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Head-up Tilt (head-up + tilt)
Terms modified by Head-up Tilt Selected AbstractsThe role of the ,-adrenergic receptor in the leg vasoconstrictor response to orthostatic stressACTA PHYSIOLOGICA, Issue 3 2009M. Kooijman Abstract Aim:, The prompt increase in peripheral vascular resistance, mediated by sympathetic ,-adrenergic stimulation, is believed to be the key event in blood pressure control during postural stress. However, despite the absence of central sympathetic control of the leg vasculature, postural leg vasoconstriction is preserved in spinal cord-injured individuals (SCI). This study aimed at assessing the contribution of both central and local sympathetically induced ,-adrenergic leg vasoconstriction to head-up tilt (HUT) by including healthy individuals and SCI, who lack central sympathetic baroreflex control over the leg vascular bed. Methods:, In 10 controls and nine SCI the femoral artery was cannulated for drug infusion. Upper leg blood flow (LBF) was measured bilaterally using venous occlusion strain gauge plethysmography before and during 30° HUT throughout intra-arterial infusion of saline or the non-selective ,-adrenergic receptor antagonist phentolamine respectively. Additionally, in six controls the leg vascular response to the cold pressor test was assessed during continued infusion of phentolamine, in order to confirm complete ,-adrenergic blockade by phentolamine. Results:, During infusion of phentolamine HUT still caused vasoconstriction in both groups: leg vascular resistance (mean arterial pressure/LBF) increased by 10 ± 2 AU (compared with 12 ± 2 AU during saline infusion), and 13 ± 3 AU (compared with 7 ± 3 AU during saline infusion) in controls and SCI respectively. Conclusion:, Effective ,-adrenergic blockade did not reduce HUT-induced vasoconstriction, regardless of intact baroreflex control of the leg vasculature. Apparently, redundant mechanisms compensate for the absence of sympathetic ,-adrenoceptor leg vasoconstriction in response to postural stress. [source] Effects of alcohol and smoking during pregnancy on infant autonomic controlDEVELOPMENTAL PSYCHOBIOLOGY, Issue 3 2009William P. Fifer Abstract Prenatal exposure to smoking and alcohol increases the risk for Sudden Infant Death Syndrome (SIDS). Physiological changes associated with these exposures are not well studied. Full-term infants were tested within the first 3 days of life. We hypothesized that maternal alcohol consumption and/or smoking during pregnancy would alter autonomic nervous system function. Newborns whose mothers smoked during pregnancy had lower beat-to-beat heart rate variability in quiet sleep. Infants whose mothers consumed alcohol had lower global heart rate variability, but only in active sleep. Unexposed infants demonstrated increases in heart rate with head-up tilt and decreases in heart rate with head-down tilt, but smoking and alcohol-exposed infants showed no significant responses. These results indicate that autonomic function is altered by prenatal exposure to alcohol and smoking. Such markers may provide early identification of infants at greatest risk for SIDS. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 234,242, 2009 [source] Abnormal cardiovascular responses to carotid sinus massage also occur in vasovagal syncope , implications for diagnosis and treatmentEUROPEAN JOURNAL OF NEUROLOGY, Issue 8 2010A. M. Humm Background and purpose:, Carotid sinus massage (CSM) is commonly used to identify carotid sinus hypersensitivity (CSH) as a possible cause for syncope, especially in older patients. However, CSM itself could provoke classical vasovagal syncope (VVS) in pre disposed subjects. Methods:, Retrospective analysis of CSM, cardiovascular autonomic function tests (including tilt table testing) and medical history in 388 patients with recurrent syncope to identify and characterize patients in whom an abnormal response to CSM was more likely to reflect VVS than CSH. Results:, CSM was abnormal in 79 patients. In 53 patients (77.2 ± 8.7 years), CSH was the likely cause of syncope. VVS was the more likely diagnosis in 26 younger patients (59.7 ± 12.6 years) with longstanding syncope from youth, in whom fear or pain was as a trigger; 7/26 suffered from intense chronic or intermittent neck pain and one exacerbation of syncopal attacks followed a physical and emotional trauma to the neck. In VVS, 4/26 had spontaneous VVS during head-up tilt, another six