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Acs0626 Medical Management Of Vascular Disease


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Acs0626 Medical Management Of Vascular Disease

  1. 1. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 1 26 VASCULAR AND PERITONEAL ACCESS Bernard Montreuil, M.D., M.Sc., F.A.C.S., F.R.C.S.C., and Martine Leblanc, M.D., F.R.C.P.C. Arteriovenous Access Assessment of Venous System The prevalence of end-stage renal disease (ESRD) in the A history of subclavian vein cannulation or transvenous pace- United States has increased steadily since 1980, rising from 271 to maker placement is associated with a 10% to 40% rate of central nearly 1,400/million. It is estimated that by 2030, there may be vein stenosis or thrombosis.10 Previous injuries or operative proce- 2.24 million patients with ESRD. Almost 60% of these patients dures involving the arm, the neck, or the chest, including previous are expected to be diabetic, half to be 65 or older, and half to be vascular access, also may give rise to significant venous abnormal- nonwhite.1 ities. Physical signs of venous outflow obstruction include extrem- Extracorporeal dialysis of blood was introduced in 1943 by ity edema, differences in arm size, and development of collateral Kolff and associates2; however, application of this approach was veins. All of these historical and physical findings call for investiga- hindered by the requirement for repeated and routine access to tion by means of venography. Duplex ultrasonography is an alter- the circulation. The full potential of hemodialysis for patient sal- native, but it is poor at assessing central vein stenosis.11 Central vein stenosis greater than 50% is a contraindication to creation of vage was realized only after the introduction of the external arte- an ipsilateral distal autogenous AV access: it is a predictor of riovenous (AV) shunt by Quinton and colleagues in 19603 and of venous hypertension and edema in the arm and of poor access the autogenous AV access by Brescia and coworkers in 1966.4 The function. subsequent introduction of synthetic vascular prostheses has per- Selection of the ideal vein for access is facilitated by distending mitted continued access in patients who have exhausted peripher- the veins with a tourniquet around the upper arm. In particular, al venous sites.5 the cephalic vein is palpated from the region of the anatomic The optimal vascular access route permits a flow rate that is snuff-box to the area above the elbow. Percussion of the vein is adequate for the dialysis prescription (≥ 300 ml/min), can be used performed to confirm that it is patent and to rule out stenosis from for extended periods, and has a low complication rate. Compared previous venipuncture. The fingertips of one hand are positioned with other access types, an autogenous AV access has the best over the vein at the elbow, and the vein is gently tapped distally long-term patency, gives rise to the fewest complications, and with the other hand. If the vein is patent and of substantial diam- requires the fewest interventions once fully mature.6 In 1997, the eter, a fluid wave is felt over the proximal vein. National Kidney Foundation Dialysis Outcome and Quality Initiative (NKF-DOQI)7 organized multidisciplinary work groups Assessment of Arterial System that evaluated all available data and concluded that quality of life A history of arterial trauma or catheterization, diabetes mellitus, and overall outcome could be improved significantly for or peripheral arterial disease may be associated with chronic dam- hemodialysis patients if two primary goals were achieved: age to the arterial system. Physical examination involves palpation of the pulses (including both brachial and axillary pulses) and 1. Insertion of an autogenous AV access in at least 50% of comparison of blood pressure in the arms. A difference of more long-term access patients. than 20 mm Hg between the two sides suggests proximal arterial 2. Detection of dysfunctional access before thrombosis of occlusive disease, which may cause the AV access to fail as a result the access route occurs. of inadequate inflow. An Allen test is also performed to confirm This report, which contains evidence-based clinical practice that the palmar arch is patent, to determine which artery is the guidelines, was last updated in 2000.8 Similar guidelines have also dominant vascular supply to the hand, and to ensure that the ulnar artery can support the hand if the radial artery must be divided. been published in Canada.9 Any abnormality on physical examination should be further inves- PREOPERATIVE EVALUATION tigated by means of arterial studies in the vascular laboratory; in selected cases, angiography may be indicated. At least 4 to 6 weeks—preferably 3 to 4 months—is required for an autogenous AV access to heal and mature before it can be used. Noninvasive Preoperative Assessment Therefore, access planning should be done early in the course of Systematic use of noninvasive evaluation in the vascular labora- progressive renal failure. Patients should be referred for surgical tory permits objective assessment of arterial and venous conduits. treatment when creatinine clearance approaches 15 to 20 ml/min, If necessary, venous conduits other than the cephalic and basilic the serum creatinine level reaches 300 to 500 µmol/L, or dialysis veins may be identified, and both arterial and venous segments is likely to be necessary within 1 year. Every effort should be made may be mapped with skin marks to facilitate the operative proce- not to puncture forearm veins, particularly the cephalic veins of dure. The aims are to increase the use of autogenous fistulas and the nondominant arm; the dorsal hand veins may be used for to raise the early and late patency rates by decreasing the use of venipuncture. Subclavian vein catheterization should also be suboptimal veins and arteries. When an all-autogenous policy is avoided because of the risk of central vein stenosis, which may pre- followed, approximately 80% of patients are candidates for an clude the use of any part of the ipsilateral arm for vascular access. autogenous access.12 1
  2. 2. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 2 formation; however, use of this vein in situ for needle cannulation Table 1 Noninvasive Criteria for Selection and hemodialysis may necessitate placing the forearm in an of Upper-Extremity Arteries and Veins for uncomfortable position. In the great majority of cases, such veins Dialysis Access Procedures12 can be successfully transposed to a superficial tunnel in the mid- portion of the volar aspect of the forearm, and the resulting access Venous examination theoretically has the same advantages as a radial-cephalic direct Venous luminal diameter ≥ 2.5 mm for autogenous AVFs, ≥ 4.0 mm for bridge AV grafts wrist access in terms of long-term patency and complication rates. Absence of segmental stenoses or occluded segments This aggressive approach to autogenous forearm AV access for- Continuity with the deep venous system in the upper arm mation also has the advantage of preserving more proximal ves- Absence of ipsilateral central vein stenosis or occlusion sels for future access placement. Arterial examination If duplex ultrasonography does not identify an adequate fore- Arterial luminal diameter ≥ 2.0 mm arm vein conduit, an autogenous brachial-cephalic upper-arm Absence of pressure differential ≥ 20 mm Hg between arms direct access is the next choice. It is easy to create and has the Patent palmar arch advantage of providing higher blood flow than the wrist access. The cephalic vein in the upper arm, because of its position and superficial location, is easy to cannulate and easily covered (a Complete noninvasive assessment includes segmental pressure potential cosmetic benefit).The elbow AV access has a theoretical measurements of the upper extremity, arterial waveform record- advantage in diabetic patients, in whom medial calcification of the ing, and arterial and venous duplex studies. A tourniquet should distal radial artery commonly prevents the gradual arterial dilata- be placed on the arm, and tapping and stroking maneuvers should tion required for full maturation of a wrist access. In fact, some be used to distend the vein maximally. Established criteria [see authors consider an upper-arm autogenous AV access (either Table 1] are then applied to determine whether venous outflow brachial-cephalic or brachial-basilic) the preferred approach in and arterial inflow are likely to be satisfactory. this particular subgroup of patients17; however, this view has been OPERATIVE PLANNING challenged by studies that found no difference between diabetic and nondiabetic patients with respect to prognosis for wrist fistu- Choice of Type of AV Access las.18,19 Disadvantages of brachial-cephalic accesses include high- Multiple varieties of AV access have been used in hemodialysis er frequencies of arm swelling and steal syndrome than are seen patients.The terms and definitions we employ here are those rec- with wrist accesses. ommended by the Committee on Reporting Standards of the If the cephalic vein in the upper arm is unsuitable, the remain- Society for Vascular