• NOL response after surgical incisions (area under curve) [ Time Frame: Intraoperative ]
  NOL response after surgical incisions 1 (located 2 cm inferior and 1 cm medial to posterolateral corner of acromion) of the shoulder (by calculating the area under the curve of NOL for the 5 minutes following incision 1).
• NOL response after surgical incisions (area under curve) [ Time Frame: Intraoperative ]
  NOL response after surgical incisions 2 (located slightly inferior to coracoid) of the shoulder (by calculating the area under the curve of NOL for the 5 minutes following incision 1).
• Total dose remifentanil in mcg [ Time Frame: Intraoperative ]
  Total dose of remifentanil in mcg from incision until wound dressing
• Number of remifentanil boluses (n) [ Time Frame: Intraoperative ]
  Number of remifentanil boluses administered to the patient from incision until wound dressing
• Desflurance consumption in ml [ Time Frame: Intraoperative from incision until wound dressing ]
  Intraoperative consumption of desflurane in mL
• Time to awakening in minutes [ Time Frame: Intraoperative ]
  Time to awakening in minutes.
• Time to extubation in minutes [ Time Frame: Intraoperative ]
  Time to extubation in minutes.
• PACU pain scores on a scale from 0 to 10 [ Time Frame: From entrance in PACU until PACU discharge e.g. up to 3 hours after surgery maximum ]
  PACU pain scores
• Grip strength in mmHg [ Time Frame: in PACU e.g. up to 3 hours after surgery maximum ]
  Grip strength before nerve blockade and prior to PACU discharge, as measured in mmHg by a pressure transducer connected to a 1000mL saline bag.
• Diaphragmatic paresis induced by the nerve block by ultrasound [ Time Frame: 30 minutes after nerve block and before general anesthesia and surgery, in awake patient ]
  Ipsilateral diaphragmatic excursion 30 minutes after block completion (normal, paradoxical or no movement).
• Patient dyspnea on a scale from 0 to 10 [ Time Frame: PACU e.g. up to 3 hours after surgery maximum ]
  Patient dyspnea prior to PACU discharge on a scale from 0 to 10.
• Time to readiness for discharge from PACU in minutes [ Time Frame: PACU e.g. up to 3 hours after surgery maximum ]
  Time to readiness for discharge from PACU = time in minutes to reach an Aldrete score at 9 for discharge
• 24h pain scores on a scale from 0 to 10 at rest [ Time Frame: Postoperative at H24, 24 hours after surgery ]
  24h pain scores, H24
• 48h pain scores on a scale from 0 to 10 at rest [ Time Frame: Postoperative at H48, 48 hours after surgery ]
  48h pain scores
• 24h pain scores on a scale from 0 to 10 during mobilization [ Time Frame: Postoperative at H24, 24 hours after surgery ]
  24h pain scores during mobilization
• Per os postoperative (after PACU discharge) morphine equivalent consumption in mg at 8, 16, 24, 32, 40, 48 hs postoperatively [ Time Frame: Postoperative for 2 days 48 hours after surgery ]
  Per os opioid consumption in mg of equivalent morphine (every 8 hours by nurses or with a diary in patients with same day surgery).
• Duration of motor block in minutes strength [ Time Frame: Postoperative for day 1 H24 24hours after surgery ]
  Duration of motor block in minutes, as measured by time to return of normal grip strength.
• Patient satisfaction on a scale from 0 to 100 [ Time Frame: Postoperative at 24h, 24 hours after surgery ]
  Patient satisfaction at 24 hours on a scale from 0 to 100.

Postoperative analgesia for shoulder surgery is typically achieved by providing an interscalene brachial plexus block. However, a very common side effect of this block is hemi-diaphragmatic paralysis, a state which may not be tolerated in patients with pulmonary conditions such as COPD. Recently, clinicians have explored new ways to provide satisfactory analgesia while minimizing the pulmonary side effects of the interscalene nerve block. One of these solutions might be to offer the patient a suprascapular nerve block combined to a posterior cord block. Since these blocks are performed lower in the neck or under the clavicle, the phrenic nerve is less likely to be blocked. Thus, fewer respiratory side effects have been reported when using such blocks. This prospective observational study will evaluate the NOL response to surgical stimuli and the opioid requirements intraoperatively in patients undergoing shoulder arthroscopies with either a supraclavicular and posterior cord blocks or an interscalene block.

Study Design: Prospective, randomized open label non-inferiority trial. Subject Population: Adults scheduled to undergo elective shoulder arthroscopy Sample Size: 100 patients Study Duration: Starts February 2019 - Ends February 2021 - Interim analysis at 50 patients Study Center: Maisonneuve-Rosemont Hospital, CEMTL, Montreal, Quebec, Canada

The main hypothesis of this study is that the suprascapular block combined with a posterior cord block is not inferior to the interscalene brachial plexus block in terms of intraoperative analgesia. We postulate that intraoperative opioid requirements will not differ significantly in patients who receive either block.

