The Use of Interscalene Block Prior to Shoulder Arthroscopy: Implications for Postoperative Pain Management

摘要

OVERVIEW OF BRACHIAL PLEXUS BLOCKS The development of the brachial plexus block began in 1884 when Halsted performed the first brachial plexus by injecting exposed roots of the brachial plexus with cocaine 1. It was not until 1911 that Hirschel and Kulenkampff reported a percutaneous brachial plexus block. The axillary technique was developed first, followed by a supraclavicular approach 2,3. In 1919, Mully developed the interscalene approach to brachial plexus block in order to avoid pneumothorax 4. The modern interscalene approach was developed by Winnie using the level of the sixth cervical transverse process as the reference point for needle insertion 5.The interscalene brachial plexus block is ideal for the proximal upper extremity but less reliable for neural blockade of the wrist and hand. Most patients have readily identifiable landmarks, allowing easy access to the brachial plexus via the interscalene approach. The use of a nerve stimulator to guide proper needle placement rather than relying solely on paresthesias, can increase the rate of a safe and successful block.In an effort to initiate early postoperative physical therapy, our Acute Pain Management Service was asked to provide brachial plexus blocks for all patients having shoulder surgery at a newly opened orthopedic specialty hospital. The block was performed prior to surgery. While our pain management service had been in existence for four years providing epidural analgesia and IV PCA at a large teaching hospital, we had almost no experience with brachial plexus blocks for postoperative pain. Therefore, a Continuous Quality Improvement (C.Q.I.) monitor was initiated to determine the efficacy, effectiveness and efficiency of this new procedure on our patient population. Indicators were established to capture possible complications (see CQI monitor). In addition, a follow-up patient satisfaction survey was done. METHOD After obtaining informed consent, the patient was placed in the supine position and EKG, blood pressure and oxygen saturation monitoring were initiated. Oxygen via face mask was applied and intravenous sedation with midazolam was administered. The nerve stimulator used for guidance was grounded to the patient. The patient’s head was turned at approximately a 45 degree angle away from the operative side. The neck was then prepped and draped in a sterile fashion. A twenty-two gauge insulated needle designed with two ports was used connecting to a nerve stimulator and extension tubing. The needle was connected to the nerve stimulator and the remaining port was connected to a syringe filled with 0.375% bupivacaine with epinephrine. In addition to the anesthesiologist, this technique requires an assistant to manipulate the nerve stimulator and inject the local anesthetic. The interscalene groove was then identified and the needle was inserted at the site of the groove level to the cricoid cartilage. Once the needle pierced the skin, the nerve stimulator was turned on and set to a low voltage, one second interval stimulation and an output of approximately 1.3 mA. The needle was inserted perpendicular to the skin and then angled slightly caudid. The needle was then advanced slowly, and stimulation of the extremity, diaphragm, sternomastoid and trapezius was observed. The brachial plexus lies between the course taken by the phrenic nerve anteriorly and the cervical plexus posteriorly. If diaphragmatic stimulation (phrenic nerve) occurred, then the needle direction was considered to be too anterior and was redirected. If muscles of the neck or trapezius (cervical plexus) were stimulated, then the needle was considered too posterior and was redirected.