A definition of normovolaemia and consequences for cardiovascular control during orthostatic and environmental stress

Truijen, Jasper; Bundgaard‐Nielsen, Morten; Lieshout, Johannes J. van

doi:10.1007/s00421-009-1346-5

Cited by 35 publications

(40 citation statements)

References 204 publications

(282 reference statements)

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“…HDT redistributes blood to the thoracic region, increasing central blood volume and cardiac filling pressures (8,31,32). In the present investigation, early mitral inflow and annular tissue velocities remained unchanged from the supine position with HDT, regardless of thermal condition.…”

Section: Diastolic Functionsupporting

confidence: 46%

Left ventricular systolic and diastolic function during tilt-table positioning and passive heat stress in humans

Nelson

Altamirano-Diaz

Petersen

et al. 2011

American Journal of Physiology-Heart and Circulatory Physiology

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The ventricular response to passive heat stress has predominantly been studied in the supine position. It is presently unclear how acute changes in venous return influence ventricular function during heat stress. To address this question, left ventricular (LV) systolic and diastolic function were studied in 17 healthy men (24.3 Ϯ 4.0 yr; mean Ϯ SD), using two-dimensional transthoracic echocardiography with Doppler ultrasound, during tilt-table positioning (supine, 30°h ead-up tilt, and 30°head-down tilt), under normothermic and passive heat stress (core temperature 0.8 Ϯ 0.1°C above baseline) conditions. The supine heat stress LV volumetric and functional response was consistent with previous reports. Combining head-up tilt with heat stress reduced end-diastolic (25.2 Ϯ 4.1%) and end-systolic (65.4 Ϯ 10.5%) volume from baseline, whereas heart rate (37.7 Ϯ 2.0%), ejection fraction (9.4 Ϯ 2.4%), and LV elastance (37.7 Ϯ 3.6%) increased, and stroke volume (Ϫ28.6 Ϯ 9.4%) and early diastolic inflow (Ϫ17.5 Ϯ 6.5%) and annular tissue (Ϫ35.6 Ϯ 7.0%) velocities were reduced. Combining head-down tilt with heat stress restored end-diastolic volume, whereas LV elastance (16.8 Ϯ 3.2%), ejection fraction (7.2 Ϯ 2.1%), and systolic annular tissue velocities (22.4 Ϯ 5.0%) remained elevated above baseline, and end-systolic volume was reduced (Ϫ15.3 Ϯ 3.9%). Stroke volume and the early and late diastolic inflow and annular tissue velocities were unchanged from baseline. This investigation extends previous work by demonstrating increased LV systolic function with heat stress, under varied levels of venous return, and highlights the preload dependency of early diastolic function during passive heat stress. tilt table; systolic function; left ventricle WHOLE BODY PASSIVE HEAT STRESS results in multiple cardiovascular and neural adjustments, including increases in cardiac output (14,17,29), cutaneous vascular conductance (2, 5), splanchnic and renal sympathetic vasoconstriction (15,26,28), and muscle sympathetic nerve activity (6,19). These responses occur in a coordinated effort to redistribute cardiac output to the cutaneous circulation, limit the reduction in blood pressure, and protect against syncope.In the supine heat-stressed individual, left ventricular (LV) end-diastolic volume is significantly reduced compared with normothermic conditions (17,18,34), along with reductions in central blood volume (5) and cardiac filling pressures (3,27,34,37). Despite this significant reduction in preload, stroke volume (SV) is maintained during passive heating (14,15,17,18,23,37), secondary to increased ventricular contractility (2,5,17,18) and ventricular diastolic suction (17, 18). While supine measures are helpful, an important and understudied issue is what happens when blood pressure control mechanisms are challenged during orthostasis. Likewise, because supine heat stress significantly reduces cardiac preload, an equally important issue is what happens to cardiac function when preload is restored.Passive postural changes by tilt-table...

