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Krediet C T Paul - - 2008
OBJECTIVES: Squatting is a potent physical maneuver to prevent syncope; however, a major drawback is that standing up from squatting is a large hemodynamic stressor that often causes new presyncopal symptoms. We tested the hypothesis that lower body skeletal muscle tensing (LBMT) attenuates the decrease of mean arterial blood pressure ...
GOSWAMI N - - 2009
We tested whether seal location at iliac crest (IC) or upper abdomen (UA), before and during lower body negative pressure (LBNP), would affect thoracic electrical impedance, hepatic blood flow, and central cardiovascular responses to LBNP. After 30 min of supine rest, LBNP at -40 mm Hg was applied for 15 ...
Groothuis Jan T - - 2008
Leg vascular resistance is calculated as the arterial-venous pressure gradient divided by blood flow. During orthostatic challenges it is assumed that the hydrostatic pressure contributes equally to leg arterial, as well as to leg venous pressure. Because of venous valves, one may question whether, during orthostatic challenges, a continuous hydrostatic ...
Thijs Roland D - - 2008
The effects of hyperventilation (HV) on mean arterial pressure (MAP) are variable. To identify factors affecting the MAP response to HV, we dissected the effects of hypocapnic HV (HHV) and isocapnic HV (IHV) and evaluated the effects of acute vs. prolonged HHV. In 11 healthy subjects the cardio- and cerebrovascular ...
Meininger Dirk - - 2008
BACKGROUND: The present prospective study was designed to evaluate hemodynamic changes associated with head-down positioning and prolonged pneumoperitoneum during totally endoscopic robot-assisted radical prostatectomy. METHODS: Ten American Society of Anesthesiologists (ASA) physical status I-III patients undergoing totally endoscopic robot-assisted radical prostatectomy were enrolled in the study. Invasive hemodynamic parameters were ...
Krabbendam Ineke - - 2008
OBJECTIVE: Prepregnant low plasma volume (LPV) is associated with subsequent gestational hypertensive disease. It is unknown to what extent an LPV affects the venous reserve capacity (VRC). We tested the hypothesis that LPV reduces the VRC, as indicated by presyncope or altered cardiovascular changes in response to head-up tilt. STUDY ...
Yao Yong-Jie - - 2008
Thigh cuffs are used by cosmonauts to limit fluid shift during space flight, but the appropriate level of cuff pressure and the duration of application to optimize their beneficial effects require further detailed investigations. In the present study, 10 days head-down tilt (HDT) bed rest was performed to assess the ...
Rasmussen Keith G - - 2008
Falls are common in patients receiving electroconvulsive therapy (ECT) treatments. One cause of falls is orthostatic hypotension. In an effort to deduce whether modifiable anesthetic factors are associated with posttreatment hemodynamic changes, we assessed supine and standing blood pressure and pulse in 62 patients given 295 treatments approximately 2 hours ...
Taneja Indu - - 2008
Our prior studies indicated that postural fainting relates to splanchnic hypervolemia and thoracic hypovolemia during orthostasis. We hypothesized that thoracic hypovolemia causes excessive sympathetic activation, increased respiratory tidal volume, and fainting involving the pulmonary stretch reflex. We studied 18 patients 13-21 yr old, 11 who fainted within 10 min of ...
Kamiya Atsunori - - 2008
Maintenance of arterial pressure (AP) under orthostatic stress against gravitational fluid shift and pressure disturbance is of great importance. One of the mechanisms is that upright tilt resets steady-state baroreflex control to a higher sympathetic nerve activity (SNA). However, the dynamic feedback characteristics of the baroreflex system, a hallmark of ...
Sauder Charity L - - 2008
Otolith organs have been shown to activate the sympathetic nervous system in the prone position by head-down rotation (HDR) in humans. To date, otolithic stimulation by HDR has not been comprehensively studied in the upright posture. The purpose of the present study was to determine whether otolithic stimulation increases muscle ...
Gamboa Alfredo - - 2008
Approximately 50% of patients with autonomic failure (AF) suffer from supine hypertension, even those with very low plasma norepinephrine and renin. Because NO is arguably the most potent metabolic modulator of blood pressure, we hypothesized that impaired NO function contributes to supine hypertension in AF. However, we found that AF ...
Zhou Fang - - 2008
A novel method for low electroosmotic flow (EOF) rates measurement by tilting microchip which based upon the hydrostatic pressure conception and sampling zone method is described. Sampling zone could be detected in the tilting microchip but not in non-tilting one due to the hydrostatic pressure driven. The method is fulfilled ...
