Cannulation of the Axillary Brachial Sheath in Children

To the Editor: Recent modifications of the axillary approach to brachial plexus blockade include catheter insertion for multiple dose administration and the identification of the brachial plexus by a nerve stimulator to avoid potential neurovascular complications associated with intraneuronal injections [1-7]. While nerve stimulators permit the placement of blocks in anesthetized children, the lack of equipment designed to allow safe, quick, and repeated access to the axillary neurovascular sheath in children has limited the use of cannulation techniques in this patient population [3,8,9]. In contrast, catheterization techniques for central nerve blockade for abdominal and lower extremity procedures are routinely used in both adults and children [10]. We describe our experiences with a radial artery catheterization set (#RA-04120; Arrow, Reading, PA) for catheter placement in the brachial plexus sheath in 33 anesthetized children undergoing operations of the elbow and wrist. The Arrow Registered Trademark radial artery catheterization set consists of a 20-gauge catheter over a 22-gauge thin-walled, short-beveled cutting needle, through which passes a 0.018-in. integral spring wire guide. After induction of anesthesia, the arm was abducted, the elbow flexed to 90 degrees, and the axilla scrubbed with Betadine Registered Trademark. The needle of an Arrow Registered Trademark 20-gauge arterial line kit was inserted at the apex of the axilla at an angle of 20-30 degrees to the skin and directed toward the point of maximum pulsation of the axillary artery. The distal end of the guide wire was connected by an alligator clip to the negative pole of a constant current nerve stimulator while the reference electrode was connected elsewhere on the opposite shoulder. The needle, catheter, and wire were advanced as one unit until distinct contractions of the hand muscles were noted. Optimum nerve location was achieved by adjusting the needle so that these contractions were visible with currents of <1 mA. The needle was stabilized at this site; the 0.018-in. guide wire was then extended for 1-1.5 cm, and the catheter was advanced over the wire and aspirated to rule out a vascular position of the catheter tip. The arm was positioned by the side of the patient immediately after the injection of 0.4-0.6 mL/kg of 1% lidocaine or 0.25% bupivacaine through the catheter, while distal pressure was maintained to force the anesthetic solution cephalad. The block was considered successful if cardiovascular responses to surgical stimuli were less than 20% of preincision values at end-tidal concentrations of <or=to0.5% halothane or <or=to0.7% isoflurane with 66% N2 O, and if supplemental intravenous opioid analgesia in the postanesthetic care unit (PACU) was not needed (VAS scores <60 mm). The mean (+/-SD) patient age, weight, and duration of anesthesia were 11.3 +/- 4.3 yr, 37.3 +/- 20 kg, and 177 +/- 43 min, respectively. The block was completely successful in 28 of 33 patients (85%), partially successful in 2 (6%), and a failure in 3 (9%). Thirty patients received bupivacaine for the first injection, and three received lidocaine followed 2 h later by bupivacaine. The block was completely successful in all three patients who initially received lidocaine. In the children who first received bupivacaine, the block was completely successful in 25 and partially successful in 2. In the patients with a completely successful bupivacaine-induced block, the time to the first request for analgesic medication was 522 +/- 378 min after placement of the block and 375 +/- 120 min after arrival in the PACU. Eleven inpatients received more than one injection through the catheter. (Four patients received three injections and one patient received four injections to permit postoperative physiotherapy.) The catheter was left in place for periods ranging from 6 to 48 h. Inadvertent vascular puncture or injection, local infection, neuropathy, or other complication was not observed in any patient. Our success rate in cannulating the axillary neurovascular sheath with the radial artery catheterization set and establishing a satisfactory block is in keeping with adult data [7,11,12]. We believe that our low failure rate could be further reduced if the catheterization set were modified to permit injection of local anesthetics without removal of the stimulating wire. This would permit confirmation of the position of the needle in the sheath by demonstrating an abolition of the muscle twitches when 1-2 mL of the local anesthetic is injected, and would also permit the infusion of saline to dilate the brachial sheath before the catheter is advanced. While dilation of the sheath may avoid the catheter being entangled in the nerves, it may dilute the local anesthetic, resulting in an inadequate block [6]. Any future commercially available kits for cannulation of the brachial plexus should include these improvements, and should perhaps also include a thinner, blunter needle. Our technique combined the advantages of nerve stimulation to identify the brachial plexus with the catheter technique for injection. The needle is insulated by the catheter, while the guide wire permits electrical stimuli to reach the tip of the needle, which can be placed in close proximity but not direct contact with the nerve. Catheter techniques provide advantages over the needle injection technique, including decreased trauma, the ability to provide protracted analgesia by infusions or repeated injections, and the ability to inject local anesthetics with the patient's arm by the side. When the arm is by the patient's side, the injection is made into a relaxed sheath which promotes circumferential and proximal spread of the local anesthetic [8,11]. In addition, catheters may be threaded so that the injection is made higher up in the neurovascular sheath and has a greater chance of anesthetizing the musculocutaneous nerve before it leaves the sheath [8]. In summary, we report a series of 33 children who underwent catheterization of the axillary plexus sheath for the administration of local anesthetics. We found this technique to be a useful alternative to other methods of providing perioperative analgesia during upper extremity procedures in this patient population. T. S. H. Tan, FANZCA M. F. Watcha, MD F. Safavi, FFARCS D. McCulloch, MD C. Todd Payne, BA A. Tuefel, BA Department of Anesthesiology/Pain Management, Texas Scottish Rite Hospital for Children, University of Texas Southwestern Medical Center, Dallas, TX 75235-9068