Surgery (SVS) and the American Association ing options include prosthetic access and brachial-basilic upper- for Vascular Surgery (AAVS).13 arm transposition. An AV access using transposed basilic vein has According to the NKF-DOQI report,7 the order of preference all the attributes of an autogenous access and consequently is pre- for AV access types in patients requiring long-term hemodialysis ferred to a prosthetic access despite being more difficult to create. is as follows: Its protected, deep subfascial position and large caliber make it a 1. Autogenous radial-cephalic direct wrist access (radio- high-quality conduit for hemodialysis access. Its advantages over cephalic fistula or Brescia-Cimino fistula). a prosthetic access include the avoidance of the distal venous 2. Autogenous brachial-cephalic upper-arm direct access anastomosis (which causes the majority of stenoses in prosthetic (brachiocephalic fistula). accesses) and higher primary and secondary patency rates.20 Flow If neither of these can be constructed, access may be achieved via rates are high in basilic vein fistulas because of the large size of the either of the following: vein, and the infection rate is relatively low. Furthermore, throm- bosis of a brachial-basilic AV access does not compromise the 3. Autogenous brachial-basilic upper-arm transposition. integrity of the axillary vein and thus does not preclude subse- 4. Nonautogenous (prosthetic) AV access. quent use of a prosthetic conduit at the same site.Therefore, when All of these fistulas should be established in the nondominant a functional brachial-cephalic AV access cannot be achieved, a arm, if possible. brachial-basilic transposition should be considered before an The autogenous radial-cephalic direct wrist access remains the upper-arm prosthesis is placed.21 gold standard in terms of ease of creation and long-term results. If no veins in either upper extremity are suitable for a native AV Its advantages considerably outweigh its disadvantages—namely, access, then the use of prosthetic material should be considered. a higher primary failure rate (approximately 15%)14 and a long Two options are available. First, if a segment of vein at least 15 cm maturation time (1 to 4 months). It may be constructed either in long is available but is too far from the artery to be used in the cre- the anatomic snuff-box or just above the wrist crease. Although ation of a fully native fistula, a jump graft can be constructed the radial artery is smaller in the snuff-box than it is at the classic Brescia-Cimino fistula site, the long-term results at the two sites between the artery and the vein, and the arterialized vein can be are comparable if only arteries of adequate diameter are used.15 used as the needle conduit for dialysis. Second, the graft itself can An alternative method of creating an AV access in the forearm be used as the needle conduit for dialysis.The data currently avail- that was not mentioned in the NKF-DOQI report is forearm vein able suggest that extruded polytetrafluoroethylene (ePTFE) is transposition.16 Preoperative duplex ultrasonography often identi- preferable to other prosthetic materials: ePTFE grafts are less fies veins that, except for their deep subcutaneous location, are thrombogenic, nonantigenic, and easy to handle. Grafts may be suitable for AV access formation. In addition, the basilic vein in placed in straight, looped, or curved configurations on either the the forearm is often spared and is frequently suitable for AV access forearm or the upper arm.
  3. 3. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 3 OPERATIVE TECHNIQUE Radial Artery Cephalic Vein Autogenous AV Access Autogenous radial-cephalic direct wrist access The arm is placed on an arm board in 90º of abduction. A tourniquet is applied to the upper arm to distend the cephalic vein, and the vein’s course is marked on the skin. The tourniquet is then released. Local anesthesia using 0.5% or 1% lidocaine without epineph- rine is usually adequate for construction of an autogenous AV access at the wrist or the antecubital fossa. General anesthesia may depress cardiac output and thus may, by reducing fistula flow, exert a negative impact on the success of the fistula. Conversely, brachial or supraclavicular regional anesthesia may cause periph- eral vasodilatation and thus increase arterial blood flow. A longitudinal incision is placed either in the anatomic snuff-box, Figure 2 Autogenous radial-cephalic direct wrist access (Brescia- between the tendons of the extensor pollicis longus and the exten- Cimino AV fistula). An incision is made midway between the radial sor pollicis brevis [see Figure 1], or midway between the cephalic artery and the cephalic vein, and the end of the vein is anasto- vein and the radial artery, proximal to the wrist skinfold [see Figure mosed to the side of the artery. 2]. In the anatomic snuff-box, the cephalic vein overlies the radial artery, so that minimal mobilization is required to approximate the the vein, which contributes approximately 30% of the total flow two vessels. Slightly more mobilization is required to approximate of the fistula, this approach yields maximal blood flow through the cephalic vein to the radial artery above the wrist without kink- the fistula.There is a risk of steal syndrome with such fistulas, but ing or twisting. A comparable length of radial artery, found under this problem can easily be corrected by ligating the radial artery the deep fascia, is also isolated. Care is taken to preserve the super- distal to the fistula, thereby converting the anastomosis to an end- ficial branch of the radial nerve, which lies lateral to the radial artery to-end configuration. and is separated from it by the brachioradialis muscle. Vascular control is obtained with small vessel loops or Heifets Four types of anastomoses can be constructed: side to side, end clamps. Heparinization is not needed unless the artery is an end of vein to side of artery, end to end, and end of artery to side of artery. A 1cm arteriotomy is performed, and the vein is ligated and vein.The side-to-side anastomosis [see Figure 3a] yields the highest divided distally and tailored to match the arteriotomy. Coronary flow through the fistula but may be associated with venous conges- dilators are then inserted gently to verify patency and to ensure that tion of the hand. Over time, arterial pressure may render the valves the vessel lumina are large enough: the artery should easily admit of the distal vein incompetent, resulting in retrograde flow toward a 2 mm dilator; the vein, a 3 mm dilator.The vessels are then anas- the hand and venous hypertension. The end of artery–side of vein tomosed in the desired configuration with a fine continuous mono- anastomosis [see Figure 3b] also presents a risk of venous hyperten- filament suture (6-0 or 7-0 polypropylene) placed by means of sion. This configuration reduces the risk of distal steal by prevent- standard techniques.The vessels can be probed with the coronary ing retrograde flow into the fistula, but at the price of lower flow dilators before the anastomosis is completed, to confirm that the through the fistula. Of the four options, the end of artery–end of vein is not twisted or to overcome any arterial spasm. Once vascu- vein variation [see Figure 3c] produces the least distal arterial steal lar control is released, a thrill should be easily felt over the fistula and venous hypertension but yields the lowest flow. and for a moderate distance along the venous conduit.The skin is The preferred configuration of the anastomosis is end of vein closed with an absorbable suture. to side of artery [see Figure 3d]. Dividing the vein reduces the risk of venous congestion in the hand; moreover, by allowing retro- Autogenous vein transposition in forearm (radial-bas- grade flow from the distal radial artery and the ulnar artery into ilic, ulnar-basilic, radial-cephalic, or ulnar-cephalic) The selected artery and vein are identified and mapped preoperatively by means of duplex ultrasonography. Positioning and anesthetic considerations are essentially the same as for a radial-cephalic Cephalic Vein direct wrist access. A longitudinal incision is made directly over the mapped vein, beginning at its distal end and extending toward the antecubital fossa for a distance of at least 15 cm [see Figure 4a]. The vein is gently skeletonized and mobilized by ligating and dividing all side branches. The targeted artery (either the radial or the ulnar) is identified and dissected through a separate incision. A superficial subcutaneous tunnel is made between the two incisions with a blunt tunneling instrument, and the vein is passed through the tunnel [see Figure 4b]. The vein should be marked along its length Radial Artery with a marking pen before tunneling; this step provides a visual check that allows the surgeon to confirm that the vein is not twist- Figure 1 Autogenous posterior radial branch–cephalic direct ed as it passes through the tunnel. A 1 cm anastomosis is then car- access (snuff-box fistula). The end of the cephalic vein is anasto- ried out in the same fashion as for a radial-cephalic direct wrist mosed to the side of the radial artery. access (see above).
