintain its patency and reason(s) for loss), breast and axillary dissection surgery, chest radiation, and emergency vascular cut-downs. Furthermore, a parallel “PD-focused” history should be pursued to help inform the choice of dialysis access. Factors that may affect the peritoneum, such as the presence of significant prior abdominal surgeries, may lead one to exclude PD and focus on hemodialysis VA.
Physical Examination
The focused physical exam includes a detailed inspection of the neck, chest, abdomen, and extremities. The examination must take into consideration the significance of previous chest and abdominal surgeries (for PD), pacemakers, presence of edema, and collateral vein formation that may suggest central vein pathology. The vascular examination must assess both the arterial and venous systems.
The hemodialysis VA exam requires a relaxed patient in a comfortable environment. A cold room will cause vessel vasoconstriction and potentially underestimate the size of available vessels. The use of an upper arm tourniquet or warming the extremity (e.g., with hot water), followed by asking the patient to close and open their fists, will help augment vessels for assessment. The arterial assessment includes evaluation of pulse quality, segmental blood pressure, and the Allen test. The venous system comprises a detailed inspection and palpation for vessel integrity, caliber, and size. Duplex ultrasound may be used to clarify or confirm concerns of vessel integrity and/or may be used to better define surgical and interventional anatomy.
Supportive Investigations
Duplex ultrasound is particularly useful in the obese patient but may not always add much to a careful and experienced physical exam (see later). Indeed, the quality of the duplex ultrasound examination is operator dependent; ideally, the surgeon should perform the duplex ultrasound or be present to direct the sequence of examination steps and mark the skin, documenting vessel size, intended surgery sites, and anatomical variations. The specific features assessed during duplex ultrasound are listed in Table 15.3 .
Table 15.3
Main Features Addressed by Duplex Doppler Vascular Examination
| Arterial System |
|
| Venous System |
|
⁎ A (radial) artery diameter of 2 mm or less is unlikely to mature to provide prescribed hemodialysis in North America and therefore fail from inadequate fistula flow (less than 500 mL/min). Likewise, a venous diameter of 2.5 mm or less at the time of anastomosis is likely to yield inadequate flow rate. Note that the Doppler characteristic of high arterial flow resistivity prior to the creation of a hemodialysis access should change to hyperdynamic low resistive characteristics after creating the access.
Since duplex ultrasound findings need to be considered within the context of the other variables determined by the history and physical exam, using size criteria alone to determine vessel eligibility for the desired access should be avoided. Doing so may lead to missing other important features of the vessel, including vessel quality (calcifications, distensibility), and prior vessel injury that may contribute to neointimal hyperplasia and VA failure. Imaging must document full compressibility and patency of all vessels examined with absence of any luminal defects and/or thrombosis. Outcomes are expected to be superior when duplex ultrasound involves maneuvers to assess the vessel’s characteristics, especially when directly observed by the operator performing the access surgery; however, this speculation requires proper study and confirmation.
The Allen test can be performed during duplex ultrasound to confirm findings found by physical exam. A photoplethysmography probe is used to obtain the baseline thumb arterial flow Doppler signal without any compression maneuvers. The signals are then obtained repeatedly while manually compressing the radial artery first, the ulnar artery next, and then both arteries together. If the Doppler signal demonstrates a significant reduction in the amplitude when the dominant artery is compressed, i.e., both palmar arches do not communicate ( Fig. 15.2 ), this should serve as a warning of risk for hand ischemia after access placement.
Alternatively, a modified Allen’s test may be performed. This is done by identifying the radial artery at the wrist and/or at the dorsum of the hand (posteriorly between the bases of the first and second metacarpals). The radial artery is compressed proximal to this site to occlude flow during insonation using spectral and color Doppler imaging. Reversal of blood flow distal to the proximal occlusion confirms patency of the palmar arch.
The value of preoperative vessel mapping has ranged from harmful (leading to delays in access creation and greater failures), equivocal (similar outcomes to physical exam), and superior with improved fistulas outcomes. Given the range of potential outcomes, current use of preoperative vessel mapping to assist with AV access planning and creation is not mandatory, largely dependent on the patient’s characteristics and the experience of the performing and interpreting physician.
Angiogram. If the physical exam or duplex ultrasound assessment raises concerns where confirmation or clarification of vascular anatomy is warranted, invasive imaging using contrast dye or CO 2 angiography (as appropriate) is warranted. 10–15 mL of dilute contrast dye has not been associated with accelerating the decline in GFR.
Access Site Locations
In considering VA location, there should be a carefully thought-out, systematic progression from one VA site to another. With few exceptions, there should be an attempt to preserve and use every site available to extend the patient’s ESKD “lifeline.” An “upper extremity first” followed by a “distal to proximal” approach maximizes potential access sites and takes advantage of the dilatation effect of access procedures on the vasculature; this may lead to the development of veins and arteries at sites that were initially deemed suboptimal.
Upper extremity
Fistulas
Fistulas are relatively simple to create, and different types of autogenous artery-vein anastomosis are possible, including end-to-side (end of the vein to side of the artery), terminalized side-to-side, laterolateral, and end-to-end ( Fig. 15.3 A ).
Wrist
Snuffbox radio-cephalic fistula: is an anastomosis between the distal radial artery and cephalic vein (between the tendons of the extensor pollicis brevis and extensor pollicis longus in the anatomical snuffbox).
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