Document Detail

Influence of baroreflex-mediated tachycardia on the regulation of dynamic cerebral perfusion during acute hypotension in humans.
MedLine Citation:
PMID:  19933752     Owner:  NLM     Status:  MEDLINE    
The effect of acute arterial baroreflex dysfunction on cerebral autoregulation (CA) in otherwise healthy humans is unknown. We identified dynamic CA with and without arterial baroreflex-mediated tachycardia and consequent changes in cardiac output during acute hypotension whilst continuously monitoring changes in middle cerebral artery mean blood velocity (MCA V(mean)). Acute hypotension was induced in nine healthy subjects (mean +/- s.d.; 26 +/- 3 years) by releasing bilateral thigh cuffs after 6 min of supra-systolic resting ischaemia. Hypotension was induced before and after sympathetic blockade (beta-1 receptors), and combined sympathetic-cholinergic blockade. That sequential bolus injections of sodium nitroprusside (50 microg), followed 60 s later by phenylephrine hydrochloride (50 microg), elicited < 5 beats min(-1) change in heart rate was verified to confirm that full cardiac autonomic blockade was achieved. Thigh cuff release elicited a transient drop in mean arterial pressure and resultant tachycardia. This tachycardic response was diminished in full cardiac blockade (vs. control, P = 0.029; vs. beta-1 adrenergic blockade, P = 0.031). Dynamic CA was also attenuated in the full blockade condition compared to both control (P = 0.028) and beta-1 adrenergic blockade conditions (P = 0.015), and was related with the attenuated tachycardia response (P = 0.015). These data indicate an important role of the cardiac baroreflex in dynamic CA.
Shigehiko Ogoh; Yu-Chieh Tzeng; Samuel J E Lucas; Sean D Galvin; Philip N Ainslie
Publication Detail:
Type:  Journal Article     Date:  2009-11-23
Journal Detail:
Title:  The Journal of physiology     Volume:  588     ISSN:  1469-7793     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2010 Jan 
Date Detail:
Created Date:  2010-01-18     Completed Date:  2010-03-02     Revised Date:  2013-05-31    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  365-71     Citation Subset:  IM    
Department of Biomedical Engineering, Toyo University, Kawagoe-shi, Saitama, Japan.
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MeSH Terms
Analysis of Variance
Antihypertensive Agents / pharmacology
Baroreflex / drug effects,  physiology*
Blood Flow Velocity / drug effects,  physiology
Blood Pressure / drug effects,  physiology
Cardiac Output / drug effects,  physiology
Cerebrovascular Circulation / drug effects,  physiology*
Echocardiography, Doppler
Heart Rate / drug effects,  physiology
Homeostasis / drug effects,  physiology
Hypotension / physiopathology*
Middle Cerebral Artery / drug effects
Nitroprusside / pharmacology
Phenylephrine / pharmacology
Sympathomimetics / pharmacology
Tachycardia / physiopathology*
Reg. No./Substance:
0/Antihypertensive Agents; 0/Sympathomimetics; 15078-28-1/Nitroprusside; 59-42-7/Phenylephrine

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