Intravenous Norepinephrine for Orthostatic Hypotension

Orthostatic Hypertension

Baroreceptor, Norepinephrine, Orthostatic Hypotension, Sympathetic Nervous System, Blood Pressure

Background: \- Orthostatic hypotension is a fall in blood pressure when standing up. Normally, a reflex action of the automatic nervous system makes blood vessels tighten when people stand up. The nervous system releases the chemical norepinephrine, which tightens blood vessels and keeps blood pressure in check. In orthostatic hypotension, the nervous system does not release enough norepinephrine when a person stands up, which can cause fainting or falling. Researchers are interested in determining whether norepinephrine given as a drug by vein can help maintain blood pressure during changes in body position. Objectives: \- To determine whether intravenous norepinephrine can maintain blood pressure in people with orthostatic hypotension. Eligibility: \- Individuals at least 18 years of age who have been diagnosed with orthostatic hypotension related to Parkinson's disease or pure autonomic failure. Design: * This study will require a 2-day inpatient admission to the NIH Clinical Center. The first day will involve laboratory evaluation and the second day will involve testing with norepinephrine. The second day requires an overnight stay. * Participants will be screened with a medical history and physical examination, blood samples, and an electrocardiogram or echocardiogram. * Participants who are on medications may be asked to taper or discontinue one or more medications for the purposes of this study. Participants may not take aspirin or any drugs that slow blood clotting for 7 days before study participation. * Day 1: Participants will have a clear liquid breakfast, and will have a 1-hour baseline tilt table test to monitor blood flow, skin temperature, sweating, and blood pressure. Body temperature and breathing will also be monitored. * Day 2: Participants will have a clear liquid breakfast, and will have a 2-hour tilt table test. Initial blood pressure readings will be taken, and an intravenous line will be placed. Participants will then receive norepinephrine or saline, followed by additional position changes of the tilt table to measure blood pressure differences before returning to the starting position. After about 10 minutes, the tilt table testing and infusion will be repeated with the other drug (saline or norepinephrine). * Participants will be discharged 24 hours after the testing is complete.

Objective: Patients with chronic autonomic failure (CAF) often have disabling orthostatic hypotension (OH). In CAF, OH results from deficient baroreflex-mediated release of norepinephrine (NE) from sympathetic nerves. In patients with pure autonomic failure (PAF) or Parkinson disease (PD) with OH, cardiac and extra-cardiac noradrenergic denervation exacerbates effects of baroreflex failure. OH in CAF patients is often associated with supine hypertension, which can be severe. Drugs to treat OH worsen supine hypertension. Therefore, the combination of OH with supine hypertension poses a difficult therapeutic challenge. This protocol is a first step toward development of a prosthetic baroreceptor system to maintain blood pressure during orthostasis without worsening supine hypertension. In patients with PAF or PD+OH NE is infused i.v. at doses titrated individually to maintain blood pressure during head-up tilt at increasing angles from horizontal. Blood pressure is monitored continuously directly via an intra-arterial catheter. Because of the phenomenon of denervation supersensitivity, we anticipate that patients with OH associated with sympathetic noradrenergic denervation, as in PAF and PD, should be especially responsive to i.v. norepinephrine. Study Population: Patients with Parkinson disease and orthostatic hypotension or with pure autonomic failure. Design: This is a placebo controlled study that consists of two experimental days per participant. On a day before the day of norepinephrine (NE) infusion, the patient undergoes head-up tilting (typically at 15, 30, 45, and 60 degrees from horizontal) while blood pressure is monitored. Tilt angles are increased until the patient has orthostatic symptoms, systolic pressure decreases to less than 90 mm Hg, or systolic pressure decreases by more than 80 mm Hg. On the day of NE infusion patients, receive NE and placebo with the sequence of treatments randomized. If the patient has severe supine hypertension (more than 200 mm Hg systolic), then NE is infused beginning with the patient at whatever tilt angle is required for baseline pressure to be less than 200 mm Hg. NE is infused at doses titrated to keep directly recorded systolic blood pressure at or above the baseline value during exposure to higher tilt angles. When placebo is given, angles of tilt are increased until the patient has orthostatic symptoms, systolic pressure decreases to less than 90 mm Hg, or systolic pressure decreases by more than 80 mm Hg. Outcome Measures: The extent to which NE infusion can maintain blood pressure is tested by comparison of the fractional changes in systolic blood pressure at the same tilt angles during NE infusion vs. placebo infusion. Primary: 1. Blood pressures (systolic, diastolic, mean) 2. Symptoms of orthostatic intolerance Secondary: 1. Hemodynamics (e.g., total peripheral resistance) 2. Arterial plasma levels of norepinephrine and related neurochemicals Comparison: Patients undergo head-up tilt at the same angles to verify orthostatic hypotension if norepinephrine is not infused. Participating Sites: The study is done in the NIH Clinical Center in Bethesda, MD. Contact Information: The Principal Investigator is David S. Goldstein, MD PhD, Chief, Clinical Neurocardiology Section, CNP/DIR/NINDS/NIH, phone 301-496-2103, e-mail goldsteind@ninds.nih.gov. The contact for patient care coordination is Tereza Jenkins, phone 301-496-1115, e-mail jenkinst@ninds.nih.gov. The research contact (e.g., for database coordination) is Sandra Pechnik, phone 301-435-5166, e-mail pechniks@ninds.nih.gov.

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