Plexus Irritation Caused by Interscalene Brachial Plexus Catheter for Shoulder Surgery

Continuous interscalene brachial plexus block with bupivacaine has been used successfully in our hospital for most patients undergoing open or closed shoulder procedures, and especially for postoperative analgesia during shoulder physical therapy. The catheter is usually removed when analgesia for physical therapy is no longer required. We report two cases of possible nerve irritation associated with interscalene brachial plexus catheter leading to painful burning sensations in the dorsomedial aspect of the operated shoulder. The complaints disappeared completely immediately after removal of the catheter. Case 1 A 49-yr-old female with clinical symptoms of subacromial impingement and osteoarthritis of the acromioclavicular joint for 8 mo was admitted for open shoulder surgery. One day prior to surgery, uncomplicated insertion of an interscalene brachial plexus catheter was performed on the operative side. The site of puncture was 1 cm cranial to the palpable top of the anterior interscalene groove (C3-4). After skin infiltration with local anesthetic (LA), a polyamide catheter (distal opening outer diameter 0.85 mm, Contiplex Registered Trademark; B. Braun Melsungen AG, Melsungen, Germany) was inserted caudally through a plastic plexus cannula, parallel to the interscalene muscle, into the plexus sheath. The catheter, which is rather stiff and can be inserted without a stylet, was fixed to the skin with a tight suture at 5 cm and was connected to a microfilter (0.2 mm; Portex, Hythe, England). No paresthesia was observed at the time of either needle puncture or catheter insertion. In order to confirm correct placement of the catheter, a test injection of 10 mL 0.25% bupivacaine was given, which produced complete analgesia in the dermatomes C3-5. For surgery, 20 mL 0.5% bupivacaine was injected through the catheter 30 min before light general anesthesia was induced. Postoperative, patient-controlled analgesia was achieved with 10 mL 0.25% bupivacaine, with a lockout time of 4 h, in combination with oral diclofenac 50 mg three times daily. Slight mobilization involving pendulum exercises of the operative shoulder began on the first postoperative day. More intensive physical therapy in the form of passive mobilization in all planes was initiated on the following day. When analgesia decreased, the patient noted a burning sensation in the supraspinatus muscle belly on the operative side that was different in quality and location compared with the pain from the operative site. During the next 10-mL injection of 0.25% bupivacaine prior to physical therapy on the third postoperative day, the patient felt an increase of the burning sensation. Both burning sensation and pain at the operative site disappeared approximately 15 min after LA injection and reappeared again 6 h later. Prior to this complaint, the catheter had been used successfully seven times (mean interval of 8 h) without any complications. The same problem developed during the following five injections of LA through the catheter (mean interval of 6 h). The burning sensation worsened gradually and caused more discomfort to the patient than the operative pain, which had been decreasing. Daily examination showed no signs of catheter infection, changes in skin fixation (depth and direction), or local tenderness in the newly painful area. When the catheter was removed on the sixth postoperative day, the burning pain stopped immediately and did not return. Repeated subsequent physical examinations after removal of the catheter revealed no paresthesias or neurological deficits. Case 2 A 41-yr-old female who had a previous open shoulder procedure presented with persistent intense shoulder pain arising from subacromial impingement due to a rotator cuff tear and acromioclavicular osteoarthritis. The patient was admitted for revision surgery. Again, as in Case 1, uncomplicated insertion of an interscalene brachial plexus catheter was performed on the operative side 1 day prior to surgery. Perioperative use of the catheter and management of postoperative pain were identical to those in Case 1. After passive mobilization of the operative shoulder in all planes had been initiated on the second postoperative day, the patient complained of an additional burning pain, identical to that in Case 1, located in the supraspinatus muscle belly, when analgesia was reduced. This new pain subsided for only 4 h after injection of 10 mL 0.25% bupivacaine. Until this complaint, the patient had received nine injections of LA through the catheter without difficulty (mean interval of 6 h). In the late afternoon of the second postoperative day, after analgesia from the previous injection