Influence of Osmotic Stimulation of Vasopressin on Autonomic Function

Study Overview
=================
Brief Summary
-----------------
The regulation of total body water that defines human hydration status is a complex and dynamic process. Current methods of assessing hydration status (e.g. hematologic and urinary analyses) lack the ability to track changes in hydration status in real-time due to whole-body homeostatic physiologic processes required to maintain central pressure and cardiovascular function. This project will address this problem by assessing the relationship between autonomic function (measured using heart rate variability), a brain-derived process that regulates cardiovascular function, and changes in the hydration-mediated hormone vasopressin.

Official Title
-----------------
Influence of Osmotic Stimulation of Vasopressin on Autonomic Function

Conditions
-----------------
Water Stress, Body Water Dehydration

Intervention / Treatment
-----------------
* Other: Hypertonic Saline
* Other: Normal Saline


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Males and Females between the ages of 18 - 35 Exclusion Criteria: 1) evidence of clinically relevant diseases that may alter body water regulation (e.g., diabetes, kidney disease, metabolic disorders, cardiovascular disease, and other potential fluid balance covariates such as habitual use of non-steroidal anti-inflammatory drugs or serotonin reuptake inhibitors, 2) previous surgery on the digestive tract that may impair the body's ability to normally regulate body water, 3) regular drug treatment within the previous 15 days, 4) actively attempting to gain or lose body weight, 5) For female participants, testing will take place during the early follicular phase of their menstrual cycle (days 1-8) to maintain consistency in the hydration status measures as total body water fluctuates over the course of the menstrual cycle. Females who are currently using contraceptives (e.g., IUD) that limit the number of menstrual cycles occurring in a given year will be excluded from this study to ensure accuracy in the testing periods for this study.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Participants will complete two trials under two different hydration states: isovolemic increase in plasma osmolality and isovolemic control (maintain normal plasma osmolality)
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: Control<br>Participants will be infused with normal (0.9% NaCL) saline for a 120 minute period. | Other: Normal Saline<br>* Infusion of normal saline to inhibit the secretion of the hormone vasopressin<br>|
| Experimental: Hypertonic Saline<br>Participants will be infused with hypertonic (3% NaCL) saline for a 120 minute period. | Other: Hypertonic Saline<br>* Infusion of hypertonic saline to induce an osmotic secretion of the hormone vasopressin<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in autonomic function | Changes in parasympathetic and sympathetic tone as measured by heart rate variability | 0, 15, 30, 45, 60, 75, 90, 105, 120 minutes of saline infusion period | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Vasopressin, Heart Rate Variability, Cardiovascular Function, Autonomic Function