View clinical trials related to Orthostatic Intolerance.
Filter by:This project aims to evaluate the physiological effects of Midodrine administration during orthostatic challenge in those with high level spinal cord injury. Midodrine has been shown to improve orthostatic symptoms in those with spinal cord injury but the physiological mechanisms influenced have not been identified. The investigators will examine key physiological components influencing orthostatic tolerance. The investigators will do this, by measuring the baroreflex, and brain blood flow autoregulation (the ability to maintain brain blood flow) before during and after the sit-up test. Two sit-up tests will occur; one before Midodrine administration, and one after administration of a 10mg dose of Midodrine.
This study is designed to determine the causes of "orthostatic intolerance" which occurs more commonly in women than in men. Orthostatic tolerance is the ability to remain standing up right for long periods of time, or to avoid dizziness when moving to standing from a seated or lying position.
The investigators will test whether an intravenous infusion of saline (salt water) will improve the exercise capacity in patients with postural tachycardia syndrome (POTS).
The main limitation patients with orthostatic intolerance (OI, or postural tachycardia syndrome, POTS) have to exercise is related to their increase in heart rate when standing. Main pharmacological treatment today is aimed at reducing heart rate with the use of betablockers (propanolol), this theoretically could also improve their exercise capacity; if their heart rate do not increase as much with the medication, they could exercise more. In addition, it has been suggested that in healthy volunteers subjected to head down tilt for 2 weeks (situation that produces a "simulated" transient POTS-like state) a single bout of intense exercise can improve orthostatic tolerance the day after exercising. The mechanisms involved in such response are not that clear but could be an increase in plasma volume already diminished in POTS patients. It seems likely that the same could be true for POTS patients. The purpose of the present study are to pharmacologically improve the amount of exercise POTS patients can perform by reducing their baseline heart rate (specific aim 1) and to evaluate next day heart responses to an acute bout of intense exercise. Therefore, the specific aims of this study are: 1. To test the hypothesis that lowering heart rate response with propanolol will result in an increase in exercise capacity. 2. To test the hypothesis that a single bout of exercise will result in an improvement in orthostatic tolerance the day after exercising.
The purpose of this study is to determine the cause of low blood pressure in selective patients who have problems with their involuntary (autonomic) nervous system. These patients frequently have had symptoms throughout their life, and their disorder might have a genetic basis. The biochemical, physiological and pharmacological procedures in this study should help us define the problem and perhaps lead to more effective treatment.
We propose to use actigraphy (measured by activity watches) as a tool to quantify sleep disturbances in patients with orthostatic intolerance compared with healthy control subjects. In this pilot study, we will test the null hypothesis (Ho) that there are no differences in the sleep quality between patients with orthostatic intolerance and healthy control subjects.
The purpose of the proposed research is to determine how changes in kidney dopamine (DA) activity influence urinary sodium excretion. We will decrease DA activity in the kidney by inhibiting DA synthesis via carbidopa administration. We want to compare findings in normal volunteers and in patients with postural tachycardia syndrome (POTS). We will test the null hypothesis (Ho) that the effects of oral carbidopa administration on urinary sodium excretion will not differ between patients with POTS and healthy volunteers.
The purpose of this study is to describe the mechanism of orthostatic intolerance, relying on cardiovascular physiological studies. The syndrome is of undetermined etiology, but the syndrome causes impairment of a number of young adults, females more than males, with symptoms of tachycardia, fatigue, lightheadedness, palpitations, blurred vision, chest discomfort, difficulty concentrating, and dizziness with the upright posture. It is believed that many different pathophysiological processes can give rise to this disorder.
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.
The purpose of this study is to try different medications in patients with low blood pressure and other problems with their involuntary (autonomic) nervous system. The pharmacological trials in this study will perhaps lead to more effective treatment. The protocol includes single dose trials, dose-selection trials, 5-day trials and chronic (approximately 2 months) trials, although only dose-selection trials were consistently performed and have results presented.