was reduced, the pain worsened, and 15 mL of 0.5% bupivacaine was administered to produce a more prolonged analgesia (8 hours' duration). Prior to this LA injection, physical examination revealed no neurological deficits, local tenderness, signs of catheter infection or changes in skin fixation. On the third postoperative day, the patient complained only of the burning sensation. The operative site pain had almost subsided. The catheter was removed and the pain disappeared promptly. Repeated physical examinations after removal of the catheter again did not reveal any neurological deficits. Discussion Shoulder procedures are often associated with severe postoperative pain. This not only causes discomfort for the patients but also compromises the intensive postoperative rehabilitation necessary for a good functional result. Continuous interscalene brachial plexus block is a reliable and effective method of providing anesthesia as well as postoperative analgesia in closed or open shoulder procedures. Other recognized advantages of this technique include reduced intraoperative blood loss, excellent muscle relaxation, avoidance in many cases of general anesthesia with its risks and side effects, reduced postoperative analgesia requirements, and shorter hospital stay [1-4]. However, side effects and complications have been reported. Paralysis of the phrenic nerve without dyspnea, hoarseness due to paralysis of the recurrent laryngeal nerve, Horner's syndrome, vasovagal syncope, and hematoma formation are not uncommon. The more severe complications including high epidural block, total spinal anesthesia, cardiovascular depression, nerve damage, dyspnea, pneumothorax, seizure, and cardiac arrest are rare [1-8]. Apart from the two cases reported here, we have not experienced any significant complications, and none of the side effects encountered in our patients were so severe as to require removal of the catheter. In both cases reported above, a new quality of pain (burning) at a new location (supraspinatus muscle belly), clearly different from the operatively induced pain, developed postoperatively after physical therapy, causing increasing complaints and finally necessitating removal of the catheter. This pain promptly vanished after the removal of the catheter, and there-after no signs of neurologic irritation could be observed. The catheter insertions were both uneventful. No paresthesia was observed at the time of needle puncture or catheter insertion. The initial 10-mL injection of LA produced isolated analgesia in dermatomes C3-5, as desired. The quality and extension of postoperative analgesia were satisfactory and did not change after appearance of the burning pain. These observations led us to suppose that the rather stiff catheter tip, likely moved during more intensive physical therapy, may have caused mechanical nerve irritation resulting in burning pain in the supraspinatus muscle belly correlating with the distribution of the suprascapular nerve. In Case 1, the temporary increase in the burning sensation during injection of bupivacaine may be explained by an additional nerve irritation through plexus distention as well as the injection of a cold solution, which may have induced temporary paresthesias [9]. Other possible causes, such as myofascial pain or strain to the supraspinatus muscle during physical therapy, are unlikely, since no local tenderness could be observed upon physical examination. In both cases, there was no indication of catheter infection. One would expect that the pain would persist, at least for a short time, if inflammation in tissues surrounding the nerves (i.e., from repeated plexus distention) had been the cause. The absence of neurological deficits or paresthesias after removal of the catheter argue against an intraneural injection and possible LA neurotoxicity. Intraneural injection is extremely painful [10], and bupivacaine has a low neurotoxicity potential compared with other LAs [11,12]. Peripheral nerve injury caused by needles used for regional anesthesia has been reported [10,13,14], but is usually associated with severe and persistent paresthesias. We are not aware of any similar reports in the literature associated with catheter-induced pain. Such phenomena may have escaped detection as a result of not being sufficiently distinguished from ordinary postoperative pain or by being masked by continuous injection of LA, which is frequently used for pain management [4]. We would recommend, in patients with complaints similar to those reported here, that if the interscalene brachial plexus catheter is still required for pain management, the catheter should be withdrawn 1 cm. If the symptoms do not subside with this maneuver, the catheter should be removed.