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Orthostatic Intolerance (orthostatic + intolerance)
Selected AbstractsNo effect of venoconstrictive thigh cuffs on orthostatic hypotension induced by head-down bed restACTA PHYSIOLOGICA, Issue 2 2000M.-A. Custaud Orthostatic intolerance (OI) is the most serious symptom of cardiovascular deconditioning induced by head-down bed rest or weightlessness. Wearing venoconstrictive thigh cuffs is an empirical countermeasure used by Russian cosmonauts to limit the shift of fluid from the lower part of the body to the cardio-cephalic region. Our aim was to determine whether or not thigh cuffs help to prevent orthostatic hypotension induced by head-down bed rest. We studied the effect of thigh cuffs on eight healthy men. The cuffs were worn during the day for 7 days of head-down bed rest. We measured: orthostatic tolerance (stand tests and lower body negative pressure tests), plasma volume (Evans blue dilution), autonomic influences (plasma noradrenaline) and baroreflex sensitivity (spontaneous baroreflex slope). Thigh cuffs limited the loss of plasma volume (thigh cuffs: ,201 ± 37 mL vs. control: ,345 ± 42 mL, P < 0.05), the degree of tachycardia and reduction in the spontaneous baroreflex sensitivity induced by head-down bed rest. However, the impact of thigh cuffs was not sufficient to prevent OI (thigh cuffs: 7.0 min of standing time vs. control: 7.1 min). Decrease in absolute plasma volume and in baroreflex sensitivity are known to be important factors in the aetiology of OI induced by head-down bed rest. However, dealing with these factors, using thigh cuffs for example, is not sufficient to prevent OI. Other factors such as venous compliance, microcirculatory changes, peripheral arterial vasoconstriction and vestibular afferents must also be considered. [source] The relationship between bed rest and sitting orthostatic intolerance in adults residing in chronic care facilitiesJOURNAL OF NURSING AND HEALTHCARE OF CHRONIC ILLNE SS: AN INTERNATIONAL INTERDISCIPLINARY JOURNAL, Issue 3 2010Mary T Fox MSc fox mt, sidani s & brooks d (2010) Journal of Nursing and Healthcare of Chronic Illness2, 187,196 The relationship between bed rest and sitting orthostatic intolerance in adults residing in chronic care facilities Aim., To examine the relationship between orthostatic intolerance and bed rest as it was used by/with 65 adults residing in chronic care facilities. Background., The evidence on the relationship between bed rest and orthostatic intolerance has been obtained from aerospace studies conducted in highly controlled laboratory settings, and is regarded as having high internal validity. In the studies, prolonged and continuous bed rest, administered in a horizontal or negative tilt body position, had a major effect on orthostatic intolerance in young adults. However, the applicability of the findings to the conditions of the real world of practice is questionable. Methods., Participants were recruited over the period of April 2005 to August 2006. A naturalistic cohort design was used. The cohorts represented different doses of bed rest that were naturally occurring. Comparisons were made between patients who had no bed rest (comparative dose group, n = 20), two to four days (moderate dose, n = 23) and five to seven days of bed rest (high dose, n = 22) during a one-week monitoring period. Orthostatic intolerance was measured by orthostatic vital signs and a self-report scale. Bed rest dose was measured by the total number of days spent in bed during one week. Results.,Post hoc comparisons, using Bonferroni adjustments, indicated significant differences in adjusted means on self-reported orthostatic intolerance between the comparative and high (CI: ,4·12, ,0·85; p < 0·001), and the moderate and high (CI: 0·35, 3·56, p < 0·01) bed rest dose cohorts. No group differences were found on orthostatic vital signs. Conclusions., A moderate dose of bed rest with intermittent exposure to upright posture may protect against subjective orthostatic intolerance in patients who are unable to tolerate being out of bed every day. Future research may examine the effects of reducing bed rest days on orthostatic intolerance in individuals with high doses of five to seven days of bed rest. [source] Physiologic neurocirculatory patterns in the head-up tilt test in children with orthostatic intolerancePEDIATRICS INTERNATIONAL, Issue 2 2008Zhang Qingyou Abstract Background: Orthostatic intolerance (OI) is a common clinical manifestation in clinical pediatrics. The head-up tilt (HUT) table test is considered the standard of orthostatic assessment, but the physiologic neurocirculatory profile during