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Two nerve block methods for shoulder surgery in adults with obesity

Compares two nerve blocks for shoulder surgery in adults with obesity, looking at breathing.

Key facts

Who runs it
University of North Carolina, Chapel Hill
Where
Chapel Hill, United StatesSee the site
Trial code
Registry title
Interscalene vs Phrenic-sparing Blocks in Obesity and Effect of Maximum Inspiratory Pressure
Status
Recruiting
People taking part
68 people, planned
Started
21 Jan 2026
Expected to end
15 Nov 2027
Type of study
Interventional, 2 groupsOne group gets an existing treatment, for comparison.
Treatments tested
  • Ultrasound-Guided Interscalene Brachial Plexus Block
  • Phrenic-Sparing Block Combination (Experimental)
  • Bupivacaine HCl 0.5% Injectable Solution
  • Dexamethasone 4mg
Record updated
28 January 2026

Who can take part

AI summary

From the trial's eligibility criteria. Machine-read from the registry text on this page, so it can be wrong. The registry text below and the trial team decide who can take part.

The trial is looking for adults with obesity who are having planned shoulder surgery under general anesthesia with a nerve block for pain relief.

Age
18 years or older
Sex
All sexes can join.
Disease stage
Body-mass index of 35 kg/m^2 or higher. Planned one-sided shoulder surgery (arthroscopy, arthroplasty, rotator cuff repair, reverse arthroplasty) at UNC Hospitals.
Earlier treatment
A single-injection nerve block (brachial plexus block) must be planned for pain relief after surgery. No opioid use above 100 mg oral-morphine equivalents per day in the 3 months before surgery.
Biomarker or test result
Able to do a maximal inspiratory pressure (MIP) breath test with two repeatable efforts.

Main reasons for not taking part

  • Emergency or trauma shoulder surgery, or surgery changed to open surgery
  • Pregnancy confirmed by urine test on the day of surgery
  • Severe lung disease (GOLD stage 3-4 COPD, home oxygen) or severe heart disease (NYHA Class III or IV heart failure)
  • Muscle or nerve disease affecting breathing, or a paralyzed diaphragm
  • Bleeding disorder (platelets < 100 × 10/ L or INR > 1.5), infection at block sites, or Hgb < 10 g/dl

The registry criteria, word for word

Show all 17 criteriaShow less

Who can take part

  • Age ≥ 18 years (self-report, confirmed on chart)
  • Body-mass index ≥ 35 kg m\^2 at the pre-operative clinic visit (chart)
  • Scheduled for elective unilateral shoulder surgery (arthroscopy, arthroplasty, rotator cuff repair, reverse arthroplasty) under general anesthesia at UNC Hospitals
  • Planned use of a single-injection regional brachial-plexus block for postoperative analgesia (anesthesia record)
  • Able to perform a maximal-inspiratory-pressure (MIP) maneuver at screening, producing two reproducible efforts (bedside test)
  • Able to read or understand English and provide written informed consent (consent discussion)

Who cannot take part

  • Emergent or trauma shoulder procedure or case converted to open surgery (schedule/chart)
  • Pregnancy confirmed by point-of-care urine test on day of surgery (POC test). Prisoner status or legal incapacity to consent (chart/interview)
  • Chronic opioid use > 100 mg oral-morphine equivalents per day in the three months preceding surgery (medication history, PDMP query)
  • Prior enrolment in this trial or planned participation in another interventional study that might confound outcomes (research registry)
  • Severe pulmonary disease: GOLD stage 3-4 COPD, restrictive lung disease unrelated to obesity with FVC < 50 % predicted, baseline dyspnea Borg ≥ 3, or home oxygen therapy (pulmonary clinic notes, patient interview)
  • Severe heart disease- Severe valvular heart disease, Congestive Heart Failure NYHA Class III or IV, Obstructive Coronary Artery Disease with Angina
  • Neuromuscular disorders affecting respiratory muscles (e.g., ALS, myasthenia gravis) or known diaphragmatic paralysis (chart)
  • Allergy to bupivacaine, dexamethasone, or ultrasound gel (self-report)
  • Anticipated inability to comply with postoperative assessments (e.g., profound cognitive impairment, expected early transfer to outside facility) as judged by the investigator
  • Coagulopathy (platelets < 100 × 10/ L or INR > 1.5) or local infection at block sites (pre-op labs/assessment)
  • Anemia and hemoglobinopathies: Hgb <10 g/dl, clinically significant hemoglobinopathy

