Actively Recruiting
Interscalene vs Phrenic-sparing Blocks in Obesity: Effect of Pre-operative Maximum Inspiratory Pressure in a Randomized Trial
Led by University of North Carolina, Chapel Hill · Updated on 2026-01-28
68
Participants Needed
1
Research Sites
2 weeks
Total Duration
On this page
Sponsors
U
University of North Carolina, Chapel Hill
Lead Sponsor
A
American Society of Regional Anesthesia
Collaborating Sponsor
AI-Summary
What this Trial Is About
Researchers are evaluating whether a phrenic-sparing nerve block can reduce early breathing difficulties after shoulder surgery in adults with obesity. The study compares this new nerve block approach to the standard interscalene block to see if it lowers breathlessness or oxygen need shortly after surgery while maintaining similar pain control and opioid use. The study also tests if a simple breathing-strength test called maximum inspiratory pressure (MIP) can identify patients at higher risk for breathing issues. Participants will be randomly assigned to receive either the standard interscalene block involving a single injection of bupivacaine and dexamethasone at the C5-C6 level or a phrenic-sparing combination of two nerve blocks (infraclavicular and distal suprascapular) designed to minimize phrenic nerve involvement. Both procedures are ultrasound-guided and part of routine care. The doses of local anesthetic and dexamethasone differ between groups but remain within safe limits. During the study, participants will have a MIP breath test before surgery and, if age 65 or older, a brief thigh muscle ultrasound. After surgery, breathing and oxygen use will be monitored in the recovery room at 30 to 60 minutes. Pain medication use will be recorded from anesthesia start until recovery discharge. Researchers may review medical charts up to 24 hours after surgery and conduct a follow-up call within 24 to 48 hours. The main outcomes include early breathing problems, oxygen saturation, opioid consumption, and pain scores.
CONDITIONS
Brief Title
Interscalene vs Phrenic-sparing Blocks in Obesity and Effect of Maximum Inspiratory Pressure
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Age 18 years or older
- Body-mass index of 35 kg/m2 or higher at pre-operative visit
- Scheduled for elective unilateral shoulder surgery under general anesthesia
- Planned use of single-injection regional brachial-plexus block for postoperative pain
- Able to perform a maximum inspiratory pressure (MIP) breathing test with two reproducible efforts
- Able to read or understand English and provide written informed consent
You will not qualify if you...
- Emergency or trauma shoulder surgery or surgery converted to open procedure
- Pregnancy confirmed by urine test on day of surgery
- Prisoner status or legal inability to consent
- Severe lung disease such as GOLD stage 3-4 COPD, severe restrictive lung disease, high baseline breathlessness, or home oxygen use
- Severe heart disease including advanced valvular disease, heart failure class III or IV, or angina
- Neuromuscular disorders affecting breathing muscles or known diaphragmatic paralysis
- Blood clotting problems or infection at nerve block sites
- Anemia with hemoglobin below 10 g/dl or significant blood disorders
- Allergy to bupivacaine, dexamethasone, or ultrasound gel
- Chronic opioid use over 100 mg oral morphine equivalents daily in past 3 months
- Prior enrollment in this trial or participation in conflicting interventional studies
- Expected inability to comply with postoperative assessments due to cognitive impairment or transfer to outside facility
AI-Screening
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Your Study Journey
Duration - 2 to 4 weeks
Participants are screened for eligibility to participate in the trial.
1 visit (in-person)
Duration - Single administration on the day of surgery
Participants receive a single ultrasound-guided nerve block before shoulder surgery as part of standard care or with a phrenic-sparing technique to manage postoperative pain.
1 visit (in-person)
Duration - Up to 24 hours after surgery
Participants are monitored for respiratory function, oxygen use, pain, and diaphragmatic movement in the post-anesthesia care unit (PACU) after surgery.
1 to 2 visits depending on PACU assessments
Trial Site Locations
Total: 1 location
1
University of North Carolina Hospitals
Chapel Hill, North Carolina, United States, 27599
Actively Recruiting
Research Team
M
Monika Nanda
How is the study designed?
Study Type
INTERVENTIONAL
Masking
SINGLE
Allocation
RANDOMIZED
Model
PARALLEL
Primary Purpose
TREATMENT
Number of Arms
2
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