  4. 4. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 4 a b c d Figure 3 Autogenous AV access. Four anastomotic configurations are possible: (a) side of artery to side of vein, (b) end of artery to side of vein, (c) end of artery to end of vein, and (d) end of vein to side of artery (the preferred configuration). An alternative technique that may be employed in patients with patent, sufficiently wide, and in continuity with the cephalic vein, atherosclerotic disease of the forearm arteries involves mobilizing it is dissected so that the perforating branch of the antecubital the forearm segment of either the cephalic or the basilic vein, venous system (vena mediana cubiti profunda) can be located. transposing it to form a U-shaped loop, and anastomosing it to the The bicipital aponeurosis is divided, and the perforating branch is brachial, proximal radial, or proximal ulnar artery in the antecu- followed down to the deep system. In the process, the brachial bital fossa.22 artery is also exposed, as are the origins of the radial and ulnar arteries. Autogenous brachial-cephalic upper-arm direct access The confluence of the brachial vein and the perforating vein is After adequate local anesthesia, a transverse incision is made 1.5 identified, and part of the brachial vein is excised so as to form a cm distal to the antecubital crease to expose the superficial ante- venous patch. The perforating vein is gently dilated, so that any cubital venous system [see Figure 5a]. If the median cubital vein is valves are rendered incompetent, and the proximal median cubital vein is ligated to prevent diversion of blood flow into the basilic vein. Either the patient is fully heparinized, or the arterial inflow and outflow vessels are flushed with a heparinized solution. The a perforating vein is then anastomosed to the brachial artery in an end-to-side fashion [see Figure 5b].23 To prevent subsequent steal syndrome, the arteriotomy should be no larger than 5 to 6 mm. Other techniques may be used if the perforating vein is very large or very small. If the perforating vein is 5 mm or more in diameter, it may be anastomosed directly to the artery without a patch. If the vein is less than 2.5 mm in diameter, it should not be used; instead, the median cubital vein should be ligated and divid- ed and the cephalic end of the vein anastomosed directly to the b brachial artery in an end-to-side fashion [see Figure 5c]. If the Radial Artery median cubital vein is too small, the incision is extended laterally and proximally to allow mobilization of the cephalic vein. The length of this incision depends on the extent to which the cephal- ic vein must be mobilized to ensure a tension-free end-to-side anastomosis.The accessory cephalic vein, though located far later- ally, may also be used. Repeated venipunctures in the antecubital fossa frequently render the antecubital venous system unsuitable for AV access construction. In such cases, two options are available if the Figure 4 Autogenous vein transposition in forearm. (a) The selected vein, identified by duplex ultrasonography, is completely patient has at least 15 cm of good-quality cephalic vein in the mobilized. (b) The vein is transposed through a superficial tunnel upper arm. The first option is to mobilize a sufficient length of in the midportion of the volar aspect of the forearm and anasto- the cephalic vein in the distal upper arm through a longitudinal mosed to the radial artery in an end-to-side fashion. incision, to transpose it medially through a superficial tunnel,
  5. 5. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 5 a b Median Accessory Cubital Cephalic Vein Vein Cephalic Basilic Vein Vein Perforating Vein c Brachial Artery Figure 5 Autogenous brachial-cephalic upper-arm direct access. (a) A transverse incision exposes the antecubital venous system (including the perforating branch) and the brachial artery under the bicipital aponeurosis. (b) An end-to-side anastomosis is made between the perforating vein and the brachial artery. (c) If the perforating vein is too small, the cephalic vein is mobilized and anastomosed to the brachial artery in an end-to-side fashion. and then to anastomose it in an end-to-side fashion to the brachial artery, which has been exposed above the elbow through a separate incision. The second, which avoids extensive dissection of the cephalic vein, is to place two short longitudinal incisions over the brachial artery and the cephalic vein a few cen- timeters above the elbow crease, to tunnel a short segment of 6 Brachial Artery mm ePTFE graft between the two incisions, and to anastomose the ePTFE graft to both the brachial artery and the cephalic vein in an end-to-side fashion [see Figure 6].24 The cephalic vein ePTFE Jump Graft is used as the needle conduit for this type of AV access. Autogenous brachial-basilic upper-arm transposition The technique for constructing a brachial-basilic access was described first by Dagher and associates in 197625 and then by LoGerfo and colleagues in 1978.26 Local anesthesia can be used, but an axillary block eases the procedure considerably. An oblique Cephalic Vein incision overlying the median basilic vein is made in the antecu- bital fossa, and the vein is mobilized. The brachial artery is exposed as usual by dividing the bicipital aponeurosis. The inci- sion is extended along the medial aspect of the upper arm (the so- called hockey-stick incision), and the basilic vein is mobilized from beneath the fascia, with care taken to preserve the medial cuta- neous nerve of the forearm [see Figure 7a].The basilic vein usual- Figure 6 Autogenous upper-arm AV access. If the antecubital ly pierces the brachial fascia just below the middle of the upper venous system is unsuitable for AV fistula construction, one option arm, then parallels the course of the brachial artery and vein while is to place an ePTFE interposition graft between the brachial remaining superficial to them. At the axillary level, the basilic vein artery and the cephalic vein.
