Vascular Adjustments to Increased Transmural Pressure in Cat and Man with Special Reference to Shifts in Capillary Fluid Transfer

Mellander, Stefan; ÖBerg, Bengt; Odelram, H.

doi:10.1111/j.1748-1716.1964.tb02940.x

Cited by 147 publications

(74 citation statements)

References 20 publications

(20 reference statements)

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“…3 and 4). The CFC measured in male subjects was of similar magnitude, as described earlier, with similar techniques (26,36). This low CFC of 0.003-0.004 (ml⅐100 ml Ϫ1 ⅐min Ϫ1 ⅐mmHg Ϫ1 ) may have decreased from its basal level due to local myogenic, as well as axon reflex responses to the increased transmural pressure (19,31).…”

Section: Discussionsupporting

confidence: 51%

“…Further, CFC may have been affected not only by local increase in transmural pressure but also by increased sympathetic discharge in response to the reduced central blood volume during LBNP. Thus CFC might have deteriorated to some extent from the value determined by the local transmural pressure changes only, because of an increase in pre-and postcapillary resistance ratio, and a concomitant decrease in capillary pressure, as well as opening of precapillary sphincters due to sympathetic activation (27,36). However, differences in sympathetic activation (e.g., high as opposed to low LBNP, or differences in peripheral resistance) do not seem to affect CFC in the leg during LBNP (Fig.…”

Section: Discussionmentioning

confidence: 99%

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Sex-related effects on venous compliance and capillary filtration in the lower limb

Lindenberger

Länne²

2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Recent studies in humans have suggested sex differences in venous compliance of the lower limb, with lower compliance in women. Capillary fluid filtration could, however, be a confounder in the evaluation of venous compliance. The venous capacitance and capillary filtration response in the calves of 12 women (23.2 Ϯ 0.5 years) and 16 men (22.9 Ϯ 0.5 years) were studied during 8 min lower body negative pressure (LBNP) of 11, 22, and 44 mmHg. Calf venous compliance is dependent on pressure and was determined using the first derivative of a quadratic regression equation that described the capacitance-pressure relationship [compliance ϭ ␤ 1 ϩ (2 ⅐ ␤2 ⅐ transmural pressure)]. We found a lower venous compliance in women at low transmural pressures, and the venous capacitance in men was increased (P Ͻ 0.05). However, the difference in compliance between sexes was reduced and not seen at higher transmural pressures. Net capillary fluid filtration and capillary filtration coefficient (CFC) were greater in women than in men during LBNP (P Ͻ 0.05). Furthermore, calf volume increase (capacitance response ϩ total capillary filtration) during LBNP was equivalent in both sexes. When total capillary filtration was not subtracted from the calf capacitance response in the calculation of venous compliance, the sex differences disappeared, emphasizing that venous compliance measurement should be corrected for the contribution of CFC. lower body negative pressure; capillary filtration coefficient; venous capacitance THE VENOUS SECTION OF THE cardiovascular system can be looked upon as a voluminous blood reservoir (70% of total blood volume), designed to preserve a proper inflow of blood into the heart during various cardiovascular adjustments. Thus central venous pressure and filling of the heart may be maintained at a fairly stable level, despite variations in venous blood volume (49). During upright posture, however, the pooling of blood in the veins of the lower part of the body decreases central blood volume and venous return (4, 5, 16). The venous compartment in the legs, rather than the pelvic or abdominal region, seems to have a hemodynamic impact during lower body negative pressure (LBNP) (16), and in studies on men, a greater calf venous compliance has been linked to an increased venous capacitance response with a concomitant reduction in central blood volume (44,56). This, in turn, elicits an increased sympathetic response with higher peripheral resistance and increased heart rate (4, 5, 10, 16, 44, 58). Thus venous compliance of the lower limb may have an impact on cardiovascular responses to orthostatic stress and orthostatic tolerance, although there might be differences between sexes confounding such a link (4).Women are more susceptible to orthostatic stress than men (4,10,13,40,51,58), and in accordance with some findings in the arterial tree, it may be hypothesized that women have greater venous compliance in the lower limbs predisposing to orthostatic intolerance (52). This seems to be refuted however, by recent fi...

