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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many of the primary symptoms of orthostatic intolerance (fatigue, diminished concentration) as well as some of the premonitory symptoms of neurally mediated syncope (NMS) are thought to be due to cerebral hypoperfusion. Transcranial Doppler measurements of middle cerebral artery blood velocity (CBV) is at present the only technique for assessing rapid changes in cerebral blood flow, and hence for evaluating dynamic cerebral autoregulation. However, controversies exist regarding data interpretation. At syncope, during the collapse of blood pressure (BP), diastolic CBV diminishes, whereas systolic CBV is maintained. Some consider this increase in CBV pulsatility to be indicative of a paradoxical increase in cerebrovascular resistance (CVR) prior to syncope. Others note that mean CBV decreases much less than does mean BP, implying that cerebral autoregulatory mechanisms are intact and functioning at syncope. Similarly, there is no evidence of impaired dynamic cerebral autoregulation, as measured by standard linear transfer-function analysis, in patients with NMS. Some patients with exaggerated postural tachycardia (POTS) have been found to have an excessive decrease in CBV during head-up tilt. Controversy exists as to whether this decrease results from an excessive sympathetic outflow to the cerebral vasculature or from hyperventilation. However, many other equally symptomatic patients with a similar hemodynamic profile of exaggerated tachycardia during head-up tilt have normal CBV changes during this maneuver and have normal dynamic cerebral autoregulation as determined by transfer-function analysis. Whether these discrepancies reflect different pathologies in patients with POTS is currently unknown.
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PMID:Cerebral autoregulation in orthostatic intolerance. 1145 6

(1) Clozapine, a neuroleptic known to carry a risk of agranulocytosis, can also induce myocarditis and dilated myocardiopathy. (2) Patients taking clozapine who develop dyspnoea, fatigue, chest pain or collapse should be screened for myocarditis, especially during the first weeks of treatment.
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PMID:Myocarditis due to clozapine. 1171 72

Severe stenosis may cause critical flow and wall mechanical conditions related to artery fatigue, artery compression, and plaque rupture, which leads directly to heart attack and stroke. The exact mechanism involved is not well understood. In this paper a nonlinear three-dimensional thick-wall model with fluid-wall interactions is introduced to simulate blood flow in carotid arteries with stenosis and to quantify physiological conditions under which wall compression or even collapse may occur. The mechanical properties of the tube wall were selected to match a thick-wall stenosis model made of PVA hydrogel. The experimentally measured nonlinear stress-strain relationship is implemented in the computational model using an incremental linear elasticity approach. The Navier-Stokes equations are used for the fluid model. An incremental boundary iteration method is used to handle the fluid-wall interactions. Our results indicate that severe stenosis causes considerable compressive stress in the tube wall and critical flow conditions such as negative pressure, high shear stress, and flow separation which may be related to artery compression, plaque cap rupture, platelet activation, and thrombus formation. The stress distribution has a very localized pattern and both maximum tensile stress (five times higher than normal average stress) and maximum compressive stress occur inside the stenotic section. Wall deformation, flow rates, and true severities of the stenosis under different pressure conditions are calculated and compared with experimental measurements and reasonable agreement is found.
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PMID:Steady flow and wall compression in stenotic arteries: a three-dimensional thick-wall model with fluid-wall interactions. 1178 25

During sleep upper airway resistance increases proportionally with a slightly diminished air flow. This can however be compensated for by increasing inspiratory force that further aggravates airway collapse and resistance. Apnea during sleep results from an interaction between the different respiratory and pharynx muscles. Sleep modifies the activity of these muscles leading to increased resistance and muscle fatigue, then eventually histological modifications. Electrical activity is not always proportional to the generated force and muscle shortening, so the effect is not always an increased permeability. In apneic patients, the efficacy of these muscles is preserved but tissue response may be poor. Histological adaptations are variable and depend on the level of the pharynx and the variability of the site of obstruction. This raises the question of electrical stimulation of certain muscles and the choice of the site of stimulation.
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PMID:[Motor control of the upper airways]. 1192 44

Rear support walking frames provide predetermined vertical support for patients with dysfunctional lower limbs that have limited active control; the support is provided through a spring-loaded boom hinged on an upright stanchion mounted at the rear of a wheeled frame within which the patient ambulates. The application of these frames for total-body-involved cerebral palsy patients, in combination with a walking orthosis, has highlighted a number of practical problems that need to be addressed for the system to become fully viable. A composite material prototype walking frame has been developed that permits the patient to be transferred by a single carer without the need to use inappropriate manual handling techniques. The frame has improved structural properties, with stiffness in the sagittal and coronal planes increasing by between 50 and 100 per cent. Evaluation with patients showed that the greater structural stiffness permitted the objective of improved continuity of walking to be achieved. The strength of the frame is such that it can accommodate patients of up to 80 kg, more than twice that possible in the earlier system. Since the structural yield point is approximately twice the maximum working load, the device should not be prone to unacceptable fatigue characteristics. Despite the use of carbon composite materials (which have brittle failure characteristics), the mode of failure is of progressive collapse and is therefore inherently safe. The successful outcome of prototype testing has justified production development. Work is now proceeding on a design that incorporates further improvements in structural performance and ease of manufacture.
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PMID:Structural design and performance of a rear support walking frame. 1213 87

