Arthroscopic shoulder surgery is increasingly performed in an outpatient setting and post-operative pain management is often a real challenge as those surgeries are well recognized for their high level of pain which often affects physical rehabilitation. The interscalene block is a largely used anesthetic technique to perform these surgeries whilst avoiding general anesthesia (GA) and to provide postoperative analgesia. However, the painful period often exceeds the duration of a single shot block, thus affecting patient recovery. Some specialized centers use a continuous catheter and elastomeric pump in order to prolong the duration of analgesia. However, several logistical, professional and financial constraints limit the use of these catheters and pumps in a great number of outpatient centers. On the other hand, perineural dexmedetomidine is increasingly used as an adjuvant to improve block onset, analgesia duration and patient satisfaction.

The use of adjuvants such as perineural dexmedetomidine added to a single shot interscalene block appears to be an interesting option to prolong postoperative analgesia without the limitations imposed by a continuous catheter and elastomeric pumps in arthroscopic shoulder surgeries.

A growing number of arthroscopic shoulder surgeries are performed in an ambulatory setting. For these patients, postoperative pain management is an important factor for analgesia and optimal rehabilitation. Peripheral nerve blocks, and more particularly the interscalene brachial plexus block (ISB), is the method of choice to provide adequate surgical conditions and satisfactory postoperative pain control for shoulder surgeries. Even before the advent of ultrasound guidance , interscalene blocks resulted in a high level of patient satisfaction, fewer post-operative complications and a reduction of hospital stay compared to general anesthesia.

Shoulder surgeries are well recognized to cause severe postoperative pain, mainly in the first 48h, and the use of a single shot interscalene block (SSISB) is limited by its duration of action, which often fails to cover the duration of postoperative analgesia beyond 24 hours.

On the other hand, ultrasound-guided continuous interscalene blocks (CISB) have shown a significant reduction of pain compared to single shot interscalene blocks. However, CISB are limited by many logistical problems which make their use difficult in most ambulatory centers. Indeed, catheter placement is often a technically challenging procedure and accidental catheter removal is a complication that limits their usefulness. However, when the necessary technical resources and medical expertise is available, CISB have been associated with a superior level of analgesia, reduction of opioid consumption, improvements in rest and dynamic pain, and lower instances of postoperative nausea and vomiting than SSISB in major shoulder surgery. A recent study has demonstrated that automated intermittent boluses did not provide better analgesia nor reduced rescue opioid consumption compared to continuous infusion of ropivacaine despite both groups describing insufficient pain relief.

The persistence of pain despite the use of SSISB or CISB has lead several anesthesia teams to use adjuvants to improve the effect and duration of analgesia. Over the years, several adjuvants have been administered to enhance the brachial plexus block onset and duration. Thus, intravenous dexamethasone administered at the time of performing ISB is widely used to improve the duration of analgesia following shoulder surgeries. In addition to the benefits already provided by the addition of intravenous dexamethasone, there is also an added value to perineural dexmedetomidine in order to accelerate the onset of motor and sensory block, extend the duration of the block and reduce the pain score 14 hours postoperatively in elective shoulder surgery.

The combination of intravenous or perineural dexmedetomidine, an α-2 adrenoceptor agonist, with ropivacaine prolongs the duration of SSISB analgesia and reduces opioid consumption postoperatively without prolonging the duration of motor blockade during outpatient shoulder surgeries. Patients undergoing elective shoulder surgery under general anesthesia with perineural dexmedetomidine added to ropivacaine for interscalene block had a faster sensory and motor block onset, an increased duration of nerve blockade and improved postoperative pain up to 14h after the block. Even when a peripheral nerve block is used as the primary anesthetic, SSISB with perineural dexmedetomidine added to ropivacaine in arthroscopic rotator cuff repair has shown lower pain and improved patient satisfaction within 48 h postoperatively. The perfect perineural dexmedetomidine dose should provide optimal analgesia with minimal side effects such as hypotension and bradycardia. Over the years, it has been used in wide-ranging doses and 2 mcg/kg seems to be the optimal dose in SSISB for arthroscopic shoulder surgery to obtain a suitable duration of analgesia. A recent meta-analysis demonstrates the safety of perineural dexmedetomidine as well as its effectiveness during brachial plexus block to accelerate the onset of action and prolong the duration of analgesia. Indeed, no neurological complications or neurotoxic symptoms were reported in patients who received perineural dexmedetomidine.

