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Brown Clive M - - 2003
The aim of this study was to determine whether lower body negative pressure (LBNP), combined with noninvasive methods of assessing changes in systemic and cerebral vascular resistance, is suitable as a method for assessing cerebral autoregulation. In 13 subjects we continuously assessed heart rate, blood pressure, cerebral blood flow velocity ...
Julu P O O - - 2003
To study cardiovascular control in the period leading to vasovagal syncope we monitored beat-to-beat blood pressure, heart rate (HR) and forearm blood flow in 14 patients with posturally related syncope, from supine through to tilt-induced pre-syncope. Signals of arterial blood pressure (BP) from a Finapres photoplethysmograph and an electrocardiograph (ECG) ...
Eckberg D L - - 2003
AIM: Astronauts return to Earth with reduced red cell masses and hypovolaemia. Not surprisingly, when they stand, their heart rates may speed inordinately, their blood pressures may fall, and some may experience frank syncope. We studied autonomic function in six male astronauts (average +/- SEM age: 40 +/- 2 years) ...
Sundblad Patrik - - 2003
It has recently been shown that the phase relationship between respiration-induced changes in arterial pressure (AP) and heart rate (HR) are different in supine and upright postures. We wanted to further analyse the coupling between respiration, arterial blood pressure and HR in the time domain, and how this coupling was ...
Franchi Franco - - 2003
BACKGROUND: Defective baroreflex function has been suggested as a potential mechanism accounting for the development of syncopal episodes. The present study was therefore aimed at assessing the non-invasive, indirect hemodynamic profile and baroreflex function by means of tilting, which is a natural stimulation crucial to physiological baroreflex activity, in syncopal ...
Franke Warren D - - 2003
This study tested the hypotheses that trained swimmers would have greater orthostatic tolerance than runners and, if present, it would be due to differences in their autonomic and hemodynamic responses to graded central hypovolemia. Twenty intercollegiate male athletes [11 runners and 9 swimmers; .VO(2max) =70.0 (1.6) vs 69.5 (2.6) ml.kg(-1).min(-1), ...
Béchir Markus - - 2003
BACKGROUND: The interplay of resting muscle sympathetic nerve activity (MSA) and the baroreceptor reflex in patients with vasovagal syncope remains elusive. Hence, the aim of the present study was to investigate MSA, baroreceptor sensitivity, heart rate, and blood pressure under resting conditions and during orthostatic stress in patients with a ...
Journeay W Shane - - 2003
The hypothesis that reduced cardiac filling, as a result of lower body negative pressure (LBNP) and postexercise hypotension (PEH), would attenuate the reflex changes to heart rate (HR), skin blood flow (SkBF), and mean arterial pressure (MAP) normally induced by facial immersion was tested. The purpose of this study was ...
Hakeman Amy L - - 2003
Tolerance to +G(z) stress is reduced by preceding exposure to -G(z) (push-pull effect). The mechanism(s) responsible for this effect are not fully understood, although the arterial baroreceptor reflexes have been implicated. We investigated the integrative response of the autonomic nervous system by studying responses to gravitational stress before and after ...
Suzuki Masaru - - 2003
The vasovagal reaction is thought to be caused by sympathetic withdrawal and vagal augmentation. While measurements of muscle sympathetic nerve activity support sympathetic withdrawal in tilt induced syncope, the results of previous attempts to quantify vagal control using spectral analyses of heart rate variability (HRV) remain controversial. The sampling period ...
Brown Clive M - - 2003
Patients with familial dysautonomia (FD) frequently have profound orthostatic hypotension without compensatory tachycardia. Although the aetiology is presumed to be sympathetic impairment, peripheral vascular responses to orthostasis have not been assessed. The aim of this study was to evaluate the control of vascular responses to postural stress in FD patients. ...
Franke Warren D - - 2003
This study tested the hypotheses that differences in the adrenergic, central venous pressure (CVP), cardiovascular, or baroreflex responses to lower body negative pressure (LBNP) or differences in body size would be associated with gender differences in orthostatic tolerance. Subjects (24 females, 22 males) underwent graded LBNP to -100 mmHg or ...
Perrault Hélène - - 2003
BACKGROUND: Tetralogy of Fallot (TOF) and its surgical repair are associated with alterations in right ventricular systolic and diastolic functions. The cardiopulmonary baroreflex describes the peripheral vasoconstriction response to the volume-unloading deactivation of left and possibly right ventricular receptors. Alterations in cardiac geometry or distensibility and pulmonary vasculature of operated ...