  6. 6. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 6 the vein remains in its medial location, its new superficial position facilitates cannulation for dialysis. a It should be mentioned that the basilic vein can be elevated either at the time of brachial-basilic AV access creation (the one- stage technique) or as part of a second procedure (delayed eleva- tion) approximately 4 weeks later. The advantage of the latter approach is that operative dissection is facilitated by the use of an arterialized thick-walled vein. In addition, delayed elevation allows assessment of the fistula for size and flow rate before the second stage, which can be abandoned if the vein has failed to mature.28 Prosthetic AV Access Basilic Vein Prosthetic AV access procedures involve placing an interposi- tion graft between an artery and a vein and using that graft as the needle conduit for dialysis. In the forearm, the most common con- Median Cubital figurations are loop grafts between the brachial artery and an ante- Vein cubital vein (including the brachial veins)29 and straight grafts from the radial artery to an antecubital vein.There are data to sug- Basilic Vein gest superior patency rates with a loop configuration, but it is b unclear whether this difference is related to the graft configuration or to the size of the inflow artery.30 Acceptable results may be obtained with a straight graft in the forearm if the radial artery is at least 2.5 to 3.0 mm in diameter. Secondary options for prosthetic AV access construction include a variety of unusual configurations, including reverse grafts between the axillary artery and the brachial or the antecu- bital vein and axilloaxillary grafts, which may be looped in the upper arm or may cross the sternum. It is also possible to con- Brachial Artery struct a looped graft between the proximal superficial femoral artery and the proximal saphenous vein or a straight, reversed graft Figure 7 Autogenous brachial-basilic upper-arm transposition. between the distal superficial femoral or popliteal artery and the (a) The basilic vein is completely mobilized from underneath the fascia in continuity with a section of the median cubital vein in proximal saphenous or femoral vein [see Figure 8]. Generally, such the antecubital fossa. (b) The vein is transposed in a subcuta- lower-limb AV accesses are associated with an increased risk of neous tunnel on the anterior surface of the arm and anastomosed potentially life- or limb-threatening infection; however, infection to the brachial artery in an end-to-side fashion. rates as low as 22% have been reported, making these grafts a viable option when a prosthetic AV access in the upper extremity cannot be constructed.31 joins the brachial vein to form the axillary vein; this junction con- Either local anesthesia or axillary block is usually appropriate stitutes the proximal limit of the dissection. In 5% of cases, how- for upper-extremity prosthetic accesses. A single dose of a ever, the basilic vein empties into the brachial vein in the middle cephalosporin should be given before the procedure. Separate lon- of the upper arm. This anatomic variation should be identified gitudinal incisions are placed to expose the artery and the vein— preoperatively on the duplex examination; if present, the proce- except when the procedure involves the brachial artery and the dure cannot be carried out, because there will be insufficient antecubital venous system, which are better exposed through a venous length for transposition. single transverse incision. A 6 mm or a tapered 4 to 7 mm ePTFE The distal end of the conduit vein may consist of either the graft is then passed through a superficial tunnel between the two basilic vein or a section of the median cubital vein, which is already incisions. Both anastomoses are constructed in an end-to side exposed. All venous tributaries are ligated and divided.The vein is fashion, beginning with the venous side. Systemic heparinization divided distally, and its anterior surface is marked to help the sur- is used if an end artery is occluded for the arterial anastomosis. geon avoid axial rotation during transposition. The vein is then passed through a subcutaneous tunnel on the anterior surface of TROUBLESHOOTING the arm and anastomosed in an end-to-side fashion to the brachial artery in the antecubital fossa with 6-0 or 7-0 polypropylene [see Autogenous AV Access Figure 7b]. This transposition places the vein in a more superficial Although the quality of the AV conduit is assessed preoperative- location and positions it anterolaterally on the arm, thereby facili- ly by means of physical examination and noninvasive studies, it tating cannulation during hemodialysis sessions. Closure involves should also be confirmed intraoperatively for optimal results. approximating the fascia and the subcutaneous tissue in two sep- arate layers. Arterial inflow Normally, a strong pulse is felt over the tar- A modification of the procedure just described is the so-called geted artery; however, dissection may cause spasm, which can ren- elevated basilic vein AV access.27 In this variant, the vein is left in der intraoperative assessment difficult. The following three mea- situ rather than transposed anterolaterally, but it is elevated by sures will help minimize this problem: closing the deep fascia and the subcutaneous tissue beneath the vein.The brachial artery anastomosis is created, and the overlying 1. Elimination of epinephrine from the anesthetic solution. skin is reapproximated with clips or interrupted sutures. Although 2. Gentle dissection and avoidance of direct manipulation of
  7. 7. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 7 a b c d e f g h Figure 8 Prosthetic AV access. Options for prosthetic access construction include (a) prosthetic forearm straight access, (b) prosthetic brachial-antecubital forearm loop access, (c) prosthetic brachial-axillary straight access, (d) prosthetic axillary-axillary loop access, (e) prosthetic axillary-axillary chest straight access, (f) pros- thetic axillary-femoral body wall access (g) prosthetic femoral-femoral straight access, and (h) prosthetic femoral-femoral looped inguinal access. the arterial wall. It may be preferable to use a proximal Webs, thickened valve leaflets, and areas of sclerosis from pre- tourniquet for inflow occlusion so that there is no need to vious phlebitis or punctures are common in upper-extremity veins place clamps on small arteries. and may be the cause of poor venous outflow and access failure. 3. Local application of a papaverine solution, which relaxes Passage of the coronary dilator helps to localize such obstructive vascular smooth muscle. lesions, which should be corrected when found. The patency of the proximal vein can be demonstrated by free flow of injected If spasm occurs, gentle probing of the artery with coronary dila- heparinized saline or by successful passage of a Fogarty catheter. tors may help relieve the spasm and restore full flow. The evoked thrill is also a useful maneuver: intermittent, pulsatile Stiff, calcified arteries can sometimes be successfully used in injection of saline into the vein, mimicking arterial flow, should the creation of fistulas, but it is difficult to assess flow in such ves- produce a palpable thrill over the proximal vein.32 The absence of sels. Quantitative and qualitative analyses of the arterial waveform an evoked thrill suggests the presence of stenosis or areas of thick- and the intraluminal diameter by means of duplex scanning can ened, nondistensible vein wall proximally. Intraoperative phlebog- help confirm the adequacy of the vessel.Arteries smaller than 1.5 mm raphy is indicated in any doubtful situation. are less likely to provide sufficient flow for a fistula. It is particu- larly important not to place clamps on calcified arteries; a tourni- AV anastomosis Both the artery and the vein should be quet is always preferred in this situation. mobilized sufficiently to ensure that the anastomosis is tension- free once completed. As noted (see above), marking the most Venous outflow A venous diameter of at least 2.5 to 3.0 mm superficial aspect of the vein with a sterile pen before mobilization is required for successful maturation of an autogenous AV access. helps ensure that the vein is not rotated when it is approximated The diameter of the target vein should be known preoperatively to the artery. The ideal anastomosis is constructed by transecting from the duplex examination and should be confirmed intraopera- the vein just distal to a bifurcation and using the branch vessel as tively by calibration with coronary dilators. No attempt should be made a patch. Such a spatulated venous conduit facilitates the anasto- to dilate the vein, however, because endothelial injury may result. mosis and minimizes the risk of anastomotic stenosis.