Rationale for this study:

The addition of dexmedetomidine to ropivacaine for SSIB could improve the duration of postoperative analgesia and patient satisfaction for arthroscopic shoulder surgeries without the limitations and potential complications of an CISB catheter and elastomeric pump. Moreover, the use of a catheter is a complex procedure compared to a single injection and thus limited in some centers due to logistical limitations. Therefore, SSISB with perineural dexmedetomidine could be an interesting alternative to perform shoulder surgeries in centers where the use of a continuous catheter is limited by technical, professional or financial resources. Ultimately, this improvement in postoperative analgesia could lead to early patient mobilization, better physical rehabilitation and improved patient satisfaction. This study will focus on recovery, to better understand patient outcomes and experiences as a whole, in this era of personalized medicine and patient oriented research.

Methods: A predetermined sample size of patients of more than18 years old, ASA status I-III scheduled to undergo elective minor ambulatory shoulder surgery are included. Patients with known allergy to local anesthetics, contraindication to interscalene brachial plexus nerve block or superficial cervical plexus block will be excluded. The premedication and peripheral nerve block technique will be standardized for both groups. Patients will be randomized to receive either a single shot interscalene block with 150 mg of isobaric ropivacaine 0.5% (125 mg at the interscalene brachial plexus level and 25 mg at the superficial cervical plexus) with 2 mcg/kg (IBW) of dexmedetomidine or a continuous interscalene block with an initial dose of 150 mg of isobaric ropivacaine 0.5% (125 mg at the interscalene brachial plexus level and 25 mg at the superficial cervical plexus) and an infusion using an elastomeric pump of 300 mL at a rate of 5 mL/h of isobaric ropivacaine 0.2% for 60 hours. The primary endpoint will be the Quality of Recovery (QoR-15) questionnaire at 48h. The secondary endpoints will be: QoR-15 at 24h and 72h, time before the first analgesic request, time before the end of sensory block, time before the end of motor block, patient satisfaction, total post-operative opioid consumption, major and minor complications.

Study design: Prospective, randomized controlled trial.

Subject population: Adult patients scheduled to undergo elective arthroscopic ambulatory shoulder surgery

Sample size: 96

Study duration: 12 months

Study center: CIUSSS de l'Est de l'Ile de Montréal, Montreal, QC, Canada

Adverse Events: None expected

Subvention: applications to the Canadian Society of Anesthesia as well as to the Foundation of the Association of the Anesthesiologists of Quebec and to the department of anesthesiology of the UdeM will be proposed within the coming year 2021-2022.

Inclusion Criteria:

• Patients over 18 years old
• ASA status of I-III
• Patients undergoing elective arthroscopic ambulatory shoulder surgery
• Anticipated return home the same day (less than 12 hours in-hospital) in any operating theater of the CIUSSS.

Exclusion Criteria:

• less than 18 years old
• Patient refusal
• Pregnancy
• Patients with known allergy to local anesthetics
• Contraindication to interscalene brachial plexus nerve block or superficial cervical plexus block: coagulopathy, contralateral phrenic nerve dysfunction, infection at the puncture site, severe chronic obstructive pulmonary disease
• Technical inability to proceed with the interscalene brachial plexus nerve block
• Surgery requiring general anesthesia
• Body weight less than 50 kg
• Patient with no family member or caring adult at home during the first 72h postoperative (contraindication to elastomeric pump)
• Unable to communicate with the investigators, unable to read the questionnaire, unable to keep track and notes of the medication taken at home
• Significant psychiatric or cognitive condition interfering with the ability to provide consent or assessment
• Preexisting neurologic deficits or neuropathy affecting the brachial plexus
• Any contra-indication to same-day surgery identified by the pre-operative clinic such as, but not limited to, any cognitive disorder, any physical limitation other than the one leading to surgery that might impair the patient to take care of himself/herself at home, any severe pulmonary or cardiac disorder, bleeding disorder, etc,
• Any cardiac or pulmonary condition that precludes the risk of bradycardia or hypotension such as but not limited to symptomatic coronary disease, severe aortic stenosis, moderate to severe pulmonary hypertension, congestive heart failure, second or third degree block, pre-existing bradycardia (HR lower than 50), pre-existing hypotension (SBP lower than 100 mmHg), etc.
• History of chronic pain with daily opioid use during the 3 months before surgery

The patient, the anesthesiologist that will perform the block and the operating room staff cannot be blinded for treatment group allocation since the material differs in the 2 groups. We did not want to remain blind at all costs by installing catheters in all participants, with a continuous infusion of saline for the dexmedetomidine group, since the insertion of a catheter is not without risk for the patient and the initial bolus would have been diluted.

The nurse staff, anesthesiologists and the research staff evaluating the patient by phone on postoperative days 1,2 and 3 will not be blinded to the patients' study care group allocation because they will also be looking for minor complications that involve the catheter or the infusion pump.