{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,25]],"date-time":"2026-02-25T09:48:14Z","timestamp":1772012894408,"version":"3.50.1"},"reference-count":22,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"4","content-domain":{"domain":["www.ahajournals.org"],"crossmark-restriction":true},"short-container-title":["Hypertension"],"published-print":{"date-parts":[[1998,10]]},"abstract":"<jats:p>\n            <jats:italic>Abstract<\/jats:italic>\n            \u2014Patients with idiopathic orthostatic intolerance (IOI) exhibit symptoms suggestive of cerebral hypoperfusion and an excessive decrease in cerebral blood flow associated with standing despite sustained systemic blood pressure. In 9 patients (8 women and 1 man aged 22 to 48 years) with IOI, we tested the hypothesis that volume loading (2000 cc normal saline) and \u03b1-adrenoreceptor agonism improve systemic hemodynamics and cerebral perfusion and that the decrease in cerebral blood flow with head-up tilt (HUT) could be attenuated by \u03b1-adrenoreceptor blockade with phentolamine. At 5 minutes of HUT, volume loading (\u221220\u00b13.2 bpm) and phenylephrine (\u221218\u00b13.4 bpm) significantly reduced upright heart rate compared with placebo; the effect was diminished at the end of HUT. Phentolamine substantially increased upright heart rate at 5 minutes (20\u00b13.7 bpm) and at the end of HUT (14\u00b15 bpm). With placebo, mean cerebral blood flow velocity decreased by 33\u00b16% at the end of HUT. This decrease in cerebral blood flow with HUT was attenuated by all 3 interventions. We conclude that in patients with IOI, HUT causes a substantial decrease in cerebrovascular blood flow velocity. The decrease in blood flow velocity with HUT can be attenuated with interventions that improve systemic hemodynamics and therefore decrease reflex sympathetic activation. Moreover, \u03b1-adrenoreceptor blockade also blunts the decrease in cerebral blood flow with HUT but at the price of deteriorated systemic hemodynamics. These observations may suggest that in patients with IOI, excessive sympathetic activity contributes to the paradoxical decrease in cerebral blood flow with upright posture.\n          <\/jats:p>","DOI":"10.1161\/01.hyp.32.4.699","type":"journal-article","created":{"date-parts":[[2012,6,12]],"date-time":"2012-06-12T00:53:46Z","timestamp":1339462426000},"page":"699-704","update-policy":"https:\/\/doi.org\/10.1161\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":42,"title":["Raised Cerebrovascular Resistance in Idiopathic Orthostatic Intolerance"],"prefix":"10.1161","volume":"32","author":[{"given":"Jens","family":"Jordan","sequence":"first","affiliation":[{"name":"From the Clinical Research Center, Franz Volhard Clinic, Berlin, Germany (J.J.); and the Nathan Blaser Shy-Drager Research Program, Autonomic Dysfunction Center, Vanderbilt University, Nashville, Tenn (J.J., J.R.S., B.K.B., S.Y.P., J.B., D.R.)."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"John R.","family":"Shannon","sequence":"additional","affiliation":[{"name":"From the Clinical Research Center, Franz Volhard Clinic, Berlin, Germany (J.J.); and the Nathan Blaser Shy-Drager Research Program, Autonomic Dysfunction Center, Vanderbilt University, Nashville, Tenn (J.J., J.R.S., B.K.B., S.Y.P., J.B., D.R.)."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bonnie K.","family":"Black","sequence":"additional","affiliation":[{"name":"From the Clinical Research Center, Franz Volhard Clinic, Berlin, Germany (J.J.); and the Nathan Blaser Shy-Drager Research Program, Autonomic Dysfunction Center, Vanderbilt University, Nashville, Tenn (J.J., J.R.S., B.K.B., S.Y.P., J.B., D.R.)."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sachin Y.","family":"Paranjape","sequence":"additional","affiliation":[{"name":"From the Clinical Research Center, Franz Volhard Clinic, Berlin, Germany (J.J.); and the Nathan Blaser Shy-Drager Research Program, Autonomic Dysfunction Center, Vanderbilt University, Nashville, Tenn (J.J., J.R.S., B.K.B., S.Y.P., J.B., D.R.)."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"John","family":"Barwise","sequence":"additional","affiliation":[{"name":"From the Clinical Research Center, Franz Volhard Clinic, Berlin, Germany (J.J.); and the Nathan Blaser Shy-Drager Research Program, Autonomic Dysfunction Center, Vanderbilt University, Nashville, Tenn (J.J., J.R.S., B.K.B., S.Y.P., J.B., D.R.)."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"David","family":"Robertson","sequence":"additional","affiliation":[{"name":"From the Clinical Research Center, Franz Volhard Clinic, Berlin, Germany (J.J.); and the Nathan Blaser Shy-Drager Research Program, Autonomic Dysfunction Center, Vanderbilt University, Nashville, Tenn (J.J., J.R.S., B.K.B., S.Y.P., J.B., D.R.)."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"276","reference":[{"key":"e_1_3_2_1_2","doi-asserted-by":"publisher","DOI":"10.1161\/circ.96.2.575"},{"key":"e_1_3_2_2_2","first-page":"1","volume":"40","year":"1997","unstructured":"Jordan J, Shannon JR, Robertson D. The physiological conundrum of hyperadrenergic orthostatic intolerance. 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Augmented regional cerebrovascular resistance with upright posture in idiopathic orthostatic intolerance. Am J Med. 1998. In press.","DOI":"10.1016\/S0002-9343(98)00364-7"},{"key":"e_1_3_2_13_2","doi-asserted-by":"publisher","DOI":"10.1002\/ana.410260410"},{"key":"e_1_3_2_14_2","doi-asserted-by":"publisher","DOI":"10.1161\/str.28.8.1564"},{"key":"e_1_3_2_15_2","doi-asserted-by":"crossref","unstructured":"Hurn PD Traystman RJ. Overview of cerebrovascular hemodynamics. In: Welch KMA Caplan LR Reis DJ Siesjo BK Weir B eds. Primer on Cerebrovascular Diseases. New York NY: Academic Press; 1997:42\u201344.","DOI":"10.1016\/B978-012743170-3\/50012-1"},{"key":"e_1_3_2_16_2","doi-asserted-by":"publisher","DOI":"10.1016\/0165-1838(91)90043-3"},{"key":"e_1_3_2_17_2","doi-asserted-by":"publisher","DOI":"10.1161\/01.hyp.8.6.471"},{"key":"e_1_3_2_18_2","doi-asserted-by":"crossref","unstructured":"Goadsby PJ Edvinsson L. 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