  8. 8. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 8 If the arterial inflow site is either the radial or ulnar artery, the anastomosis should be about 10 mm long to ensure that a gradual increase in flow through the fistula can occur. An anastomosis that is too small may impair the normal dilation of the artery and the vein. For AV access in the antecubital space and the upper arm, in contrast, the arteriotomy should be limited to 5 to 6 mm to pre- vent excessive shunting. The anastomosis can be performed with standard vascular techniques. However, construction of the anastomosis with a sin- gle continuous suture may have a purse-string effect; accordingly, the use of two separate running sutures may be preferable for small vessels. Interrupted stitches are preferable for very small ves- Figure 9 Prosthetic brachial-antecubital forearm loop access. sels. Using nonpenetrating vascular clips for the anastomosis is With a loop forearm graft, tunneling of the graft is facilitated by quicker and may improve patency.33 making an incision 1.5 cm distal to the elbow crease to expose the When the anastomosis is completed, vascular control should be brachial artery and the antecubital venous system, followed by a counterincision at the apex of the tunnel 3 to 4 cm proximal to released from the proximal vein and the distal artery first; the the wrist skinfold. resultant back-bleeding will confirm the patency of the palmar arch and reveal any major anastomotic defects. Gentle compres- sion is usually sufficient to obtain hemostasis. Any additional ated to prevent venous hypertension and arm edema. sutures deemed necessary should be placed with great caution If no veins of adequate diameter are available, either two adja- because of the risk that they may narrow the anastomosis. cent veins or a portion of a transverse communicating vein can be The presence of a pulse rather than a thrill in the arterialized used to construct a venoplasty that will increase the net diameter vein indicates inadequate outflow, whereas the absence of either a of the venous outflow tract. Alternatively, the deep brachial or axil- thrill or a pulse indicates poor inflow.The draining vein should be lary veins can be used for outflow. The latter option is often examined for kinking, twisting, or compression by a fibrous band. required when the superficial veins have been exhausted in a If the vein appears to be satisfactory, the anastomosis and the dis- patient who has previously had autogenous AV accesses. tal vein are inspected and probed with dilators through a venous side branch or a transverse phlebotomy. If no abnormality is iden- Arterial anastomosis The artery should have a lumen of at tified, the fistula is examined with I.V. contrast studies and fluo- least 3 mm, and the arteriotomy should be no more than 5 to 6 roscopy. Focal lesions may be corrected by placement of a vein mm long to prevent distal ischemia. ePTFE sutures are useful for patch or a short interposition graft or by resection and primary arterial anastomoses: because they have the same diameter as the reanastomosis. Alternatively, a short segment of the vein may be attached needles, needle-hole bleeding is minimized. excised and the anastomosis repositioned more proximally. Before the arterial anastomosis is completed, the graft is Prosthetic AV Access unclamped and allowed to fill with venous blood; this step pre- vents air embolism when arterial control is released. When the Skin incisions Incisions should be placed so that neither the anastomosis is complete, a thrill should be palpable over the graft nor the anastomoses lie directly beneath them. Proper place- venous outflow tract rather than directly over the graft. ment reduces the risk of skin erosion, minimizes the risk that the graft will become infected if a surgical site infection occurs, and Graft type The choice between a tapered 4 to 7 mm ePTFE maximizes the length of conduit available for needle insertion.The subcutaneous tissue and skin should be closed in separate layers to graft and a 6 mm straight graft is a matter of personal preference. minimize the risk of graft infection in the event of skin dehiscence. The tapered graft was introduced to reduce the incidence of steal syndrome by increasing the resistance to flow through the prosthe- Tunneling The tunnel should be made atraumatically with a sis; however, it has not been shown to provide consistent Kelly-Wick bidirectional tunneler. It should be superficial to the protection from ischemic complications. Various modifications in muscle fascia but no more than 5 mm beneath the skin surface.To wall thickness, external wraps, ring support, and configuration of decrease the risk of hematoma, there should be a close fit between the venous end (e.g., hooded versus nonhooded) have been mar- the diameter of the graft and that of the tunnel, and the graft keted by manufacturers of ePTFE grafts; although these modifi- should be placed before systemic heparinization is initiated. cations may influence outcome, none has yet demonstrated a clear For a loop configuration, a counterincision at the apex of the superiority.34 tunnel permits the tunnel to be created in two passes of the Kelly- FOLLOW-UP Wick tunneler.This approach gives the tunnel a smooth curve and limits kinking of the graft. In the forearm, this transverse counter- Upon discharge, the patient is instructed to elevate the arm so incision is usually made 3 to 4 cm proximal to the wrist skinfold as to reduce edema. Regular hand and arm exercise, though not of [see Figure 9]. Careful observation of the stripe on the graft as it is proven benefit, is nonetheless recommended until the access passed through the tunnel helps prevent twisting. matures. Physical examination of the access, including inspection and Venous anastomosis To minimize arterial occlusion time, palpation for pulse and thrill, should be done on a weekly basis. the venous anastomosis is usually performed first. The vein must The patient should also be advised to seek prompt medical atten- be at least 4 mm in diameter; venous diameter and patency are tion if the quality of the thrill changes. Normally, a thrill is palpa- verified by passing coronary dilators or a Fogarty catheter through ble throughout the cardiac cycle, though it is more intense during the vessel and irrigating it with heparinized saline. Before the anas- systole. Disappearance of the diastolic component of the thrill is tomosis is performed, the distal vein and all side branches are lig- generally a consequence of outflow obstruction. Such obstruction
  9. 9. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 9 may also cause the thrill to be converted to a pulse. Any of these tive prepump pressure. Arterial stenosis may be suspected even abnormal findings is an indication for a diagnostic procedure: sal- before dialysis is initiated if a patent vein does not enlarge signifi- vage attempts are much more likely to succeed if carried out cantly within several weeks of fistula creation. Angiography pro- before thrombosis has occurred. vides a definitive diagnosis. Stenosis of the distal artery, the anas- ePTFE grafts should not be used until at least 14 days have tomosis, or the distal vein is best treated with reanastomosis prox- passed since placement and until the swelling has subsided imal to the stenotic area. More proximal stenosis may have to be enough to allow palpation of the graft. This waiting period allows treated with conventional arterial reconstruction. adhesions to form between the subcutaneous tunnel and the graft, thereby decreasing the risk of hematoma in the graft tunnel, which Early Thrombosis may ruin the access site. A minimum of 1 month is required Early thrombosis is defined as thrombosis occurring within 3 before an autogenous AV access may be cannulated. It is prefer- months of access construction. It is usually the result of technical fac- able, however, to wait until the fistula matures fully, which may tors or of inadequate assessment of the arterial or venous conduit. take 3 to 4 months. The following are the most common causes of early thrombosis: COMPLICATIONS 1. Inadequate arterial inflow caused by proximal arterial disease. Venous Stenosis 2. Narrowing of the anastomosis during construction. 