Hemodialysis Access
In 1972, an amendment to the Social Security Act provided Medicare coverage for patients suffering from end-stage renal disease (ESRD). The magnitude of the current expenditure is impressive, with over $19 billion spent on almost half a million patients with ESRD in 2005. Nearly 350,000 patients are dialysis dependent, with diabetes and hypertension the leading causes of ESRD, respectively. Patients with ESRD also suffer from a higher incidence of comorbid conditions such as chronic anemia, congestive heart failure, peripheral arterial disease, and metabolic bone disease. The five-year life expectancy of a patient on dialysis is merely 25%, with the largest percentage of deaths occurring from cardiac causes. With an aging population of ESRD patients, the magnitude of medical care and economic burden is expected to rise dramatically.
Procedures involving dialysis access are the most common vascular surgical procedures performed in the United States. A well-functioning and durable vascular access is truly a “lifeline” for patients on hemodialysis. Patients with a poorly functioning access or central venous dialysis catheters have increased morbidity and suffer frequent hospitalization for access-related complications such as thrombosis or infection. Management of vascular access requires the coordinated efforts of health care providers and a well-informed patient. The ideal care paradigm uses a multidisciplinary team of nephrologists, surgeons and interventionalists, dialysis nurses and technicians, diabetes educators, dieticians, and social workers. Patients with ESRD should be referred early to a vascular surgeon, prior to initiating dialysis, in hopes of establishing autogenous access (e.g., native arteriovenous fistula). Unfortunately, one of the most predictable aspects of chronic hemodialysis is the need for additional procedures in order to achieve, maintain, or restore access patency. Consequently, this chapter focuses on essentials in the initial evaluation, placement, and revision of hemodialysis accesses.
I. Indications for dialysis.
Chronic kidney failure from a loss of nephrons is measurable by a decrease in the glomerular filtration rate (GFR). A patient’s GFR can be estimated from a formula using variables for serum creatinine, age, race, and gender. Chronic kidney failure with a GFR <15 mL/min is considered ESRD and correlates with the need for dialysis. Acute renal failure, which can result from a variety of etiologies, may also require dialysis. Dialysis is indicated when one or more of the following of the following clinical problems are present:
A.
Hyperkalemia (>6 mEq/L), especially when accompanied by ECG or neuromuscular abnormalities, requires immediate dialysis. Dietary restriction and potassium-bonding resins may suffice for lower levels of hyperkalemia.
B.
Fluid overload is another indication for both acute and chronic dialysis. This includes patients who have not responded satisfactorily to fluid restriction and diuretics.
C.
Worsening acidosis results from the kidneys’ inability to excrete hydrogen and resorb bicarbonate, and represents an indication for hemodialysis.
D.
Drug overdose is a less common indication for hemodialysis but one that occasionally arises in an emergency room or critical care practice.
E.
Uremic signs and symptoms are the most common indication for chronic dialysis as blood-urea-nitrogen (BUN) and serum creatinine levels rise. Neurologic symptoms related to uremia include lethargy, seizures, myoclonus, and peripheral neuropathy, and it has been shown that mortality and morbidity can be reduced if the BUN level is maintained below 100 mg/dL.
II. Access Planning.
First, whether dialysis is intended to be temporary or permanent must be ascertained. Patients who develop acute renal failure in the setting of previously normal renal function will often recover over a period of days to weeks. In contrast, patients who develop acute renal insufficiency in the setting of chronic renal failure are likely to require chronic dialysis. Patients with chronic renal failure (GFR <25 mL/min) should be referred to a vascular surgeon, preferably months to a year in advance of dialysis. The goal of initial consultation should be to obtain a thorough history and to perform an examination, with a focus on the potential options for vascular access. This visit should allow enough time for the creation and maturation of an autogenous arteriovenous (AV) fistula, whenever possible. Even when an autogenous fistula is not an option, establishing a rapport between surgeon and patient helps to facilitate realistic expectations regarding the location and durability of future access procedures.
