Clinical Trial: Dietary Sodium's Effect on Urinary Sodium and Dopamine Excretion in Patients With Postural Tachycardia Syndrome

Study Status: Active, not recruiting
Recruit Status: Active, not recruiting
Study Type: Interventional

Official Title: Dietary Sodium's Effect on Urinary Sodium and Dopamine Excretion in Patients With Postural Tachycardia Syndrome

Brief Summary: Patients with Postural Tachycardia Syndrome (POTS) may not adequately expand their plasma volume in response to a high sodium diet. Mechanisms involved in the regulation of plasma volume, such as the renin-angiotensin-aldosterone system and renal dopamine (DA), may be impaired in POTS and may respond inappropriately to changes in dietary sodium. The investigators propose that the changes in urinary sodium and dopamine excretion caused by consuming low-sodium and high-sodium diets will be different between patients with POTS and healthy volunteers. The purpose of this study is to determine (1) whether changes in dietary sodium level appropriately influence sodium excretion in POTS; (2) whether changes in dietary sodium level appropriately influence DA excretion in POTS; (3) whether a high dietary sodium level appropriately expands plasma volume in POTS; and (4) whether patients with POTS have improvements in their orthostatic tachycardia and symptoms as a result of a high dietary sodium level.

Detailed Summary:

Study Day 1

  • Start 150 mEq Na+/day diet (POTS patients as inpatients; healthy control subjects with CRC provided outpatient diet); consume 1.5-2 liters of water per day
  • Start a 24h urine collection (for Na+, K+, Cr, fractionated catecholamines)
  • Blood work

Study Days 2-5

  • Continue 24h urine collection
  • Start STUDY DIET (10 mEq Na+/day or 300 mEq Na+/day in a random order) after 3 meals of 150 mEq Na+/day are complete; consume 1.5-2 liters of water per day
  • On Day 5, a 24 hr Holter combined ECG monitor and BP monitor will be placed on the subjects.

Study Day 6

  • Continue STUDY DIET; consume 1.5-2 liters of water per day
  • Remove 24h Holter combined ECG monitor and BP monitor from subject
  • Continue 24h urine collection (for Na+, K+, Cr, fractionated catecholamines)
  • Admit to CRC in afternoon (healthy control subjects only, as POTS patients will have already been admitted). Each subject will spend the night in the CRC and remain supine
  • NPO after midnight for study next day

Study Day 7

  • Awaken early (~6am) to void (still collecting 24h urine)
  • Patient returns to bed, IV catheter inserted
  • Posture Study (in
    Sponsor: Vanderbilt University

    Current Primary Outcome:

    • Urinary sodium [ Time Frame: after 6 days of each dietary sodium level ]
      Amount of sodium excreted in urine over 24hr will be measured.
    • Urinary dopamine [ Time Frame: after 6 days of each dietary sodium level ]
      Amount of dopamine excreted in urine over 24 hours will be measured.


    Original Primary Outcome: Same as current

    Current Secondary Outcome:

    • Blood Volume [ Time Frame: after 6 days of each dietary sodium level ]
      DAXOR (131-I labelled albumin) blood volume assay
    • Change in Heart Rate with Standing [ Time Frame: After 6 days of each dietary sodium level ]
      Heart rate is measured while supine and standing during a Posture Study and the change in heart rate with standing is calculated.
    • Orthostatic Symptoms [ Time Frame: After 6 days of each dietary sodium level ]
      Symptoms will be assessed in the supine and upright postures to determine the Vanderbilt Orthostatic Symptoms Score.
    • Change in Urinary Sodium following Change in Dietary Sodium [ Time Frame: Days 1-5 of each dietary sodium level ]
      Urinary sodium excretion will be measured every 24 hours as the participant adapts from the 150 mEq Na/day diet to the 10 and 300 mEq Na/day diets.
    • Change in Urinary Dopamine following Change in Dietary Sodium [ Time Frame: Days 1-5 of each dietary sodium level ]
      Urinary dopamine excretion will be measured every 24 hours as the participant adapts from the 150 mEq Na/day diet to the 10 and 300 mEq Na/day diets.


    Original Secondary Outcome: Same as current

    Information By: Vanderbilt University Medical Center

    Dates:
    Date Received: March 22, 2012
    Date Started: March 2012
    Date Completion: March 2018
    Last Updated: April 3, 2017
    Last Verified: April 2017