Our secondary objectives will consist in looking at the differences in intraoperative anesthetic consumption, NOL index alterations, postoperative opioid consumption, pain scores, arm motor block, diaphragmatic paresis, patient satisfaction and time for readiness to discharge from PACU. We hypothesize that these outcomes will be similar in both groups, with the exception of a potential reduction in arm motor block and diaphragmatic paresis in the combined suprascapular and posterior cord block group.

After having obtained institutional ethics board approval of the study, patients older than 18 years old, scheduled for a first elective shoulder arthroscopy under general anesthesia will be screened in the pre-anesthesia clinic. They will be approached and the whole study procedures will be explained extensively. Interested patients will be invited to sign the consent form (see appendix). Patients will have the right to opt out at any time. The investigators will meet the patients again on the morning of the surgery to address any concerns. After consent, a study number will be allocated to the patient in ascending order.

Two groups will be evaluated:

• Group A: single shot US-guided suprascapular nerve block with 5 mL ropivacaine 0.5%, then single shot US-guided posterior cord block with 10 ml ropivacaine 0.5%.
• Group B: single shot US-guided interscalene brachial plexus block with 15 mL ropivacaine 0.5%.

Tests will be done to evaluate the nerve block-induced loss of sensation to ice prior to entering the operating room (OR). Diaphragmatic excursion will be evaluated using an abdominal curvilinear ultrasound probe, and will be classified as being normal, paradoxical or immobile. Normal motion is caudad movement during inspiration. Paradoxical motion is cephalad movement during inspiration.

Once in the operating room, all routine monitors are connected. Moreover, the PMD TM monitor as well as the BIS® monitor are connected to the anesthesia machine and to the patient. Both study monitors are switched on and will record their respective indices continuously for the duration of the anesthesia. General anesthesia will be induced with propofol (1-2 mg/kg IV; Pharmascience Inc, Canada), remifentanil (1 µg/kg IV bolus; Teva, Canada) and rocuronium (0.6-1 mg/kg IV; Sandoz Canada Inc). A bolus of dexamethasone 4mg IV will be administered after induction of general anesthesia.

Patients will also have received oral acetaminophen 1g and celecoxib 400 mg preoperatively. Intubation with an endotracheal tube is performed once the patient is adequately paralyzed (no responses to the TOF stimulation). All drugs are given according to the adjusted body weight of the patient. This is calculated with Robinson's formula: where TBW is total body weight and IBW is ideal body weight (21-22). Immediately after intubation, anesthesia is maintained with desflurane while targeting a BIS value between 45 and 55, and a remifentanil infusion and boluses are used for a NOL below 25. At the end of anesthesia, when the surgeon starts closing the wounds, an IV bolus of hydromorphone 7 mcg/kg of adjusted body weight is administered. The remifentanil infusion and desflurane are discontinued when dressing starts. Emergence and extubation are done in the OR. All times (start skin closure, start dressing, stop desflurane and remifentanil) will be precisely reported in the CRF.

• Shoulder Surgery
• Regional Anesthesia Morbidity

• Procedure: Suprascapular Nerve Block + Posterior Cord Block
  The patient lies supine with the head turned to the contralateral side to the block. Using a linear high-frequency ultrasound probe, the proximal suprascapular nerve is visualized before it turns toward the suprascapular notch. It is blocked using 5mL of ropivicaine 0.5%. The posterior cord is readily visualized when performing an infraclavicular brachial plexus block. It is blocked using 10mL of ropivicaine 0.5%.
  Other Name: SSNB+PCB
• Procedure: Interscalene Brachial Plexus Block
  The patient lies supine with the head turned to the contralateral side to the block. Using a linear high-frequency ultrasound probe, the interscalene groove is visualized along with the roots of the brachial plexus. The block is performed with 15mL of ropivacaine 0.5%.
  Other Name: ISPB

• Experimental: SSNB + PCB
  Single shot US-guided suprascapular nerve block (SSNB) with 5 mL ropivacaine 0.5%, then single shot US-guided posterior cord block (PCB) with 10 ml ropivacaine 0.5%.
  Intervention: Procedure: Suprascapular Nerve Block + Posterior Cord Block
• Active Comparator: ISBPB
  Single shot US-guided interscalene brachial plexus block (ISBPB) with 15 mL ropivacaine 0.5%.
  Intervention: Procedure: Interscalene Brachial Plexus Block

Inclusion Criteria:

• ASA status 1,2,3.
• Age 18 years or older
• Elective shoulder arthroscopic surgery under general anesthesia and nerve block performed preoperatively

Exclusion Criteria:

• Serious cardiac arrhythmias (including atrial fibrillation) or unstable coronary artery disease.
• Coagulation disorders.
• Patient refusal.
• Anatomical disorders and/or neuropathic disease.
• BMI above 40.
• History of substance abuse.
• Chronic use of psychotropic and/or opioid.
• History of psychiatric diseases needing treatment.
• Contraindications to nerve block for shoulder surgery.
• Allergy to remifentanil or any drug in the study protocol.
• Failure of nerve block performed in the preoperative block room