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At least 1,189 records · Page 66Linked to original sources
PubMed1992

Prolonged asystole during head-up tilt table testing after beta blockade.

Neurally mediated vasodepressor syncope is a common clinical problem. The diagnosis is generally associated with a benign prognosis, however, a less common "malignant" form has been identified. Head-up tilt table testing is helpful in the confirmation of the diagnosis of neurally mediated vasodepressor syncope and may be useful in the selection of therapy. One form of therapy commonly used is beta blockade. In this case report we describe a patient with neurally mediated vasodepressor syncope who developed asystole during head-up tilt table testing after treatment with a beta blocker.

Adrenergic beta-Antagonists↗
PubMed2004

Incorrect instruction in the use of the Valsalva manoeuvre for paroxysmal supra-ventricular tachycardia is common.

OBJECTIVE: Success rates for the Valsalva manoeuvre (VM) in treatment of paroxysmal supraventricular tachycardia (SVT) vary with performance technique. This study aimed to assess whether ED doctors instruct their patients to perform the recommended VM technique (supine position for 15 s). METHODS: A multicentre, observational study of 35 ED registrars and 17 emergency physicians. Each doctor was asked to describe how he/she would instruct a patient in SVT to perform the VM. RESULTS: Only five (9.6%) doctors would position their patient correctly and 31 (59.6%) would incorrectly instruct their patient to assume a sitting or semirecumbent position. Only five (9.6%) doctors would give specific instructions to blow for at least 15 s and 34 (65.4%) would instruct their patient to blow 'as long as you can'. Only four (7.4%) doctors would use a sphygmomanometer to measure intrathoracic pressure during the VM. There were no significant differences (P > 0.05) between the registrar and physician group responses for any study endpoint. CONCLUSION: Few ED doctors correctly instruct their patients in the VM technique recommended for management of SVT. Hence, maximal vagal tone and SVT conversion rates may not be achieved in many cases. The use of the recommended VM technique is encouraged.

Clinical Competence↗
PubMed1981

Duration of increase in vascular volume during venous stasis.

Duration of increase in vascular volume in the crus following application of venous stasis was studied in 3 healthy subjects placed in a supine position. Changes in calf volume during venous stasis was measured by plethysmography. In one series of experiments changes in vascular volume were studied by measurements of accumulation of 133Xenon proximal to a depot located in the anterior tibial muscle. In another series of experiments changes in activity of 99mTc-labelled erythrocytes were used as indicator for changes in vascular volume. Following application of venous stasis in the horizontal position the rate of increase in calf volume declined to a steady level after about 5 min. Both the studies with 133Xenon and with 99mTc-erythrocytes indicate that vascular volume continued to increase for 3, 3.5 and 5 min following venous stasis of 20, 30 and 40 mmHg, respectively. When the crus was lowered 50 cm below heart level the duration of increase in vascular volume following an additional increase in venous pressure induced by venous stasis was shorter than in the horizontal position. When the calf is placed at heart level the results indicate that for up to 5 min after application of venous stasis of 40 mmHg both increase in vascular volume and transcapillary fluid filtration contribute to the observed increase in calf volume. Using the rate of increase in calf volume within 5 min after induction of venous stasis thus leads to overestimation of CFC. After 5 min vascular volume appears to remain constant and the observed increase in calf volume seems to be solely due to a net increase in interstitial fluid volume.

Axons↗
PubMed1981

Eye movements in patients with Wallenberg's syndrome.

We studied electro-oculographic and videotape recordings of eye movements in six patients with Wallenberg's syndrome. With fixation, all patients had a spontaneous rotatory nystagmus with the fast phase directed toward the intact side. With loss of fixation, the patients' eyes deviated tonically toward the side of the lesion. Voluntary and involuntary saccades had larger amplitude when directed toward the side of the lesion than away from it. The spontaneous nystagmus predictably interacted with all slow eye movements, producing asymmetric smooth-pursuit, optokinetic, and vestibular responses. In addition, smooth-pursuit and optokinetic responses were decreased significantly in both directions compared to normal subjects. Fixation suppression of vestibular nystagmus also was impaired in both directions. We concluded that two different types of oculomotor bias were present in these patients--a velocity bias and a position bias. The former resulted from damage to the caudal lateral vestibular nuclei, and the latter from interruption of cerebellopontine pathways.

