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

NCT07216820 | Recruiting

• 1 other identifier: 23-3332
• Study Type: interventional
• Target: 68
• Locations: 1 country
• Sites: 1

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

Obesity; Shoulder Surgery

Keywords

interscalene block; phrenic-sparing block; brachial plexus block

Outcome Measures

Primary Outcomes (2)

• Incidence of Early Postoperative Respiratory Compromise

  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.

  Within 60 minutes after arrival to PACU

• Effect Modification by Preoperative Maximum Inspiratory Pressure (MIP)

  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).

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

Secondary Outcomes (5)

• Lowest Oxygen Saturation (SpO₂) in PACU

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

• Total Duration of Supplemental Oxygen Use

  0-24 hours post-surgery.

• Post-Induction Opioid Consumption

  0-6 hours post-surgery.

• Diaphragmatic Excursion Change from Baseline

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

• PACU Pain Score

  Within 1 hour after PACU arrival.

Other Outcomes (1)

• Exploratory: Association of Frailty and Sarcopenia Measures With Respiratory Outcomes

  Baseline preoperative assessment; outcome analyzed at PACU.

Study Arms (2)

Arm 1: Standard Interscalene Block

ACTIVE COMPARATOR

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).

Procedure: Ultrasound-Guided Interscalene Brachial Plexus Block; Drug: Bupivacaine HCl 0.5% Injectable Solution; Drug: Dexamethasone 4mg

Arm 2: Phrenic-Sparing Block Combination

EXPERIMENTAL

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.

Procedure: Phrenic-Sparing Block Combination (Experimental); Drug: Bupivacaine HCl 0.5% Injectable Solution; Drug: Dexamethasone 4mg

Interventions

Dexamethasone 4mg DRUG

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

Also known as: Decadron, Dexamethasone Intensol, De-Sone LA, Dxevo, Dexacorten

Arm 1: Standard Interscalene Block; Arm 2: Phrenic-Sparing Block Combination

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)

Arm 1: Standard Interscalene Block

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)

Arm 2: Phrenic-Sparing Block Combination

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).

Also known as: Bupivacaine Hydrochloride Injection

Arm 1: Standard Interscalene Block; Arm 2: Phrenic-Sparing Block Combination

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• 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).

You may not qualify if:

• 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

Sponsors & Collaborators

• American Society of Regional Anesthesia: collaborator
• University of North Carolina, Chapel Hill: lead

Study Sites (1)

University of North Carolina Hospitals

Chapel Hill, North Carolina, 27599, United States

RECRUITING

MeSH Terms

Conditions

Obesity

Interventions

Bupivacaine; Dexamethasone; Calcium Dobesilate

Condition Hierarchy (Ancestors)

Overweight; Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Intervention Hierarchy (Ancestors)

Anilides; Amides; Organic Chemicals; Aniline Compounds; Amines; Pregnadienetriols; Pregnadienes; Pregnanes; Steroids; Fused-Ring Compounds; Polycyclic Compounds; Steroids, Fluorinated; Benzenesulfonates; Benzene Derivatives; Hydrocarbons, Aromatic; Hydrocarbons, Cyclic; Hydrocarbons; Arylsulfonates; Arylsulfonic Acids; Sulfonic Acids; Sulfur Acids; Sulfur Compounds

Study Officials

• Monika Nanda

  University of North Carollina at Chapel Hill

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Monika Nanda

CONTACT

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

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: October 13, 2025
• First Posted: October 15, 2025
• Study Start: January 21, 2026
• Primary Completion (Estimated): November 1, 2027
• Study Completion (Estimated): November 15, 2027
• Last Updated: January 28, 2026

Record last verified: 2026-01

Data Sharing

• IPD Sharing: Will share
• Time Frame: beginning 9 and continuing for 36 months following publication
• Access Criteria: Investigator has approved IRB, IEC, or REB and an executed data use/sharing agreement with UNC.

Locations

US (1)