Autonomic Control of the Circulation and VDR

Conditions

• Blood Pressure
• Venous Distension Reflex

Eligibility Criteria

Sex

ALL

Age

21 Years - 35 Years

Healthy Volunteers

Accepted

Interventions

• Wrist-to-elbow (W-E) occlusion — OTHER
  An IV will be inserted in the antecubital fossa of one arm. The arm will be fitted with occlusion cuffs arranged in a continuous fashion from the wrist to the elbow. A final cuff will be placed on the upper arm. The cuffs from the wrist to the elbow will be inflated to the same pressure of up to 300 mmHg using a pressurized air tank. First, the subject?s arm will be elevated and the subject will make a fist to squeeze blood from the hand. Then the wrist cuff will be inflated. Once that cuff is fully inflated, the next cuff in the sequence will be inflated. Cuffs are inflated in sequence until the elbow cuff is inflated. After a 10-15 second period to allow blood to drain, the upper arm cuff will inflate (up to 250 mmHg) to keep any additional blood from entering the forearm. Next, the cuffs on the forearm will be removed but the upper arm cuff will remain inflated.
• ketorolac tromethamine — DRUG
  In the COX blockade trial, just after the Wrist-to-elbow occlusion, 6 mg ketorolac tromethamine in 10 ml saline will be infused into the forearm over 1 minute. After 10 minutes, a second infusion of ketorolac tromethamine (up to 3 mg) in 5% of the forearm volume of saline,( \~40-60 ml) will be infused into the occluded forearm at a rate of \~ 30 ml/min. Five minutes of data will then be collected before releasing the upper arm cuff. Infusion 1 is to block the COX pathway, while infusion 2 is to induce venous distension.
• saline control — DRUG
  In the saline control trial performed on a separate day, saline (without ketorolac) in identical volumes as those in the COX blockade trial, will be infused.

Study Details

The study objective of this project is to examine the mechanisms of the venous distension reflex (VDR) in humans. We hypothesize that COX blockade with ketorolac tromethamine, an intravenous NSAID, will attenuate the muscle sympathetic nerve activity (MSNA) response to limb venous distension. To gain further insight into whether the COX byproducts directly stimulate chemically-sensitive afferents, or enable venodilation and indirectly evoke afferent stimulation, we will measure vein size using 3T MRI during venous distention with and without ketorolac infusions.

Key Dates

Start date

Aug 14, 2019

Status verified

May 2026

Primary completion

Jun 1, 2027

Completion

Aug 31, 2027

Study Design

Enrollment

18 participants (estimated)

Allocation

RANDOMIZED

Intervention model

CROSSOVER

Primary purpose

BASIC_SCIENCE

Arms

• Experimental: Ketorolac
  The Wrist-to-Elbow occlusion procedure will be performed followed by 2 ketorolac tromethamine + saline infusions into the occluded arm.
• Placebo Comparator: Control
  The Wrist-to-Elbow occlusion procedure will be performed followed by 2 saline only infusions into the occluded arm.

Primary Outcome Measure

Microneurography (MSNA) [ Time Frame: Recorded continuously during the 3-4 hour study visit ]

Locations (1)

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