McManus John G - - 2008
OBJECTIVE: This study tested the hypothesis that pulmonary end-tidal CO(2) (PETCO(2)) tracks reductions in central blood volume in human volunteers exposed to progressive central hypovolemia. METHODS: Measurements of PETCO(2), systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures, heart rate (HR), stroke volume (SV), and respiratory rate (RR) were ...
Jans Ø - - 2008
BACKGROUND: Based on maximisation of cardiac stroke volume (SV), peri-operative individualised goal-directed fluid therapy improves patient outcome. It remains, however, unknown how fluid therapy by this strategy relates to filling of the heart during supine rest as reference for the anaesthetised patient and whether the heart becomes distended. To answer ...
Verheyden Bart - - 2008
Tilt training is a useful therapeutic option in neurally mediated syncope (NMS). We tested the hypothesis that tilt training will restore orthostatic tolerance by increasing the degree of vasomotor reserve during sustained orthostatic stress. METHODS AND RESULTS In this follow-up study we enrolled 17 patients (age 31 +/- 22 years, ...
Robertson David - - 2008
Orthostatic Hypotension (OH) is a common manifestation of blood pressure dysregulation. OH takes a heavy toll on quality of life. It has many potential etiologies, and many effects of aging can increase susceptibility to OH. Neurological disorders are especially likely to cause severe OH. In this brief review, the pathogenesis ...
Low Phillip A - - 2008
Orthostatic hypotension (OH) is defined as a fall in blood pressure of at least 20 mmHg systolic or 10 mmHg diastolic when standing or during head-up tilt testing. The prevalence of OH increases with age, with disorders that affect autonomic nerve transmission, and with increasingly severe orthostatic stress. In normal ...
Kaufmann Horacio - - 2008
Neurogenic orthostatic hypotension results from failure to release norepinephrine, the neurotransmitter of sympathetic postganglionic neurons, appropriately upon standing. In double blind, cross over, placebo controlled trials, administration of droxidopa, a synthetic amino acid that is decarboxylated to norepinephrine by the enzyme L: -aromatic amino acid decarboxylase increases standing blood pressure, ...
Moldovanova Iryna - - 2008
Gender differences in human cardiovascular norepinephrine transporter function may be mediated through female sex hormones. We studied 16 healthy eumenorrheic women (25+/-1 years) during the early follicular phase (day 5+/-0) and midluteal phase (day 22+/-0) of the menstrual cycle. In a randomized, crossover, double-blind fashion, subjects ingested 8 mg of ...
Andersson M - - 2008
OBJECTIVES: To determine whether orthostatic hypotension (OH) is more common in patients with dementia than in older people without cognitive impairment and to identify key differences in the profile of the orthostatic response and the pulse drive during orthostatic challenge between Alzheimer's disease (AD) and dementia with Lewy bodies (DLB). ...
Galland Barbara C - - 2008
This study aimed to define cardiovascular and heart rate variability (HRV) changes following head-up tilt (HUT) in children/adolescents with chronic fatigue syndrome (CFS) in comparison to age- and gender-matched controls. Twenty-six children/adolescents with CFS (11-19 y) and controls underwent 70-degree HUT for a maximum of 30 min, but returned to ...
Gao Yunfang - - 2008
AIM: Recent results from animal experiments have shown that radix astragali (RA), a traditional Chinese herbal tonic, alleviates muscle atrophy under simulated weightlessness conditions, rendering RA a candidate for human use as a countermeasure against muscular atrophy. Possible cardiovascular side effects have not yet been investigated. We analyzed the effects ...
Chan Gregory S H - - 2008
BACKGROUND: Change in cardiac preload caused by mild hypovolemia can alter left ventricular ejection time (LVET) without noticeable change in blood pressure (BP). Previously our group has explored a novel method of LVET monitoring using a noninvasive finger photoplethysmographic pulse oximetry wave form. The current study investigated the ability of ...
Carapetian Stephanie - - 2008
The increase in orthostatic systolic blood pressure associated with the shift in posture from lying to standing requires several compensatory mechanisms to ensure adequate cerebral perfusion. Decreased efficiency in the various mechanisms controlling orthostatic blood pressure regulation can result in dizziness, lightheadedness, and syncope. The degree of effectiveness of orthostatic ...
