Determining the Minimal Effective Volume (MEAV95) for Interscalene Brachial Plexus Block for Surgical Anesthesia

Study Overview
=================
Brief Summary
-----------------
Interscalene block (ISB) consistently demonstrates superior pain relief after shoulder surgery. However, patients can experience complications such as blurred vision, hoarseness and shortness of breath with the standard volumes of local anesthetic used in contemporary practice. Patients with respiratory diseases are precluded because of the potential effects on respiration. However, they are then exposed to the risks of general anesthesia and opioid medications which can also have detrimental effects on respiration. Ultrasound guided ISB can reduce the local anesthetic volume required to produce anesthesia for shoulder surgery; this may reduce the complications from ISB to allow patients previously unable to benefit to have this technique, such as patients with obesity and respiratory disease. In order to do so the investigators will use an up-down methodology to find the minimum volume of local anesthetic to provide sufficient anesthesia for shoulder surgery.

Official Title
-----------------
Determining the Minimal Effective Volume (MEAV95) for Interscalene Brachial Plexus Block for Surgical Anesthesia

Conditions
-----------------
Shoulder Pain

Intervention / Treatment
-----------------
* Procedure: Dose of of ropivacaine 0.75% used in block procedure


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Patients undergoing elective arthroscopic shoulder surgery in the sitting position Patients aged >=18 and <=75 years ASA I-III Exclusion Criteria: Patient refusal for surgery under ISBPB with sedation Lack of capacity to provide informed consent Pre-existing COPD, unstable asthma or diaphragmatic dysfunction Coagulopathy Infection at injection site Allergy to local anesthetics Opioid tolerance (>30mg oral morphine or equivalent/day for >1 week) BMI>40 Inability to complete questionnaires and assessments (consent, follow-up phone call) due to language barrier Pregnancy or lactation

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Local Anesthestic Dose<br> | Procedure: Dose of of ropivacaine 0.75% used in block procedure<br> <br> |

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| MEAV95 of ropivacaine 0.75% | to determine the MEAV95 of ropivacaine 0.75% at the level of root C5-6 using the dose-finding protocol. The success of surgical anesthesia is defined by the presence of sensory blockade (no sensation/score of 0 to pinprick testing) 30 minutes post injection of local anesthetic | 30 minutes post injection | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Motor blockade | The C5 myotome covers the deltoid muscle (the most powerful motion being shoulder abduction) and the biceps brachii muscle. Biceps brachii is also innervated by C6. Therefore, motor blockade will be assessed by testing shoulder abduction and forearm flexion. Motor function will be classified as present (any movement) or absent (no movement) | 30 minutes | 
| Bedside spirometry | Bedside spirometry (FEV1, FVC, PEFR) and Pulse oximetry on air: at baseline, 30 minutes post block, 30min post-surgery, and 2 hours post surgery | 30 minutes post block, 30min post-surgery, and 2 hours post surgery | 
| Diaphragmatic excursion | Diaphragmatic excursion: ultrasound examination at baseline, 30 minutes post block, and 2 hours post surgery | 30 minutes post block, and 2 hours post surgery | 
| Complications | Complications: Hoarseness, Horner's syndrome, intravascular injection | 30 minutes | 
| Pain Scores on Visual Analog Scale | Visual analog scale (VAS) - at baseline, after surgery at 30 and 60 minutes in the PACU, and at 1 hour intervals until discharge | at baseline, after surgery at 30 and 60 minutes in the PACU, and at 1 hour intervals until discharge | 
| Total opioid consumption until discharge | Total opioid consumption until discharge | 24 hours (at discharge) | 
| Opioid related side effects | Opioid related side effects: nausea, vomiting, dizziness, pruritis | 24 hours (at discharge) | 
| Time to first analgesic use | Time to first analgesic use in hospital and after discharge | within 24 hours post surgery | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
ISPB, Brachial Plexus Block, Anesthesia, Pain Management, Surgery