Regulation of subcutaneous blood flow during head‐up tilt (45°) in normals

Skagen, Knud; Bonde-Petersen, F

doi:10.1111/j.1748-1716.1982.tb06948.x

Cited by 39 publications

(32 citation statements)

References 20 publications

(12 reference statements)

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“…U showed a rapid increase of calf volume (assessed by plethysmography) immediately upon head-up tilt.The shifted blood volume is located mainly in the venous vascular system leading to stretch on the venous vascular walls [6]. According to Skagen and Bonde-Petersen [26], Skagen et al [27], Henriksen et al [13] and Andersen et al [2] an increase of pressure by 25 mmHg in the venous vascular system will result in a 40-50 % increase in arterial vascular resistance via the VAR, which has been suggested by these researchers to run via a sympathetic nerve axon. It has also been shown that specific triggers, like bladder distension, lead to spinal sympathetic reflex activity and leg vasoconstriction [32].…”

Section: Discussionmentioning

confidence: 95%

Does peripheral nerve degeneration affect circulatory responses to head-up tilt in spinal cord-injured individuals?

et al. 2005

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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.

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Section: Discussionmentioning

confidence: 95%

Does peripheral nerve degeneration affect circulatory responses to head-up tilt in spinal cord-injured individuals?

et al. 2005

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“…Skagen and Bonde-Petersen (1982) showed that proximal nervous blockade in healthy human subjects can block the vasoconstriction in the arms but not in the legs, indicating that leg vasoconstriction is not induced by centrally mediated sympathetic activity.…”

Section: Discussionmentioning

confidence: 98%

“…The shifted blood volume is located mainly in the venous vascular system leading to stretch on the venous vascular walls (Buckey et al 1988). An increase in pressure of 25 mmHg in the venous vascular system will result in a 40-50% increase in arterial vascular resistance via the veno-arteriolar reflexes, which runs via a sympathetic axon (Andersen et al 1991;Henriksen et al 1983;Skagen and Bonde-Petersen 1982;Skagen et al 1982b;Skagen and Henriksen 1983). However, against the hypothesis of veno-arteriolar reflexes or spinal sympathetic reflex activity (the latter normally induced by specific triggers like pain and bladder distension rather than by head-up tilt; Webborn 1998) seems to be the fact that noradrenaline hardly shows an increase in P individuals (Mathias et al 1975) suggesting that the activity of the Fig.…”

Section: Discussionmentioning

confidence: 99%

Leg vascular resistance increases during head-up tilt in paraplegics

et al. 2005

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Despite loss of centrally mediated sympathetic vasoconstriction to the legs, spinal cord-injured individuals cope surprisingly well with an orthostatic challenge. This study assessed changes in leg vascular resistance following head-up tilt in healthy (C) and in paraplegic (P) individuals. After 10 min of supine rest, subjects were tilted 30 degrees head-up. Mean arterial pressure (MAP) and total peripheral resistance (TPR) increased in C (MAP from 76.7 +/ -6.6 mmHg to 80.6 +/- 8.2 mmHg; TPR from 1.12 +/- 0.26 AU to 1.19 +/ -0.31 AU) while both remained unchanged in P. Echo Doppler ultrasound determined red blood cell velocity in the femoral artery, which decreased (P from 18.9+/-6.2 cm/s to 12.5 +/- 4.5 cm/s, P = 0.001; C from 16.3 +/- 6.2 cm/s to 10.8 +/- 5.0 cm/s, P = 0.001) and leg vascular resistance, which increased (P from 402 +/- 137 AU to 643 +/- 274 AU, P = 0.001; C from 238 +/- 68 AU to 400 +/- 122 AU, P = 0.003) from supine to upright. The present study shows that independent of supraspinal sympathetic control, humans are able to increase leg vascular resistance and maintain blood pressure during head-up tilt.

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“…local circulatory control; axon reflex WHEN VENOUS PRESSURE in a limb is elevated to pressures Ͼ25 mmHg, cutaneous, subcutaneous, and muscle vascular resistances increase within that region, resulting in a reduction in blood flow of ϳ40% (2,5,16,17,31,32). This reflex has been termed the venoarteriolar response (VAR), because stretch receptors reported to be located in small veins are hypothesized to cause changes in arteriolar vascular tone "upstream" of the veins (15).…”

mentioning

confidence: 98%

Vasoconstriction during venous congestion: effects of venoarteriolar response, myogenic reflexes, and hemodynamics of changing perfusion pressure

Okazaki

Fu²,

Martini

et al. 2005

American Journal of Physiology-Regulatory, Integrative and Comp

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We dissected the relative contribution of arteriovenous hemodynamics, the venoarteriolar response (VAR), and the myogenic reflex toward a decrease in local blood flow induced by venous congestion. Skin blood flow (SkBF) was measured in 12 supine subjects via laser-Doppler flowmetry 1) over areas of forearm and calf skin, in which the VAR was blocked by using eutectic mixture of local anesthetics (EMLA sites) and 2) over the contralateral forearm or calf skin (control sites), using two different techniques: limb dependency of 23-37 cm below the heart and cuff inflation to 40 mmHg. During limb dependency, SkBF decreased at the control sites, whereas it remained unchanged at the EMLA sites. In contrast, during cuff inflation, SkBF decreased at the control sites and also decreased at the EMLA sites. The percent change in SkBF from baseline was greater during cuff inflation than limb dependency at both the control sites and the EMLA sites. Estimated skin vascular resistance remained unchanged at the EMLA sites during cuff inflation, as well as limb dependency. Thus the decrease in SkBF during venous congestion with cuff inflation is not solely due to the cutaneous VAR but also to a reduction in local perfusion pressure. The VAR is therefore most specifically quantified by venous congestion induced by limb dependency, rather than cuff inflation. Finally, from both techniques, we calculated that during venous congestion induced by limb dependency (calf), approximately 45% of the nonbaroreflex vasoconstriction is induced by the VAR and approximately 55% by the myogenic reflex.

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Regulation of subcutaneous blood flow during head‐up tilt (45°) in normals

Cited by 39 publications

References 20 publications

Does peripheral nerve degeneration affect circulatory responses to head-up tilt in spinal cord-injured individuals?

Does peripheral nerve degeneration affect circulatory responses to head-up tilt in spinal cord-injured individuals?

Leg vascular resistance increases during head-up tilt in paraplegics

Vasoconstriction during venous congestion: effects of venoarteriolar response, myogenic reflexes, and hemodynamics of changing perfusion pressure

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