Vol. 91, Issue 5, 2199-2204, November 2001
Changes in cerebral oxygenation and blood flow during LBNP in
spinal cord-injured individuals
Sibrand
Houtman1,
Jorge M.
Serrador2,
Willy N. J. M.
Colier1,
Derek W.
Strijbos1,
Kevin
Shoemaker2, and
Maria T. E.
Hopman1
1 Department of Physiology, University Medical Center
Nijmegen, 6500 HB Nijmegen, The Netherlands; and
2 Neurovascular Research Laboratory, School of
Kinesiology, University of Western Ontario, London, Ontario, Canada
N6A 3K7
Spinal cord-injured (SCI) individuals,
having a sympathetic nervous system lesion, experience hypotension
during sitting and standing. Surprisingly, they experience
few syncopal events. This suggests adaptations in cerebrovascular
regulation. Therefore, changes in systemic circulation, cerebral
blood flow, and oxygenation in eight SCI individuals were compared with
eight able-bodied (AB) individuals. Systemic circulation was
manipulated by lower body negative pressure at several levels down to
60 mmHg. At each level, we measured steady-state blood pressure,
changes in cerebral blood velocity with transcranial Doppler, and
cerebral oxygenation using near-infrared spectroscopy. We found
that mean arterial pressure decreased significantly in SCI but not in
AB individuals, in accordance with the sympathetic impairment in the
SCI group. Cerebral blood flow velocity decreased during orthostatic stress in both groups, but this decrease was significantly greater in
SCI individuals. Cerebral oxygenation decreased in both groups, with a
tendency to a greater decrease in SCI individuals. Thus present data do
not support an advantageous mechanism during orthostatic stress in the
cerebrovascular regulation of SCI individuals.
tetraplegia; postural syncope; lower body negative pressure
