Document Detail

Clonidine reduces sympathetic activity but maintains baroreflex responses in normotensive humans.
MedLine Citation:
PMID:  1443738     Owner:  NLM     Status:  MEDLINE    
Clonidine, an alpha 2-adrenergic agonist, has been shown to modify the hemodynamic responses to surgery. To examine further the mechanism underlying this action, we evaluated the neurocirculatory effects of oral clonidine and the ability of clonidine to alter the hemodynamic and sympathetic responses to a noxious stimulus (cold pressor test) and to baroreceptor perturbations in nine healthy men (ages 20-29 yr). Heart rate (ECG), blood pressure (radial artery catheter), central venous pressure (jugular vein), and cardiac output (impedance cardiography) were monitored before and after oral clonidine (0.3 mg) or placebo. Plasma norepinephrine was measured with high-performance liquid chromatography. Sympathetic nerve activity (SNA) to skeletal muscle blood vessels was recorded from a Tungsten needle positioned within the peroneal nerve. Baroreceptor testing was carried out by intravenous bolus injections of nitroprusside (100 micrograms) followed 60 s later by intravenous phenylephrine (150 micrograms). The slope of the linear relationship between the change in R-R interval versus the change in mean pressure (cardiac baroslope) or change in SNA versus change in diastolic pressure (sympathetic baroslope) was determined at baseline and 75 min after clonidine or placebo. In addition, peak responses to the cold pressor test (60-s hand immersion in ice water) were determined at the same intervals. Clonidine progressively decreased blood pressure and muscle SNA over the 75-min session. Clonidine subtly reduced the sympathoexcitation produced by the cold pressor test but did not alter the gain of the baroreceptor reflex regulating cardiac interval or peripheral SNA; baroslope relationships were simply shifted leftward (to operate at lower pressures).(ABSTRACT TRUNCATED AT 250 WORDS)
M Muzi; D R Goff; J P Kampine; D L Roerig; T J Ebert
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial    
Journal Detail:
Title:  Anesthesiology     Volume:  77     ISSN:  0003-3022     ISO Abbreviation:  Anesthesiology     Publication Date:  1992 Nov 
Date Detail:
Created Date:  1992-12-03     Completed Date:  1992-12-03     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  1300217     Medline TA:  Anesthesiology     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  864-71     Citation Subset:  AIM; IM    
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee.
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MeSH Terms
Administration, Oral
Clonidine / administration & dosage,  pharmacology*
Depression, Chemical
Hemodynamics / drug effects,  physiology
Pressoreceptors / drug effects*,  physiology
Reflex / drug effects*,  physiology
Single-Blind Method
Sympathetic Nervous System / drug effects*,  physiology
Reg. No./Substance:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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