Regional Nerve Block Allows for Optimization of Planning in the Creation of Arteriovenous Access for Hemodialysis by Improving Superficial Venous Dilatation
Article Outline
Durable vascular access for hemodialysis remains a critical issue in end-stage renal disease patients. Creation of an autogenous arteriovenous (AV) fistula in the most distal location of the nondominant extremity is the preferred technique and provides superior patency over an AV graft. Others have shown that regional anesthesia in the form of axillary block results in the dilatation of the native veins and allows for their increased utilization in creating AV fistulae. We report on 26 patients undergoing creation of a vascular access for hemodialysis. Regional anesthesia consisting of axillary nerve block was used in all cases. All surgical plans with regard to the site and type of access were made based on the physical exam and ultrasound vein measurements taken prior to surgery. On the day of surgery patients were reevaluated with venous ultrasound using tourniquet before and after administration of the regional block. The previously determined operative plan either remained unchanged or was modified depending on the venous dilatation noted after administration of regional block. Among 26 patients, average vein diameter increased from 0.29 ± 0.12 cm to 0.34 ± 0.11 cm (P = 0.008). Twenty-one of 26 patients had no modification in operative plan (group 1). Five had some modification of the original operative plan (group 2): AV graft to a brachial vein transposition (n = 2), AV graft to a Cimino fistula (n = 2), and brachiocephalic to a Cimino (n = 1). The average follow-up for all patients was 82.6 ± 75.6 days and did not differ between the groups. There was one failure in a patient from group 1, and there was no significant difference in the patency rate between study groups (P = 0.29). Following regional nerve block, operative plans in patients undergoing AV access surgery were modified in 29.4% of patients undergoing creation of an AV access for hemodialysis; either from graft to fistula creation or from the proximal to more distal fistula site. The routine use of regional anesthesia as well as intraoperative ultrasound during AV access surgery can lead to improved site selection and increased opportunity for AV fistula creation.
Introduction
The increasing rate of end-stage kidney disease continues to be a challenging problem in the United States and worldwide, leading to a growing number of patients becoming dialysis-dependent. Hemodialysis is the most common modality of renal replacement therapy. Indeed, many patients require life-long treatments secondary to organ donor shortage or medical contraindications to transplantation. Judicious planning prior to creation of arteriovenous fistulae (AVF) is mandatory in order for health-care providers to maximize access options for this growing population of patients.1
Although the history of hemodialysis dates back to the 1940s, the first autologous AVF by Cimino, almost 20 years later, introduced a durable and convenient technique with a relatively low risk of complications.2 Since then vascular access procedures have evolved substantially, with utilization of veins from upper and lower extremities as well as prosthetic conduits (polytetrafluoroethylene, PTFE) for fistula creation.3, 4 There are obvious advantages to PTFE-based fistulae, including relative ease of placement, no need for the presence of autologous veins, and a short period required for access site maturation. However, numerous studies comparing PTFE to autologous vessels have concluded that permanent hemodialysis access utilizing native vessels is superior in terms of patency and complication rates in comparison to PTFE-based fistulae.5, 6 These observations led to the establishment of clinical practice guidelines by the Kidney Disease Outcomes Quality Initiative, which state that natural hemodialysis access should be a primary choice when considering AV access. The Centers for Medicare and Medicaid guidelines currently recommend that native fistulae should be encountered in 66% of hemodialysis patients by 2006.
Brachial block for regional anesthesia in the creation of vascular access has been previously shown to increase diameter of veins in the extremity.7 In this study we investigated whether routine use of regional anesthesia impacted our preoperative planning of hemodialysis access surgery performed in regard to anatomic location of the fistula on the extremity as well as to the selection of native vessel over the graft material. We prospectively followed those patients postoperatively with regard to patency rates and maturation of created AV hemodialysis access.
Materials and Methods
Twenty-six patients undergoing creation of AV access for hemodialysis were included in the study. There were 16 men and 10 women. Mean patient age was 52.9 and 56.7 years, respectively. Two vascular surgeons performed all procedures. The study design required that the surgeon made initial operative plans based on the patient's physical exam. On the day of surgery patients were evaluated using physical exam as well as venous ultrasound by the surgeon performing the procedure immediately before and after administration of the regional anesthetic block. A portable ultrasound machine, Sonosite 180 Plus equipped with an 11 mm broadband (7-4 MHz) transducer model C 11, for vascular access applications was used (SonoSite, Bothell, WA). Basilic and cephalic veins at the mid-arm antecubital fossa and the cephalic vein at the wrist level were measured after placement of the proximal arm tourniquet. The inner wall to inner wall diameter was measured, assuring for the minimal vein compression and most circular vein shape. The measurements of all visualized veins of the selected arm and the forearm were taken before and after administration of regional anesthesia. The operating surgeon used those findings to determine the type of operation to be performed, which involved the level at which the fistula was to be created and the selection of either autologous vein or a prosthetic graft material. Patient demographics and details of operative procedure, including preoperative plan, type of fistula created, and all measurement data, were recorded on a standardized study sheet. Patients were subsequently followed on the basis of telephone interview or clinic visit and questioned for the ability to use the created hemodialysis fistula as well as any complications. In case of AV access failure, date of last successfully performed hemodialysis treatment was recorded.
For the purpose of regional anesthesia, a standard infraclavicular block with 2% lidocaine with epinephrine 1:200,000 and sodium bicarbonate (0.9 mEq/10 mL) under ultrasound guidance was performed as described by Sandhu and Capan.8 Onset of the block was defined by diminished response to pain and motor weakness.
