The Pathophysiology of Orthostatic Hypotension

stand upright or tilt table test

Recording from sympathetic nerve

quantitative sweat testing

Blood pressure receptors in the neck arteries may be stimulated by applying suction through a collar around the neck.

"IV Pharmacological Testing~phenylephrine 12.5 - 400 ug, isoproterenol 0.1 - 0.4 ug or higher until desired effect, nitroprusside 0.1 - 1.6 ug/kg, propranolol 1.1 mg/min, edrophonium maximum of 10 mg, atropine .01 mg/kg, tyramine 250-4000 ug or higher until desired effect"

"Oral Pharmacological Testing~clonidine 0.1-0.3 mg, yohimbine 5-10 mg, metoclopramide 10 mg, alpha-methyldopa 62.5 mg, placebo"

Determination of body composition

"Examination of pressure in the eye and eyelid fatiguability. The following eyedrops might be used:~1. 0.5% proparacaine (Alcaine, Allergan, Inc)~2. Fluress (0.4% benoxinate hydrochloride, fluorescein sodium, Akorn, Inc)~3. 0.5%, 1% tropicamide (Mydriacyl, Alcon)~4. Over-the-counter preservative-free artificial tears~5. 0.25%, 2.5% and 10% phenylephrine (Bausch and Lomb)~6. 1% cyclopentolate hydrochloride (Alcon)"

Recording of sleep pattern overnight

Subjects will rate the quality and intensity of 2 pain tasks.

Determination of metabolic rate via 24hr stay in whole-room indirect calorimeter

Questionnaires and computer tasks, an EEG and an MRI may be used to assess brain function.

Blood pressure and heart rate may be monitored while exercising on a stationary bicycle.