Vascular access in hemodialysis

Vascular access in hemodialysis

J Michael Lazurus, MD Alfred P Morgan, MD Vascular access in hemodialysis Vascular access is one of the unsolved problems in maintenance hemodialysis...

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J Michael Lazurus, MD Alfred P Morgan, MD

Vascular access in hemodialysis Vascular access is one of the unsolved problems in maintenance hemodialysis. The perfect method for making a connection between the patient's circulation and the dialyzer should be painless, uncomplicated, and useful as long as needed. Unfortunately, all available methods have significant disadvantages. For some patients, usually those whose vascular anatomy is suitable and who avoid septic and thrombotic complications, access is only a detail in dialytic therapy. For others, it is a major source of morbidity and disability. Optimal vascular access with existing techniques depends not only on choice of a method best suited to the individual patient, but also on care by the patient and dialysis personnel. The importance of patient instruction and supervision in access care, which is part of nursing responsibility in most units, cannot be overemphasized. Because each access method has something wrong with it, there are several of them to compensate for the deficiencies. The Quinton-Scribner shunt, the oldest and simplest,' was the mainstay of chronic hemo81 0

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Fig I . Cannulation technique for one limb of a Quinton-Scribner shunt. Adequate anesthesia is obiained wiih local infiltration. No more difficult than a cuidown, this can be a bedside procedure when necessary, but full OR technique is preferred whenever possible.

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f i g 2. The Thomas femoral shunt is usually placed in the femoral vein af the sapheno-femoral junction rather than high under the inguinal ligament as shown here. hsertion with local anesthesia is possible, but spinal or general is more satisfactory.

dialysis for five or six years. It consists of two Telfon tips attached t o Silastic tubing. One tip is placed in the artery, the other in a nearby vein. The tubing is exteriorized through a subcutaneous tunnel and joined to the opposite limb of the shunt (Fig 1).Shunts can be placed in either the arm or the leg; the first one is usually placed as far distally as possible. When shunts fail, they can be moved proximally to a new site on the same vessel pair. In general, four or five shunt revisions are possible in each forearm, perhaps three in each ankle. Variations and modifications of the basic external loop shunt exist; their use is determined mostly by local preference. One, the Thomas femoral shunt, is significantly different.* We

reserve it for those patients whose simpler and perhaps safer options have been exhausted. The Thomas prosthesis (Fig 2) is a straight Silastic tube. Its subcutaneous part is velour-covered; a glued-on fabric patch is sewn into a n incision in the common or superficial femoral vessel to form what is functionally an artificial branch. The Thomas shunt works well and may provide a route for dialysis in patients without other more peripheral vessels available. However, it can be hazardous. The risk of sepsis in the femoral triangle is real, and both limb loss and mortality are associated with its use. The principal disadvantages of any external arteriovenous shunt are infection and clotting. Shunts are foreign bodies; the tubing transverses

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the skin, and local infection occurs. It is most often staphylococcal and may result in septicemia or septic pulmonary emboli if not treated properly and early. Another major problem of the arteriovenous shunt i s frequent clotting. When caught early, declotting by aspiration, irrigation, and sometimes use of fibrinolysin is possible, but eventually the vessel containing the shunt tip becomes strictured or infected, and a new shunt will be required. Complications of declotting include infection related to manipulation of the shunt and retrograde arterial emboli from excessive flushing. Some patients with an arteriovenous shunt need systemic anticoagulation to maintain its patency. Anticoagulation, of course, carries a risk of bleeding from the gastrointestinal tract or elsewhere, and this risk is increased in patients with renal failure. There are less objective, but still very real, liabilities. A bandage must be worn. Patients with arteriovenous shunts are instructed to use the extremity as little a s possible and

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to keep it dry. Bathing and swimming are both difficult. Nevertheless, shunts have substantial advantages. Most of all, they can be used after insertion and may be the technique of choice in acute renal failure or for a patient in urgent need of hemodialysis. There are some patients who prefer the inconvenience of a shunt t o the repeated venipuncture necessary when an arteriovenous fistula is used for dialysis. The arteriovenous Cimino fistula was first described in 1966.3An anastomosis, usually between the radial artery and the cephalic vein, sometimes the ulnar artery and basilic vein, allows dialyzer connections to be made by venipuncture of the arterialized superficial vein (Fig 3). An arteriovenous fistula made between vessels of good size may be used immediately, but there are other patients for whom weeks to months are necessary for fistula maturation. Adequate hernodialysis requires a minimum of 150 to 200 cc per minute flow through the dialyzer. The simpler primary methods for

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access do not work for every patient. As more and more patients remain on chronic dialysis for longer and longer periods, an increasing fraction of them have expended all available sites for Scribner shunts and Cimino fistulas. Other patients are access problems from the start: elderly, arteriosclerotic, or those whose superficial veins have been thrombosed by prolonged intravenous therapy. These individuals need one of the secondary access methods. They are more extensive procedures which require hospital admission, general or major block anesthesia, and which carry a higher risk of vascular or septic complications. The Thomas femoral shunt, described above, is an example of a secondary external shunt. There is a group of secondary procedures which employs some prosthesis to form an internal fistula. The prosthesis provides a large substitute vein where Fig

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vein Fig 3. The end-to-side arteriovenous fistula is shown here between radial artery and cephalic vein. It is not a true microsurgical procedure, but magnification is helpful. Fig 4. Saphenous vein graft in the groin. The vein is freed from its bed as far as the joint line of the knee; branches are ligated; a distal incision is

made in the anterior thigh and the vein drawn through a subcutaneous tunnel forming a U-shaped loop. Fig 5. Saphenous vein graft in the arm. The venous anastomosis shown here is to the cephalic vein. The basilic or the commitant veins of the brachial artery are sometimes used.