A. A history of all prior access procedures should be recorded.
The original date, type (fistula or graft), and location (forearm, upper arm, or thigh) for each access should be noted, in addition to the dates and methods of failure (e.g., thrombosis, infection, failure to mature). It is also important to ask about the number, location, and duration of prior central venous catheters. Patients with a history of indwelling catheter access have a significant probability of central venous stenoses or occlusions in the subclavian, jugular, and/or innominate veins. Right or left handedness is also noted, with preference for access placement given to the nondominant arm. However, even when the dominant arm harbors a more suitable vein the authors prefer an autogenous fistula in this arm rather than a prosthetic graft in the nondominant arm.
1. Medical comorbidities such as poor cardiac function should be determined, as these can limit the long-term success of hemodialysis access. The choice of anesthesia (general, regional, or local) may also be influenced by the presence of serious comorbidities. Lastly, the presence of diabetes should be noted, as diabetics have overall the worst results with dialysis and pose a higher risk for hand ischemia due to steal from access procedures.
2. The use of antiplatelet and anticoagulant medications should be noted and in some cases these should be held, depending upon the type of medication and/or planned access operation. These medications are particularly
important to note, as patients with ESRD typically have platelet dysfunction as a consequence of associated uremia or thrombocytopenia. Generally, aspirin can be continued throughout most if not all access operations, although for those such as a basilic vein transposition that require larger incisions, one may consider stopping aspirin 5 days prior to the case. Because clopidogrel (Plavix) is a more potent antiplatelet agent, it should be held 7 to 10 days prior to elective access operations to reduce the risk of bleeding complications such as hematoma (Chapter 7). Similarly, because warfarin provides full anticoagulation, it should be held prior to access operations, although the anticoagulant effects typically wear off within 4 to 5 days. This can be confirmed by drawing a coagulation panel from the patient prior to the access operation.
important to note, as patients with ESRD typically have platelet dysfunction as a consequence of associated uremia or thrombocytopenia. Generally, aspirin can be continued throughout most if not all access operations, although for those such as a basilic vein transposition that require larger incisions, one may consider stopping aspirin 5 days prior to the case. Because clopidogrel (Plavix) is a more potent antiplatelet agent, it should be held 7 to 10 days prior to elective access operations to reduce the risk of bleeding complications such as hematoma (Chapter 7). Similarly, because warfarin provides full anticoagulation, it should be held prior to access operations, although the anticoagulant effects typically wear off within 4 to 5 days. This can be confirmed by drawing a coagulation panel from the patient prior to the access operation.
3. Smoking negatively influences long-term access patency and all patients should be encouraged to quit preoperatively and provided access to formal smoking cessation programs if available (Chapter 7).
B.
Physical examination is the primary determinant for the hemodialysis access site.
1. Surgical scars and location of previous access procedures are noted, including percutaneous or tunneled central venous catheters. Skin conditions must be noted for signs of infection or other dermatologic disorders that would impair healing.
2. The axillary, brachial, radial, and ulnar pulses should be palpated and blood pressure recorded in both arms. Decreased pulses or a difference in blood pressure of more than 10 mm Hg may indicate proximal arterial occlusive disease on the side with the lower pressure. The proximal subclavian arteries in the area of the supraclavicular fossa should also be auscultated, as the presence of a bruit would suggest an underlying arterial stenosis. Underlying arterial occlusive disease (i.e., inflow disease) is critical to recognize prior to the access procedure, as once the fistula is created, flow across any proximal arterial disease will increase, resulting in a decrease in pressures. This phenomenon is well recognized and can result in failure of the dialysis access, distal ischemia (i.e., steal), or both.
3. Perfusion of the hand should be thoroughly examined prior to creation of an upper-extremity dialysis access site. Specifically, performance of the Allen test provides a good assessment of radial and ulnar artery patency as well as patency of the palmar arch in the hand. This evaluation is especially important when planning for an access configuration that will use the radial artery as the inflow vessel (e.g., radiocephalic fistula). The dominant artery to the hand in more than 85% of patients is the ulnar artery, and confirmation of this indicates that diversion of flow from the radial artery will not significantly reduce perfusion to the hand. If during the Allen test the radial artery is found to be the dominant artery supplying the hand, one should consider using a different inflow vessel.