3. Kinking or twisting of the vein proximal to the anastomo- Venous stenosis resulting from neointimal hyperplasia is a com- sis or in a subcutaneous tunnel. mon long-term complication of AV access construction. In a wrist 4. Undetected occlusion of venous outflow. access, the most common site of stenosis is at or around the anas- 5. Compression of the fistula by a hematoma resulting from tomosis; in an upper-arm (elbow) access, it is in the proximal either inadequate hemostasis during the procedure or early draining vein. Prophylactic intervention for venous stenoses puncture of the fistula with subsequent extravasation of reduces the rate of thrombosis and graft loss, and stenoses detect- blood. ed before thrombosis occurs are more responsive to therapy than those detected afterward.35 Intervention is indicated when steno- If early thrombosis is thought to be caused by technical compli- sis exceeding 50% of the lumen diameter (documented by duplex cations and not by the use of marginal vessels, reexploration is ultrasonography or fistulography) is accompanied by a hemody- worthwhile. Reexploration usually involves takedown of the anas- namic, functional, or clinical abnormality (e.g., decreased access tomosis, thrombectomy of the conduit, reevaluation of both arte- blood flow, elevated static or dynamic venous pressure, increased rial inflow and venous outflow, corrective measures as needed, recirculation, reduced delivered dialysis dose, or arm edema).8 and reanastomosis. Both autogenous and prosthetic AV accesses Prophylactic intervention for anatomic stenosis is not warranted may be profitably reexplored.With an autogenous access, reexplo- when such findings are absent.36 ration should be done within 24 hours of thrombosis to minimize The question of whether angioplasty or surgical revision is the ischemic endothelial injury. preferable method of intervention remains controversial. Because endovascular treatment is less invasive and more expedient for Late Thrombosis both patient and surgeon, it may be the preferable initial approach Autogenous AV access Little information is available on in many cases. As a rule, if angioplasty is required more than twice success rates for treatment of thrombosis in an autogenous AV within 3 months, the patient should be evaluated for possible sur- access; however, it seems that neither percutaneous nor surgical gical revision. Treatment options include patch angioplasty for techniques offer good results. Thrombosis of an autogenous localized or anastomotic stenoses, bypass for longer stenoses, relo- access most commonly results from an aneurysm of the fistula, cation of the venous anastomosis to a new vein, and resection of hyperplastic stenosis at the anastomosis or in the vein just distal to the stenotic segment with interposition grafting. the anastomosis, fibrosis at an area of repeated needle punctures, or kidney transplantation. Central venous stenosis Stenotic or occlusive lesions of the The surgical approach should include exposure of the vein just central veins develop in as many as 40% of patients who have pre- distal to a clinically apparent or suspected venous stenosis. The viously undergone subclavian hemodialysis catheter placement for vein is opened longitudinally and the thrombus evacuated. temporary vascular access.10 When a vascular access graft or fistula Adequacy of venous outflow is assessed with a Fogarty catheter or is placed distal to these lesions, they may become symptomatic, coronary dilators. If a segment less than 4 mm in diameter is resulting in venous hypertension, arm edema, low access flow, or encountered, the problem is corrected with patch angioplasty, thrombosis. Percutaneous intervention with transluminal angioplas- vein bypass, or resection and primary anastomosis. (The last of ty is the preferred treatment; the tendency for central venous steno- these three approaches is often easy to perform because the tortu- sis to recur soon after treatment37 may be circumvented by the addi- osity of the vein allows easy mobilization and length extension.) tion of a stent, but the effect of stenting on long-term patency remains Central vein stenosis is corrected with intraoperative balloon unproven. Stents are particularly helpful for treating rigid or kinked angioplasty. stenoses, for sealing dissections or circumscribed perforations, and When the venous side of the access is in satisfactory condition, for reestablishing the patency of chronically occluded veins. Surgical the thrombus is removed from the arterial limb. Any suspected repair of central venous obstruction is a major undertaking and is anastomotic or proximal arterial stenosis should be corrected [see reserved for those occasional cases in which percutaneous proce- Prosthetic AV Access, below]. If the thrombosis resulted from a dures have failed in a patient with no alternative access site. venous aneurysm containing adherent thrombus, the aneurysm should be repaired to prevent recurrent thrombosis. Arterial Stenosis Arterial stenosis is relatively uncommon. It should be corrected Prosthetic AV access The majority of prosthetic graft if it is associated with diminished access flow and elevated nega- thromboses are caused by stenosis of the venous anastomosis or
  10. 10. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 10 of the draining vein as a result of intimal hyperplasia.38 Treatment tomosis. If the stenosis is short, smooth, and hyperplastic, a small of a thrombosed graft has only a 10% chance of success if the patch angioplasty is adequate for repair. If the stenosis is long or if underlying venous stenosis is not addressed. Although arterial the vein is sclerotic, revision to a new venous outflow site is pre- stenoses are less common causes of late thrombosis, they should ferred.The graft can be reanastomosed to another nearby vein, or be sought out and corrected as well. Before treatment is initiated, the stenosis can be bypassed by anastomosing an ePTFE graft of information about recent graft performance should be obtained. appropriate size to a more proximal segment of the original vein. Signs of venous or outflow stenosis include increasing venous Joints may be crossed if necessary, in which case an externally sup- resistance and prolonged bleeding from puncture sites. ported prosthesis is used. Inadequate flow rates and increased negative pressures during dialysis are associated with stenosis of the arterial inflow. Steal Syndrome Hypotension or excessive graft compression can explain sponta- The reported incidence of symptomatic steal syndrome ranges neous thrombosis in a previously well-functioning graft. from 1% to 9%.39 Ischemic complications result from preferential Graft thrombosis may be corrected either with surgical diversion of arterial flow into the low-pressure venous outflow of thrombectomy or with pharmacomechanical or mechanical the AV access.When collateral arterial flow is inadequate or when thrombolysis. On the whole, technical success and long-term proximal or distal occlusive arterial disease is present, distal patency rates are similar for the two approaches, and neither has ischemia occurs. In some cases, the flow into the venous side of the demonstrated clear superiority over the other.The choice between access is sufficient to induce reversal of the flow in a portion of the these two approaches continues to be controversial, and the deci- artery distal to the access, a phenomenon referred to as steal. sion should generally be based on local expertise. To date, neither Unfortunately, there is no reliable method of predicting the devel- surgical treatment nor endovascular management has resulted in opment of symptomatic steal after the construction of an autoge- long-term function for the majority of patients with graft throm- nous or prosthetic AV access. bosis. If graft thrombosis occurs repeatedly in a given patient, The Committee on Reporting Standards of the SVS and the plans for a new access site should be considered. AAVS suggests that steal be graded into four categories as follows13: If surgical treatment is chosen, it should be carried out in an • Grade 0: No steal. operating suite with the capacity for intraoperative fluoroscopy. • Grade 1: Mild (extremity is cool; symptoms are few but are Unless preoperative findings indicate that an arterial lesion is pre- demonstrable by flow augmentation with access occlusion); sent, the incision is made at the venous anastomosis, and an ade- no treatment is needed. quate length of graft and outflow vein is mobilized. A transverse • Grade 2: Moderate (intermittent ischemia occurs only dur- graftotomy is made within 1 or 2 mm of the suture line, any clot ing dialysis or claudication); intervention is sometimes found on the venous side is removed with suction and a forceps, needed. and the anastomosis is inspected. The anastomosis is calibrated • Grade 3: Severe (ischemic pain is experienced at rest; tissue but not dilated: if a 5 mm dilator passes easily through the venous loss occurs); intervention is mandatory. anastomosis, then thrombectomy alone is often sufficient treat- ment. A 4 French Fogarty catheter is passed proximally into the In most cases, the ischemia is mild and is characterized by cold- right atrium and pulled back slowly with the balloon inflated to ness, numbness, and pain during dialysis. The radial pulse is usu- check for proximal venous stenosis and to evacuate clot. Any ally absent, and the relief of symptoms and reappearance of distal abnormality encountered is an indication for operative phlebogra- pulses with manual compression of the venous limb of the access phy. The presence of a venous abnormality does not rule out the are highly suggestive of clinically significant steal. Usually, the possibility of a coexisting arterial defect; both should be corrected problem resolves without treament within a few weeks. If the if found. patient experiences constant pain, severe numbness, a nonhealing After the venous anastomosis is examined, a 4 French Fogarty ischemic fissure, digital cyanosis or gangrene, or finger