after venepuncture (performed in 17/26). In 6/26, the abnormal response to CSM was delayed, occurring 62.8 ± 28.4 s after completion of CSM. The response to CSM was predominantly of the mixed type (20/26) and abnormal on both sides in 14/26. Conclusions:, An abnormal response to CSM may not indicate syncope caused by CSH and needs to be considered in the light of the patient's age, duration of syncopal episodes and detailed history of provocative stimuli. Differentiating CSH from VVS with an abnormal response to CSM has various implications from advice on driving to treatment strategies. [source] Reliability of orthostatic responses in healthy men aged between 65 and 75 yearsEXPERIMENTAL PHYSIOLOGY, Issue 4 2005Tim J. Gabbett The purpose of this study was to investigate the short-, medium- and long-term reproducibility of cardiovascular responses during 90° head-up tilt (HUT) in healthy older men. Twenty-eight healthy male subjects aged 69 (95% confidence intervals, 68,70) years participated in the study. Eight subjects underwent duplicate 90° HUT tests on consecutive days, while 20 subjects underwent four 90° HUT tests performed at baseline, and after 1 week, 1 month and 1 year. Following a 20-min supine resting period, each subject was rapidly tilted to the upright vertical position (90° HUT) and remained in that position for 15 min. Beat-by-beat recordings of mean (MAP), systolic (SBP) and diastolic (DBP) pressures were made via Finapres, while heart rate (HR) was monitored continuously from an electrocardiogram. No significant test,retest differences (P > 0.05) were observed for the changes in HR, MAP, SBP or DBP during 90° HUT. These measurements demonstrated high reproducibility (intraclass correlation coefficient, r= 0.91,0.99, P < 0.05). The supine resting and tilted HR, MAP, SBP and DBP over the 1-week, 1-month and 1-year period were not significantly different (P > 0.05) from baseline, and demonstrated high reproducibility (intraclass correlation coefficient, r= 0.82,0.98, P < 0.05). The results of this study demonstrate that in healthy older men, cardiovascular responses during orthostasis are highly reproducible, and this reproducibility is maintained over a 12-month period. These findings demonstrate that the 90° HUT test offers a reproducible method of monitoring longitudinal orthostatic responses in healthy older men. [source] Pneumoperitoneum versus abdominal wall lift: effects on central haemodynamics and intrathoracic pressure during laparoscopic cholecystectomyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2003L. Andersson Background:, It has been shown repeatedly that laparoscopic cholecystectomy using pneumoperitoneum (CO2 insufflation) may be associated with increased cardiac filling pressures and an increase in blood pressure and systemic vascular resistance. In the present study, the effects on the central circulation during abdominal wall lift (a gasless method of laparoscopic cholecystectomy) were compared with those during pneumoperitoneum. The study was also aimed at elucidating the relationships between the central filling pressures and the intrathoracic pressure. Methods:, Twenty patients (ASA I), scheduled for laparoscopic cholecystectomy, were randomised into two groups, pneumoperitoneum or abdominal wall lift. Measurements were made by arterial and pulmonary arterial catheterization before and during pneumoperitoneum or abdominal wall lift with the patient in the horizontal position. Measurements were repeated after head-up tilting the patients as well as after 30 min head-up tilt. The intrathoracic pressure was monitored in the horizontal position before and during intervention using an intraesophageal balloon. Results:, After pneumoperitoneum or abdominal wall lifting there were significant differences between the two groups regarding MAP, SVR, CVP, CI, and SV. Analogous to previous studies, in the pneumoperitoneum group CVP, PCWP, MPAP, and MAP as well as SVR were increased after CO2 insufflation (P < 0.01), while CI and SV were not affected. In contrast, in the abdominal wall lift group, CI and SV were significantly increased (P < 0.01), as was MAP (P < 0.01), while CVP, PCWP, MPAP, and SVR were not significantly affected. There was a significant difference in intraesophageal pressure between the two groups. In the pneumoperitoneum group, the intraesophageal pressure was increased by insufflation (P < 0.01) while, in the abdominal wall lift group, it was unaffected. In the pneumoperitoneum