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Section: Diastolic Functionsupporting

confidence: 46%

Left ventricular systolic and diastolic function during tilt-table positioning and passive heat stress in humans

Nelson

Altamirano-Diaz

Petersen

et al. 2011

American Journal of Physiology-Heart and Circulatory Physiology

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“…In a healthy human, passive movement from supine to upright on a tilt table causes right ventricular diastolic pressure to decrease by 0.5-1 kPa (about 5 mmHg), stroke volume to drop by up to 50%, and cardiac output to drop by about one-third (Blomqvist and Stone 1983;Smith and Ebert 1990;Matzen et al 1991;Rowell 1993;Cai et al 2000;Truijen et al 2010). Head-up tilt instantaneously affects brain perfusion; the larger the difference between pressure at heart and brain level, the larger the impact on brain perfusion will become.…”

Section: The Hydrostatic Indifference Locationmentioning

confidence: 97%

Gravity, the hydrostatic indifference concept and the cardiovascular system

Hinghofer‐Szalkay

2010

Eur J Appl Physiol

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Gravity, like any acceleration, causes a hydrostatic pressure gradient in fluid-filled bodily compartments. At a force of 1G, this pressure gradient amounts to 10 kPa/m. Postural changes alter the distribution of hydrostatic pressure patterns according to the body's alignment to the acceleration field. At a certain location--referred to as hydrostatically indifferent--within any given fluid compartment, pressure remains constant during a given change of position relative to the acceleration force acting upon the body. At this specific location, there is probably little change in vessel volume, wall tension, and the balance of Starling forces after a positional manoeuvre. In terms of cardiac function, this is important because arterial and venous hydrostatic indifference locations determine postural cardiac preload and afterload changes. Baroreceptors pick up pressure signals that depend on their respective distance to hydrostatic indifference locations with any change of body position. Vascular shape, filling volume, and compliance, as well as temperature, nervous and endocrine factors, drugs, and time all influence hydrostatic indifference locations. This paper reviews the physiology of pressure gradients in the cardiovascular system that are operational in a gravitational/acceleration field, offers a broadened hydrostatic indifference concept, and discusses implications that are relevant in physiological and clinical terms.

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“…According to the Frank-Starling phenomenon, systolic blood pressure proportionally relates to left ventricular pressure and contractile force (Duncker and Bache, 2008;Truijen et al, 2010). Therefore, one plausible explanation for the greater reduction in systolic pressure is the reduction in venous return and subsequently lesser stretch of the heart during diastole (Truijen et al, 2010) and dimin- …”

Section: Ethanol-clonidine Hemodynamic Interaction In Shrs 855mentioning

confidence: 99%

Reduced Cardiac Contractile Force Due to Sympathovagal Dysfunction Mediates the Additive Hypotensive Effects of Limited-Access Regimens of Ethanol and Clonidine in Spontaneously Hypertensive Rats

El‐Mas

Abdel‐Rahman²

2010

J Pharmacol Exp Ther

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Our previous attempts to investigate the long-term hemodynamic interaction between ethanol and clonidine in telemetered spontaneously hypertensive rats (SHRs) were hampered by the lack of a sustained hypotensive response to continuous clonidine exposure. This limitation was circumvented when we adopted a limited-access clonidine (8:30 AM-4:30 PM) paradigm in a recent study. The latter paradigm was employed here to evaluate the ethanol-clonidine interaction and possible roles of myocardial function and autonomic control in this interaction. Changes in blood pressure (BP), heart rate, maximum rate of rise in BP wave (ϩdP/dt max ), and spectral cardiovascular autonomic profiles were measured by radiotelemetry in pair-fed SHRs receiving clonidine (150 g/kg/day), ethanol [2.5% (w/v)], or their combination during the day for 12 weeks. Ethanol or clonidine elicited long-term decreases in BP, and their combination caused additive hypotensive response. Significant reductions in ϩdP/dt max were observed upon concurrent treatment with ethanol and clonidine, in contrast to no effect for individual treatment. In addition, the combined treatment increased the high-frequency (HF) spectral band of interbeat interval (IBI-HF nu , 0.75-3 Hz) and decreased low-frequency (IBI-LF nu , 0.2-0.75 Hz) bands and IBI LF/HF ratios. Clonidineevoked reductions in plasma and urine norepinephrine and BP-LF spectral power (measure of vasomotor sympathetic tone) were not affected by ethanol. In conclusion, concurrent treatment with ethanol and clonidine shifts the sympathovagal balance toward parasympathetic dominance and elicits exaggerated hypotension as a result of a reduction in cardiac contractile force.

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A definition of normovolaemia and consequences for cardiovascular control during orthostatic and environmental stress

Cited by 35 publications

References 204 publications

Left ventricular systolic and diastolic function during tilt-table positioning and passive heat stress in humans

Left ventricular systolic and diastolic function during tilt-table positioning and passive heat stress in humans

Gravity, the hydrostatic indifference concept and the cardiovascular system

Reduced Cardiac Contractile Force Due to Sympathovagal Dysfunction Mediates the Additive Hypotensive Effects of Limited-Access Regimens of Ethanol and Clonidine in Spontaneously Hypertensive Rats

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