Comparing phrenic-sparing and interscalene nerve blocks for shoulder surgery in people with obesity
Interscalene vs Phrenic-sparing Blocks in Obesity: Effect of Pre-operative Maximum Inspiratory Pressure in a Randomized Trial
This trial tests whether a phrenic-sparing nerve block, compared with the standard interscalene block, lowers early breathing problems after shoulder surgery in adults with obesity and whether a quick breathing-strength test (MIP) helps predict who is at higher risk.
Quick facts
| Phase | Not applicable |
|---|---|
| Study type | Interventional |
| Enrollment | 68 (estimated) |
| Ages | 18 Years and up |
| Sex | All |
| Sponsor | University of North Carolina, Chapel Hill Academic / other |
| Locations | 1 site (Chapel Hill, North Carolina) |
| Trial ID | NCT07216820 on ClinicalTrials.gov |
What this trial studies
Adults with a body mass index ≥35 undergoing elective unilateral shoulder surgery at UNC are randomly assigned to receive either the standard ultrasound-guided interscalene brachial plexus block or a phrenic-sparing combination block (infraclavicular plus distal suprascapular), with standardized local anesthetic and adjuncts. A maximal inspiratory pressure (MIP) measurement is performed before surgery (and thigh muscle ultrasound if age ≥65) to explore whether it predicts respiratory risk. Primary early respiratory outcomes include patient-reported breathlessness and need for supplemental oxygen in the recovery room 30–60 minutes after arrival, with secondary outcomes of pain control, opioid use, and breathing-related complications or unplanned admissions within 24 hours. All procedures and follow-up occur at the University of North Carolina Hospitals using ultrasound-guided single-injection regional techniques.
Who should consider this trial
Good fit: Adults (age ≥18) with BMI ≥35 scheduled for elective unilateral shoulder surgery at UNC who can perform a maximal inspiratory pressure (MIP) maneuver and are planned to receive a single-injection brachial plexus block are ideal candidates.
Not a fit: Patients with emergent/trauma procedures, severe pulmonary disease (GOLD stage 3–4 or unrelated restrictive lung disease), pregnancy, inability to consent, or those not receiving a single-injection regional block are unlikely to benefit or be eligible.
Why it matters
Potential benefit: If successful, the phrenic-sparing approach could reduce early postoperative breathing problems and oxygen needs after shoulder surgery in people with obesity while maintaining pain control.
How similar studies have performed: Previous work has shown phrenic-sparing block techniques can reduce hemidiaphragm involvement compared with standard interscalene blocks, but evidence is limited specifically in people with obesity and for predicting risk using preoperative MIP.
Eligibility criteria
Show full inclusion / exclusion criteria
Inclusion Criteria: * 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). Exclusion Criteria: * 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). * 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). * 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. * Allergy to bupivacaine, dexamethasone, or ultrasound gel (self-report). * 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). * Anticipated inability to comply with postoperative assessments (e.g., profound cognitive impairment, expected early transfer to outside facility) as judged by the investigator
Where this trial is running
Chapel Hill, North Carolina
- University of North Carolina Hospitals — Chapel Hill, North Carolina, United States (Recruiting)
Study contacts
- Principal investigator: Monika Nanda — University of North Carollina at Chapel Hill
- Study coordinator: Monika Nanda
- Email: mnanda@aims.unc.edu
- Phone: 919-966-5136
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.