Bellard Elisabeth - - 2003
We determined whether early changes in central haemodynamics, as determined by transthoracic impedance, induced by a 70 degrees head-up tilt (HUT) test could predict syncope. Heart rate, arterial blood pressure and central haemodynamics [pre-ejection period and rapid left ventricular ejection time ( T (1)), slow ejection time ( T (2)) ...
Tschakovsky M E - - 2003
The purpose of this study was to test the hypothesis that sympathetic vasoconstriction is rapidly blunted at the onset of forearm exercise. Nine healthy subjects performed 5 min of moderate dynamic forearm handgrip exercise during -60 mmHg lower body negative pressure (LBNP) vs. without (control). Beat-by-beat forearm blood flow (Doppler ...
Witting Michael D - - 2003
The study objective was to describe the distribution of normal changes in vital signs related to moving from a sitting to a standing position. Subjects were free of cardiovascular disease and determined to be euvolemic by structured interview. Vital signs were measured after a minimum of 5 minutes of sitting ...
Razumovsky Alexander Y - - 2003
BACKGROUND AND PURPOSE: During head-up tilt (HUT), patients with chronic fatigue syndrome (CFS) have higher rates of neurally mediated hypotension (NMH) and postural tachycardia syndrome (POTS) than healthy controls. The authors studied whether patients with CFS were also more likely to have abnormal cerebral blood flow velocity (CBFV) compared with ...
Hao W Y - - 2003
To investigate the role played by hypovolaemia in the mechanism of orthostatic intolerance, a mathematical model was developed. The model consisted of seven sub-models that describe: the redistribution of blood induced by lower body negative pressure (LBNP); filling of the left ventricle; contracting of the left ventricle; interaction between the ...
Shi Shang-Jin - - 2003
Insomnia is a common symptom, not only in the adult population but also in many astronauts. Hypnotics, such as temazepam (a benzodiazepine) and zolpidem (an imidazopyridine), are often taken to relieve insomnia. Temazepam has been shown clinically to have hemodynamic side effects, particularly in the elderly; however, the mechanism is ...
Radtke Andrea A Virchow Klinikum der Charité, Augustenburger Platz 1, 13353 Berlin, FRG, Germany. - - 2003
We examined the hypothesis that vestibular signals may exert a rapid control on the heart adjusting cardiovascular function to maintain homoestasis during changes in body posture. Short- and long-latency effects of vestibular stimulation on heart rate (HR), systolic blood pressure (SP), diastolic pressure (DP) and digital blood flow (BF) were ...
Shamim Tabassum - - 2003
PURPOSE: To determine the amount of time necessary for stabilization of blood pressure and heart rate in patients with anorexia nervosa (AN) and the percentage of ideal body weight (IBW) at which this occurs. METHODS: A retrospective study was conducted on 36 adolescent patients (33 F, 3 M) with AN, ...
Belz Gustav Georg - - 2003
Independent, double-blinded, randomized, placebo-controlled studies using sublingual/oral administration of D-camphor, an extract from fresh crataegus berries, and a combination of the two (CCC) yielded the following results: Both the D-camphor and the extract from fresh crataegus berries, the components of CCC, contribute to the pressoric effects of the combination. The ...
Kawakami Kazunobu - - 2003
A 71-year-old man, who was diagnosed with familial amyloidosis type I, was admitted for treatment of severe orthostatic hypotension associated with recurrent syncopal attacks. Head-up tilt testing demonstrated severe orthostatic hypotension (114/72 mmHg in the supine position and 62/34 mmHg in the upright position) with syncope or presyncope. Oral midodorine ...
Kozłowski Dariusz - - 2003
One of the hypotheses put forward concerning the mechanism of vasovagal syncope is that the vagal afferent fibres are activated during vigorous contractions against a partly empty left ventricle. The aim of the study was to confirm this hypothesis by using 2D echocardiography during a head-up tilt test. The study ...
Frishman William H - - 2003
Orthostatic hypotension is a common problem, estimated to occur in 5 out of every 1000 individuals and in as many as 7% to 17% of patients in an acute care setting. Moreover, orthostatic hypotension may be more prominent in elderly patients due to the increased intake of vasoactive medications and ...
Stewart Julian M - - 2002
BACKGROUND: Adrenergic agents are commonly used in the treatment of chronic orthostatic intolerance with postural tachycardia syndrome (POTS). POTS may be associated with increased limb blood flow ("high flow") and defective orthostatic vasoconstriction or decreased limb blood flow ("low flow") and potentially with small blood volume. METHODS AND RESULTS: We ...