For creation of the fistula and graft placement, the standard surgical technique was used, employing atraumatic dissection of the appropriate level artery and corresponding vein, creation of the vascular anastomosis using standard atraumatic vascular clamps, and running 6.0 Prolene suture on an atraumatic vascular needle. For the bridged AV graft, a standard-walled 6 mm PTFE graft (W. L. Gore and Associates, Flagstaff, AZ) was used.
For statistical analysis, Microsoft Office Excel (Microsoft, Redmond, WA) software as well as Web Chi Square Calculator (http://www.georgetown.edu/faculty/ballc/webtools/web_chi.html) were used.
Results
Among all 26 patients undergoing the creation of vascular access, 20 patients were to undergo AVF creation using native vein and six to undergo AVF with prosthetic PTFE graft. There were nine patients planned for the Cimino fistula a priori and excluded from subsequent calculations. Twelve patients had no modification in operative plan (group 1), whereas five patients had a modified operative plan (group 2).
Complete infraclavicular brachial plexus block was achieved in all cases and confirmed by the loss of motor and sensory neurological function. As previously reported by others,7 no side effects and no postoperative complications from the block placement were observed. Preoperatively, nine Cimino, seven brachiocephalic and PTFE grafts, and two basilica vein transpositions were planned. Five of 17 patients had a change in operative plan following administration of regional anesthesia (29.4%). The change of operative plan included AV graft to basilic vein transposition (n = 2), AV graft to a Cimino fistula (n = 2), and brachiocephalic to a Cimino fistula, the average vein diameter increased from 0.29 to 0.34 cm (P = 0.008) (Fig. 1). Dilated vessels were clearly visualized, as seen in Figure 2. The average follow-up for all patients was 82.6 ± 75.6 days and did not differ between the groups. There was one failure in a patient from group 1, and there was no significant difference in the patency rate between study groups (P = 0.29, chi squared).
Fig. 1
Average vessel diameter increase after axillary block.
Fig. 2
A Poor visualization of cephalic vein. B Cephalic vein visualized following administration of axillary block with increased vessel diameter to 2.4 mm.
Discussion
The use of native veins in creating AVFs for hemodialysis is most optimal and is recommended prior to the placement of artificial grafts. Maximal utilization of autologous veins can provide patients with AV access that lasts longer and carries a lower risk of complications. Our study for the first time demonstrated that the routine use of regional anesthesia for AV access surgery resulted in a significant change in the operative plan without adverse effect on the patency of the created access.
Operative plans from less to more favorable surgical option for AV access creation took place in approximately 30% of patients following regional supraclavicular block. In four cases AV graft was converted to autologous AVF, and in one case a more distal AVF was created. Nine patients qualified for Cimino fistula surgery before the block placement and thus were excluded from analysis as they already had achieved the optimal surgical plan (i.e., Cimino fistula). The shortcomings of our study include the relatively small study group size and the large variation in length of follow-up. Nevertheless, for the group that underwent a change in operative plan, the follow-up was uniform and averaged 140 ± 60.7 days.
There is no clear explanation in the literature for the mechanism of dilatation of the upper arm vasculature following regional block. It is believed that sympathetic innervation blockade plays a similar role to that seen in regional spinal anesthesia and its resultant sympathetic autonomic neural blockade. Examples of this include decreased bowel motility, peripheral vascular vasodilatation leading to increased skin temperature, and hypotension secondary to decreased vascular tone.9, 10, 11 Interestingly, only patients undergoing a successful placement of the axillary block have a significant dilatation of the venous system present.7 Although no clear physiological mechanism was elucidated, possible explanations include a direct effect on the muscularis of the venous wall as well as increased vein diameter secondary to the arterial dilatation leading to an increased venous return in the affected extremity. In our study two physicians who used exactly the same technique performed all axillary blocks. This allowed for minimal variations in results and high reproducibility. Two main operating surgeons performed venous ultrasound measurements. They were not blinded to the timing of the measurement—pre- or post-block placement—which could potentially contribute to the observational bias. Because of logistical constrains, it would have been very difficult for us to perform blinded ultrasound measurement.
Despite certain shortcomings of this study, we were able to demonstrate that the routine use of regional axillary block for upper extremity AV access surgery led to a change in the preoperative planning to a more favorable operation in 30% of cases. We also showed that such changes did not result in poorer patency in this patient cohort.
Although further studies are needed, vasodilatation seems to be the responsible mechanism.
We believe that regional axillary block and perioperative ultrasound evaluation should be the standard methods used during AV access surgery and could lead to a better utilization of native veins in dialysis-dependent patients.
References
- United States Renal Data Systems. Treatment Modalities (Table D). Accessed August 2006. http://www.usrds.org/2006/ref/D_modality_06.pdf.
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- Sympathectomy-like effects of brachial plexus block in arteriovenous access surgery. Ultrasound Med Biol. 2006;32:817–822
- . The effect of intraoperative thoracic epidural anesthesia and postoperative analgesia on bowel function after colorectal surgery: a prospective, randomized trial. Dis Colon Rectum. 2001;44:1083–1089
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PII: S0890-5096(07)00250-6
doi:10.1016/j.avsg.2007.07.001
© 2007 Annals of Vascular Surgery Inc. Published by Elsevier Inc All rights reserved.