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Section: Discussionsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 99%

Sex-related effects on venous compliance and capillary filtration in the lower limb

Lindenberger

Länne²

2007

American Journal of Physiology-Regulatory, Integrative and Comp

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“…This venoarteriolar reflex has been reported to be able to reduce the lower limb blood flow up to 30-45% during orthostatic stress (Hendriksen & Sjersen, 1977;Skagen & Bonde-Petersen, 1982;Hendriksen & Skagen, 1988). A myogenic response in the resistance arterioles of the dependent regions (in response to increased transmural pressure) (Folkow, 1962;Mellander et al 1964;Folkow & Mellander, 1964) may also contribute to the rise in vascular resistance, but this effect is now thought to be less important than the venoarteriolar reflex. In contrast to the venoarteriolar reflex the myogenic response is not regarded as a sustained response (Johnson, 1980;R adegran & Saltin, 1998).…”

Section: Regulation Of Blood Pressure and Venous Capacitance In Healtmentioning

confidence: 99%

Pathophysiological basis of orthostatic hypotension in autonomic failure

Smit

Halliwill²,

Low

et al. 1999

The Journal of Physiology

319

207

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Patients with autonomic failure may be seriously incapacitated in activities of daily living due to orthostatic hypotension. Their low blood pressure is ascribed to a defective increase in arterial resistance and an excessive venous pooling upon standing. Effective pharmacological treatment is now available, but may aggravate supine hypertension and have other undesirable effects. Additionally, pharmacological treatment is less successful for hypotension with physical exercise or in warm surroundings (Bannister & Mathias, 1992). Non-pharmacological measures are regarded as a cornerstone in the treatment of orthostatic hypotension. These measures consist of chronic expansion of the extracellular volume or reducing the vascular volume in which pooling occurs (Bannister & Mathias, 1992). The latter includes protective measures like physical countermanoeuvres which can be applied by those patients with no major additional neurological and musculo-skeletal disorders, and external support garments which can be recommended to all patients. We reasoned that selection and use of appropriate protective measures would be facilitated by understanding the fundamental physiological mechanisms that prevent excessive orthostatic pooling in healthy subjects, why these mechanisms fail in patients with autonomic failure, and how these protective measures work. Therefore we reviewed the literature and summarized the available data about the amount and location of venous pooling in patients with autonomic failure and the effectiveness of physical countermanoeuvres and external support garments.

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“…Henriksen et al 7 also showed that in chronically sympathetic enervated limbs, in which the veno-arteriolar response was absent, venous pressure elevation caused a linear increase in capillary filtration rate, whereas in the opposite intact limb, the capillary filtration rate increased by only a portion of that predicted by changes in hydrostatic pressure. 8,9 This autoregulatory vasoconstrictor mechanism consists of two main components: (1) a locally-evoked sympathetic axoaxonic reflex triggered by limb venous congestion; 7,10 and (2) an acute arteriolar reaction to increasing transmural pressure, 11 the so-called myogenic response. 12 Experimental studies have shown that myogenic responses result from cell membrane depolarisation, opening of L-type DHPsensitive voltage-gated channels and extracellular calcium ion entry into the cell (see Davis and Hill 12 for a review).…”

Section: Introductionmentioning

confidence: 99%

Calcium channel blockers, postural vasoconstriction and dependent oedema in essential hypertension

2001

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Treatment with calcium channel blocker (CCB)s, dihydropyridines and others, is frequently complicated by dependent oedema in the absence of sodium retention or cardiac failure, a bothersome side effect of unclear aetiology. The present paper reviews our own and other work dealing with the antagonism exerted by such drugs on postural vasoconstriction, a mechanism triggered by limb venous congestion during orthostasis and controlled through a local sympathetic axo-axonic reflex and increased myogenic tone in response to changes in transmural pressure. By stabilising capillary pressure, postural vasoconstriction counteracts fluid

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Vascular Adjustments to Increased Transmural Pressure in Cat and Man with Special Reference to Shifts in Capillary Fluid Transfer

Cited by 147 publications

References 20 publications

Sex-related effects on venous compliance and capillary filtration in the lower limb

Sex-related effects on venous compliance and capillary filtration in the lower limb

Pathophysiological basis of orthostatic hypotension in autonomic failure

Calcium channel blockers, postural vasoconstriction and dependent oedema in essential hypertension

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