Knowledge of the fatigability of the genioglossus muscle is of interest because this muscle prevents pharyngeal collapse, especially during sleep. In the present investigation, signs of fatigue in the genioglossus muscle were studied by measuring the tongue endurance using a force transducer and electromyographic (EMG) activity of the genioglossus muscle in eight nonapnoeic men. Mean absolute EMG values and spectrum analysis were calculated at three levels of submaximal effort. Median frequency and the force:mean absolute EMG value ratio were independent of force level (F = 0.37, P = 0.93; F = 0.35, P = 0.94, respectively) but dependent on effort duration (F = 52, P < 0.0001; F = 16, P < 0.0001). Force:mean absolute EMG value and logarithmic median frequency decreased linearly with respect to time and were similar at the three force levels when time was expressed as a percentage of total test time (F = 0.37, P = 0.93). The decrease in median frequency was ascribable to a larger increase in low- than in high-frequency components, as shown by the significant decrease in the high-frequency:low-frequency ratio (F = 27, P < 0.0001) with time. The method of investigation used in this study allowed detection of the behaviour of the tongue during fatigue and, therefore, should be useful in disorders where mechanical failure of the tongue is suspected, such as the sleep apnoea syndrome or in neuromuscular disorders.
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PMID:Genioglossal electromyogram during maintained contraction in normal humans. 1243 87

Multiple myeloma (MM) is a plasma cell malignancy characterized by infiltration of bone marrow, bone destruction, infiltration of soft tissues with plasma cells, and suppression of normal hematopoiesis. The production of monoclonal immunoglobulins with or without light chains is a major feature of the disease. Full spectrum of plasma cell dyscrasias include monoclonal gammapathy of undetermined significance, smouldering myeloma, indolent multiple myeloma, and fully developed, symptomatic multiple myeloma. The usual presenting features of MM include bone pain, weakness, fatigue, fever and infection. Neurologic symptoms are less common but one must not forget that MM may present with a neurologic disease. Careful neurologic history and examination are mandatory in patients with MM. Neurologic symptoms may be a direct manifestation of MM or may be due to the immune effect of monoclonal proteins directed against different neural structures. Finally, metabolic consequences (uremia, hypercalcemia, hyperviscosity) of MM may produce a broad spectrum of different neurologic symptoms including headache, blurring of vision, drowsiness, precoma, coma, vertigo, ataxia, hemiparesis and epileptiform seizures. The most common location of bone changes in MM is the thoracic spine, where it causes osteolytic changes with consequent compressive fractures. The most disastrous sequel is paraplegia. Multiple vertebral involvement with the evidence of osteolytic changes in other bones is usual, but solitary vertebral myeloma may occur. Myeloma usually involves the bone of the vertebral body and then spreads into the extradural space. However, patients with solitary extradural myeloma have been reported. Skull myeloma is frequently asymptomatic. It may grow externally or, rarely, there is intracranial expansion. Involvement of the cranial nerves is not rare, with II, V, VI, VII and VIII cranial nerves being most often affected. Isolated intracerebral plasmacytomas are extremely rare. Diagnostic approach includes plain X-rays of the skeleton, which was found to be the method of choice for demonstration of osteolytic changes, whereas magnetic resonance with gadolinium enhancement most reliably displays the degree of vertebral involvement and demonstrates any associated soft tissue mass. Current treatment of osteolytic changes in multiple myeloma include chemotherapy, radiotherapy in combination with dexamethasone, monthly infusions of bisphosphonates, surgical decompression, and kyphoplasty. Therapeutic approach is dictated by the presenting symptoms. In case of pain as the predominant symptom, treatment with chemotherapy and radiotherapy may be appropriate. Compressive symptoms are relieved with dexamethasone followed by radiotherapy and chemotherapy. Surgical decompression is used in patients with vertebral collapse and vertebral instability. Kyphoplasty is a new method used in the treatment of osteolytic changes of vertebral bodies. A viscous cement is injected into the cavity by a balloon-like inflatable bone tampon. It has been successfully employed to improve the quality of life, to reduce pain, and to increase overall functioning in patients with vertebral compression fractures by restoring most of the original height of the vertebral body. Bisphosphonates reduce pain associated with osteolytic changes in multiple myeloma, but also significantly reduce skeletal events (pathologic fracture, spinal cord compression, surgery or irradiation of bone) via unknown mechanism. It seems that bisphosphonates, by inhibiting bone resorption, alter the microenvironment in which the MM cells grow.
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PMID:[Neurologic sequelae of bone changes in multiple myeloma and its therapy]. 1263 Mar 41

