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Titolo:
Orthostasis fails to produce active limb venoconstriction in adolescents
Autore:
Stewart, JM; Lavin, J; Weldon, A;
Indirizzi:
New York Med Coll, Ctr Pediat Hypotens, Dept Pediat, Valhalla, NY 10595 USA New York Med Coll Valhalla NY USA 10595 pt Pediat, Valhalla, NY 10595 USA New York Med Coll, Ctr Pediat Hypotens, Dept Physiol, Valhalla, NY 10595 USA New York Med Coll Valhalla NY USA 10595 t Physiol, Valhalla, NY 10595 USA
Titolo Testata:
JOURNAL OF APPLIED PHYSIOLOGY
fascicolo: 4, volume: 91, anno: 2001,
pagine: 1723 - 1729
SICI:
8750-7587(200110)91:4<1723:OFTPAL>2.0.ZU;2-0
Fonte:
ISI
Lingua:
ENG
Soggetto:
BODY NEGATIVE-PRESSURE; CHRONIC HEART-FAILURE; RADIONUCLIDE PLETHYSMOGRAPHY; TACHYCARDIA SYNDROME; VENOUS FUNCTION; HUMAN CALF; INTOLERANCE; SYNCOPE; STRESS; VOLUME;
Keywords:
vasoconstriction; heart rate variability; autonomic; head-up tilt;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
43
Recensione:
Indirizzi per estratti:
Indirizzo: Stewart, JM New York Med Coll, Ctr Pediat Hypotens, Dept Pediat, Suite 618,Munger Pavil, Valhalla, NY 10595 USA New York Med Coll Suite 618,Munger Pavil Valhalla NY USA 10595
Citazione:
J.M. Stewart et al., "Orthostasis fails to produce active limb venoconstriction in adolescents", J APP PHYSL, 91(4), 2001, pp. 1723-1729

Abstract

Orthostasis is characterized by translocation of blood from the upper bodyand thorax into dependent venous structures. Although active splanchnic venoconstriction is known to occur, active limb venoconstriction remains controversial. Based on prior work, we initially hypothesized that active venoconstriction does occur in the extremities during orthostasis in response tobaroreflex activation. We investigated this hypothesis in the arms and legs of 11 healthy volunteers, aged 13-19 yr, using venous occlusion strain gauge plethysmography to obtain the forearm and calf blood flows and to compute the capacitance vessel volume-pressure compliance relation. Subjects were studied supine and at -10, +20, and +35 degrees to load the baroreflexes. With +20 degrees of tilt, blood flow decreased and limb arterial resistance increased significantly (P < 0.05) compared with supine. With +35<degrees> of tilt, blood flow decreased, limb arterial resistance increased, and heart rate increased, indicating parasympathetic withdrawal and sympathetic activation with arterial vasoconstriction. The volume-pressure relation was unchanged by orthostatic maneuvers. The results suggest that active venoconstriction in the limbs is not important to mild orthostatic response.

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Documento generato il 01/04/20 alle ore 23:56:52