Raffai G - - 2009
Microgravity or simulated microgravity induces acute and chronic cardiovascular responses, whose mechanism is pivotal for understanding of physiological adaptation and pathophysiological consequences. We investigated hemodynamic responses of conscious Wistar rats to 45? head-down tilt (HDT) for 7 days. Arterial blood pressure (BP) was recorded by telemetry. Heart rate (HR), spectral ...
Strempel Sebastian - - 2008
Sympathetically mediated tachycardia and vasoconstriction maintain blood pressure during hypergravitational stress, thereby preventing gravitation-induced loss of consciousness. Norepinephrine transporter (NET) inhibition prevents neurally mediated (pre)syncope during gravitational stress imposed by head-up tilt testing. Thus it seems reasonable that NET inhibition could increase tolerance to hypergravitational stress. We performed a double-blind, ...
Medow Marvin S - - 2008
Orthostatic hypotension (OH) occurs in 0.5% of individuals and as many as 7-17% of patients in acute care settings. Moreover, OH may be more prevalent in the elderly due to the increased use of vasoactive medications and the concomitant decrease in physiologic function, such as baroreceptor sensitivity. OH may result ...
Aoki Mitsuhiro - - 2008
OBJECTIVES: A number of animal studies have confirmed that the otolith organs may contribute to the maintenance of blood pressure during positional change; however, the contribution of such organs remains to be elucidated in humans. METHODS: This study investigated whether acute dizzy patients (n = 11) with an abnormal deviation ...
Soller Babs R - - 2008
OBJECTIVE: To compare the responses of noninvasively measured tissue oxygen saturation (StO2) and calculated muscle oxygen tension (PmO2) to standard hemodynamic variables for early detection of imminent hemodynamic instability during progressive central hypovolemia in humans. DESIGN: Prospective study. SETTING: Research laboratory. SUBJECTS: Sixteen healthy human volunteers. INTERVENTIONS: Progressive lower body ...
Suzuki Koji - - 2008
OBJECTIVE: Near infrared spectroscopy (NIRS) is a non-invasive optical technique to monitor cerebral tissue oxygen saturation (ScO(2)). The purpose of this study was to reveal the usefulness of ScO(2) monitoring in evaluating cerebral circulation in patients with autonomic failure. METHODS: Nineteen patients with multiple system atrophy (MSA), who had autonomic ...
Yoshida Masayoshi - - 2008
Central baroreflex failure in patients with spinal cord injury results in serious orthostatic hypotension. We examined if transcutaneous electrical stimulation regulates arterial pressure in those patients. We identified skin regions capable of increasing arterial pressure and determined respective transfer function. Using the transfer function, we designed the feedback regulator (i.e., ...
Ding Dan - - 2008
This study examined the usage of powered seating functions, including tilt-in-space, backrest recline, and seat elevation, among a group of wheelchair users during their typical daily activities. Twelve individuals who used a power wheelchair with seating functions participated in the study. They drove their own wheelchair and used the seating ...
Wyller Vegard Bruun - - 2008
The chronic fatigue syndrome (CFS) has been shown to be associated with orthostatic intolerance and cardiovascular dysregulation. We investigated the cardiovascular responses to combined orthostatic stress and isometric exercise in adolescents with CFS. We included a consecutive sample of 15 adolescents 12-18 years old with CFS diagnosed according to a ...
Ejaz A Ahsan - - 2007
The presence of orthostatic hypotension has been shown to be a significant, independent predictor of all-cause mortality. Systolic and diastolic orthostatic hypotension, reversal of the circadian pattern, and postprandial hypotension are some of the hemodynamic factors that may contribute to the increased mortality seen in patients with orthostatic hypotension. The ...
Thijs Roland D - - 2007
We evaluated the use of strain gauge plethysmography (SGP) for the assessment of orthostatic fluid shifts during head up tilt (HUT). Subjects wore a parachute harness fixed to the tilt table to avoid muscle tension in the lower limbs during HUT. 22 Healthy subjects (9 women) were tilted for 5 ...
Alexandrova N P - - 2007
Effects of central hypervolemia on respiratory function and compensatory capabilities of the respiratory system were studied in the anesthetized, vagally intact or vagotomized rats. Central hypervolemia was induced by a head-down tilt on -30 degree rotation. The tilt evoked an elevation of central venous pressure (from -2+/-0.4 cmH2O to 3.9+/-0.8 ...