HUT has not been fully realized in children with OI. The present study, therefore, was designed to investigate the physiologic patterns that occur during HUT in children with OI. Methods: Ninety children (56 girls; mean age, 11.6 ± 2.3 years) with OI underwent HUT under quiet circumstances. Blood pressure and heart rate were monitored simultaneously. Results: Forty-nine children with OI (54.4%) had vasovagal response with HUT testing; 33 (36.7%), vasodepressor response; six (6.7%), cardioinhibitory response; and 10 (11.1%), mixed response. Twenty-eight children (31.1%) had postural orthostatic tachycardia; one (1.1%), orthostatic hypotension (OH); and 12 (13.3%), normal physiologic response. Patterns of cerebral syncope response and chronotropic incompetence were not observed. Conclusions: Classical vasovagal response was the major physiologic pattern seen in children with OI during HUT testing, and postural orthostatic tachycardia response ranked second. [source] The relationship between bed rest and sitting orthostatic intolerance in adults residing in chronic care facilitiesJOURNAL OF NURSING AND HEALTHCARE OF CHRONIC ILLNE SS: AN INTERNATIONAL INTERDISCIPLINARY JOURNAL, Issue 3 2010Mary T Fox MSc fox mt, sidani s & brooks d (2010) Journal of Nursing and Healthcare of Chronic Illness2, 187,196 The relationship between bed rest and sitting orthostatic intolerance in adults residing in chronic care facilities Aim., To examine the relationship between orthostatic intolerance and bed rest as it was used by/with 65 adults residing in chronic care facilities. Background., The evidence on the relationship between bed rest and orthostatic intolerance has been obtained from aerospace studies conducted in highly controlled laboratory settings, and is regarded as having high internal validity. In the studies, prolonged and continuous bed rest, administered in a horizontal or negative tilt body position, had a major effect on orthostatic intolerance in young adults. However, the applicability of the findings to the conditions of the real world of practice is questionable. Methods., Participants were recruited over the period of April 2005 to August 2006. A naturalistic cohort design was used. The cohorts represented different doses of bed rest that were naturally occurring. Comparisons were made between patients who had no bed rest (comparative dose group, n = 20), two to four days (moderate dose, n = 23) and five to seven days of bed rest (high dose, n = 22) during a one-week monitoring period. Orthostatic intolerance was measured by orthostatic vital signs and a self-report scale. Bed rest dose was measured by the total number of days spent in bed during one week. Results.,Post hoc comparisons, using Bonferroni adjustments, indicated significant differences in adjusted means on self-reported orthostatic intolerance between the comparative and high (CI: ,4·12, ,0·85; p < 0·001), and the moderate and high (CI: 0·35, 3·56, p < 0·01) bed rest dose cohorts. No group differences were found on orthostatic vital signs. Conclusions., A moderate dose of bed rest with intermittent exposure to upright posture may protect against subjective orthostatic intolerance in patients who are unable to tolerate being out of bed every day. Future research may examine the effects of reducing bed rest days on orthostatic intolerance in individuals with high doses of five to seven days of bed rest. [source] Recurrent Syncope in a Patient After Myocardial InfarctionPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4p1 2003SUSANNE C. CREDNER CREDNER, S.C., et al.: Recurrent Syncope in a Patient After Myocardial Infarction. A patient with ischemic cardiomyopathy presented with burning pain of his body surface with consecutive orthostatic intolerance and recurrent syncopes. A diagnosis of acute autonomic dysfunction was made and the patient was treated with midodrine, resulting in restoration of orthostatic tolerance after 6 weeks of therapy. (PACE 2003; 26[Pt. I]:920,921) [source] Physiologic neurocirculatory patterns in the head-up tilt test in children with orthostatic intolerancePEDIATRICS INTERNATIONAL, Issue 2 2008Zhang Qingyou Abstract Background: Orthostatic intolerance (OI) is a common clinical manifestation in clinical pediatrics. The head-up tilt (HUT) table test is considered the standard of orthostatic assessment, but the physiologic neurocirculatory profile during HUT has not been fully realized in children with OI. The present study, therefore, was designed to investigate the physiologic patterns that occur during HUT in children with OI. Methods: Ninety children (56 girls; mean age, 11.6 ± 2.3 years) with OI underwent HUT under quiet