Introduction
The estimated prevalence of chronic kidney disease (CKD) in India is 17.2%, with approximately
130,000 patients on dialysis and annual growth of 10 to 20%.[1]
[2]
[3]
[4] In patients on long-term renal replacement therapy (RRT), the major challenge is
inadequate dialysis facilities & support systems, nonaffordability, vascular access
issues, and lack of surveillance systems, leading to a high dropout rate. Vascular
access is the lifeline for a patient on hemodialysis (HD), aptly described as the
Achilles heel due to associated morbidity.[5]
[6] By creating an effective and long-lasting arteriovenous fistula (AVF), we can improve
life expectancy and quality of life for these patients.
Only 9 to 13% of CKD patients in need of HD have AVF created before initiation of
dialysis.[7] A holistic multidisciplinary center with monitoring and surveillance programs goes
a long way to achieve this objective. Primary physicians or nephrologists have to
consider the resources, longevity, and affordability of patients before recommending
AVF. It is imperative to identify the site and preserve the veins by avoiding venipuncture.
Ideal Vascular Access and Options
International guidelines and various study groups such as National Kidney Foundation-Kidney
Disease Outcomes Quality Initiative (NKF-KDOQI) 2006 CPG 2.1 (Clinical Practice Guidelines),
European Best Practice Guidelines, and Canadian Society of Nephrology recommend autogenous,
native vessel AVFs over the central venous catheters (CVCs) for initiation of HD.[8]
[9]
[10] Patients who receive dialysis across a functional AVF have lower complication rates
and longer duration of event-free patency than with catheter access and arteriovenous
grafts (AVGs).[11]
[12]
[14]
[15]
The ideal AVF should have early placement, easy accessibility, minimal primary failure
rates, early maturation, long-term patency, and minimal complications. Despite a reported
failure rate of 7 to 40% with an average of 15.3%, a well-made AVF lasts as long as
10 to 12 years when used carefully.[16]
[17]
The order of preference of NKF-KDOQI guidelines suggest radiocephalic, brachiocephalic,
and brachiobasilic transposition fistulae and then prosthetic grafts as vascular access
options.[8]
[9]
Arteriovenous Fistula
Brescia, Cimino, Appell and Hurwich (1966—New York, US) created the first surgical
subcutaneous side-to-side AVF between radial artery and adjacent superficial vein
and published a landmark series of 14 patients.[18] Cimino fistulas are currently accepted as the ideal mode of vascular access for
HD. Various factors which guide the timing of fistula creation are summarized in [Table 1].[8]
[9] “Fistula first” initiative was implemented as the national vascular access improvement
initiative, with a goal to create AVF in 50% of newly diagnosed CKDs, and to have
a functioning AVF 6 months before the anticipated need for HD.[8]
[9]
[20]
Table 1
Timing of placement of AVF (NKF guidelines)
|
Abbreviations: AVF, arteriovenous fistula; HD, hemodialysis; NKF, National Kidney
Foundation.
|
|
Creatinine clearance—25 mL/min or less
|
|
Serum creatinine—4 mg/dl or less
|
|
Within 1 year of anticipated need of HD
|
|
Modified diet for renal disease estimated glomerular filtration rate drops below 15
mL/min[19]
|
Preoperative Evaluation
The history of recent venous injections for blood sampling or intravenous (IV) access
must be accurately recorded. Any associated comorbidities like diabetes, vascular
disease, history of multiple central venous catheters, collagen vascular disease,
etc. should be noted ([Table 2])
Table 2
Contraindications for AVF creation
|
Abbreviations: AVF, arteriovenous fistula; BP, blood pressure; EF, ejection fraction.
|
|
Absolute contraindications
|
Amputation of extremities
|
|
Advanced peripheral vascular disease with ischemic ulcerations
|
|
Relative contraindications
|
Poor or suboptimal veins
|
|
Low BP (normal BP for these patients is sys 180\170 so 110/120 may be a low BP for
these patients)
|
|
EF < 20% or impending cardiac failure
|
|
Severe orthopnea or inability to lie supine, indicating overload and pulmonary hypertension
|
|
Central venous stenosis in the same limb[21]
|
|
Limited life expectancy and advanced disease[22]
|
Patient's ability to lie supine for a period of 1 to 2 hours without suffering from
breathlessness is crucial. In cases of fluid overload with orthopnea, it is advisable
to dialyze the patient the day before the procedure.