Garland Emily M - - 2002
Orthostatic intolerance, seen predominantly in young women, is characterized by symptoms of lightheadedness, fatigue and palpitations in the upright posture. With standing, plasma norepinephrine levels rise dramatically and heart rate often increases by more than 30 beats per minute, although blood pressure does not usually fall. A theory recently popularized ...
Cooke William H - - 2002
Recent studies suggest that an underlying mechanism for susceptibility of patients and astronauts to presyncope includes hypoadrenergic responses to orthostatic stress. However, data used to reach this conclusion are open to various interpretations. In this report, maintenance of sympathetic neural activity (MSNA; peroneal nerve microneurography) during -60 mmHg lower body ...
Faghri Pouran D - - 2002
OBJECTIVE: To evaluate the central haemodynamic responses during position changes from supine to sitting and during 30 min of standing between able-bodied and spinal cord-injured subjects. Also to assess the effects of the physiologic muscle pump in both groups during 30 min of standing. DESIGN: A repeated measure design. Both ...
Hakeman Amy L - - 2002
Brief exposure to -G(z) ("push") reduces eye-level blood pressure (elbp) during subsequent exposure to +G(z) ("pull"). This is called the "push-pull effect." To evaluate the influence of gender and the axis of rotation (pitch vs. roll) on the push-pull effect, 10 isoflurane-anesthetized male and 10 female Sprague-Dawley rats were restrained ...
Schroeder Christoph - - 2002
BACKGROUND: Orthostatic symptoms and syncope are common, even in apparently healthy subjects. In patients with severe autonomic dysfunction, water drinking elicits an acute pressor response and improves orthostatic hypotension. We tested the hypothesis that water drinking also improves orthostatic tolerance in healthy subjects. METHODS AND RESULTS: In a randomized, controlled, ...
Weiss Avraham - - 2002
BACKGROUND: Orthostatic hypotension (OH) is a common finding among older patients. We designed a study to examine the prevalence and consistency of OH during the day. METHODS: A total of 502 inpatients (241 men and 261 women) with a mean age of 81.6 years were included in the study. Orthostatic ...
Romano Salvatore M - - 2002
BACKGROUND: The aim of this study was to assess whether a non-invasive automatic evaluation of the pulse wave characteristics could provide clinical clues when monitoring the hemodynamic adjustments to head-up tilting. METHODS: A continuous assessment of the peripheral pulse wave characteristics (systolic, diastolic, dicrotic and pulse pressures) in 8 control ...
Jones Reese T - - 2002
Marijuana and delta9-tetrahydrocannabinol (THC) increase heart rate, slightly increase supine blood pressure, and on occasion produce marked orthostatic hypotension. Cardiovascular effects in animals are different, with bradycardia and hypotension the most typical response. Cardiac output increases, and peripheral vascular resistance and maximum exercise performance decrease. Tolerance to most of the ...
Monahan Kevin D - - 2002
Aging attenuates the increase in muscle sympathetic nerve activity (MSNA) and elicits hypotension during otolith organ engagement in humans. The purpose of the present study was to determine the neural and cardiovascular responses to otolithic engagement during orthostatic stress in older adults. We hypothesized that age-related impairments in the vestibulosympathetic ...
Khurana Ramesh K - - 2002
The role of trigeminal afferents in a patient with eye examination - induced syncope was investigated. A head-up tilt test precipitated presyncope with a reduced blood pressure. On a separate day, the application of Schirmer's lacrimation test strips in each conjunctival sac caused vasodepression and cardioinhibition. Topical administration of 0.5 ...
Belz G G - - 2002
In order to test the efficacy of a combination of natural D-camphor and an extract of fresh crataegus berries (Korodin Herz-Kreislauf-Tropfen) on orthostatic hypotension, two similar, controlled, randomized studies were carried out in a balanced crossover design in 24 patients each with orthostatic dysregulation. The camphor-crataegus berry combination (CCC) was ...
Akiyama Katsuyoshi - - 2002
KMD-3213 ((-)-1-(3-hydroxypropyl)-5-((2R)-2-[[2-([2-[(2,2,2-trifluoroethyl)oxy]phenyl]oxy)ethyl]amino]propyl)-2,3-dihydro-1H-indole-7-carboxamide), an alpha(1A)-adrenoceptor antagonist with potency similar to that of tamsulosin, is under development for the treatment of bladder outlet obstruction in patients with benign prostatic hypertrophy. In the present study, we investigated the effects of KMD-3213 on the tilt-induced blood pressure response in anesthetized normotensive rats. Male normotensive ...