circumstances. Blood pressure and heart rate were monitored simultaneously. Results: Forty-nine children with OI (54.4%) had vasovagal response with HUT testing; 33 (36.7%), vasodepressor response; six (6.7%), cardioinhibitory response; and 10 (11.1%), mixed response. Twenty-eight children (31.1%) had postural orthostatic tachycardia; one (1.1%), orthostatic hypotension (OH); and 12 (13.3%), normal physiologic response. Patterns of cerebral syncope response and chronotropic incompetence were not observed. Conclusions: Classical vasovagal response was the major physiologic pattern seen in children with OI during HUT testing, and postural orthostatic tachycardia response ranked second. [source] Functional alterations of mesenteric vascular bed, vas deferens and intestinal tracts in a rat hindlimb unloading model of microgravityAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 2 2004G. De Salvatore Summary 1 Prolonged bed rest or exposure to microgravity may cause several alterations in autonomic nervous system response (ANSR). 2 Hindlimb unloading (HU) rats were used as an animal model of simulated microgravity to investigate ANSR changes. The experiments were carried out to investigate the effects of simulated microgravity on the autonomic nervous response of the perfused mesenteric vascular bed (MVB), vas deferens and the colon and duodenum from 2-week HU rats. 3 In MVB preparations of HU rats, the frequency-dependent increases in perfusion pressure with perivascular nerve stimulation (PNS; 8,40 Hz) were inhibited, whereas the noradrenaline (NA) concentration-dependent (1,100 ,m) perfusion pressure increases were potentiated. The latter most probably reflected up-regulation of , -adrenergic receptor function. Relaxant responses of NA-precontracted MVB to PNS (4,30 Hz) or isoprenaline were not different between control and HU preparations, while vasodilation induced by the endothelial agonist ACh was reduced. 4 Transmural stimulation (2,40 Hz) induced frequency-dependent twitches of the vas deferens which were reduced in vas deferens of HU rats, while the sensitivity to NA-induced contraction was significantly increased. 5 In the gastroenteric system of HU rat, direct contractile responses to carbachol or tachykinin as well as relaxant or contractile responses to nervous stimulation appeared unchanged both in the proximal colon rings and in duodenal longitudinal strips. 6 In conclusion, HU treatment affects peripheral tissues in which the main contractile mediators are the adrenergic ones such as resistance vessels and vas deferens, probably by reducing the release of neuromediator. This study validates NA signalling impairment as a widespread process in microgravity, which may most dramatically result in the clinical phenotype of orthostatic intolerance. [source] L-Dihydroxyphenylserine (L-DOPS): A Norepinephrine ProdrugCARDIOVASCULAR THERAPEUTICS, Issue 3-4 2006David S. Goldstein ABSTRACT L- threo -3,4-dihydroxyphenylserine (L-DOPS, droxydopa) is a synthetic catecholamino acid. When taken orally, L-DOPS is converted to the sympathetic neurotransmitter, norepinephrine (NE), via decarboxylation catalyzed by L-aromatic-amino-acid decarboxylase (LAAAD). Plasma L-DOPS levels peak at about 3 h, followed by a monoexponential decline with a half-time of 2 to 3 h. Plasma levels of NE and of its main neuronal metabolite, dihydroxyphenylglycol (DHPG) peak approximately concurrently but at much lower concentrations. The relatively long half-time for disappearance of L-DOPS from plasma, compared to that of NE, explains their very different attained plasma concentrations. In patients with neurogenic orthostatic hypotension, L-DOPS increases blood pressure and ameliorates orthostatic intolerance. Inhibition of LAAAD, such as by treatment with carbidopa, which does not penetrate the blood-brain barrier, prevents the blood pressure effects of the drug, indicating that L-DOPS increases blood pressure by augmenting NE production outside the brain. Patients with pure autonomic failure (which usually entails loss of sympathetic noradrenergic nerves), and patients with multiple system atrophy (in which noradrenergic innervation remains intact) have similar plasma NE responses to L-DOPS. This suggests mainly non-neuronal production of NE from L-DOPS. L-DOPS is very effective in treatment of deficiency of dopamine-beta-hydroxylase (DBH), the enzyme required for conversion of dopamine to NE in sympathetic nerves. L-DOPS holds promise for treating other much more common conditions involving decreased DBH activity or NE deficiency, such as a variety of syndromes associated with neurogenic orthostatic hypotension. [source] | ||||||||||