Document Detail

Lack of sympathetic vasoconstriction in hypoxemic humans at rest.
MedLine Citation:
PMID:  3752269     Owner:  NLM     Status:  MEDLINE    
A three-part experiment was designed to show whether hypoxemia alters splanchnic vasomotor responses to other stresses by vasodilating splanchnic organs, preventing norepinephrine (NE)-induced vasoconstriction, or altering total sympathetic nervous activity (SNA) assessed by plasma levels of NE and epinephrine (Epi). Splanchnic blood flow (SBF) was measured by plasma clearance and hepatic extraction of indocyanine green (constant infusion). Part I: two degrees of hypoxemia [fractional concn of inspired O2 (FIO2) = 10.4 and 7.6%, arterial PO2 (PaO2) = 34.8 and 27 Torr] caused a small splanchnic vasodilation; resistance fell 16 and 26%, respectively, in five men; and SBF rose from 1.78 to 2.04 (10.4% O2) and to 2.02 1 X min-1 (7.6% O2). Plasma NE was unaffected by hypoxemia and by a fall in mean arterial pressure from 82 to 63 Torr at FIO2 = 7.6%. Part II: NE infused intravenously to raise pressure by 20 Torr in five subjects breathing air and 10.3% O2 caused splanchnic vasoconstriction irrespective of PaO2. Part III: in six subjects, two levels of hypoxemia (FIO2 = 10.4 and 7.7%) did not increase NE levels in five men, and Epi increased in two men only at FIO2 = 7.7%. We conclude that hypoxemia caused only a small splanchnic vasodilation not mediated by Epi, did not prevent transient NE-induced vasoconstriction, and either did not significantly increase SNA or prejunctionally inhibited NE release. Severe hypoxemia abolished the rise in NE and heart rate in response to falling pressure.
L B Rowell; J R Blackmon
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  251     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1986 Sep 
Date Detail:
Created Date:  1986-10-21     Completed Date:  1986-10-21     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H562-70     Citation Subset:  IM    
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MeSH Terms
Anoxia / blood,  physiopathology*
Blood Gas Analysis
Epinephrine / blood
Norepinephrine / blood
Splanchnic Circulation
Sympathetic Nervous System / physiopathology*
Grant Support
Reg. No./Substance:
51-41-2/Norepinephrine; 51-43-4/Epinephrine

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