MINIMUM EFFECTIVE VOLUME OF BUPIVACAİNE FOR ANTERIOR SUPRASCAPULAR NERVE BLOCK
Condition: Shoulder Pain; Supraspinatus Tendinitis; Bankart Lesions
MeSH terms: Shoulder Pain; Tendinopathy; Bankart Lesions
Study type: Observational

Summary: 
      Various local anesthetic volumes are used in the literature for anterior suprascapular nerve
      block (ASSB). There are different studies between 15 ml and 5 ml. Effective local anesthetic
      volume studies for ASSB have not yet been performed. Our study is aimed to investigate the
      minimum effective local anesthetic volume for ASSB.
    

Detailed description: 
      Peripheral nerve blockade reduces pain scores and opioid consumption and increases patient
      satisfaction within the first 24 h after shoulder surgery. In the absence of neuraxial and
      peripheral nerve blocks, opioid consumption after shoulder surgery has been purported to
      rival the one recorded for thoracotomy. Interscalene brachial plexus blocks (ISBB) constitute
      the gold standard for analgesia after shoulder procedures. Compared with parenteral opioids,
      ISBB results in lower pain scores improved patient satisfaction [4]. ISBB is highly utilized
      in clinical practice as it provides anesthesia and analgesia to the shoulder and lateral
      aspects of the arm and the forearm, reducing opioid consumption and subsequent opioid-related
      adverse effects [5]. However, ISB is associated with numerous complications and adverse
      effects3 such as phrenic nerve palsy (100%), recurrent laryngeal nerve block (3 - 21%),
      stellate ganglion block (5 - 75%) (Horner's syndrome), spinal (0.4 - 4%) and epidural
      anesthesia (2.2%), and convulsions (0.2 - 3%) at standard volumes of 20 - 30 ml. Phrenic
      nerve block is associated with significant reductions in ventilatory function including a 21
      - 34% decrease in forced vital capacity (FVC), 17 - 37% decrease in forced expiratory volume,
      and 15.4% decrease in peak expiratory flow rate. The most common adverse effect after ISB
      remains the occurrence of ipsilateral phrenic nerve block. Although well tolerated by healthy
      subjects, HDP becomes a prohibitive risk for patients with pulmonary pathology, who may be
      unable to withstand the 30% reduction in FVC. Viable diaphragm-sparing alternatives to ISB
      should achieve three separate and distinct goals: adequate surgical anesthesia (without
      general anesthesia), adequate postoperative analgesia, and low incidence of HDP. Alternative
      nerve blocks are performed in shoulder surgery to prevent HDP. Therefore, different
      approaches such as suprascapular nerve block, costoclavicular block, shoulder block,
      supraclavicular block, combined infraclavicular and suprascapular block, which are defined as
      diaphragm sparing blocks, are recommended.

      Our study aimed to investigate the minimum effective local anesthetic volume in postoperative
      analgesia of the anterior suprascapular nerve block (ASSB) and the maximum local anesthetic
      volume that can be diaphragm-sparing. Our secondary aim is to reveal an important parameter
      in the diaphragm sparing nerve blocks. The volume of a local anesthetic to be administered
      should be expected to have a common volume that is the most effective and protects the
      diaphragm. We envisioned that this should be defined as the minimum target-specific volume
      (MTsV).

      Adults (over 18 years of age) with the American Society of Anesthesiologists Physical
      Condition classification I to III who are scheduled to undergo unilateral ambulatory
      arthroscopic shoulder surgery under general anesthesia will be included in the study. Written
      informed consent will be obtained from all study subjects before participation in this study.
      Surgical procedures are planned to include shoulder arthroscopy, rotator cuff repair,
      acromioplasty, Bankart repair, and superior labrum anterior-posterior repair. Patients with a
      history of serious broncho-pulmonary disease, known phrenic nerve pathology, existing
      neurological deficits or neuropathy involving the brachial plexus on the surgical side,
      contraindications to nerve blocks (infection, bleeding diathesis, allergy to local
      anesthetics), or history will be excluded from the study. A full pre-operative evaluation
      will be performed with the necessary laboratories the day before the surgery, and written
      informed consent will be obtained.

      The 0.5% initial injected volume of bupivacaine was 10 mL, providing a complete sensory block
      of anterior suprascapular nerve block based on our clinical experience. According to the
      Dixon and Massey [10] up-down method, the 0.5% bupivacaine volume used for a given patient
      was determined by the result of the previous block, as defined above as block success. Once
      effective ASSB is achieved, the volume of bupivacaine 0.5% to the next patient will be
      reduced by 1 mL. Conversely, in case of block failure, the volume of 0.5% bupivacaine will be
      increased by 1 mL in the next patient.

      An independent observer will assess ipsilateral hemidiaphragmatic motion by real-time M-mode
      ultrasonography using a 1 to 5 MHz broadband phased array US probe (Philips CX50). Patients
      were examined in an upright sitting position and scanned from a low intercostal or subcostal
      approach using the liver or spleen as the acoustic window. The range of diaphragm movement
      from the resting expiratory position to deep inspiration (sigh test) and the range of
      diaphragm movement from the resting expiratory position when quickly inhaling through the
      nose (sniffing test) will be recorded. More than 75% hemidiaphragmatic movement reduction, no
      movement, or paradoxical movement will be considered complete paresis. Between 25% and 75%,
      hemidiaphragmatic movement decrease was considered partial paresis, and less than 25%
      hemidiaphragmatic movement decrease paresis was considered absent. The movement of the
      diaphragm will be measured in centimeters. The normal caudal movement was positive (+),
      paradoxical head movement was negative (-). Each test will be performed three times, and the
      values will be averaged. All measurements will be made before (beginning) and 30 minutes
      after the block.

      Fifty minutes after the block performance, general anesthesia will be given using a standard
      protocol of intravenously administered propofol 2 mg/kg, Fentanyl 1 ug/kg, and rocuronium 0.6
      mg/kg. Pain scores of the patients will be recorded for 48 hours postoperatively.
    

Intervention name(s): anterior supra scapular nerve block
Intervention type(s): Procedure
Intervention description(s): nerve block for postoperative pain
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Age greater than 18 years with American Society of Anesthesiologists Physical Status
        classification I to III scheduled to undergo unilateral arthroscopic shoulder surgery
        patients under general anesthesia.
      
Keywords: regional anesthesia; shoulder arthroscopy; ortopaedic anesthesia; brachial plexus blocks; diaphragm sparing nerve blocks