Leg vascular resistance increases during head-up tilt in paraplegics

Groothuis, Jan T.; Boot, Cécile R. L.; Houtman, S.; Langen, H. van; Hopman, Maria T. E.

doi:10.1007/s00421-005-1340-5

Cited by 22 publications

(24 citation statements)

References 39 publications

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“…The angle of the table can be altered in situations when 60 ° may be difficult to sustain, for example when evaluating orthostatic intolerance in spinal cord injured populations. In such cases, tilting to 30-35 ° may be more appropriate and tolerable [54][55][56] . If desired, the protocol may be shortened in specific populations by stopping after completion of LBNP at -20 mmHg -individuals who reach the end of this phase essentially have a normal OT ( Table 1).…”

Section: Discussionmentioning

confidence: 99%

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

Protheroe

Ravensbergen²,

Inskip³

et al. 2013

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Orthostatic tolerance (OT) refers to the ability to maintain cardiovascular stability when upright, against the hydrostatic effects of gravity, and hence to maintain cerebral perfusion and prevent syncope (fainting). Various techniques are available to assess OT and the effects of gravitational stress upon the circulation, typically by reproducing a presyncopal event (near-fainting episode) in a controlled laboratory environment. The time and/or degree of stress required to provoke this response provides the measure of OT. Any technique used to determine OT should: enable distinction between patients with orthostatic intolerance (of various causes) and asymptomatic control subjects; be highly reproducible, enabling evaluation of therapeutic interventions; avoid invasive procedures, which are known to impair OT 1

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Section: Discussionmentioning

confidence: 99%

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

Protheroe

Ravensbergen²,

Inskip³

et al. 2013

JoVE

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“…34 With time post injury, however, it has been demonstrated that individuals with thoracic SCI exhibit an increase in leg vascular resistance during head-up tilt that is consistent with that in the AB population. [35][36][37] The increase in leg vascular resistance was attributed to a local myogenic response triggered by changes in vascular pressure changes during head-up tilt. 35 It should be noted, however, that those studies [35][36][37] were all delimited to paraplegics with injuries between T4 and L1, some of whom would be expected to retain partial-to-full supraspinal sympathetic control of the critical splanchnic bed, which may explain the reduced severity of orthostatic hypotension in those studies.…”

Section: Organization Of the Autonomic Nervous Systemmentioning

confidence: 99%

“…[35][36][37] The increase in leg vascular resistance was attributed to a local myogenic response triggered by changes in vascular pressure changes during head-up tilt. 35 It should be noted, however, that those studies [35][36][37] were all delimited to paraplegics with injuries between T4 and L1, some of whom would be expected to retain partial-to-full supraspinal sympathetic control of the critical splanchnic bed, which may explain the reduced severity of orthostatic hypotension in those studies. It is highly likely that paraplegics with an injury at or above T6, who exhibit no remaining supraspinal sympathetic control of the splanchnic bed, would exhibit marked orthostatic hypotension; however, this postulate remains to be tested.…”

Section: Organization Of the Autonomic Nervous Systemmentioning

confidence: 99%

“…Although a reduction in leg vascular resistance in individuals with SCI has been reported in one study, 83 the majority of studies report the opposite, that is, leg vascular resistance, measured during supine rest, is increased following SCI. 35,[84][85][86] The mechanism(s) responsible for the increased leg vascular resistance do not appear to be related to loss of centrally mediated sympathetic tonic control, as graded infusions of phentalomine (competitive antagonist of a-adrenoceptors) during b-adrenoceptor blockade induced a similar degree of upper-leg vasodilation in SCI compared with AB, indicating that a-adrenergic tone is relatively well preserved in the legs of individuals with SCI. 84 Instead, increased vascular resistance may be accounted for by alterations in vasoconstrictor pathways.…”

Section: Functional Adaptationsmentioning

confidence: 99%

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Peripheral vascular function in spinal cord injury: a systematic review

