Document Detail

Does peripheral nerve degeneration affect circulatory responses to head-up tilt in spinal cord-injured individuals?
MedLine Citation:
PMID:  15834766     Owner:  NLM     Status:  MEDLINE    
Despite the loss of centrally mediated sympathetic vasoconstriction, spinal cord-injured (SCI) individuals cope surprisingly well with orthostatic challenges. In the pathophysiology of this intriguing observation spinal sympathetic-, veno-arteriolar-(VAR), and myogenic reflexes seem to play a role. The purpose of this study was to assess whether central (stroke volume, heart rate, blood pressure and total peripheral resistance) and peripheral (leg blood flow, leg vascular resistance and femoral arterial diameter) hemodynamic responses to head-up tilt are different in two groups of SCI patients, i. e., SCI individuals with upper motor neuron lesions (who have spinal reflexes, VAR and myogenic reflexes) (U; n=6) and those with lower motor neuron lesion (who have no spinal reflexes, perhaps no VAR due to nerve degeneration, but intact myogenic reflexes) (L; n=5). Ten healthy male individuals served as controls (C) (normal supraspinal sympathetic control and presence of all reflexes). After 10 min supine rest all individuals were tilted to 30 degrees head-up tilt. Red blood cell velocity (measured by echo Doppler ultrasound) in the femoral artery decreased and vascular resistance increased significantly in all three groups in the upright position compared with supine. Mean arterial pressure (MAP) remained unchanged in U and L and increased significantly in C in the upright versus supine position. The present study shows that all SCI individuals were able to maintain MAP by increasing leg vascular resistance during head-up tilt, despite nerve degeneration in L and lack of centrally mediated sympathetic control in all SCI individuals. Results of the present study suggest that not spinal reflexes but local (myogenic) reflex activity plays a pivotal role in peripheral vascular responses upon head-up tilt when central control mechanisms fail.
Jan T Groothuis; Cécile R L Boot; Sibrand Houtman; Herman van Langen; Maria T E Hopman
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Publication Detail:
Type:  Clinical Trial; Journal Article    
Journal Detail:
Title:  Clinical autonomic research : official journal of the Clinical Autonomic Research Society     Volume:  15     ISSN:  0959-9851     ISO Abbreviation:  Clin. Auton. Res.     Publication Date:  2005 Apr 
Date Detail:
Created Date:  2005-04-18     Completed Date:  2005-07-27     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  9106549     Medline TA:  Clin Auton Res     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  99-106     Citation Subset:  IM    
Dept. of Physiology, UMCN, 9101, 6500 HB, Nijmegen, The Netherlands.
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MeSH Terms
Blood Pressure / physiology
Femoral Artery / physiopathology,  ultrasonography
Heart Rate / physiology
Hemodynamics / physiology*
Leg / blood supply
Motor Neurons / physiology
Nerve Degeneration / physiopathology*
Peripheral Nerves / physiopathology*
Regional Blood Flow / physiology
Spinal Cord Injuries / physiopathology*
Supine Position
Vascular Resistance / physiology

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

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