Skip to main content
OpenTrials
Recruiting

NCT Number: NCT07216820

Interscalene vs Phrenic-sparing Blocks in Obesity and Effect of Maximum Inspiratory Pressure

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).

Recruiting

Interested in participating?

Request Info

Key information

Conditions

Shoulder Surgery Body Weight Nutrition Disorders Nutritional and Metabolic Diseases Obesity Overnutrition Overweight Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of North Carolina Hospitals

Chapel Hill, North Carolina, 27599, United States

Location status: Recruiting

Location contact

Monika Nanda

CONTACT

[email protected]

919-966-5136

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Ultrasound-Guided Interscalene Brachial Plexus Block

Procedure

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)

Procedure

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

Drug

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

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

Other names: Bupivacaine Hydrochloride Injection

Dexamethasone 4mg

Drug

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

Other names: Decadron, Dexamethasone Intensol, De-Sone LA, Dxevo, Dexacorten

Primary outcomes

  1. Incidence of Early Postoperative Respiratory Compromise

    Time frame: Within 60 minutes after arrival to PACU

    Composite outcome defined as either (a) a Modified Borg Dyspnea Score ≥ 3 in the post-anesthesia care unit (PACU, 30-60 minutes after surgery) or (b) continued need for supplemental oxygen at the PACU assessment.

    Outcome Type: Primary Unit of Measure: Percentage of participants meeting composite endpoint.

  2. Effect Modification by Preoperative Maximum Inspiratory Pressure (MIP)

    Time frame: Baseline (preoperative MIP test) and PACU assessment (30-60 minutes post-surgery).

    Assess whether the magnitude of treatment benefit from the phrenic-sparing block varies by baseline inspiratory-muscle strength. The effect is modeled as the interaction between block type and continuous MIP (cm H₂O) on the composite respiratory-compromise endpoint.

    Unit of Measure: Interaction odds ratio (per 10 cm H₂O decrement in MIP).

Secondary outcomes

  1. Lowest Oxygen Saturation (SpO₂) in PACU

    Time frame: From PACU arrival to discharge (typically 60-120 minutes)

    Minimum oxygen saturation recorded by pulse oximetry during the PACU stay Unit of Measure: Percent (%)

  2. Total Duration of Supplemental Oxygen Use

    Time frame: 0-24 hours post-surgery.

    Total number of hours on oxygen from PACU arrival until hospital discharge (maximum 24 hours).

    Unit of Measure: Hours.

  3. Post-Induction Opioid Consumption

    Time frame: 0-6 hours post-surgery.

    Total opioid dose administered from anesthesia induction to PACU discharge, converted to oral morphine milligram equivalents (OMME).

    Unit of Measure: mg OMME.

  4. Diaphragmatic Excursion Change from Baseline

    Time frame: Baseline (pre-block) and 30-60 minutes post-surgery in PACU.

    Percent change in diaphragmatic excursion (ultrasound-measured) from baseline to PACU.

    Unit of Measure: Percent change (%).

  5. PACU Pain Score

    Time frame: Within 1 hour after PACU arrival.

    Numeric Rating Scale (NRS) for pain recorded at 30-60 minutes post-surgery. Unit of Measure: 0-10 NRS scale.

Other outcomes

  1. Exploratory: Association of Frailty and Sarcopenia Measures With Respiratory Outcomes

    Time frame: Baseline preoperative assessment; outcome analyzed at PACU.

    Explore whether rectus femoris index (cm/height²) or Clinical Frailty Scale (CFS) scores predict postoperative respiratory compromise in participants ≥ 65 years.

    Unit of Measure: Correlation coefficient or adjusted risk ratio.

Study contacts

Contact information is provided by the study sponsor or research team.

Monika Nanda

CONTACT

[email protected]

919-966-5136

Sponsors and collaborators

Lead sponsor

University of North Carolina, Chapel Hill

Other

Collaborators

  • American Society of Regional Anesthesia

Registry information

Official study title

Interscalene vs Phrenic-sparing Blocks in Obesity: Effect of Pre-operative Maximum Inspiratory Pressure in a Randomized Trial

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Oct 15, 2025
Registry last updated
Jan 28, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.