Sarasin Francois P - - 2002
We sought to determine the prevalence of orthostatic hypotension as a cause of syncope in the emergency setting, and describe the characteristics of patients diagnosed with this condition. Blood pressure orthostatic changes were measured prospectively in a standardized fashion up to 10 minutes, or until symptoms occurred, in all consecutive ...
Youde J - - 2002
INTRODUCTION: Abnormalities of cardiac baroreceptor sensitivity (BRS) may contribute towards the high prevalence of orthostatic hypotension and falls in the elderly. Most mathematical analyses used to determine BRS in the time or frequency domains assume a stationary physiological state and cannot be performed under dynamic change and therefore are not ...
Watenpaugh Donald E - - 2002
We hypothesized that vestibular otolith organ stimulation contributes to human orthostatic responses. Twelve subjects underwent three 60 degrees upright tilts: (1) with the neck flexed from 0 degrees to 30 degrees relative to the body during 60 degrees tilt, such that the head moved from horizontal to 90 degrees above ...
Krediet C T Paul - - 2002
BACKGROUND: Posture-related vasovagal syncope is by far the most frequent cause of transient loss of consciousness, and present pharmacological and cardiac pacing treatment remains unsatisfactory. A simple maneuver to prevent or diminish vasovagal reactions would be beneficial. METHODS AND RESULTS: Twenty-one patients with recurrent syncope (age 17 to 74 years, ...
Takata Theodore S - - 2002
BACKGROUND: The purpose of this study was to assess the effect of the serotonin reuptake inhibitor paroxetine hydrochloride (Paxil, SmithKline Beecham) on cardiovascular reflexes. We hypothesized that Paxil prevents neurally mediated syncope (NMS) by attenuating the sympathoinhibition and vagotonia associated with a vasovagal reaction. METHODS AND RESULTS: In a double-blind ...
Kaufmann Horacio - - 2002
Neurally mediated syncope is the most frequent cause of syncope in patients without structural heart disease. Its most common trigger is a reduction in venous return to the heart due to excessive venous pooling in the legs. We conducted a double-blind, randomized, crossover trial to investigate the efficacy of midodrine, ...
Cooper V L - - 2002
During orthostatic stress, an increase in peripheral vascular resistance normally results in arterial blood pressure being well maintained, despite a decrease in cardiac output. The present study was undertaken to determine whether the sensitivity of the carotid baroreceptor reflex was increased during orthostatic stress and whether failure to develop this ...
Braune S - - 2002
The potential health risks of radiofrequency electromagnetic fields (EMFs) emitted by mobile phones are of considerable public interest. The present study investigated the hypothesis, based on the results of our previous study, that exposure to EMFs can increase sympathetic vasoconstrictor activity. Forty healthy young males and females underwent a single-blind, ...
Flevari Panagiota P - - 2002
Heart rate changes to hypotensive stimuli (baroreceptor sensitivity [BRS]) and forearm blood flow (FBF) reduction during head-up tilt are mediated by arterial and cardiopulmonary baroreceptors. Regarding baroreflexes in neurocardiogenic syncope (NCS), an apparent variation exists in findings reported in the literature. This may be due to the existence of different ...
Timmers H J L M - - 2002
BACKGROUND: Data on the prevalence of orthostatic intolerance (OI) in patients with chronic fatigue syndrome (CFS) are limited and controversial. We tested the hypothesis that a majority of CFS patients exhibit OI during head-up tilt. METHODS: Hemodynamic and neurohumoral responses to 40 minutes of head-up tilt were studied in 36 ...
Freeman Roy - - 2002
Venous denervation and increased venous pooling may contribute to symptoms of orthostatic intolerance. We examined venous compliance in the calf and forearm in 11 orthostatic-intolerant patients and 15 age-matched controls over a range of pressures, during basal conditions and sympathetic excitation. Occlusion cuffs placed around the upper arm and thigh ...
Jordan Jens - - 2002
Water drinking elicits a large, acute, pressor response in patients with autonomic failure who experience severe orthostatic hypotension. This essentially cost-free intervention has been successfully employed therapeutically in these patients to attenuate orthostatic and postprandial hypotension. In orthostatic intolerance patients, water drinking blunts the orthostatic tachycardia but has only a ...
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