contrac- catheter is used to evacuate any clot in the graft itself. ture, the ischemia should be corrected. Thrombectomy at the arterial anastomosis is delayed until any A classic indicator of clinically significant steal is that digital structural problems in the body of the graft are corrected; this pulse waves are absent or markedly diminished on digital photo- delay permits the structural corrections to be carried out in a plethysmography (PPG) or pulse volume recordings (PVR) but bloodless field. Narrowing in the body of the graft is usually rise to normal amplitude and contour when the venous limb of the caused by fibrous material adherent to the wall, which can be access is compressed [see Figure 10]. Digital pressures lower than removed with the aid of a curette, an endarterectomy instrument, 50 mm Hg and a digital-brachial index lower than 0.47 are also or suction. Once the body of the graft is clear, any thrombus pre- indicative of clinically significant distal ischemia.40 A significant sent at the arterial anastomosis is removed. Free passage of the difference in segmental or digital pressure between the two arms Fogarty balloon catheter suggests that there is no arterial anasto- with the AV access compressed may be indicative of superimposed motic stenosis. The arterial anastomosis may be examined under arterial disease proximal or distal to the access, in which case arte- direct vision if necessary to ensure complete removal of the com- riography is indicated before surgical correction. Identification of pacted thrombus at the arterial end of the graft. reversed flow distal to the AV access on duplex studies is not, in The graft is filled with heparinized saline before the arterial or itself, sufficient reason to conclude that clinically significant steal the venous anastomosis is repaired. When the arterial side of the is present: steal is a common phenomenon and is a physiologic graft is involved, a new arterial anastomosis usually suffices to consequence of the rheology of the access in 73% of autogenous solve the problem. A new arterial site proximal to the old one is AV accesses and 92% of prosthetic AV accesses.41 selected, and either the graft is moved to the new site or a new free The differential diagnosis of vascular steal syndrome includes segment is added. carpal tunnel syndrome, diabetic neuropathy, uremic neuropathy, More commonly, the defect is at the venous anastomosis. In this bone pain from hyperparathyroidism, and ischemic monomelic case, the graftotomy is extended longitudinally through the anas- neuropathy (IMN). Carpal tunnel syndrome can become manifest
  11. 11. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 11 Before Fistula Compression During Fistula Compression 2. Reducing the flow but maintaining patency. Usually, this option involves narrowing a portion of the access to reduce flow. One technique for accomplishing this narrowing is to excise an elliptical portion of the graft or vein just distal to the anastomosis and reapproximate the edges or to plicate the graft or outflow vein with mattress or continuous Figure 10 Shown are digital photoplethysmographic waveforms on sutures [see Figure 11a through c].42 Another technique is an arm with steal syndrome before and during fistula compression. to band the fistula or graft with a crossed ePTFE band.43 The tails of the band are secured with hemostatic clips, and once the appropriate degree of narrowing has been or be exacerbated after access surgery, possibly as a consequence achieved, the clips are held in place with a figure-eight of edema, venous hypertension, and relative ischemia in the area suture of 5-0 polypropylene [see Figure 11d]. Both tech- of the flexor retinaculum. This condition can be differentiated niques should narrow the outflow over a fairly long dis- from steal on the basis of characteristic symptoms and elec- tance (≥ 1 cm). A third technique involves interposing a tromyographic findings. IMN is a rare but distinct entity that small-diameter (4 mm) ePTFE graft between the artery should be diagnosed early to prevent irreversible neurologic and the vein or graft [see Figure 11e].44 With any of these deficits.39 It occurs in diabetic patients within minutes to hours techniques, the main problem is determining the optimal after placement of an AV access originating from the brachial degree of narrowing required to eliminate the steal while artery and is the result of a sudden steal of blood to the nerve of maintaining patency. In practice, the long-term results of the forearm and hand. Patients present with acute pain, weakness, banding have been disappointing, with a high rate of post- sensory loss, and paralysis of the muscles of the forearm and hand. operative thrombosis.45 The hand usually remains warm, with no signs of distal ischemia. 3. Ligation of the source of steal, with distal revascularization The diagnosis is confirmed by nerve conduction studies and elec- when necessary. When steal occurs in a patient who has a tromyography and prompt urgent ligation of the access. radial-cephalic direct wrist access with flow reversal in the distal radial artery (documented by duplex scans) and Treatment Treatment of steal syndrome aims at reducing whose ulnar artery and palmar arch are patent and compe- steal to a level where there is both adequate residual flow volume tent to perfuse the hand, it is easily treated by ligating the for dialysis and adequate perfusion to the hand. Therapeutic radial artery distal to the anastomosis.46 The effect of this options include the following: treatment is easily demonstrated preoperatively by com- 1. Elimination of the AV access. This is the simplest form of pressing the radial artery distal to the fistula, which should treatment and invariably corrects ischemia; however, it relieve the ischemia. With a more proximal AV access, in raises the vexing problem of reestablishing access in anoth- which ligation of a terminal artery would inevitably result er extremity. in severe distal ischemia, the distal artery is ligated and an a b c d e Figure 11 One option for treat- ing steal is to decrease blood flow in the access conduit. Methods that may be used include (a) excision of a portion of the vein or graft, (b) plication with mat- tress sutures, (c) plication with continuous sutures, (d) place- ment of a crossed ePTFE band with application of hemostatic clips, and (e) interposition of a 4 mm ePTFE graft.
  12. 12. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 12 ination combined with Doppler ultrasonography or fistulography should identify the underlying cause. If stenosis is not identified in a nonmaturing radiocephalic fistula, venous side branches may be draining critical flow from the primary vessel; ligation of these branches sometimes leads to successful maturation. Median cubital vein ligation may be attempted, as may temporary banding of the main venous channel in the antecubital fossa. Banding is accomplished by narrowing the vein with a 3-0 Vicryl tie over a 4 mm probe.The Vicryl resorbs in 3 to 4 weeks, during which peri- AV Graft od it is hoped that the increased resistance to flow will cause dilata- tion of the vein.50 If none of these measures succeed, another access site should be sought. True Aneurysm (Autogenous AV Access) Aneurysmal dilatation of the vein develops as a result of high pressure applied to a vein wall weakened by repeated punctures. Arterial Bypass Usually, the course of such aneurysms is benign and does not preclude use of the access; however, large aneurysms containing mural thrombus have been reported to cause late thrombosis and embolization. On rare occasions, progressive enlargement can compromise circulation to the skin above the aneurysmal vein, leading to incomplete hemostasis when the needle is with- drawn and ultimately to graft rupture. Skin compromise and progressive enlargement are therefore indications for surgical correction. Surgical revision is also recommended if the aneurysm involves the arterial anastomosis or is associated with stenosis of the venous outflow. Arterial Ligature Options for revision include total excision of the aneurysm with primary reanastomosis, exclusion of the aneurysm with vein bypass grafting, and partial excision in which part of the vein wall is kept as the arterial conduit.The last option frequently results in early recurrence as the vein wall continues to weaken and dilate with time. Figure 12 Another option for treating steal is to ligate the Pseudoaneurysm (AV Grafts) source. Shown is the so-called DRIL procedure, which involves Pseudoaneurysms occur in prosthetic AV grafts and are usually arterial ligation distal to the takeoff of the prosthetic or autoge- nous access and arterial bypass from a point 5 cm proximal to small and asymptomatic. They can be prevented by allowing suf- the fistula to a point just distal to the ligation. ficient time after graft placement to ensure firm fibrous encapsu- lation of the graft and by avoiding repeated needle insertion at the same site. On occasion, however, pseudoaneurysms are precipitat- arterial bypass established from a point 5 cm proximal to ed by underlying venous stenosis, which should be