The late occurrence of complete atrio-ventricular block (CAVB) after cardiac surgery is rare but potentially responsible for cases of late sudden death. We searched for factors allowing prediction of this complication, retrospectively reviewing the case notes of 11 patients in hospital with complete AVB, 2 months to 10 years after correction of a cardiac malformation. All had a normal pre-operative ECG. The diagnosis had been made based on symptoms in 8 patients: syncope or collapse (4 cases) symptoms on effort (3 cases) or fatigue (1 case). In the others the diagnosis had been made on ECG. The block was infra-His in 5 patients who had electrophysiology. ECG analysis showed that all the patients had CAVB immediately post-operatively lasting 3-14 days. After restoration of conduction the ECGs showed the following anomalies compared to the pre-operative ECGs: long PR (1 case), long PR + right bundle branch block (2 cases), long PR + left axis deviation (1 case), RBBB + left deviation or rotation of the QRS axis (3 cases), long PR + RBBB + left axis deviation (4 cases). All of these patients had been fitted with a cardiac stimulator. In conclusion, the children who had CAVB immediately post-operatively lasting more than 48 hours and who then had an ECG showing different QRS compared to the pre-operative QRS and/or long PR had a risk of late complete AVB. These patients should have electrophysiology and a stimulator must be implanted in those who have an infra-His block.
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PMID:[Predictive factors for late complete atrio-ventricular block after surgical treatment for congenital cardiopathy]. 1283 40

The new demands placed upon application equipment by the introduction of modern insecticides have revealed the deficiencies of this equipment when required for continuous use on a large scale. If adequate equipment is to be produced, specifications must be based not only on basic materials tests but also on "use" tests, in which the conditions of field use are simulated.THE AUTHOR OUTLINES SUGGESTED TECHNIQUES TO BE FOLLOWED AND STANDARDS TO BE ADOPTED IN TESTING THE PERFORMANCE OF COMPRESSION SPRAYERS AND ALLIED EQUIPMENT, WITH REFERENCE TO THE FOLLOWING FEATURES: compression-sprayer tank fatigue; tank impact; pump resistance to bursting; pump resistance to collapse; pump friction; cut-off valve durability; constant-pressure valves; cut-off valve actuation; hose flexure; hose tension and bursting-pressure; hose friction; gaskets, valve faces, and similar non-metallic parts; nozzle-orifice erosion; and nozzle pattern.
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PMID:Suggested techniques, equipment, and standards for the testing of hand insecticide-spraying equipment. 1436 89

During the U.S. Food and Drug Administration's advisory panel hearings to evaluate the premarket approval for conventional silicone gel implants on October 14 and 15, 2003, panel members and patient advocate representatives focused on four specific areas of concern: reoperation rates in primary breast augmentation; levels, depth, and methods of patient education and informed consent; modes, frequency, and management of silicone gel implant device failures, including management of "silent" ruptures; and methods of monitoring and managing symptoms or symptom complexes that may or may not be associated with connective tissue disease or other undefined symptom complexes. These concerns, with a reported 20 percent reoperation rate for primary augmentation within just 3 years, and a lack of concise, definitive management protocols addressing these areas of concern may have contributed to the Food and Drug Administration's rejection of the premarket approval, despite the panel's recommendation for approval. This article presents decision and management algorithms that have been used successfully for 7 years in a busy breast augmentation practice (Tebbetts and Tebbetts). The algorithms have been further expanded and refined by a group of surgeons with diverse experiences and expertise to address the following clinical situations that coincide with concerns expressed by patients and the Food and Drug Administration: implant size exchange, grade III to IV capsular contracture, infection, stretch deformities (implant bottoming or displacement), silent rupture of gel implants, and undefined symptom complexes (connective tissue disease or other). In one practice (Tebbetts and Tebbetts) that uses the TEPID system (tissue characteristics of the envelope, parenchyma, and implant and the dimensions and fill distribution dynamics of the implant), implant selection is based on quantified patient tissue characteristics, pocket selection is based on quantified soft-tissue coverage, and anatomic saline implants have fill volumes that are designed to minimize shell collapse and fold fatigue; in this practice, the algorithms contributed to a 3 percent overall reoperation rate in 1662 reported cases with up to 7 years of follow-up, compared with a 20 percent reoperation rate at 3 years in the 2003 premarket approval study.
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PMID:Decision and management algorithms to address patient and food and drug administration concerns regarding breast augmentation and implants. 1545 45


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