et al. 2012

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Background: During the past 20 years, significant advances in patient care have resulted in individuals with spinal cord injury (SCI) living longer than before. As lifespan increases, cardiovascular complications are emerging as the leading cause of mortality in this population, and individuals with SCI develop cardiovascular disease at younger ages than their able-bodied counterparts. To address this increasing clinical challenge, several recent studies investigated the central cardiovascular adaptations that occur following SCI. However, a somewhat less recognized component of cardiovascular dysfunction in this population is the peripheral vascular adaptations that also occur as a result of SCI. Study design: Literature review.Objective: To present a comprehensive overview of changes in arterial structure and function, which occur after SCI. Setting: Canada. Methods: A systematic literature review was conducted to extract studies that incorporated measures of arterial structure or function after SCI in animals or humans. Results: Individuals with SCI exhibit vascular dysfunction below the lesion that is characterized by a reduction in conduit artery diameter and blood flow, increased shear rate and leg vascular resistance, and adrenoceptor hyper-responsiveness. There is also recent alarming evidence for central arterial stiffening in individuals with SCI. Conclusion: Although physical deconditioning is the primary candidate responsible for the maladaptive remodeling of the peripheral vasculature after SCI, there is emerging evidence that blood pressure oscillations, such as those occurring in the large majority of individuals with SCI, also exacerbates vascular dysfunction in this population.

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“…It might be that different mechanisms are involved in blood flow and shear rate changes in SCI and able-bodied controls. Indeed, our laboratory recently reported that SCI subjects are able to increase leg vascular resistance (14) and maintain blood pressure (13) during upright tilt, a response that was originally thought to be regulated through the SNS. Taken together, our findings suggest that supraspinal sympathetic control is not obligatory for the changes in shear rate pattern during exercise in humans and that, in the absence of intact sympathetic innervation, redundant mechanisms contribute to vascular control.…”

Section: H183 Arm Exercise and Blood Flow In Nonactive Regionsmentioning

confidence: 99%

Sympathetic vasomotor control does not explain the change in femoral artery shear rate pattern during arm-crank exercise

Thijssen

Green

Steendijk

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

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Thijssen DH, Green DJ, Steendijk S, Hopman MT. Sympathetic vasomotor control does not explain the change in femoral artery shear rate pattern during arm-crank exercise. Am J Physiol Heart Circ Physiol 296: H180 -H185, 2009. First published November 21, 2008 doi:10.1152/ajpheart.00686.2008.-During lower limb exercise, blood flow through the resting upper limbs exhibits a change characterized by increased anterograde flow during systole, but also large increases in retrograde diastolic flow. One explanation for the retrograde flow is that increased sympathetic nervous system (SNS) tone and concomitant increased peripheral resistance generate a rebound during diastole. To examine whether the SNS contributes to retrograde flow patterns, we measured femoral artery blood flow during arm-crank exercise in 10 healthy men (31 Ϯ 4 yr) and 10 spinal cord-injured (SCI) subjects who lack sympathetic innervation in the legs (33 Ϯ 5 yr). Before, and every 5 min during 25-min arm-crank exercise at 50% maximal capacity, femoral artery blood flow and peak anterograde and retrograde shear rate were assessed using echo Doppler sonography. Femoral artery baseline blood flow was significantly lower in SCI compared with controls. Exercise increased femoral artery blood flow in both groups (ANOVA, P Ͻ 0.05), whereas leg vascular conductance did not change during exercise in either group. Mean shear rate was lower in SCI than in controls (P Ͻ 0.05). Peak anterograde shear rate was higher in SCI than in controls (P Ͻ 0.05), whereas peak retrograde shear rate did not differ between groups. Arm-crank exercise induced an increase in peak anterograde and retrograde shear rate in the femoral artery in controls and SCI subjects (P Ͻ 0.05). This suggests that the SNS is not obligatory to change the flow pattern in inactive regions during exercise. Local mechanisms may play a role in the arm-crank exercise-induced changes in flow pattern in the femoral artery. inactive areas; shear pattern AT THE ONSET OF EXERCISE, substantial cardiovascular adjustments are necessary to continue exercise for more than a few seconds (6). To optimally meet the increased metabolic demands of the contracting muscles, blood flow to inactive regions is relatively decreased, resulting in a net redistribution of blood toward vascular beds in metabolically active regions (1,6,21). Recent studies suggest that changes in the pattern of blood flow in inactive areas during exercise may have important effects on exercise training-mediated improvements in vascular function in these nonactive regions (11,12). Green et al. (11) recently observed that, during lower limb cycle exercise, brachial artery blood flow in the resting upper limbs exhibits an oscillatory pattern of anterograde flow during systole, followed by substantial retrograde diastolic flow. This reproducible change in blood flow pattern during cycling exercise results in a shear rate-mediated release of endothelium-derived nitric oxide (NO) (10, 11). The synthesis of NO is of special interest, given the anti-ather...

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Leg vascular resistance increases during head-up tilt in paraplegics

Cited by 22 publications

References 39 publications

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

Peripheral vascular function in spinal cord injury: a systematic review

Sympathetic vasomotor control does not explain the change in femoral artery shear rate pattern during arm-crank exercise

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