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| Journal of Vascular Access 2002; 3: 140 - 146 |
| Creation of native arteriovenous fistulas with interrupted anastomoses using a self-closing clip device - one clinic’s experience |
J.R. Ross1
1General Surgery, Bamberg County Hospital, Bamberg, South Carolina - USA
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ABSTRACT
The nitinol U-CLIPTM Anastomotic Device (Coalescent Surgical, Inc., Sunnyvale, CA) is a self-closing penetrating vascular clip that reduces suture management and eliminates knot tying, thus enabling rapid and precise interrupted suture placement and facilitating creation of an optimal vascular anastomosis. This report describes the use of U-CLIP devices in the surgical creation of native arteriovenous fistulas in 68 chronic hemodialysis patients. Overall, 61 of the 65 fistulas created matured successfully within 8–9 weeks. Radial cephalic fistulas: 93% were mature at 8 weeks. Brachiocephalic fistulas: 69% were mature at 8 weeks. One-stage basilic vein transposition: 100% were mature at 9 weeks. Two-stage basilic vein transposition: 100% were mature at 8 weeks after second stage. The results in this report show the excellent performance of U-CLIP vascular clips in the creation of several types of native arteriovenous fistulas in chronic hemodialysis patients. The fistulas created using the U-CLIP devices had a high maturation rate within a relatively short time period, and provided uniformly high flow rates. The patients in this study were a challenging population, with a high incidence of diabetes mellitus (81% of the patients) and vein sizes that were smaller than typically used for fistula creation. The U-CLIPTM Anastomotic Device offers the opportunity to create superior interrupted anastomoses for AV fistulas, even in patients who would otherwise be considered poor candidates for fistula creation.(The Journal of Vascular Access 2002; 3: 140-6)
Key Words. Arteriovenous fistula, Suture technique, Vascular clip, Vascular anastomosis
INTRODUCTION
Surgical construction of a vascular anastomosis creates an area of constriction with a drop in vascular compliance (1). As compared to interrupted suture techniques, continuous suturing of an anastomosis causes decreased compliance with greater focal constriction, flow turbulence, shear stress, and intimal hyperplasia, thereby decreasing flow and predisposing to thrombosis (2-5). Continuous suturing is associated with greater loss of compliance and greater total compliance mismatch at the anastomosis, as compared to interrupted sutures or vascular clips (6).
The nitinol U-CLIPTM Anastomotic Device (Coalescent Surgical, Inc., Sunnyvale, CA) consists of a self-closing penetrating vascular clip that is attached to a flexible member and needle (Fig. 1). The nitinol clip is released from the flexible member, closes automatically, and functions like an interrupted suture to hold vascular tissue together. Unlike traditional interrupted sutures, the U-CLIP device reduces suture management (suture tensioning and positioning) and eliminates knot tying, thus enabling rapid and precise interrupted suture placement and facilitating vascular anastomosis (7). The use of vascular clips in the creation of anastomoses (6, 8-13) requires less surgical time than placement of traditional interrupted sutures and produces results equal to anastomoses created with interrupted sutures (6, 8, 10) and superior to anastomoses created with continuous sutures (6, 8-13).
The U-CLIP device can simplify a variety of vascular surgical procedures, including coronary artery bypass grafting (7) and endoscopic/minimally invasive procedures. It has also been used successfully in peripheral vascular, arteriovenous access, transplant, and general surgery. The U-CLIP device facilitates creation of a vascular anastomosis with excellent results. Use in a bovine coronary anastomosis model demonstrated biocompatibility of the U-CLIP device, with smooth neointimal resurfacing, minimal inflammatory response, and an absence of vessel wall necrosis upon histologic examination (7). Angiographic examination also showed no stenosis and widely patent anastomoses in the animals receiving U-CLIP closures (7).
This device allows creation of successful fistulas in hemodialysis patients who would otherwise not be considered fistula candidates due to diabetes or small vessels. The superior performance and pulsatile compliance of anastomoses created with vascular clips, as compared to continuous suturing, improves fistula development and patency (13). Use of the U-CLIP device may facilitate increased use of native fistulas to meet the goals recommended in the latest National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF-K/DOQI) Clinical Practice Guidelines for Vascular Access (14).
This report describes the excellent results obtained with the use of U-CLIP devices in the surgical creation of native arteriovenous fistulas in 68 chronic hemodialysis patients at Bamberg County Hospital over 8 months.
PATIENTS AND METHODS
Patient demographics
A total of 68 patients had fistulas created using U-CLIP Anastomotic Devices (Tab. I). Fifty-five (81%) of the patients had diabetes. Patients were between 24 and 72 years of age. The sizes of the veins used in the anastomoses varied between 1.0 and <2.0 mm for lower arm fistulas and between 3.0 and 6.0 mm for upper arm fistulas (Tab. I). These vein sizes were smaller than typically used for fistula creation.