Clinical evaluation should include both arterial and venous assessment ([Table 3]). The superficial venous system should be mapped with an outflow obstruction, using
a tourniquet at the upper arm. Preferably, a straight segment should be marked, checking
the compressibility, distensibility, emptying, and evidence of needle pricks or thrombophlebitis.
Table 3
Preoperative vascular assessment for AVF creation
|
Arterial requirements
|
Venous requirements
|
|
Abbreviation: AVF, arteriovenous fistula.
|
|
Good strong radial and brachial pulsations
|
Diameter of 2–2.5 mm (at least 2 mm)
|
|
Diameter—2 mm or more at the site of anastomosis
|
Straight segment within 1 cm of surface
|
|
Patent palmar arch (Negative Allen’s test)
|
Continuity with proximal veins without any central venous stenosis or obstruction
|
|
Pressure differential of less than 20 mm Hg between two upper limbs
|
|
Although NKF guidelines advise preprocedure objective Doppler evaluation in all cases,
we prefer to selectively do it only when clinical findings are inconclusive or doubtful.[8]
[9] Central venous stenosis is clinically evident by dilated superficial veins in the
axilla and lateral torso and confirmed by a Doppler examination.[20]
For patients with unsuitable and nondiscernible veins who are unlikely to improve
with physiotherapy, the decision to do a proximal fistula should be made if early
availability of vascular access is required.
Decision Making for Fistula Creation
Proximal Versus Distal AVF
The preferred sequence is distal fistula in a nondominant hand, followed by proximal
brachiocephalic, and brachiobasilic fistula with or without primary vein transposition.
In case of failure or nonavailability of nondominant hand, the same sequence is followed
in the dominant hand. Although the proximal or brachiocephalic fistulae have lesser
primary failure rates and faster maturation, they have a higher complication rate,
such as persistent distal edema, steal phenomenon, and aneurysm formation. It is essential
to advise patients and caregivers on protecting the proposed extremity from needle
pricks and IV accesses.
End-to-Side Versus Side-to-Side
End of vein to side of artery anastomosis has minimum postoperative complications
like distal swelling, necrosis, or ulcerations.[23] In side-to-side fistula creation, authors have described a modified technique of
side-to-side brachiobasilic fistula with equivalent results.[24]
[25] It involves manual distal valve dysfunction with a vein dilator, which leads to
development of forearm veins for HD access, thereby avoiding long incision for vein
transposition and its complications. Basilic vein can be superficialized secondarily,
if and when forearm veins become unusable, as a backup plan, without the need to create
a new fistula.
The final decision on whether to opt for an end-to-side or a side-to-side anastomosis
is predominantly guided by surgeon preference and local anatomical factors.
Operative Technique
Surgical creation of AVF is a day care or an outpatient procedure done under local
anesthesia and loupe magnification without a tourniquet control.
Distal AVF (Radiocephalic)
A 2.5 to 3 cm S-shaped incision is marked (
[Fig. 1] A) for adequate exposure and with a provision to extend it proximally along the course
of the vein if required. Around 10 mL local anesthetic is infiltrated (2% plain lignocaine),
taking care not to puncture the vein. The cephalic vein and radial artery are dissected,
preserving the superficial radial nerve (
[Fig. 1] B)
Fig. 1 Radiocephalic (distal) arteriovenous fistula (AVF). A—exploratory S-shaped incision,
B—dissected radial artery (a), cephalic vein (b) with preservation of superficial radial nerve (c), C—oblique venotomy, D—completed anastomosis with dilated venous segment.
The geometry of the anastomosis, that is the angle at which the vein meets the artery
at site of fistula, is an important predictor of the flow and maturation.[26] It is advisable to keep vein to artery angle as acute as possible (18°) to have
an optimum flow across the fistula and minimum wall shear stress.[27] Backflow from the vein and its lie is checked and confirmed before anastomosis.
If the artery is atherosclerotic, noncompressible segment should be avoided while
selecting site of arteriotomy. After securing vascular double clamps in position,
an arteriotomy of approximately 6 to 7 mm in length is done with an 11 number surgical
blade or microscissors. Anastomosis is done either in continuous or interrupted fashion
with 7–0 polypropylene or 8–0 monofilament nylon. Care is taken to clip the side branches
of the vein, so as to prevent the development of accessory veins and distal limb complications.
