Case Scenario: Neurologic Complication after Continuous Interscalene Block

Abstract

A 33-YR-OLD woman, American Society of Anesthesiologists risk classification I, was referred for surgical treatment of left shoulder instability. Her medical history was unremarkable, but she had undergone two previous shoulder surgeries: anterior stabilization of left shoulder 3 yr ago followed by a posterior Bankart stabilization 2 yr later because of recurrent luxation and pain. At examination, she still complained about pain in her left shoulder, and movement was severely limited. A left Bankart operation and capsulotomy were scheduled. A preoperative interscalene catheter was placed according to the modified lateral approach. The interscalene brachial plexus was identified using a nerve stimulator (Stimuplex® HNS II, B. Braun Melsungen AG, Melsungen, Germany) connected to the proximal end of the metal inner part of a short beveled needle. A contraction of the deltoid muscle was observed with a current output of 0.35 mA, with an impulse duration of 0.1 ms. The insertion of the perineural catheter was performed using the cannula-over-needle technique with a plastic cannula (Polymedic®, Polyplex N-50 T, 20 gauge external diameter, te me na, Bondy, France). The catheter was introduced distally between the anterior and middle scalene muscle up to 3 cm. A bolus of 30 ml ropivacaine (0.5%) was administered, and the procedure was uneventful. No pain, dysesthesias, or paresthesias occurred at any time. Fifteen minutes later, a complete sensorimotor block of the left arm was observed. Then, general anesthesia with targetcontrolled infusion (TCI Diprifusor, SIMS Graseby Ltd., Watford, Herts, United Kingdom) of propofol and remifentanil was administered. The patient was positioned in the beach chair for surgery. The procedure lasted 3 h 30 min and was described by the surgeon as difficult. Postoperative analgesia was performed with patient-controlled interscalene analgesia using ropivacaine (0.2%) and was started 4 h after the end of the surgery. The pump settings were basal rate of 5 ml/h with supplementary boli of 4 ml for every 20 min. The patient was pain free, and the patient-controlled interscalene analgesia was stopped after 54 h. Even after 36 h of termination of patient-controlled interscalene analgesia, no motor or sensory recovery was observed. An ultrasonography of the brachial plexus was performed to exclude a hematoma and revealed no irregular finding. A complete neurologic examination including neurophysiologic recordings on the following day (72 h after surgery) demonstrated a motor and sensory incomplete lesion of nerve fibers originating from the upper brachial plexus (involving the following muscles: deltoid M0/5, biceps M0/5, and triceps M3/5). Motor nerve conduction studies (figs. 1 and 2) and somatosensory-evoked potentials (SSEPs) of the median and ulnar nerves that originate from the lower brachial plexus revealed normal recordings. Electromyography at the initial examination did not show signs of denervation (fibrillation or positive waves) but resulted in complete paralysis (no retrievable voluntary electromyography activity). The later finding at this early stage after injury can be in line with a neurapraxia (conduction failure) or axonotmesis (structural neural damage). Eventually, 1 month later, at the first follow-up, electromyographies showed signs of denervation most severe within the deltoid and biceps muscles, disclosing objective signs of neural damage (fig. 3) congruent to the clinical condition in which no motor improvement was observed. Six months later, although no clinical improvement occurred, a surgical exploration was performed that revealed no pathologic findings. At this time, a perioperative stimulation of the trunks of the brachial plexus elicited reliable responses for the three trunks. In repeated electromyographic recordings during a period of 2 yr, increasing signs of motor recovery could be observed, although the patient still demonstrated severe proximal muscle weakness that could not be * Professor and Chief-of-Staff, † Consultant, Department of Anesthesiology, ‡ Professor and Chairman, Spinal Cord Injury Center, University of Zurich, Balgrist University Hospital, Zurich, Switzerland.