The investigators will test the hypothesis that patients with chronic orthostatic intolerance or postural orthostatic tachycardia syndrome (OI or POTS) will be unable to conserve urinary sodium as compared to healthy control subjects.
Patients with chronic OI appear to be hypovolemic with abnormalities in hormones that regulate salt \& water handling. Increases in dietary salt have salutary effects on orthostatic tolerance in a physiological laboratory. The infusion of intravenous saline acutely decreased heart rate in this patient population. Preliminary data from Vanderbilt suggests abnormal salt handling in patients with chronic OI in a few patients. These data need to be confirmed and a better understanding of sodium handling in response to acute salt loads is required in these patients.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
DIAGNOSTIC
Masking
NONE
Enrollment
30
liter normal saline over 30 minutes x 1 dose
Vanderbilt University
Nashville, Tennessee, United States
Urinary Na excretion
Time frame: 24h and then hourly post saline load
Catecholamine levels
Time frame: 1 day
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