Adult↗
PubMed1981

Postural imbalance with head extension: improvement by training as a model for ataxia therapy.

Head extension may cause a physiological vertigo and postural imbalance separate and distinct from basilar insufficiency. This physiological imbalance mainly is due to a vestibular sensory deficiency when the utricular otoliths are beyond their working range because of the change in head position. Since the intact visual and somatosensory control hope widely compensate for the vestibular deficiency, head-extension vertigo is of particular concern only in certain stimulus situations or diseases in which the stabilizing input from the eyes or joint receptors is reduced. Balance training on foam rubber with head extension and closed eyes improved postural-sway activity up to 50% within five days. A daily short-term training effect and a long-term training effect together form a typical exponential sawtooth curve of postural stability over time. After termination of training, learned balance skill exponentially returns to the pretraining values within weeks. The percentage of improvement through training depends on the amount of initial instability. Clinicians should treat ataxia by exposing patients to stimulus situations producing increasing body instability in order to activate sensorimotor rearrangement.

Adolescent↗
PubMed1992

Mislocalizations of visual elevation and visual vertical induced by visual pitch: the great circle model.

The elevation visually perceived as eye level (VPEL) changes linearly with the pitch of an illuminated visual field. The magnitude of influence is only slightly less when the visual field contains only two dim vertical lines in darkness than when it is complexly structured and normally illuminated. Pitching a visual field consisting of only a single line in darkness produces an influence that is only slightly smaller than the 2-line stimulus. The slopes of the VPEL-vs.-pitch functions for the complex room, 2-line stimulus, and 1-line stimulus are +0.63, +0.56, and +0.52 respectively. Although VPEL is systematically influenced by the pitch of the 2-line stimulus, the orientation of a small line within a frontal plane that is visually perceived as vertical is unaffected. However, when the two lines are pitched by equal amounts in opposite directions, the offset of VPV from true vertical changes linearly with pitch magnitude but VPEL is unaffected. These results are identical to those obtained when the two vertical lines are rolled within the frontal plane, a result that depends on some identities between roll and pitch: roll of two parallel lines in the same direction influences VPV but not VPEL; roll of the two lines in opposite directions influences VPEL but not VPV. The interaction between stimulus conditions and discriminations demonstrates that separate mechanisms are in control of VPEL and of VPV. The slope of the VPEL-vs.-pitch function increases exponentially with line length for the 1-line stimulus (space constant = 15.1 degrees). Summation of influences on VPEL for two lines horizontally separated by 50.3 degrees is as great as for two coextensive lines. The above results are predicted from the Great Circle Model which assumes (1) central projection on a spherical approximation to an erect stationary eye; (2) the sign and magnitude of influence of each line on VPEL and on VPV are determined by the direction and magnitude of the separation between the upper pole of the spherical eye and the intersection of the great circle containing the line's image with the central vertical retinal meridian and with the midfrontal retinal meridian, respectively; (3) the influence of individual nonparallel lines is determined by a weighted average of the influences of individual sets of parallel lines; (4) a generalized version of the Great Circle Model is indicated in which extraretinal signals from head and eye are taken into account.

Curare↗
PubMed1996

Vestibular influences on the autonomic nervous system.

Considerable evidence exists to suggest that both sympathetic and respiratory outflow from the central nervous system are influenced by the vestibular system. Otolith organs that respond to pitch rotations seem to play a predominant role in producing vestibulo-sympathetic and vestibulo-respiratory responses in cats. Because postural changes involving nose-up pitch challenge the maintenance of stable blood pressure and blood oxygenation in this species, vestibular effects on the sympathetic and respiratory systems are appropriate to participate in maintaining homeostasis during movement. Vestibular influences on respiration and circulation are mediated by a relatively small portion of the vestibular nuclear complex comprising regions in the medial and inferior vestibular nuclei just caudal to Deiters' nucleus. Vestibular signals are transmitted to sympathetic preganglionic neurons in the spinal cord through pathways that typically regulate the cardiovascular system. In contrast, vestibular effects on respiratory motoneurons are mediated in part by neural circuits that are not typically involved in the generation of breathing.

Animals↗