Krediet C T Paul - - 2007
IOH (initial orthostatic hypotension) comprises symptoms of cerebral hypoperfusion caused by an abnormally large transient MAP (mean arterial pressure) decrease 5-15 s after arising from a supine, sitting or squatting position. Few treatment options are available. In the present study, we set out to test the hypothesis that LBMT (lower ...
Claybaugh John R - - 2007
INTRODUCTION: Hyperbaria-induced diuresis is accompanied by decreased basal and stimulated release of arginine vasopressin (AVP) and decreased blood volume possibly contributing to the reported orthostatic intolerance. Since hyperosmolality is not a consistent finding, the explanation of blood volume reduction at hyperbaria must involve an osmotic component to the diuresis. Investigations ...
Mehlsen Jesper - - 2008
AIMS: Cardioinhibitory syncope (CS) is a neurally mediated response causing bradycardia or asystole. This study reports on changes in blood pressure, heart rate variability (HRV), and ECG patterns before and after syncope with asystole. METHODS AND RESULTS: Thirty-five patients with CS and a matched control group were submitted to 60 ...
Porta C - - 2008
OBJECTIVE: To analyse the influence of breathing activity on cerebrovascular dynamics during presyncope. DESIGN: Retrospective study. SETTING: University hospital. PATIENTS: 38 subjects developing neurocardiogenic syncope (syncope group), and 61 age-matched control subjects with negative tilt. INTERVENTIONS: Middle cerebral artery mean blood flow velocity (MCFV), continuous non-invasive blood pressure (BP), end-tidal ...
Deegan B M T - - 2007
Orthostatic hypotension (OH) is a clinical condition, which frequently results in symptoms such as syncope, dizziness during standing, weakness, blurred vision and fatigue. It is defined as a sustained drop in blood pressure exceeding 20 mmHg systolic or 10 mmHg diastolic occurring within 3 min of assuming upright posture, and ...
Gupta Vishal - - 2007
Orthostatic hypotension is a common problem among elderly patients, associated with significant morbidity and mortality. While acute orthostatic hypotension is usually secondary to medication, fluid or blood loss, or adrenal insufficiency, chronic orthostatic hypotension is frequently due to altered blood pressure regulatory mechanisms and autonomic dysfunction. The diagnostic evaluation requires ...
Maggi R - - 2007
Syncope is a transient, self-limited loss of consciousness, usually leading to falling. The underlying mechanism is a transient global cerebral hypoperfusion. Since there are many causes of syncope, a specific treatment cannot be administered without knowing of the exact mechanism responsible of loss of consciousness. Drugs are ineffective. The main ...
Wilson T E - - 2007
Central venous pressure (CVP) provides information regarding right ventricular filling pressure, but is often assumed to reflect left ventricular filling pressure. It remains unknown whether this assumption is correct during thermal challenges when CVP is elevated during skin-surface cooling or reduced during whole-body heating. The primary objective of this study ...
Ramsey Michael W - - 2007
The purpose of this investigation was to determine mean arterial pressure (MAP) and regional vascular conductance responses in young and aged Fisher-344 rats during orthostatic stress, i.e., 70 degrees head-up tilt (HUT). Both groups demonstrated directionally different changes in MAP during HUT (young, 7% increase; aged, 7% decrease). Vascular conductance ...
Fischer D - - 2007
This study tested the hypothesis that cardiovascular and hormonal responses to lower body negative pressure (LBNP) would be altered by 4-h head down bed rest (HDBR) in 11 healthy young men. In post-HDBR testing, three subjects failed to finish the protocol due to presyncopal symptoms, heart rate was increased during ...
Vaddadi Gautam - - 2007
Postural syncope is a transient loss of consciousness secondary to a reduction in cerebral blood flow and is typically precipitated by standing. It is the commonest cause of recurrent transient loss of consciousness. Recurrent unexplained postural syncope is most often due to one of the five disorders of circulatory control: ...
Choi Yong Seon - - 2007
OBJECTIVE: During one-lung ventilation, surgical positions significantly affect deterioration of oxygenation, and the lateral decubitus position is superior in preventing dangerous hypoxemia compared with the supine position. However, additional head-down tilt causes more compression of the dependent ventilated lung by the abdominal contents and may result in dangerous hypoxemia, as ...
Naschitz Jochanan E - - 2007
According to the 1996 consensus definition, orthostatic hypotension (OH) is diagnosed when a fall in systolic blood pressure of at least 20 mm Hg and/or diastolic blood pressure of at least 10 mm Hg within 3 min of standing is recorded. The elements of orthostatic blood pressure drop that are ...
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