Dialysis Unit, Krankenhaus Merheim, Köln, Germany
Correspondence and offprint requests to: Klaus Konner MD, Dialysis Unit, Krankenhaus Merheim, Ostmerheimerstr. 200, D-51109 Köln, Germany.
Introduction
The first surgical creation of an arteriovenous fistula for the purpose of haemodialysis was performed in 1965 by Brescia, Cimino and co-workers at New Yorka real break-through in the field of vascular access [1]. More than 30 years later, two basic aspects have changed: First, more and more elderly and diabetic patients are accepted for long-term dialysis treatment and a rising proportion of patients with a history of dialysis therapy over more than 20 years is observed presenting special vascular, mainly arterial, problems. Second, graft materials, permanent central venous catheters, diagnostic and interventional radiological techniques and ultrasonographic investigations have been introduced.
When to establish the first av fistula?
It is a poor strategy to start dialysis treatment when residual renal function is lower than the accepted optimum for patients on dialysis treatment. At a serum creatinine level of more than 68 mg/dl in non-diabetic patients and of more than 46 mg/dl in diabetic patients dialysis therapy should be started.
That means that a vascular access should be created before then. A well-functioning vascular access at the start of haemodialysis treatment saves costs of hospitalization and avoids large-bore central venous catheters for temporary access with all their potential complications.
What is the procedure of choice?
A matter of course
One remark may be allowed: it is indispensable for the nephrologist to have some knowledge concerning haemodynamics of the arteriovenous fistula and some aspects of the surgical techniques. In addition, the vascular surgeon should also become familiar with dialysis-related mechanisms and problems that will frequently influence his decisions with regard to the creation and revision of vascular access.
Normally these operations are regarded as `simple procedures' performed by the younger vascular surgeon. This is a basic misunderstanding because these first operations require high technical skill and experience. The aim of the procedure is to achieve a vascular access suitable for long-term cannulation, not only to create an arteriovenous anastomosis. It is important to know, that we create one anastomosis, but we arterialize the total of the venous system of one extremity.
It is useful to draw attention to some basics of haemodynamics: The nephrologists wait for the venous dilatation for easy cannulation. But both, the artery and the vein, must be able to undergo dilatation, the prerequisite of the high blood flow needed for successful haemodialysis treatment (Figure 1).
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That means that a calcified radial artery with a small lumen and a thickened wall (as found in many diabetic and hypertensive patients) will never provide adequate fistula function as needed for haemodialysis. In such cases, early thrombosis and insufficient arterial blood flow are observed frequently. Since life expectancy of these patients is usually limited, the decision to start with an elbow fistula is made easier. These patients will profit from a well-constructed elbow fistula instead of suffering from the complications of a peripheral anastomosis.
Save the veins!
Absolute priority must be given to the patient's native vessels. Creating a primary arteriovenous fistula means choosing a type of anastomosis and a location that provide the best chances to achieve good functional results in case of revision or new anastomosis.
There is no place for prosthetic grafts in constructing first arteriovenous accessexept in very, very few patients. Grafts require sufficiently high arterial inflow and venous outflow and this will not be provided in a patient with tiny vessels.
Types of anastomosestechnical considerations
Brescia and Cimino described the artery-side-to- vein-side anastomosis in 1966 [1]. One year later, the artery-end-to-vein-end anastomosis was published [2], followed by the artery-side-to-vein-end anastomosis in 1968 [3]. The artery-end-to-vein-side anastomosis never gained popularity. Any surgeon involved in creating vascular access must be familiar with these different types of anastomoses. Experience, skill, and patience are prerequisites of success.
The end-to-end-anastomosis had gained widespread acceptance by the first half of the seventies. Technical problems arose because of the difference in the lumen of the artery and of the vein. With the increasing number of patients with arterial problemsdiabetic and elderly patientsthis variant was abandoned. It is not possible to construct the necessary curve of the vessels, a semicircle, required for the anastomosis when the arterial wall is thickened and calcified. Furthermore, the peripheral disruption of the radial artery in these patients with vascular problems may be very risky.
Today the preferred techniques are the original side-to-side or the side-to-end anastomosis (artery first, vein second).
The side-to-side anastomosis is a reliable technique. If the distal venous limb is left open, venous hypertension may occur in many patients. In addition, the proximal venous limb may undergo obliteration. Such venous hypertension can be avoided by ligation of the distal venous limb after creation of the side-to-side anastomosis; in other words, a functional side-to-end-anastomosis is created. An additional advantage is that the quality of the proximal veinopen lumen, absence of narrowing, ability to dilatecan be tested by venotomy in the distal venous limb by means of catheterization and injection of heparinized saline against proximal digital pressure. The area of the anastomosis remains untouched when performing these essential manoeuvres. The use of a Fogarty catheter to test such tiny veins is a professional blunder.
There exists a very simple technique to construct these side-to-side anastomoses: instead of the common surgical technique of starting the suture in both corners, then completing the suture of the back wall transluminally, here the suture starts in the middle of the arterial and venous back wall and is then continued to the corners [4]. At any moment, the situation is very clear and easy to achieve. This `open' technique is extremely advantageous in handling very small vessels, for example in creating arteriovenous fistulae in children (Figure 2, adapted to an artery-side-to-vein-end anastomosis).