Any fibrous or fascial band compressing the outflow segment of the vein is released.
Skin is closed with single-layer interrupted sutures after confirming hemostasis.
A noncompressible and noncircumferential dressing is given.
Proximal AVF (Brachiocephalic fistula)
The technique and operative principles of an end-to-side proximal AVF creation are
similar to the distal radiocephalic fistula with a few differences (
[Fig. 2]
) The arteriotomy size is reduced to approximately 5 to 6 mm because of the higher
flow at brachial artery and so as to prevent any steal phenomenon and distal complications.
Fig. 2 Brachiocephalic (proximal) arteriovenous fistula (AVF). A—Exploratory S shaped incision,
B—adequately dissected venous segment with an oblique venotomy (a) and dissected brachial artery with a 5 to 6 mm arteriotomy (b), C—completed anastomosis.
Proximal AVF (Brachiobasilic Transposition Fistula) and Basilic Vein Superficialization
In cases where cephalic venous system is unavailable or unsuitable for the fistula
creation, basilic vein can be used. The basilic vein by virtue of its subfascial location
in arm is naturally protected from damage caused by venipuncture. However, due to
its deeper location, vascular access is difficult; therefore, it needs to be superficialized
in the suprafascial plane and transposed anteriorly in line of cephalic vein, either
in the same sitting or after maturation.
The surgical technique of superficialization includes taking a long linear incision
on medial aspect of the arm, safeguarding the medial cutaneous nerve of forearm. As
there are hardly any major tributaries present in this course of the vein, dissection
is easy, vein is transposed anteriorly in the subcutaneous plane, and fascia is closed
beneath the vein, thus superficializing it (
[Fig. 3]
).
Fig. 3 Basilic vein superficialization. A—markings of basilic vein (a) and brachial artery at elbow with a long linear extension (b) of the S-shaped exploratory incision, B—completed anastomosis (a) and superficialization of the basilic vein with closure of deep fascia layer (b) below the vein and anteriorly/superficially transposed dilated basilic vein (c).
The advantages of this procedure are that it produces a long length of the straight
superficial vein with a high flow rate. However, the disadvantages include need for
long length of incision, increased chances of hematoma formation, requirement of regional
or general anesthesia, long duration of surgery, increased stay in the hospital, and
thus increase in the overall costs incurred.
Author’s Modification
We have modified the technique of proximal brachiobasilic fistula to address the limitations
of the conventional technique ([Table 4]).[24]
[25]We perform a side-to-side anastomosis between the brachial artery and basilic or
median cubital vein at elbow. After completion of the posterior wall of the anastomosis
with7–0 polypropylene, a long arm vessel dilator is introduced into the distal part
of the basilic/antecubital vein to dysfunction the first valve toward the wrist end.
This allows retrograde flow in the distal vein toward the forearm, which is confirmed
by flushing it with heparinized saline and looking for thrill on the forearm. Once
this flow is confirmed, the anterior wall anastomosis was completed.
Table 4
Advantages of author’s modification of proximal brachiobasilic AVF
|
Abbreviation: AVF, arteriovenous fistula.
|
|
Small incision with limited dissection
|
|
Lesser chances of hematoma, lymphorrhea and wound infection
|
|
Availability of distal forearm veins as access sites
|
|
Possibility of secondary superficialization if required
|
The Endpoint of Surgery on the Operation Table
After completing the anastomosis, the patency and flow are confirmed by filling up
the vein and palpation of thrill. Return of distal pulsations and hand vascularity
is confirmed after releasing the clamps. The authors established a direct correlation
between the presence of bruit heard on the table and thrill felt at the end of surgery
with long-term patency and maturation of AVF.[24]
Postoperative Care
Patients and their relatives are instructed to avoid venipunctures on the operated
side, blood pressure cuffs, tight clothing or ornaments, and any prolonged pressure.
Handball exercises are taught to patients before discharge. Further, they are taught
to feel the thrill every day and report to the surgeon immediately if the thrill disappears
and are counselled about the warning signs like coldness, numbness, ulcers, or discoloration
at fingertips. Anticoagulation is given in the form of single dose of low-molecular
weight heparin (LMWH) (1 mg/kg body weight). Patients are called for review at around
day 3 for first follow-up and then on 10 to 12 days where the thrill is assessed and
sutures are removed, and again reviewed at 4 weeks, for features of maturation.
