SPARK Study - Sympathetic Periarterial Radial Block in Healthy Volunteers (SPARK)

SPARK Study - Sympathetic PeriArterial Radial blocK Study

The SPARK Study evaluates changes in peripheral sympathetic vasomotor activity following a targeted, ultrasound-guided periarterial sympathetic block of the distal radial artery in healthy volunteers. Autonomic reactivity will be assessed before and after the block using digit-specific pulse-amplitude index and infrared thermography during standardized cold pressor testing.

Study Overview

• Status: Not yet recruiting
• Conditions: Healthy Volunteers; Sympathetic Activity
• Intervention / Treatment: Drug: Lidocaine 2%

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Phase 4

Contacts and Locations

Study Locations

• United States
  • North Carolina
    • Durham, North Carolina, United States, 27710
      • Duke University Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• 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 Criteria:

• 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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Left Wrist Block; Ultrasound-guided periarterial block with 2% lidocaine at left wrist.	Drug: Lidocaine 2%; Small-volume injection (5 mL) of 2% lidocaine around radial artery under ultrasound guidance.
Experimental: Right Wrist Block; Ultrasound-guided periarterial block with 2% lidocaine at right wrist.	Drug: Lidocaine 2%; Small-volume injection (5 mL) of 2% lidocaine around radial artery under ultrasound guidance.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pulse amplitude index (PAI)	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.	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.
Hand temperature	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.	Thermal 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.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Temporal Changes in Cold Pressor Test-Induced Vasomotor Responses Pre- and Post-Block	Temporal changes in cold pressor test (CPT)-induced vasomotor responses pre- and post-block refer to time-dependent alterations in peripheral vascular tone before and after periarterial radial block-induced sympathetic modulation. In this study, CPT-induced vasomotor responses will be assessed by evaluating changes in pulse amplitude index (PAI) and hand skin temperature across predefined time points. Measurements will be obtained immediately following CPT, and at serial intervals. CPT will be performed before and after the periarterial radial block. Comparisons of these temporal response patterns before and after the block will be used to characterize the effects of sympathetic modulation on peripheral vasoconstriction and vasodilation.	Data 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.
Change in Vasomotor Measures in the Fifth Finger	Change in vasomotor measures in the fifth finger refers to alterations in peripheral perfusion and skin temperature measured in the fifth digit ipsilateral to the periarterial radial block, an area predominantly innervated by the ulnar nerve. In this study, the fifth finger will serve as an internal control for comparison with the radial-innervated index finger. Changes will be assessed using pulse amplitude index (PAI) and infrared thermographic imaging. Measurements will be obtained at baseline, following cold pressor testing, after periarterial radial block, and following repeat cold pressor testing. Responses in the ulnar-innervated fifth finger will be used to evaluate regional vasomotor changes and to track potential extension of radial sympathetic modulation to adjacent, non-radial territories.	PAI and thermal images 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.
Change in Vasomotor Measures in the Contralateral Index Finger	Change in vasomotor measures in the contralateral index finger refers to alterations in peripheral perfusion and skin temperature measured in the index finger of the hand opposite to the periarterial radial block. This contralateral finger serves as an internal control to account for systemic sympathetic responses to cold pressor testing that are independent of the local effects of the block and to compare sympathetic reactivity between hands. Vasomotor measures will be assessed using pulse amplitude index (PAI) derived from photoplethysmography and infrared thermographic imaging. Measurements will be obtained at baseline, following cold pressor testing, after periarterial radial block, and following repeat cold pressor testing. Changes across time points will be used to distinguish local from systemic vasomotor effects.	PAI and thermal images 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.

Collaborators and Investigators

• Sponsor: Duke University
• Investigators: Principal Investigator: David Macleod, Duke University

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): April 1, 2027

Study Registration Dates

• First Submitted: February 18, 2026
• First Submitted That Met QC Criteria: February 18, 2026
• First Posted (Actual): February 24, 2026

Study Record Updates

• Last Update Posted (Actual): April 1, 2026
• Last Update Submitted That Met QC Criteria: March 27, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Radial Artery; Sympathetic Block; Cold Pressor Test; Periarterial block
• Other Study ID Numbers: Pro00119632

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No