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A very common technique is the artery-side-to-vein-end anastomosis, the preferred variant in patients where the vein is found to be more distant from the artery. Some technical tricks merit mentioning. The length of the arteriotomy depends on two parameters: The diameter of the vein and the angle between artery and vein. The more this angle approaches 90°, the closer one will come to the original venous diameter (Figure 3). If the vein approaches the artery in this rectangular position, the vein should undergo an outward directed rotation to avoid kinking which will lead to stenosis or early thrombosis (Figure 4
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Location
With these simple rules, construction of an arteriovenous anastomosis is possible at various locations, depending on the quality of vein and artery. The first anastomosis should be positioned as far in the periphery as possible. The more proximal the location of the anastomosis chosen, the more the diameter of the anastomosis should be reduced.
The majority of first arteriovenous fistulae will be established along the (non-calcified!) radial artery in the forearm. Any segment of the radial artery can be used, depending on the availability of a suitable vein. In this case, a good vascular access will result over many years. Post-anastomotic stenoses can be repaired electively by creating a new anastomosis a few centimetres more proximally, mostly on an outpatient basis. This strategy requires a high standard of access monitoring by the nephrologist and his staff. The failing fistula should undergo revision, not the failed one.
Do not forget the ulnar artery! In any patients with lack of or exhaustion of a cephalic antebrachial vein, this region should be examined for a suitable basilic antebrachial vein. This vein is never used for taking blood samples or for intravenous infusions. A high level of skill is required to handle this extremely thin-walled vein. Prolonged maturation is needed to establish a good blood flow.
Construction of arteriovenous fistulae in the elbow region offers a series of possibilities with regard to the location and the type of anastomosis, depending on the individually varying arrangement of the native vessels, mainly of the venous network. In most cases the anastomosis will result in arterialization of the cephalic as well as of the basilic vein.
Because of its superficial position, the cephalic vein can be cannulated easily over many years. First cannulations are possible within 2 weeks of the operation. In extremely obese patients, the cephalic vein has to be brought into a subcutaneous position, usually by a second-step operation. If the origin of the cephalic vein is missed, the cephalic vein can be mobilized from the lateral aspect of the elbow region and sutured to the brachial artery.
The basilic vein can easily be anastomosed to the brachial artery, resulting in an additional arterialization of the cephalic vein with the above-mentioned advantage of easy and early cannulation. Problems will arise in cases where a cephalic vein is not available: the first superficial segment of the basilic vein in the region of the elbow is too short in many patients, thus providing only a limited stretch for cannulation. Here, the superficialization of the basic vein along the medial aspect of the upper arm can give good long-term results. It should be emphasized that the proximal one-third of the basilic vein must be left untouched to preserve it as venous drainage, e.g. for an ePTFE bridge graft later.
Special attention should be paid to a variant of elbow fistula, the Gracz fistula. The perforating vein, originating from various sites of the venous triangle in the elbow region, is anastomosed to the brachial or the beginning of the radial artery [5].
In contrast to the original publication, the deep venous system should not be interrupted [6]. The length of the anastomosis35 mmis limited by the diameter of the perforating vein, resulting in a significant reduction of the risk of peripheral ischaemia. Furthermore, the entire superficial venous system is arterialized and remains suitable for cannulation. The anastomosis is buried in the depth of the elbow and protected from accidental arterial puncture while placing the dialysis cannulae.
In addition, elbow and upper arm arteriovenous fistulae are indicated in all patients with an exhausted peripheral venous network. A superficialized basilic vein can provide an excellent long-term vascular access as well as the cephalic vein. In some patients with upper arm fistulae and a history of multiple revisions, the change to the contralateral arm with creation of a new anastomosis will be better.
Perioperative aspects
The majority of access procedures can be done with local anaesthesia. One adverse factor is spasm of both the arteries and veins. Any spasm must be eliminated before closure of the skin. Most of these patients undergo access surgery on an outpatient basis.
Regional anaesthesia is chosen for more difficult and time-consuming access operations. An advantage is the significant reduction of spasm. The site of operation can be changedif necessaryduring the session without problems.
General anaesthesia is mandatory in a rising proportion of severely ill and elderly patients with comorbidity.
Antibiotics are not routinely used. Only in high-risk patients, e.g. diabetic and elderly patients or patients on immunotherapy, a single dose of an antibiotic should be considered when a time-consuming revision or the insertion of graft material is planned.
Routine use of anticoagulants or similar substances is not indicated. Surgical errors cannot be corrected by pharmacotherapy!
It is commonly thought that arteriovenous fistulae require 36 weeks for maturation. But the optimal choice of access location and suitable arteries and veins will shorten this time substantially. Tiny vessels need a longer time for maturation. Training by daily repeated congestion can be practised.
Thrombosis
Thrombosis is reported to be the most frequent complication of BresciaCimino fistulae. Commonly, thrombosis is the result of anatomic problems such as stenoses, aneurysms, paravascular haematomas ora rare event in native fistulasinfection. Early diagnosis of initial fistula dysfunction with immediate elective surgical or interventional repair is required to prolong fistula function before onset of thrombosis. The nephrologists and their staff should be trained to be able to monitor the patients using the well-known clinical and dialysis-related parameters. Most thrombotic events are avoidable. Every case with a thrombosis is an emergency, often requiring central venous catheterization and hospitalization whereas most elective procedures can be done on an outpatient basis.
Some rules to be considered
No success without qualitiy and no quality without continuous learning from errors in one's own technical and underlying strategies.
Notes
Please see also Dialysis and Transplantation News by Ezzahiri et al. and Bonucchi et al. (pp. 21102115 and 21162118 respectively).
References