To perform the Allen test, first the hand should be elevated for a brief period of time. Then, with the patient
making a tight fist, the examiner should compress the radial and ulnar arteries simultaneously. Separately, the radial and then the ulnar artery should be released as the examiner observes the opened hand for return of perfusion. If the ulnar artery is the dominant vessel, perfusion (i.e., color) will not return to the hand until it is released.
making a tight fist, the examiner should compress the radial and ulnar arteries simultaneously. Separately, the radial and then the ulnar artery should be released as the examiner observes the opened hand for return of perfusion. If the ulnar artery is the dominant vessel, perfusion (i.e., color) will not return to the hand until it is released.
4. The extremities should be examined for swelling or edema, which would suggest the presence of central venous outflow obstruction (e.g., subclavian or innominate veins). Just as arterial inflow disease can be exacerbated by creation of a high-flow AV fistula, a central venous outflow obstruction can become quite symptomatic following creation dialysis access in the effected arm.
5. The cephalic and basilic veins should be inspected for patency and size. They should be palpated carefully for compressibility (normal vein) or firm cords (chronic thrombosis). Application of an upper arm tourniquet to increase distal venous filling is sometimes helpful in delineating veins that may be suitable for use in dialysis access configurations.
6. When peritoneal dialysis is being considered, the abdomen should be examined for prior surgical scars. Prior abdominal operations may compromise the placement of a chronic peritoneal dialysis catheter.
C.
Noninvasive vascular laboratory testing is a critical part of the preoperative evaluation for hemodialysis access and has been shown to increase effectiveness and durability of access procedures.
1. Duplex ultrasound of the upper-extremity veins should be performed before access configuration is considered. Suitable veins for fistula formation can be identified by ultrasound that may be otherwise under-appreciated on basic physical examination. Additionally, direct and indirect evaluation of the central venous system can be achieved by duplex, which is especially important in individuals who have had prior central venous dialysis catheters. Studies have shown an increase in the ability of the surgeon to provide autogenous AV fistulas to his or her patients if use of preoperative duplex is maximized. These same studies report higher patency rates of such fistulas with the use of preoperative duplex, and this modality has also been found to be useful in sorting out patients who have had previous access sites that have failed.
2. Measurement of segmental pressures of the upper extremities can be helpful in select instances if the pulse examination is abnormal or arterial occlusive disease is suspected. Furthermore, formal duplex assessment of arterial flow can provide anatomic and hemodynamic information in complicated cases. In our experience, when bilateral upper extremity blood pressures are equivalent and the Allen test is normal, significant arterial inflow disease is rarely present.
3. Duplex ultrasound of the central veins can be performed if a proximal stenosis is suspected based on a history of multiple catheters, arm edema, or prominent venous collaterals. This examination is relatively sensitive for the detection of subclavian venous stenosis or occlusion,
although complete visualization is limited by the structure of the thoracic outlet. Central venous stenosis may occur in 10% to 50% of patients with a history of indwelling dialysis catheters.
although complete visualization is limited by the structure of the thoracic outlet. Central venous stenosis may occur in 10% to 50% of patients with a history of indwelling dialysis catheters.
III. Vascular access options.
Hemodialysis works by filtering the patient’s blood to remove fluid, electrolytes, and toxins—functions that are normally performed by the kidneys. To achieve this end, the patient must have a dialysis access established that can withstand high flows and repeated trauma from cannulation. Establishing a connection between the arterial and venous system is the most effective way to create such a high-flow circuit. A direct connection between an artery and vein (i.e., AV fistula) results in enlargement and thickening of the outflow vein. As the vein matures, it undergoes “arterialization,” making it strong enough to support hemodialysis. A prosthetic bridge graft can also be used to connect an artery and vein (i.e., arteriovenous graft), so that the graft and not a vein is punctured for dialysis. An extremity is the most accessible and common location for either type of dialysis access.
In 1997, The National Kidney Foundation published evidence-based guidelines on all aspects of vascular access, referred to as Kidney Disease Outcome Initiative (K/DOQI)
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