documented the AV anastomosis to a point just distal to the ligation [see and corrected whenever present. Urgent surgical repair is indicat- Figure 12]. This so-called distal revascularization–interval ed if the pseudoaneurysm is expanding rapidly or is causing ligation (DRIL) procedure, originally reported by Schanzer ischemia of the overlying skin. Elective repair is indicated if the and coworkers,47 is an elegant way of both preserving ade- diameter of the false aneurysm is more than twice that of the graft. quate flow through the fistula and reversing the ischemia. Infection The pathway of steal is eliminated, and antegrade flow into the extremity is restored through the bypass.48 This tech- Infection is the second most common cause of loss of AV nique is particularly helpful when concomitant arterial access, occurring in 0% to 3% of autogenous accesses and 6% to stenosis proximal or distal to the access contributes to the 25% of prosthetic accesses.51 Infection may be acquired during distal ischemic process, because the bypass can be posi- surgery or cannulation of the conduit and is most often caused by tioned so as to bypass the arterial stenosis as well. Staphylococcus aureus. The most common clinical presentation is an exposed graft or a draining sinus tract. With any of these techniques, intraoperative assessment is required to ensure adequate residual flow volume in the access Autogenous AV access Infection of an autogenous access and adequate distal perfusion (assessed by evaluation of digital should be treated aggressively with 6 weeks of antibiotic therapy, much PPG or PVR waveforms).The goal is to achieve a digital pressure as subacute bacterial endocarditis or endovasculitis would be. Local of at least 60 mm Hg, a digital-brachial index of 0.6 or greater, and measures, such as drainage of a perifistular abscess, may be neces- a residual flow of at least 300 ml/min in the access.49 sary. In rare instances, infection-induced anastomotic pseudo- aneurysm or septic emboli necessitate takedown of the fistula. Inadequate Maturation of Vein Failure of an autogenous AV access to mature may result from Prosthetic AV access Generally, both antibiotic therapy and either inadequate inflow or a venous abnormality. Physical exam- surgical treatment are necessary for cure. An antibiotic regimen
  13. 13. © 2007 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 26 VASCULAR AND PERITONEAL ACCESS — 13 that covers gram-negative organisms, staphylococci, and strepto- Data should be tabulated and tracked within each dialysis center cocci should be given until culture results are available.Total graft as part of a quality assurance/continuous quality improvement excision, along with vein patch reconstruction of the artery, is (QA/CQI) program.8 required51 when the infection is responsible for systemic sepsis or hemorrhage at the anastomosis. Wounds are left open to heal by second intention. If the anastomosis is intact and encased in scar Vascular Access via Percutaneous Catheters tissue, a small cuff of ePTFE may be left on the arterial side Percutaneous venous catheterization is a useful method of gain- (subtotal graft excision) and used to close the arterial defect; this ing immediate access to the circulation; however, this type of measure does not seem to alter the prognosis, and it reduces the access has a shorter use-life than an AV access does, and it is asso- risk of nerve injury and hemorrhage. ciated with significant risks. There is, in fact, a gradient of patient In selected cases of well-localized infection (as documented by mortality risk that is correlated with access type, and the highest the absence of fluid around the uninfected portions of the graft on risk is observed with central venous catheters.53 Percutaneous preoperative ultrasonography), it is possible to resect only the catheterization should therefore be reserved for (1) patients with infected portion of the graft and to restore the continuity of the acute renal failure who have an immediate need for dialysis and fistula by placing a new conduit in a clean subcutaneous tunnel (2) patients with chronic renal failure in whom a permanent vas- away from the infected area (partial graft excision).52 cular or peritoneal access route either cannot be established or has Superficial surgical wound infections occurring in the postop- not yet matured. erative period can sometimes be treated successfully with aggres- sive local debridement in combination with systemic administra- PREOPERATIVE EVALUATION tion of antibiotics. Deeper wound infections occurring in the post- A history is taken, a physical examination is performed, labora- operative period must be assumed to involve the entire graft, given tory data are reviewed, and radiologic studies are ordered as for an that the graft is not yet well incorporated. AV access. Any finding that might affect the integrity of the cen- tral venous system should be noted. OUTCOME EVALUATION A history or physical signs of previous central venous catheter- Thrombotic events are the leading cause of access loss. For the ization, a history of major injury or operation in the area where the most part, they result from venous outflow stenosis that can be catheter is to be inserted, a body mass index greater than 30 or less detected before thrombosis occurs. An organized monitoring than 20, and an increasing number of insertion attempts are all approach that includes regular assessment of the clinical parame- known risk factors for perioperative complications from the inser- ters of the access and of the adequacy of the dialysis should be tion of venous access devices.7 If there is any question about the implemented in every dialysis center.7 Such a proactive approach patency of the central venous system, duplex scanning 54 or venog- can be expected to reduce the incidence of thrombosis and raphy is indicated. increase patency. On physical examination, the surgeon should note the patient’s Physical examination of the AV graft or autogenous AV access body type, assess the flexibility of the patient’s neck and shoulders, should be performed weekly and should include not only inspec- and evaluate the patient’s ability to tolerate the Trendelenburg tion and palpation for changes in the physical characteristics of the position without dyspnea or discomfort. Chest x-rays are reviewed pulse or thrill but also a search for indirect signs of graft dysfunc- to verify the patient’s pleuropulmonary status and to identify any tion (e.g., arm swelling, prolonged bleeding after needle with- bony deformities. drawal, and aneurysm or pseudoaneurysm). In addition to physi- The only laboratory study absolutely necessary is a complete cal examination, the NKF-DOQI committee recommends rou- blood count (including the platelet count and the differential tine access monitoring at least monthly with one or more of the count); prothrombin and partial thromboplastin times are following techniques: required if the patient is receiving anticoagulant therapy. The 1. Intra-access flow assessment using Doppler flow, magnetic effects of warfarin or heparin should be reversed before the proce- resonance imaging, or ultrasound dilution online during dure; patients with platelet counts lower than 50,000/mm3 should dialysis. Either a drop in access flow exceeding 20% of undergo platelet transfusion immediately before and during baseline or a flow rate lower than 600 ml/min for an AV catheter placement.55 graft and lower than 200 to 300 ml/min for an autogenous OPERATIVE PLANNING AV fistula is predictive of a high likelihood of access steno- sis and eventual thrombosis. Choice of Type of Catheter 2. Static or dynamic venous pressure measurement. Progres- sively increasing pressures or pressures that exceed the Different catheter designs have been studied and used, but at threshold value determined by each center’s own protocol present, none of them appears to have a proven advantage over are predictive of significant venous outlet stenosis. the others. Generally, the catheters best suited for hemodialysis 3. Urea and nonurea recirculation measurement. Recircula- are high-flow, large-diameter (12 French or larger) devices with tion is defined as the percentage of flow that is recirculated external ports. Silicone catheters are more flexible, are less likely from the venous line into the dialyser inflow by retrograde to give rise to injury or thrombosis, and remain patent longer blood flow through the fistula. A recirculation value than polyethylene, polyvinyl chloride, and polytetrafluoroethyl- exceeding 10% to 20% is significant and usually indicates ene catheters. Silicone catheters are available in both nontun- low arterial blood flow or venous stenosis. neled (noncuffed) and tunneled (cuffed or noncuffed) double- 4. Delivered dialysis dose. A decrease is associated with lumen configurations through which flow rates of 250 ml/min or venous outflow stenosis. higher can be achieved [see Figure 13]. The venous and arterial 5. Arterial prepump pressure. An elevated negative pressure is orifices are separated by 1 to 2 cm; recirculation is thereby limit- a sign of inflow insufficiency. ed to less than 10%.