Understanding Rebound Pain After Regional Anesthesia Resolution in Healthy Volunteers

Study Overview
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Brief Summary
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Regional anesthesia decreases postoperative pain scores and opioid consumption, and may prevent chronic pain after surgery in patients undergoing surgery. However, some patients experience an increase of pain into the severe range when the nerve block wears off, also known as rebound pain. The investigators are studying if a nerve block (numbing injection) in the arm causes hyperalgesia (increased pain) when the nerve block is wearing off.

Detailed Description
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This is a prospective, randomized study in healthy volunteers who will undergo sensory testing using quantitative sensory testing (QST), complete psychosocial and pain questionnaires, and ultrasound-guided peripheral nerve block of the arm (axillary nerve block) in a supervised, monitored setting (BWH Clinical Investigation Center). The investigators plan to assess the association between different QST modalities at different time points pre- and post-nerve block resolution. Semi-structured interviews and qualitative analysis will be used to explore patient's experiences with nerve block placement.

Official Title
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Understanding Rebound Pain After Regional Anesthesia Resolution: Mechanistic Trial in Healthy Volunteers

Conditions
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Regional Anesthesia Morbidity, Pain, Acute, Healthy

Intervention / Treatment
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* Drug: Mepivacaine


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age ≥ 18 years old, ≤ 65 years old BMI >18, < 35 Able to speak and understand English Willingness to undergo psychophysical testing (e.g., QST, pain questionnaires) Willingness to have nerve block performed Exclusion Criteria: Ongoing acute or chronic pain in upper extremities Skin or tissue infection affecting upper extremities Previous hypersensitivity to mepivacaine or lidocaine Previous neuropathy (numbness, paresthesia, or motor weakness) in either upper extremity Loss of any limb Bleeding issues or bleeding disorder History of alcohol or drug abuse Currently pregnant or breastfeeding History of seizure or epilepsy

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Participants will be randomized to which arm will receive a nerve block.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Block upper extremity (arm)<br>Upper extremity with a nerve block | Drug: Mepivacaine<br>* Injection of 1.5% Mepivacaine in nerve block<br>* Other names: Prilocaine;|
| No Intervention: Control upper extremity (arm)<br>Upper extremity without a nerve block | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heat pain detection threshold at time 1 hr | Heat pain detection threshold (°C) between block arm and control arm using a heat probe at 1 hour after nerve block resolution | 1 hour after nerve block resolution | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heat pain detection threshold and tolerance | Heat pain detection threshold and tolerance (°C) between block arm and control arm using a heat probe at different time points up to 3 hours nerve block resolution | 0-3 hours after nerve block resolution | 
| Pressure pain threshold and tolerance | Pressure pain threshold and tolerance (N of force) between block arm and control arm using an algometer at different time points up to 3 hours nerve block resolution | 0-3 hours after nerve block resolution | 
| Temporal summation and sharp pain | Temporal summation and sharp pain (evaluated by numerical rating scale 0-10 pain score) between block arm and control arm using a pinprick device at different time points up to 3 hours nerve block | 0-3 hours after nerve block resolution | 
| Light touch detection | Light touch detection (mN of force) between block arm and control arm using von Frey filaments at different time points up to 3 hours nerve block | 0-3 hours after nerve block resolution | 
| Light touch pain threshold | Light touch pain threshold (mN of force) between block arm and control arm using von Frey filaments at different time points up to 3 hours nerve block | 0-3 hours after nerve block resolution | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Healthy volunteer, Regional anesthesia, Rebound pain