Distant Extrafascial Injection vs Subfascial Injection for Interscalene Block: Acute Pain Outcomes and Rates of Complications
Condition: Ultrasound-guided Regional Anesthesia; Shoulder Surgery; Interscalene Block; Postoperative Analgesia; Respiratory Function
Study type: Interventional

Summary: 
      The objective of this randomized controlled trial is to compare the analgesic efficacy and
      the safety profile between two techniques of injection for the interscalene block. The
      interscalene block consists of injecting local anesthetic around the cervical roots of the
      brachial plexus and allows analgesia after shoulder surgery.

      Stated differently, the dual objective of that study is:

        1. to confirm that an injection at a distance of 4 mm away from the lateral sheath of the
           plexus (distal injection) provides similar analgesia as a classical injection within the
           plexus (subfascial injection);

        2. to demonstrate that a distant extrafascial injection produces less respiratory
           complications than a subfascial injection, defined as hemidiaphragmatic paresis.
    

Detailed description: 
      This is a prospective randomized controlled double-blinded trial on patients undergoing
      shoulder surgery (shoulder arthroscopy or open shoulder surgery), aged between 18 and 85
      years old.

      The exclusion criteria will be contraindications to brachial plexus block (e.g., allergy to
      local anesthetics, coagulopathy, malignancy or infection in the area); existing neurological
      deficit in the area to be blocked; severe respiratory disease; inability to understand the
      informed consent and patient refusal.

      Prior to the procedure, all patients will be fully informed about the risks and benefits of
      participating in the study and written informed consent will be obtained.

      Interscalene brachial plexus block will be performed with the patient lying lateral on the
      non-operative side, following our routine clinical practice, with twenty milliliters of local
      anesthetic containing bupivacaine 0.5% with 1:200,000 epinephrine. For patients in the
      subfascial injection group, the needle tip will be positioned lateral to the brachial plexus
      at a distance of 4 mm, measured with a caliper.

      Block assessment and definition of a successful block Evaluation of sensory and motor
      blockades will be performed by a blinded research assistant every 5 min, for a total of 30
      min, after local anesthetic (LA) injection. Sensory block and motor blockades will be tested
      in the C4, C5, C6, C7, and C8 dermatomes using a blunt tip needle pinprick test and muscular
      testing. A successful block will be defined as complete sensory and motor blockade in the
      distribution of the C5 and C6 nerve roots within 30 minutes of performing the ISB. In cases
      of a failed block, the ISB will be repeated at the discretion of the attending
      anesthesiologist and these patients will be excluded from the intraoperative and
      postoperative secondary outcome analyses.

      Definition of hemidiaphragmatic paresis Diaphragmatic movement will be assessed by real-time
      M-mode ultrasonography on each side using a curvilinear 2 - 5 MHz US probe, following
      previous published descriptions [16]. Patients will be examined in the lying position. The
      presence of paradoxical cephalad movement will represent a hemidiaphragmatic paresis.

      Assessment of the ventilatory function (pulmonary function tests) A bedside spirometer
      (EasyOneTM Spirometer; ndd Medical Technologies, Andover, UK) will be used to assess
      ventilatory function. After instructions, the full vital capacity (VC) in supine and sitting
      upright positions will be measured. The percent fall of vital capacity from sitting to supine
      position will be considered as an index of diaphragmatic dysfunction.

      Intraoperative and postoperative procedure After application of routine monitors in the
      operating theatre, patients will receive a standardized general anesthetic. Following
      surgery, pain (Numeric rating scale [NRS] ≥ 4 or patient request for analgesia) will be
      treated with morphine 2 mg every 10 min as needed, in the postanesthetic recovery unit. On
      the ward, patients will receive oxycodone 5-10 mg per os every 2 hours as needed and
      acetaminophen 1000 mg per os every 6 h for pain. All these managements represent the current
      standard of care at Centre Hospitalier Universitaire Vaudois.

      Outcomes

      The dual primary outcomes will be:

        -  The rate of successful block defined as above;

        -  The rate of hemidiaphragmatic paresis 30 minutes after completion of the block.

      Secondary outcomes will include presence of paresthesia during the procedure; pain scores
      (NRS out of 10) upon arrival in PACU, and at 2 hours postoperatively; postoperative morphine
      consumption in PACU; duration of analgesia; and total consumption of oxycodone during the
      first 24 postoperative hours.

      Finally, the blinded research assistant will contact the patients on day 7 by telephone to
      record post block complications such as persistent paresthesia and limb weakness.
    

Intervention name(s): Distant extrafascial injection; Subfascial injection
Intervention type(s): Procedure; Procedure
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment