regional anesthesia for arteriovenous fistula

Conditions: Arteriovenous Fistula

Summary: once kidney function goes below 10 to 15 percent of normal, dialysis treatments or a kidney transplant are necessary to sustain life. one type of dialysis is hemodialysis which cleans blood by removing it from the body and passing it through a dialyzer, or artificial kidney. to maximize the amount of blood cleansed during hemodialysis treatments, there should be continuous high volumes of blood flow. a fistula used for hemodialysis is a direct connection of an artery to a vein. once an arteriovenous fistula (avf) is created it is a natural part of the body. this is the preferred type of access because once the fistula properly matures and gets bigger and stronger; it provides an access with good blood flow that can last for decades. after the fistula is surgically created, it can take weeks to months before the fistula matures and is ready to be used for hemodialysis. there have been surgical factors identified; one of them being the anesthetic used which may cause a fistula not to survive. this study will look at comparing 3 anesthetic techniques: axillary block (ab) versus stellate ganglion (sgb) block+local anesthetic versus local anesthetic (la).

to allow for chronic hemodialysis (hd), patients with end-stage renal disease (esrd) require permanent vascular access in the form of either arteriovenous graft (avg) or arteriovenous fistula (avf). the latter option is the preferred form of vascular access given the lower rate of thrombosis, fewer interventions required, longer survival for vascular access and lower rate of infection as compared to avg (1). despite this, earlier reports have suggested that the initial failure rate of avf approximates to 25% (2). a permanent vascular access is considered adequate when it has sufficient size (i.e. greater than 0.6 cm) for easy cannulation and a flow rate of approximately 600 ml/min for dialysis (1, 3). however, postoperative avf blood flow may be compromised by arterial vasospasm and sympathetic activity from surgical manipulations (4, 5). inadequate flow rate in the postoperative period can result in early thrombus formation at the fistula and, if left untreated, can lead to permanent loss of vascular access(6). over the years, researchers have identified a number of patient and surgical factors that may influence the success and long-term survival of avf, and recent evidence suggests that the choice of anesthetic techniques may play a significant role (7). vascular access surgery is usually conducted under either a) general anesthesia (ga), b) local anesthetics (la) infiltrations with sedations, or c) regional anesthesia in the form of brachial plexus block (bpb). ga, while providing both anesthesia and analgesia, can present a challenge for maintaining intraoperative hemodynamic stability as patients with esrd often have other significant comorbidities. la infiltrations, though offering simplicity, does not provide motor blockade and patient movement can be a surgical challenge. la requires multiple injections during the case. bpb thus presents as an attractive option as it provides both dense and prolonged sensory and motor blockade while avoiding the cardiopulmonary stress imposed by ga. additionally, the sympathectomy associated with bpb has been shown to improve postoperative avf blood flow through decreasing peripheral vascular resistance and increasing vasodilation and blood flow velocity (8-11). similarly, stellate ganglion block (sgb), which offers sympathetic blockade without analgesic effect, has also been shown to augment postoperative avf blood flow and average peak flow velocity and shorten maturation time when combined with la infiltrations (5, 12). though it has been shown that regional anesthesia can affect a number of physiological parameters following avf formation, it is not yet clear how fistula survival can be affected by the modification of these parameters. the investigators conducted a literature search in july 2013 using medline database. two key words, one from list a and one from list b, were joined with the term "and" in all possible combinations for the literature search. key words from list a included "arteriovenous fistula", "avf", "vascular access", "dialysis", and "dialysis access". list b included "regional anesthesia", "brachial plexus block," "bpb", "brachial plexus", "stellate ganglion", "sgb", "sympathectomy", "supraclavicular", "infraclavicular", "axillary", and "interscalene". search results were limited to english articles only. abstracts were not included in the search results. to the investigators knowledge, no randomized trial has been conducted to directly compare the effect of axillary block (ab) against la infiltration with or without sgb on avf success in patients with esrd. this will be the primary objective of the investigators study. to do so, the investigators intend to conduct a prospective randomized controlled trial at a tertiary vascular surgical center in hamilton.

Eligibility criteria:
inclusion criteria: * patients with esrd undergoing radio-cephalic avf exclusion criteria: * previous avf procedures * significant stenosis (\>50% diameter reduction) * calcifications of radial artery or cephalic vein * radial artery diameter \<1.6mm * cephalic vein diameter \<2.0mm * history of pre-existing unilateral recurrent laryngeal nerve palsy * pre-existing unilateral phrenic nerve palsy * coagulopathy or pre-existing conditions that require anticoagulants or anti-platelet therapies * history of iv drug use * documented allergic reactions to local anesthetics * pregnancy * morbid obesity.