title: Orthostatic hypotension in aging humans.
abstract: We tested the hypothesis that hypotension occurred in older adults at the onset of orthostatic challenge as a result of vagal dysfunction. Responses of heart rate (HR) and mean arterial pressure (MAP) were compared between 10 healthy older and younger adults during onset and sustained lower body negative pressure (LBNP). A younger group was also assessed after blockade of the parasympathetic nervous system with the use of atropine or glycopyrrolate and after blockade of the beta(1)-adrenoceptor by use of metoprolol. Baseline HR (older vs. younger: 59 +/- 4 vs. 54 +/- 1 beats/min) and MAP (83 +/- 2 vs. 89 +/- 3 mmHg) were not significantly different between the groups. During -40 Torr, significant tachycardia occurred at the first HR response in the younger subjects without hypotension, whereas significant hypotension [change in MAP (DeltaMAP) -7 +/- 2 mmHg] was observed in the elderly without tachycardia. After the parasympathetic blockade, tachycardiac responses of younger subjects were diminished and associated with a significant hypotension at the onset of LBNP. However, MAP was not affected after the cardiac sympathetic blockade. We concluded that the elderly experienced orthostatic hypotension at the onset of orthostatic challenge because of a diminished HR response. However, an augmented vasoconstriction helped with the maintenance of their blood pressure during sustained LBNP.
authors.affiliation: Departments of Integrative Physiology and Internal Medicine, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas 76107, USA. xshi@hsc.unt.edu
authors.forename: X
authors.initials: X
authors.lastname: Shi
authors.forename: D W
authors.initials: DW
authors.lastname: Wray
authors.forename: K J
authors.initials: KJ
authors.lastname: Formes
authors.forename: H W
authors.initials: HW
authors.lastname: Wang
authors.forename: P M
authors.initials: PM
authors.lastname: Hayes
authors.forename: A H
authors.initials: AH
authors.lastname: O-Yurvati
authors.forename: M S
authors.initials: MS
authors.lastname: Weiss
authors.forename: I P
authors.initials: IP
authors.lastname: Reese
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D005260:Female; D006024:Glycopyrrolate / Q000494:pharmacology; D006329:Heart Conduction System / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007022:Hypotension / Q000139:chemically induced; D007024:Hypotension, Orthostatic / Q000209:etiology*; D008150:Lower Body Negative Pressure; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D008875:Middle Aged; D009407:Nerve Block; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000502:physiology; D013610:Tachycardia / Q000139:chemically induced / Q000209:etiology
chemical_list: D000319:Adrenergic beta-Antagonists; D001285:Atropine; D008790:Metoprolol; D006024:Glycopyrrolate