group the mean increases in cardiac filling pressures were of the same magnitude as the mean increase in the intraesophageal pressure. Conclusions:, In healthy patients, abdominal wall lift increased cardiac index while pneumoperitoneum did not. Cardiac filling pressures and systemic vascular resistance were increased by pneumoperitoneum but unaffected by abdominal wall lift. The recorded elevated cardiac filling pressures during pneumoperitoneum may be only a reflection of the increased intra-abdominal pressure. [source] Effects of Head-Up Tilt-Table Test on the QT IntervalANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2010Michael Findler M.D. Background. The QT interval shortens in response to sympathetic stimulation and its response to epinephrine infusion (in healthy individuals and patients with long QT syndrome) has been thoroughly studied. Head-up tilt-table (HUT) testing is an easy way to achieve brisk sympathetic stimulation. Yet, little is known about the response of the QT interval to HUT. Methods. We reviewed the electrocardiograms of HUT tests performed at our institution and compare the heart rate, QT, and QTc obtained immediately after HUT with the rest values. Results. The study group consisted of 41 patients (27 females and 14 males) aged 23.9 ± 8.4 years. Head-up tilting led to a significant shortening of the RR interval (from 825 ± 128 msec at rest phase to 712 ± 130 msec in the upward tilt phase, P < 0.001) but only to a moderate shortening of the QT interval (from 363.7 ± 27.9 msec during rest to 355 ± 30.3 msec during upward tilt, P = 0.001). Since the RR interval shortened more than the QT interval, the QTc actually increased (from 403 ± 21.5 msec during rest phase to 423.2 ± 27.4 msec during upward tilt, P < 0.001). The QTc value measured for the upward tilt position was longer than the resting QTc value in 33 of 41 patients. Of those, 4 male patients and 2 female patients developed upward-tilt QTc values above what would be considered abnormal at rest. Conclusions. During HUT the QT shortens less than the RR interval. Consequently, the QTc increases during head-up tilt. Ann Noninvasive Electrocardiol 2010;15(3):245,249 [source] Orthostatic heart rate variability analysis in idiopathic Parkinson's diseaseACTA NEUROLOGICA SCANDINAVICA, Issue 5 2006E. Mihci Objectives ,, We evaluated time and spectral analyses of 24-h heart rate variability (HRV) and the heart rate responses to passive tilt in patients with idiopathic Parkinson's disease (IPD) in order to investigate cardiovascular autonomic functions. Material and methods ,, Twenty-three subjects with IPD without autonomic symptoms and 15 age-matched healthy controls were enrolled. Frequency- and time-domain HRV parameters were studied during resting and passive head-up tilt (HUT) test. Results ,, All time-domain parameters were found to be low in patients with IPD. In patients with IPD, both low frequency (LF) and high frequency (HF) decreased during HUT period and no significant change in LF to HF ratio was noted. Both time- and frequency-domain HRV indices showed no correlation with age, disease severity and duration, and with l -dopa medication. Conclusion ,, The results indicate that impairment of autonomic nervous system function in IPD without autonomic symptoms is frequent, and does not show clear association with clinical stage and the age of the patients. [source] Hemodynamic significance of heart rate in neurally mediated syncopeCLINICAL CARDIOLOGY, Issue 11 2004Wan Leong Chan M.D. Abstract Background: Vasovagal and vasodepressor syncope are used interchangeably in the literature to describe the common faint syndrome, now collectively named neurally mediated syncope. The significance of heart rate (HR) in these reflex-induced reactions remains unclear. Hypothesis: The study was undertaken to investigate the hemodynamic significance of HR in tilt-induced neurally mediated syncope. Methods: In all, 113 patients with syncope of unknown etiology were studied by head-up tilt test with invasive hemodynamic monitoring. Thirty-five patients (15 women, 20 men, age range 21 to 72 years) developed syncope and were enrolled for analysis. The hemodynamic data were compared between patients who developed bradycardia (vasovagal group, n = 15) and those without bradycardia (vasodepressor group, n = 20). Results: The baseline hemodynamic data (mean ± standard deviation) and the hemodynamic responses after 10-min head-up tilt were similar between