Where in United States

  • University of North Carolina HospitalsChapel Hill, United StatesContact: Monika NandaTaking people

About the trial

What the trial wants to find out

The goal of this clinical trial is to learn whether a phrenic-sparing nerve block can lower early breathing problems after shoulder surgery in adults with obesity, and whether a simple breathing-strength test (maximum inspiratory pressure, MIP) helps identify who is at higher risk. The main questions are:

Read full original descriptionShow less

Does the phrenic-sparing approach reduce breathlessness or oxygen need in the recovery room (30-60 minutes after arrival)? Do patients have similar pain control and opioid use compared with the standard interscalene block (ISB)? Are there any breathing-related complications or unplanned admissions within 24 hours? Researchers will compare the phrenic-sparing block (infraclavicular + distal suprascapular) to the standard ISB, both commonly used at UNC.

Participants will:

Have a quick MIP breath test before surgery (and, if age ≥65, a brief thigh muscle ultrasound).

Be randomly assigned to receive either the standard ISB or the phrenic-sparing block (both ultrasound-guided and part of routine care).

Receive usual anesthesia/surgery; have a brief recovery check at 30-60 minutes (breathlessness score, oxygen use, oxygen level).

Have pain medicines recorded from anesthesia start to PACU discharge; the team may review the chart up to 24 hours and make a short follow-up call (24-48 hours).

The 2 groups in the trial

  • Arm 1: Standard Interscalene BlockExisting treatment, for comparison

    Standard Interscalene Brachial Plexus Block (Control) Description: Participants receive a single 16 mL interscalene block at the C5-C6 level under ultrasound guidance. The injectate contains 15 mL of 0.5% bupivacaine HCl (75 mg) mixed with 1 mL preservative-free dexamethasone (4 mg).

    Treatment: Ultrasound-Guided Interscalene Brachial Plexus Block, Bupivacaine HCl 0.5% Injectable Solution, and Dexamethasone 4mg

  • Arm 2: Phrenic-Sparing Block CombinationTreatment being tested

    Combined Infraclavicular + Distal Suprascapular Block (Phrenic-Sparing Technique) Description: Participants receive two ultrasound-guided peripheral nerve blocks designed to minimize phrenic nerve involvement: Infraclavicular block: 15 mL 0.5% bupivacaine + 1 mL dexamethasone (total 16 mL) Distal suprascapular block: 12 mL 0.5% bupivacaine + 1 mL dexamethasone (total 13 mL) Total local-anesthetic dose = 135 mg bupivacaine + 8 mg dexamethasone, within accepted safety limits.

    Treatment: Phrenic-Sparing Block Combination (Experimental), Bupivacaine HCl 0.5% Injectable Solution, and Dexamethasone 4mg

Questions to ask the study team

  1. How often do I need to come in, and for how long each time?
  2. Are travel costs paid?
  3. Can I keep my own doctor?
  4. What happens if I want to stop?

Contact the study team: see the registry record → Contacts and Locations

Print a page for my doctor

Data and sources

Registry record
Listed on ClinicalTrials.gov.
Official title
Interscalene vs Phrenic-sparing Blocks in Obesity: Effect of Pre-operative Maximum Inspiratory Pressure in a Randomized Trial
Plain-language title
Two nerve block methods for shoulder surgery in adults with obesityGenerated from the registry record. The registry title is the official one.
AI summary
From the trial's eligibility criteria. Read by machine on 12 November 2026.
Record updated
28 January 2026