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TABLE I
PATIENT CHARACTERISTICS AND U-CLIP DEVICE SIZES, GROUPED BY SURGICAL PROCEDURE
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Materials
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Fig. 1
The U-CLIP™ Anastomotic Device (magnified). (A) Before release (B) After release.
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The U-CLIP anastomotic device (Fig. 1) consists of a self-closing nitinol surgical clip that is attached to a conventional surgical needle by a flexible member. Nitinol is an alloy with “shape memory.” Once the nitinol clip is released from the flexible member, it returns to its original shape, automatically closing itself. Each clip was placed with a conventional needle driver; a custom clip applier is not needed. After the needle had pierced the tissue, the flexible member and release mechanism were pulled through the tissue to place the clip. The release mechanism was engaged by compressing with a needle holder, and the clip was released and automatically closed in place. After release, the needle and flexible member were discarded.
The U-CLIP devices were placed beginning on the endovascular side of the vascular wall; when the anastomosis was nearing completion, the remaining clips were placed from the outside of the vessel (Fig. 2).
Clips were deployed in a circular fashion around the anastomotic site, creating an interrupted anastomosis in the same manner as conventional interrupted sutures. The sizes of the U-CLIP devices used ranged from S18 to S25, as shown in Table I. The size refers to the diameter of the deployed clip in thousandths of an inch (e.g., S18 = 0.018 inches).
After piercing the tissue, the needle was pulled through until the tissue to be approximated rested completely inside the clip. Each bite allowed tissue to fill about three-quarters of the closed clip. If too little tissue is taken, the clip may be loose and the anastomosis may leak, requiring additional clips or sutures. If too much tissue is taken, the clip may not close properly once released.
Radial cephalic fistula creation
A curved transverse incision was made, crossing the radial artery and cephalic vein. Both vessels were mobilized and dissected from surrounding tissue, using care to preserve the cutaneous branch of the radial nerve. The distal cephalic vein was divided and anastomosed with the divided radial artery using an interrupted technique with S18–S20 U-CLIP devices.
Adequate time for maturation was allowed, as it is especially critical to wait for adequate flow, dilatation, and arterialization of the fistula in the lower arm before cannulating for dialysis.
Brachio-cephalic fistula creation
The cephalic vein was mobilized at the level of the elbow, and the brachial artery was exposed. The cephalic vein was passed through a subcutaneous tunnel and anastomosed to the brachial artery in an end-to-side configuration using an interrupted technique with S18–S25 U-CLIP devices (Fig. 3).
One-stage basilic vein transposition
This procedure was used when the cephalic vein was unsuitable, and has been described previously (15, 16). A transverse incision was made in the antecubital fossa and into the deep fascia to expose the basilic vein (Fig. 4).
The incision was extended to the medial aspect of the arm and the full length of the basilic vein was mobilized, using care to preserve the medial cutaneous nerve. Communicating branches of the vein were ligated and divided. The vein was transposed to a subcutaneous tunnel on the anterior surface of the arm and anastomosed to the brachial artery using an interrupted technique with S20–S25 U-CLIP devices.
Two-stage basilic vein transposition
A two-stage (fistula-to-fistula) procedure was used when the basilic vein was diminutive or clinical judgment indicated the final fistula would benefit from additional maturation of the vessel provided by a two-stage process. The first stage involved performing a cutdown in the antecubital area and identifying the median branch of the basilic vein. An end-to-side anastomosis between the basilic vein and the brachial or radial artery was performed, using an interrupted technique with the S20 or S25 U-CLIP devices. After 4 to 6 weeks, duplex Doppler ultrasound was used to verify that flow rates were at least 650 to 800 ml/min.
The second stage involved making a long incision from the axilla to the level of the elbow, where the fistula was readily identified. The fistula was then transected approximately 3 to 4 cm above the level of the antecubital crease. The complete basilic vein was mobilized up to the level of the axilla. A hollow tunneling device was passed laterally over the biceps muscle (Fig. 5), and endoscopy forceps were used to grasp the basilic vein and pull it through to the area of the desired anastomosis.
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Fig. 5
Second stage of the two-stage basilic vein transposition. The hollow tunneling device is visible at the top of the field, over the biceps muscle. The basilic vein is seen running through the center of the field. |
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An end-to-end anastomosis was constructed using an interrupted suture technique with either S18, S20, or S25 U-CLIP devices. Serial duplex Doppler ultrasound measurements were done to determine flow rates, which were usually between 800 and 2000 ml/min. The fistula was allowed to mature for 2 to 12 weeks; cannulation was permitted only after swelling associated with the subcutaneous tunnel subsided.
RESULTS
Overall, 61 of the 65 fistulas created matured successfully within 8-9 weeks. Results for the individual procedures are described below and shown in Table II.
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TABLE II
FISTULA FLOW RATES, MATURATION, AND OUTCOMES, GROUPED BY SURGICAL PROCEDURE
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Radial cephalic fistulas
Flow rates at the time of fistula creation were between 225 and 425 ml/min. At 8 weeks, 26 of 28 (93%) fistulas were mature. Two fistulas required elevation and transposition using the original U-CLIP anastomosis as the inflow; these fistulas became part of the two-stage basilic vein transposition group and both matured within 6 weeks.