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no suitable native veins are found. It can also be connected to the larger vessels in the groin or elbow which are not usable for shunts or primary fistulas. The patient’s own greater saphenous vein can be used. In its normal position, it is too deep for practical venipuncture, but removed from its bed and reimplanted more superficially, i t makes a useful arteriovenous fistula. Alternative sites are the anterior thigh, utilizing the saphenous vein’s normal connection t o the femoral vein (Fig 4), or the forearm, where it is anastomosed to the brachial artery and a suitable vein (Fig 5). In 100 saphenous vein grafts done in our institution, choice of the arm or leg site was determined partly by patient preference and partly by adequacy of available vascular channels a t each site. With this bias there has been no difference in duration of utility of saphenous grafts in the two locations. Other variations are possible and have been described. Other prostheses can be used. Bovine arteries, used also for arterial replacement, can be implanted in the same sites used for saphenous vein grafts. They are inert collagenous tubes - not true xenografts - and appear to be immunologically inactive. The bovine graft has had variable popularity in different centers. Our experience with them is small, but infection has been a problem. Others report good results. More recently, the Sparks mandril graft, described originally for arterial bypass, has been used to form a n arteriovenous channel for dialysis.‘ It has the same off-the-shelf availability as the bovine graft, but must mature for six weeks in the subcutaneous tissue before anastomosis to the patient’s circulation.

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Our program has experienced a n approximate 10% initial failure rate of arteriovenous fistulas. Another 20% to 30% fail later because of stricture at the site of repeated needle punctures, formation of mycotic aneurysms, or severe hematomas. A less common complication is the vascular steal, which occurs when flow is reversed in the distal radial artery. Painful hands and fingers occur more commonly than does the classic steal and may be due to nerve compression in the carpal or ulnar tunnels. All are reversible by ligation of the artery distal to the fistula. Steal syndromes have not been seen after saphenofemoral loop fistulas, but would be theoretically possible when the iliac arteries are critically occluded by arteriosclerosis. Most patients on chronic maintenance dialysis prefer the arteriovenous fistula to the shunt. The incidence of infection is higher in shunts, and the incidence of clotting much higher. Repeated trips to and from the hospital for declotting are at the least inconvenient, not only for the patient, but for dialysis personnel. The major reason for patient preference, however, seems to be cosmetic, and the ability t o lead a more normal life. The most effective and efficient form of hemodialysis is believed to be frequent treatments for short periods; for example, two hours of dialysis daily. Such therapy is not possible a t the present time not only because of the cost of the disposables required, but also because of difficulties which might occur with repeated daily venipunctures of the arteriovenous fistula. In this regard, the arteriovenous shunt appears to be a more desirable access. The development of newer access devices, such as the so-called

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single-needle, will allow for fewer and more efficient needle punctures. The patient who develops access problems usually has had multiple failures in the past and is a veteran in the operating room. Those patients who have had successful shunts or fistulas may be seen only once during the entire course of their dialysis/ transplant program. Of all the problems that can occur during chronic maintenance hemodialysis, the uremic patient most often focuses on the success of his shunts and fistulas as an indication of his overall course. Some patients are preoccupied with their access device and become most distraught when difficulties are encountered. The surgeon performing the access surgery and the operating room nurse see the dialysis patient a t the time of considerable stress and anxiety. If the access has been malfunctioning for some period of time, they may likewise be moderately uremic because of poor hemodialysis. Operating room personnel should keep in mind that patients with arterio-

venous shunts frequently have recently received heparin or coumadin and that many patients on hemodialysis have chronically positive Australia antigen. The increase rate of hepatitis infection among dialysis personnel is well known. For the patient with poor veins, compromised arterial flow, and a tendency towards hypercoagulability, the operating room nurse and physician play an important role. The patient's existence depends upon a working shunt or fistula with which to be dialyzed adequately, and the patient knows it. Constant support and optimistic encouragement are necessary for these patients. Notes I. W E Quinton, D Dillard, B H Scribner, "Cannulation of Blood Vessels for Prolonged Hemodialysir," TASAIO, 6 (1960) 104. 2. G I Thomas, "A Large Vessel Applique A-V Shunt for Hernodialysis," TASAIO, 15 (1969) 288292. 3. M J Brescia, et al, "Chronic Hernodialysis Using Venipuncture and Surgically Created Arteriovenous Fistula," New hgkund Journal of Medicine,

275 (1966) 1089-1092. 4. R K Beemer, J F Hayes, "Hernodialysis Using a Mandril-grown Graft," TASAIO, 19 (1973) 43-44.

J Michael Lazarus, MD, is codirector, dialysis, Peter Bent Brigham HOSpital, and director, dialysis, Children's Hospital Medical Center, Boston. Assistant professor of medicine at Harvard Medical School, Dr Lazarus is a graduate of Tulane University Medical School, New Orleans. Alfred P Morgan, MD, is associate professor of surgery at Peter Bent Brigham Hospital and Harvard Medical School. He is a graduate of Cornell Medical College, New York City. Editor's note: In October, the Journal published a series of articles on kidney transplantation. A second section to that series appears in this issue.

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