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SPARK Study: Lidocaine for Sympathetic Activity in Healthy Volunteers

The SPARK Study is looking for healthy volunteers aged 18-50 to understand how a specific nerve block affects your body's sympathetic activity (part of your nervous system that controls automatic functions like blood vessel constriction). This study involves a small injection of Lidocaine 2% (a common numbing medicine) around an artery in your wrist, guided by ultrasound. Researchers will measure changes in your pulse and hand temperature before and after the injection, especially during a cold pressor test (briefly putting your hand in cold water). The goal is to see how well this block works. The study plans to enroll 20 participants, but its current status is unclear.

Study design
This interventional study plans to enroll 20 healthy volunteers. It is not specified if it is randomized or blinded.
What's involved
You would undergo a small injection of Lidocaine 2% and have your pulse amplitude index and hand temperature measured multiple times, including during cold pressor tests.
Compensation
Not stated in the trial record.
Follow-up
Measurements for primary endpoints are taken at various times up to 15 minutes after the cold pressor tests and up to 10 minutes after the sympathetic block.

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NCT07429292

SPARK Study - Sympathetic Periarterial Radial Block in Healthy Volunteers

Not Yet Recruiting
PHASE4Ages 18–50InterventionalBasic science
Duke University
~20 participants
Updated 2026-06-17 on ClinicalTrials.gov
What's tested:Lidocaine 2%

At a glance

Recruiting sites
0 of 1 listed site is recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Pulse amplitude index (PAI)
Measured over PAI will be measured at: 1) Baseline; 2) after the first cold pressor test at 0, 5, 10, and 15 minutes; 3) after the sympathetic block at 5 and 10 minutes; 4) after the second cold pressor test at 0, 5, 10, and 15 minutes.
+1 more outcome measured

Conditions

Healthy Volunteers
Sympathetic Activity

Explore related trials

Healthy Volunteers

NCT07429292

Where you'd take part

This study runs at 1 site. They're the same protocol — you choose where, and that choice sets who your contact draft is addressed to.

  • Duke University Medical Center

    Durham, North Carolinano site contact published

Sites open and close at different times, so the status above is per site — it can differ from the study's overall status.

Study leadership

  • David MacLeod · PRINCIPAL_INVESTIGATOR · Duke University

Who to contact

This trial hasn't published a contact. View it on ClinicalTrials.gov

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Eligibility criteria

Inclusion

Age 18-50 years
ASA physical status I-II
Able to understand and provide informed consent
Able to comply with study procedures and follow-up
Two hands with 5 intact digits and no significant upper extremity injury

Exclusion

Allergy to lidocaine or similar anesthetics
Allergy to adhesives or ultrasound gel
Neuromuscular, autonomic, or major vascular disorders affecting upper extremities
Peripheral neuropathy
Raynaud's phenomenon or digital ischemia
Coagulopathy or anticoagulation
Active skin infection near block site
Pregnancy
BMI \> 35 kg/m²
Inability to tolerate cold exposure
Any condition interfering with study conduct

What this trial measures

  • Pulse amplitude index (PAI)PAI will be measured at: 1) Baseline; 2) after the first cold pressor test at 0, 5, 10, and 15 minutes; 3) after the sympathetic block at 5 and 10 minutes; 4) after the second cold pressor test at 0, 5, 10, and 15 minutes.

    Pulse Amplitude Index (PAI) is a noninvasive measure of digital perfusion derived from photoplethysmography (PPG) signals recorded from the fingers. PAI reflects changes in pulse waveform amplitude and serves as an indirect marker of peripheral blood flow and sympathetic vasomotor tone. In this study, PAI will be continuously recorded using digital sensors placed on the index and fifth fingers of the hand undergoing periarterial radial block, as well as the contralateral index finger. Measurements will be obtained at baseline, following cold pressor testing, after the periarterial radial block, and following repeat cold pressor testing. Changes in PAI across time points will be used to assess alterations in peripheral perfusion associated with sympathetic modulation.

  • Hand temperatureThermal images will be obtained at: 1) Baseline; 2) after the first cold pressor test at 0, 5, 10, and 15 minutes; 3) after the sympathetic block at 5 and 10 minutes; 4) after the second cold pressor test at 0, 5, 10, and 15 minutes.

    Hand temperature is a noninvasive measure of peripheral skin temperature used as an indicator of changes in local blood flow and sympathetic vasomotor activity. In this study, hand temperature will be assessed using infrared thermographic imaging of both hands. Thermal images will be acquired under standardized environmental conditions at baseline, following cold pressor testing, after the periarterial radial block, and following repeat cold pressor testing. Temperature values will be derived from predefined regions of interest on the hands based on arterial territories, and compared across time points to evaluate changes in peripheral perfusion associated with sympathetic modulation.