Recruiting

Phrenic-Sparing Block vs. ISB

Sponsor:

University of North Carolina, Chapel Hill

Code:

NCT07216820

Conditions

Shoulder Surgery

Obesity

Eligibility Criteria

Sex: All

Age: 18+

Healthy Volunteers: Not accepted

Interventions

Ultrasound-Guided Interscalene Brachial Plexus Block

Phrenic-Sparing Block Combination (Experimental)

Bupivacaine HCl 0.5% Injectable Solution

Dexamethasone 4mg

Study Details

Brief summary:

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:

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).

Conditions

Shoulder Surgery

Obesity

Study ID

NCT07216820

Start date

Jan 21, 2026

Status verified date

Jan, 2026

Completion date

Nov 15, 2027

Anticipated

Primary completion date

Nov 1, 2027

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18+

Healthy Volunteers: Not accepted

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

Study Design

Enrollment

68 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

active comparator: Arm 1: Standard Interscalene Block

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).

experimental: Arm 2: Phrenic-Sparing Block Combination

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.

Interventions

Ultrasound-Guided Interscalene Brachial Plexus Block

Single 16 mL injection (15 mL 0.5 % bupivacaine + 1 mL dexamethasone 4 mg) at the C5-C6 root level under ultrasound guidance.

Performed pre-operatively as standard care for shoulder surgery. Arm Cross-Reference: Standard Interscalene Block (Control)

Phrenic-Sparing Block Combination (Experimental)

Infraclavicular: 15 mL (75 mg) 0.5 % bupivacaine + 1 mL dexamethasone (4 mg) injected around the cords of the brachial plexus beneath the clavicle under ultrasound guidance.

Distal Suprascapular: 12 mL (60 mg) 0.5 % bupivacaine + 1 mL (4 mg) dexamethasone injected at the suprascapular notch under ultrasound guidance to provide complete shoulder coverage while minimizing phrenic nerve involvement. Total local anesthetic dose = 135 mg bupivacaine + 8 mg dexamethasone.

Arm Cross-Reference: Phrenic-Sparing Block Combination (Experimental)

Bupivacaine HCl 0.5% Injectable Solution

Infraclavicular: Adminstered as 15 mL (75 mg) injection (together with dexamethasone).

Distal Suprascapular: Adminstered as 12 mL (60 mg) injection (together with dexamethasone).

Dexamethasone 4mg

Adminstered as applicable for infraclavicular and distal suprascapular: as 1 mL (4 mg) injection (together with bupicacaine 0.5%).

Primary outcome measure

  • Incidence of Early Postoperative Respiratory Compromise [ Time Frame: Within 60 minutes after arrival to PACU ]
  • Effect Modification by Preoperative Maximum Inspiratory Pressure (MIP) [ Time Frame: Baseline (preoperative MIP test) and PACU assessment (30-60 minutes post-surgery). ]

Central Contacts and Locations

Central contacts

Monika Nanda

919-966-5136mnanda@aims.unc.edu

Locations

University of North Carolina Hospitals

Recruiting

Chapel Hill, North Carolina, United States, 27599

Contacts

Monika Nanda

919-966-5136mnanda@aims.unc.edu

More Information

Sponsor

University of North Carolina, Chapel Hill

Last update posted

Jan 28, 2026

Last verified

Jan, 2026

Keywords

  • interscalene block
  • phrenic-sparing block
  • brachial plexus block

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-09. This information was provided to ClinicalTrials.gov by University of North Carolina, Chapel Hill on 2026-01-28.