Mature and Useable Fistula – Characteristics and Guidelines
Primary fistula failure is defined as poor blood flow across a fistula (< 250 mL/
min) not sustained for a minimum of 3 hours even after to 12 weeks of its creation.
Average time taken for the fistula to mature is 4 to 6 weeks.[28]
The flow across the fistula multiplies to five to 10 times that of the normal arterial
flow. Intraoperative flow measurements immediately after fistula creation are also
a good predictor to assess the eventual maturation of an AVF.[29] The average time a nephrologist advises the fistula to be used for the HD is 6 to
8 weeks, in accordance with the rule of 6 proposed by KDOQI ([Table 5])[8]
[9]
Table 5
“Rule of 6” for a mature AVF (KDOQI guidelines)
|
Abbreviation: AVF, arteriovenous fistula; KDOQI, Kidney Disease Outcomes Quality Initiative.
|
|
Vein within 0.6 cm of skin surface
|
|
External diameter > 6 mm
|
|
Relatively straight segment of easily accessible vein for cannulation—at least 6 cm
|
|
Blood flow > 600 mL/min. to support dialysis
|
|
To be evaluated for nonmaturation at 4–6 weeks if above criteria are not met
|
The main reason for the failure of maturation of a functioning fistula is undiagnosed
central venous stenosis or proximal obstruction. Such cases do benefit from addressing
the underlying cause by endovascular techniques.
Troubleshooting for Fistula Surgery
1. No backflow from the vein
Having a good backflow from the proximal end of the vein is a good predictor of proximal
patency and continuity with central veins, although it is not an absolute prerequisite.
Palpating for a thrill when the vein is flushed with heparinized saline with a blunt
24 G IV cannula tip with a 5 mL syringe is a good maneuver to confirm the same and
rule out central venous stenosis in case of the absence of backflow.
2. No pulsations or thrill or bruit
Absence of any pulsations or thrill postanastomosis indicates a technical problem
like including the backwall in a suture, inadequate adventectomy, severe torsion or
kink, or too much traction on the vessels, due to improper siting of the arteriotomy,
soft thrombus at the anastomosis, a fascial band compressing the vein causing outflow
obstruction, or a proximal obstruction.
3. Role of anticoagulation
Authors have shown that there is no proven role of long-term postoperative heparin
or aspirin in long-term patency rates, where the anastomosis was satisfactory with
good thrill and bruit on table.[30]
4. Early Fistula Failure or Loss of Thrill
The absence of well-developed dilated veins for HD access or disappearance of thrill
within 3 months of postoperative period or prior to maturation of fistula is termed
as early fistula failure.[31] Various clinical predictors which predispose to early fistula failure are small
caliber vessels (artery < 2 mm and vein < 2 mm), distal AVFs, female gender, obesity,
diabetes, vascular disease, suboptimal blood flow on the table or on the first postoperative
day, and surgeon-related factors of skill and experience[24]
[32]
[33] ([Table 6]).
Table 6
Etiological factors for fistula failure
|
Immediate failure
|
Nonmaturing AVF
|
Delayed failure
|
|
Abbreviation: AVF, arteriovenous fistula.
|
|
Improper selection
|
Juxta anastomotic stenosis
|
Late thrombosis
|
|
Technical failure
|
Accessory veins
|
Hypotensive episode
|
|
Early thrombosis
|
Central venous stenosis
|
Cephalic arch vein stenosis
|
Interventional radiologists can also play a role in salvaging an early as well as
late failing fistula due to thrombosis or stenotic lesions, with thromboembolectomies
or dilatations by endovascular techniques, but their application is limited because
of cost constraints.[34]
[35]
[36]
[37]
Predictors of Outcome- Factors Affecting Fistula Maturation and Patency Rates
In our study of patency and outcomes of 505 AVFs using logistic regression with success
and immediate failure as the dependent variables, we have drawn various conclusions
and recommendations, which are as follows:[24]
-
Presence of on table thrill and bruit has a direct and statistically significant relation
with success and maturation of fistulas.
-
Patients with vein diameter < 2 mm are 5.4 times more prone to fistula failure.