patients in the vasovagal and vasodepressor groups. During syncope, patients with vasovagal reaction developed hypotension and paradoxical bradycardia (HR = 52.4 ± 5.9 beats/min), while patients with vasodepressor reaction developed a precipitous drop in arterial blood pressure with inappropriate HR (105 ± 21 beats/min) compensation. Patients with vasovagal syncope manifested a significantly lower cardiac index and a significantly higher systemic vascular resistance index than patients with vasodepressor syncope (1.47 ±0.29 vs. 1.97 ±0.41 l/min/m2, p< 0.001 and 2098 ± 615 vs. 1573 ± 353 dynes·s·cm,5·m2, p<0.003, respectively). A positive correlation existed between HR and cardiac index (r = 0.44, p = 0.008) during syncope in the patients studied. Conclusions: These findings suggest that the hemodynamic characteristics of vasovagal and vasodepressor reactions are different, and that HR plays a significant role in neurally mediated syncope. [source] Human in vivo study of the renin,angiotensin,aldosterone system and the sympathetic activity after 8 weeks daily intake of fermented milkCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 2 2010Lotte Usinger Summary Objective:, Milk fermented by lactic acid bacteria is suggested to have antihypertensive effect in humans. In vitro and animal studies have established an angiotensin-converting enzyme (ACE) inhibitor effect of peptides in fermented milk. However, other modes of action must be considered, because until today no human studies have confirmed an ACE inhibition in relation to the intake of fermented milk. Materials and methods:, We undertook a double-blinded randomized placebo-controlled study including 94 borderline-hypertensive persons to study the effect on human physiology of Lactobacillus helveticus fermented milk. The subjects were randomized into three groups: Cardi04-300 ml, Cardi04-150 ml or placebo. All components of the renin,angiotensin,aldosterone system were measured several times. Sympathetic activity was estimated by plasma noradrenaline and cardiovascular response to head-up tilt at baseline and after 8 weeks of intervention. Results:, No ACE inhibition of the fermented milk was demonstrated, as none of the components of the renin,angiotensin,aldosteron system changed. Plasma noradrenaline response to tilt test after intervention stayed unchanged between groups (P = 0·38), but declined in the group Cardi04-300 from 2·01 ± 0·93 nmol l,1 at baseline to 1·49 ± 0·74 nmol l,1 after 8 weeks (P = 0·002). There was no change in 24-h ambulatory blood pressure or heart rate between groups. Conclusions:, Despite a known ACE inhibitory effect in vitro and in animals, milk fermented with Lb. helveticus did not inhibit ACE in humans. Our results suggest that the intake of fermented milk decreases sympathetic activity, although not to an extent mediating reductions of blood pressure and heart rate in borderline-hypertensive subjects. [source] Cerebral oxygenation monitor during head-up and -down tilt using near-infrared spatially resolved spectroscopy,CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2003Koichi Kurihara Summary Reflectance near-infrared spectroscopy (NIRS) has become a suitable and easily manageable method to monitor cerebral oxygenation changes in presyncopal and syncopal symptoms caused by postural changing or standing. A new clinical tissue oxygenation monitor has been recently developed which measures absolute tissue haemoglobin saturation (Tissue Oxygenation Index, TOI) utilizing spatially resolved spectroscopy (SRS). The present study examined the effects of postural changes on cerebral oxygenation as reflected in SRS-NIRS findings. Cerebral oxyhaemoglobin (O2Hb), deoxyhaemoglobin (HHb), and the TOI were recorded from both sides of the forehead in five healthy male subjects (age range, 28,40 years) during 90° head-up tilt (HUT) and ,6° head-down tilt (HDT). Three series of measurements were carried out on separate days. O2Hb was decreased during HUT. TOI was significantly lower in HUT than in the supine position (SUP). There was no significant change in TOI during HDT. A significant session effect was observed in the left forehead TOI during SUP, but not in the right. SRS-NIRS measurements confirmed sub-clinical alterations of cortical oxygenation during HUT. NIRS data from the left side of the forehead, which may vary with cognitive or emotional activation, were more variable than those from the right side. [source] | ||||||||||||||||||||||