Assessment of capillary fluid shifts during orthostatic stress in normal subjects and subjects with orthostatic intolerance

Brown, Clive; Hainsworth, R.

doi:10.1007/bf02311762

Cited by 49 publications

(53 citation statements)

References 19 publications

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“…Using impedance plethysmography, we determined calf volume changes from the relative changes in calf impedance [6,7]. Recording electrodes were placed on the lateral malleolus and lateral aspect of the knee to define a calf segment.…”

Section: ■ Proceduresmentioning

confidence: 99%

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Effect of physical countermaneuvers on orthostatic hypotension in familial dysautonomia

et al. 2005

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■ Abstract Familial dysautonomia (FD) patients frequently experience debilitating orthostatic hypotension. Since physical countermaneuvers can increase blood pressure (BP) in other groups of patients with orthostatic hypotension, we evaluated the effectiveness of countermaneuvers in FD patients.In 17 FD patients (26.4 ± 12.4 years, eight female), we monitored heart rate (HR), blood pressure (BP), cardiac output (CO), total peripheral resistance (TPR) and calf volume while supine, during standing and during application of four countermaneuvers: bending forward, squatting, leg crossing, and abdominal compression using an inflatable belt. Countermaneuvers were initiated after standing up, when systolic BP had fallen by 40 mmHg or diastolic BP by 30 mmHg or presyncope had occurred.During active standing, blood pressure and TPR decreased, calf volume increased but CO remained stable. Mean BP increased significantly during bending forward (by 20.0 (17-28.5) mmHg; P = 0.005) (median (25 th -75 th quartile)), squatting (by 50.8 (33.5-56) mmHg; P = 0.002), and abdominal compression (by 5.8 (-1-34.7) mmHg; P = 0.04) -but not during leg-crossing. Squatting and abdominal compression also induced a significant increase in CO (by 18.1 (-1.3-47.9) % during squatting (P = 0.02) and by 7.6 (0.4-19.6) % during abdominal compression (P = 0.014)). HR did not change significantly during the countermaneuvers. TPR increased significantly only during squatting (by 37.2 (11.8-48.2) %; P = 0.01). However, orthopedic problems or ataxia prevented several patients from performing some of the countermaneuvers. Additionally, many patients required assistance with the maneuvers.Squatting, bending forward and abdominal compression can improve orthostatic BP in FD patients, which is achieved mainly by an increased cardiac output. Squatting has the greatest effect on orthostatic blood pressure in FD patients. Suitability and effectiveness of a specific countermaneuver depends on the orthopedic or neurological complications of each FD patient and must be individually tested before a therapeutic recommendation can be given.■ Key words physical maneuvers · familial dysautonomia · syncope · autonomic failure · impedance cardiography 1 Published in "Journal of Neurology 253(1): 65-72, 2006" which should be cited to refer to this work.

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Section: ■ Proceduresmentioning

confidence: 99%

“…An impedance monitor (Cardioscreen®, Medis GmbH, Ilmenau, Germany) supplied a 1 mA, 50 Hz current which was passed between electrodes placed 5 cm outside the recording electrodes. Changes in the impedance of the calf segment enclosed by the recording electrodes were measured and stored for analysis [6,7].…”

Section: ■ Proceduresmentioning

confidence: 99%

Effect of physical countermaneuvers on orthostatic hypotension in familial dysautonomia

et al. 2005

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“…This approach provokes presyncope in almost all subjects (allowing for symptom recognition in patients with syncope), while discriminating between patients with syncope and healthy controls, with a specificity of 92%, sensitivity of 85%, and repeatability of 1.1±0.6 min 16,17 . This allows not only diagnosis and pathophysiological assessment [19][20][21][22] , but also the evaluation of treatments for orthostatic intolerance due to its high repeatability [23][24][25][26][27][28][29][30] . For these reasons, we argue this should be the "gold standard" for orthostatic stress testing, and accordingly this will be the method described in this paper.…”

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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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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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“…9 Data have demonstrated contributions to limb enlargement from microvascular filtration. 6,10,11 Thus, we hypothesized that orthostatic limb enlargement occurs through enhanced microvascular filtration in POTS.…”

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Microvascular Filtration Is Increased in Postural Tachycardia Syndrome

Stewart

2003

Circulation

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Background— Postural tachycardia syndrome (POTS) is related to defective peripheral vasoconstriction of dependent extremities with redistributive hypovolemia. Methods and Results— To test whether enhanced microvascular filtration produces leg enlargement, we studied 12 patients 13 to 19 years of age with POTS and defective leg vasoconstriction and 13 age-matched healthy control subjects, with strain-gauge plethysmography used to measure venous pressure (P v ), forearm and calf blood flow, vascular capacitance, and the microvascular filtration coefficient (K f ). Measurements were made while the patient was supine and at steady state during upright tilt to 35°. Supine P v was not different in POTS, but upright leg P v tended to be increased above control. Arm and leg peripheral arterial resistance was decreased in the supine and upright positions in patients with POTS compared with control subjects ( P =0.01, upright legs). Supine K f was not significantly increased in the forearm in patients with POTS but was increased in the calf (9.3±2.2 versus 5.7±2.4 [10 −3 ] mL/100 mL per minute per mm Hg, P =0.04), correlating with calf blood flow (r s =0.84, P =0.002). K f was invariant with orthostasis. The hydraulic contribution to upright filtered flow at 35° tilt, the product of K f and P v , was approximately twice that of control (0.41±0.09 versus 0.19±0.04 mL/100 mL per minute, P =0.04). Conclusions— Increased microvascular filtration accounts for enhanced leg swelling in patients with POTS with increased arterial blood flow.

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Assessment of capillary fluid shifts during orthostatic stress in normal subjects and subjects with orthostatic intolerance

Cited by 49 publications

References 19 publications

Effect of physical countermaneuvers on orthostatic hypotension in familial dysautonomia

Effect of physical countermaneuvers on orthostatic hypotension in familial dysautonomia

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

Microvascular Filtration Is Increased in Postural Tachycardia Syndrome

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