-
There is no significant association between side of arm used, site of fistula creation,
type of anastomosis and suture material, and success rate.
-
Postoperative long-term anticoagulation has no major beneficial role in eventual patency
rates in uncomplicated fistula surgery.
Long-Term Complications
Distal limb edema, ulcerations, gangrenous fingertips, limb hypertrophy, and lymphorrhea
The occurrence of swelling or edema in the distal extremity is one of the more commonly
seen complications in side-to-side fistulas. This may predispose to distal necrosis
and ulcerations too due to venous hypertension. Persistent hyperdynamic circulation
and venous hypertension may also lead to limb hypertrophy in chronic setting, needing
fistula closure in severe cases.[38]
In cases of proximal brachiocephalic or brachiobasilic fistula with vein transposition,
the medial lymphatic outflow track may be damaged due to dissection and long incision
and may predispose to lymphedema distally or lymphorrhea at elbow in rare cases, which
is usually self-limiting and managed conservatively. Distal edema can be managed with
limb elevation, gentle compression dressings, and physiotherapy with antegrade massage
in most cases. In selected cases, surgical ligation of accessory veins might be necessary
to limit the distal runoff, which can be performed transcutaneously.
Aneurysm and Pseudoaneurysm Formation
Aneurysms and pseudoaneurysms are localized vascular dilatations which can either
be venous or arterial. Venous aneurysms generally occur at the site of needle pricks
due to repeated punctures at the same site, as done in the button-hole technique (preferred
as less painful) of pricking a fistula.[39] It is advised to follow the step ladder technique, where the prick site is changed
to avoid this complication. They should be evaluated for impending rupture with skin
ulcerations and ligated and excised electively under tourniquet control and regional
anesthesia.
Steal Phenomenon/Ischemic Steal Syndrome
The steal phenomenon entails that the blood from the artery flows preferentially into
the low-pressure venous system through the fistula rather than to the distal arterial
bed, creating a zone of distal arterial insufficiency.[40]
[41] It is common in patients with severe atherosclerosis, in arteries distal to AVF
site (especially in proximal AVF), and in diabetic patients.[42]
Thrombosis/Stenosis of Fistula
KDOQI guidelines define significant stenosis of the vessel lumen as a reduction by
more than 50%.[8]
[9] Stenosis can also occur due to extraluminal compression by an abscess, hematoma,
or seroma. Clinical suspicion of stenosis is confirmed by the presence of several
factors like reduced quality of dialysis, prolonged bleeding after AVF puncture, pain
in the area of the fistula, or increased venous pressure. Various options available
to deal with these complications are thromboembolectomy, angioplasty with or without
stenting, or surgical creation of a new fistula.
Cardiac Overload and Failure
Cardiac complications are better avoided than managed by careful preoperative patient
selection. They are more commonly seen in patients with preexisting chronic heart
disease (low-ejection fraction [EF]) and large diameter fistulas.[43]
The salvage of failing fistula by radiological interventions has a high immediate
technical success rate but a 1 year patency rate of 32%, needing multiple interventions
for salvage and functionality (3.3 procedures per fistula); thus, it may not be cost-effective.[8]
[34]
[35]
[44] We prefer to perform a new fistula when the previous has failed or has inadequate
flow rates on HD, as the morbidity, longevity, as well as costs for radiological fistula
salvage are inferior when compared with new fistula creation
Recent Advances and Other Options
Gracz Arteriovenous Fistula
Gracz AVF was described at the elbow with equivalent results and patency rates to
conventional side-to-side fistulas.[45] The anastomotic site is below the elbow crease. The perforating vein between the
superficial (median cubital or cephalic) and deep venous system is disconnected and
its end is anastomosed in end-to-side fashion to brachial artery or radial artery
just after its take off. This leads to the development of a Y-shaped venous system
of cephalic as well as basilic vein.
Synthetic Grafts
Prosthetic AVGs are considered as secondary or tertiary access modalities to autogenous
AVFs.[46]
[47] The available graft materials can be either biological or the more commonly used
synthetic ones like Dacron and PTFE grafts. They are generally created at the elbow
or axilla, with a looped graft distal to the major vessels.
The major drawbacks with synthetic grafts are that they are more prone to complications
and associated with higher patient morbidity and low primary and secondary patency
rates, needing more interventions for salvage.[48]