Brachio-cephalic fistulas
Flow rates at time of fistula creation were between 250 and 1150 ml/min. At 8 weeks, 11 of 16 (69%) fistulas were mature. Two patients with unrecognized central venous stenosis experienced fistula thrombosis by 3 and 4 weeks. Five fistulas required elevation and transposition using the original U-CLIP anastomosis as the inflow; these fistulas became part of the two-stage basilic vein transposition group and, and matured successfully within 3-8 weeks.
One-stage basilic vein transposition
Flow rates at the time of fistula creation were between 450 and 1250 ml/min. At 9 weeks, all 9 (100%) fistulas were mature. Subsequently, 3 patients experienced cannulation infiltration; these fistulas were not cannulated for an additional 4 weeks, during which time a temporary catheter was used for hemodialysis access.
Two-stage basilic vein transposition
Flow rates at the first stage were between 400 and 900 ml/min. After the second stage, flow rates between 950 and 2000 ml/min were achieved. By 8 weeks after the second stage, all 15 (100%) fistulas were mature. One fistula developed cannulation infiltration at 3 weeks after maturity; the patient was dialyzed with a temporary catheter while the fistula rested. Subsequently, this fistula functioned without complications.
DISCUSSION
Cast-injection modeling has shown that interrupted sutures provide better internal anastomotic configurations than continuous suture; the external appearance of the anastomosis is not a reliable indicator of the internal configuration (2, 4). The purse-string effect associated with continuous suture frequently causes a circumferential ridge deformity on the internal surface of the anastomosis (2). Interrupted suture techniques provide superior anastomotic compliance and lumen diameter, resulting in reduced flow turbulence, shear stress, and intimal hyperplasia, as compared to continuous suture techniques (5).
Vascular clips have been shown to improve anastomotic compliance and flow characteristics in smaller vessels, as well as improving primary, secondary, and overall patency in arteriovenous fistulas (13). Vascular clips have also been shown to decrease surgical time and bleeding, and significantly improve secondary patency of autologous arteriovenous fistulas (9).
The results in this report show the excellent performance of U-CLIP vascular clips in the creation of several types of native arteriovenous fistulas in chronic hemodialysis patients. The fistulas created using the U-CLIP devices had a high maturation rate within a relatively short time period, and provided uniformly high flow rates. These high flow rates may lead to lower rates of thrombosis and other complications in the long term.
The patients in this study were a challenging population, with a high incidence of diabetes mellitus (81% of the patients) and vein sizes that were smaller than typically used for fistula creation. Many of these patients would have otherwise been considered unsuitable candidates for an AV fistula and would have received a synthetic AV graft. The performance of the U-CLIP Anastomotic Device allowed creation of successful fistulas in patients who would not classically be considered good fistula candidates.
Successful creation of an arteriovenous fistula requires vessels of adequate size to sustain the anastomosis (17, 18). Successful development of an arteriovenous fistula requires adequate inflow to support dialysis and promote vein maturation and dilatation. Adequate dilatation also requires that the vein wall be exposed to sufficient pulsatile pressure (19). U-CLIP devices can help facilitate fistula maturation by providing superior pulsatile compliance of vessel wall at the anastomotic site, as compared to continuous suture techniques.
Radial cephalic arteriovenous fistulas are the first choice for permanent vascular access, but may not be feasible using traditional running suture techniques in some patients due to diabetes or small size of the distal cephalic vein (20, 21). Preoperative sonographic vascular mapping has been suggested to improve access creation outcomes by identifying suitable vessels. A recent study found that even using preoperative sonographic evaluation of the vessels, the initial adequacy rate for dialysis among AV fistulas was only 54% (22). In comparison, our results show initial maturation rates of 93% for radial cephalic fistulas and 90% for all fistulas. U-CLIP Anastomotic Devices make it possible to use these small vessels to create fistulas that can mature adequately for hemodialysis access.
In conclusion, the U-CLIPTM Anastomotic Device is a self-closing, penetrating vascular clip that offers the opportunity to create superior interrupted anastomoses for AV fistulas, even in patients who would otherwise be considered poor candidates for fistula creation. Our results in a challenging patient population show substantially higher initial maturation rates among these fistulas created using U-CLIP devices, as compared to published initial maturation rates among fistulas created using conventional techniques (22). Innovations such as the U-CLIP Anastomotic Device may help increase the use of native AV fistulas to meet NKF-K/DOQI goals and improve clinical outcomes in hemodialysis patients.
Reprint requests to:
John R. Ross, MD
Bamberg County Hospital
General Surgery
201 McGee St.
Bamberg, S.C. 29003, USA
e-mail: JRRsurgery@aol.com
Presented in part at: Access for Life - The AV Access Forum. LasVegas, NV; August 3, 2002.
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J.R. Ross
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