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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hemodynamic effects of prolonged mechanical ventilation with positive end-expiratory pressure (PEEP), with and without blood volume augmentation, were studied in 18 beagles anesthetized with halothane (0.7 per cent end-tidal). Addition of 12 cm H2O PEEP during mechanical ventilation in normavolemic dogs was associated with reductions of transmural cardiac filling pressures, cardiac index and stroke index to 50 per cent of control values. Circulatory adaptation did not occur. Filling pressures and flow remained unchanged during the ensuing 8 hours when PEEP was maintained. They returned to control levels when PEEP was discontinued, except for the transmural right ventricular end-diastolic pressure, which remained elevated above control levels. Systemic vascular resistance was unchanged, but pulmonary vascular resistance doubled upon addition of PEEP. Following autologous whole blood transfusion (25 ml/kg) during mechanical ventilation with PEEP, cardiac index returned to, and remained at, control levels. After PEEP was discontinued, cardiac index increased acutely and remained elevated for the remainder of the study period (as long as 7 hours). Comparable transfusion during mechanical ventilation without PEEP elevated cardiac index only transiently. Right atrial, pulmonary capillary wedge, and right and left ventricular end-diastolic pressures showed marked increases relative to atmospheric with PEEP and after transfusion. Calculated transmural pressures demonstrated clear reductions with application of PEEP, followed by increases to control levels with transfusion and further increases to above control when PEEP was discontinued. Study of ventricular function curves revealed that changes in filling pressures and not to changes in ventricular contractility. Transmural pulmonary arterial diastolic pressure rose throughout the 12 hours of study, despite return of pulmonary vascular resistance to control level with removal of PEEP. Thus, acute decreases in cardiac filling pressure, cardiac index, and stroke index persist consequent to application of PEEP, and circulatory adaptation does not occur. The apparent hemodynamic deterioration may be reversed by blood volume augmentation, but when PEEP is discontinued, hypervolemia with consequent increases in filling pressures and a move along a ventricular function curve will occur. Changes in cardiac index will depend upon the overall state of right and left ventricular contractility.
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PMID:Hemodynamic responses to mechanical ventilation with PEEP: the effect of hypervolemia. 23 10

The effects of mechanical ventilation with and without positive end-expiratory pressure (PEEP) on hemodynamic performance and blood-gas exchange were studied in ten patients following open-heart surgery. Ventilation at constant tidal volume (15 ml/kg body weight) with 10 cm H2O PEEP following aortic valve replacement (AVR) IN FIVE PATIENTs without pulmonary vascular disease was associated with the following significant changes: a rise in arterial Po2, a fall in the alveolar-arterial Po2 gradient when Fio2 = 1.0, decreases in calculated Qs/Qt and cardiac index. Using a similar pattern of ventilation following mitral valve replacement (MVR) in patients with elevated pulmonary vascular resistance, we found a significant decrease in cardiac index (but less than in the AVR group), a significant elevation of calculated physiologic deadspace (Vd/Vt) and no change in Qs/Qt. An hour after removal of PEEP, intravascular pressures, blood flow and blood-gas exchange values of all patients with AVR had returned to control levels; patients with MVR had persistently significantly low cardiac indices, while Vd/Vt returned to pre-PEEP values. These findings suggest that evaluation of responses to different ventilation patterns must take into account pre-existing V/Q abnormalities secondary to pulmonary vascular disease, particularly when these are secondary to chronic congestive heart failure. Following AVR, Qs/Qt changed in the same direction as cardiac index (CI) irrespective of ventilatory pattern: CI decreased and rose as CI increased. The authors conclude that with increasing severity of pulmonary vascular disease, changes in airway pressure will have an unpredictable effect on cardiac index unless the level of myocardial competence is taken into account. In the presence of ventricular failure, changes in pleural (and therefore transmural) pressures will be minimal compared with the high filling pressures and exert no influence on stroke volume. Although pulmonary venous hypertension was more pronounded in the MVR than in the AVR group, there was no significant difference between the postoperative values for Qs/Qt (Fio2 = 1.0), a condition probably fostered by marked differences in pre-existing V/Q.
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PMID:The effect of pre-existing pulmonary vascular disease on the response to mechanical ventilation with PEEP following open-heart surgery. 23 11

The palate epithelium of the frog was examined by scanning electron microscopy, light microscopy and high speed cine micrography. The cilia remain stationary for much of time in the end-of-effective stroke position. Each beat cycle begins with a forwardly-directed recovery stroke lasting about 60 ms, followed by an effective stroke towards the oesophagus lasting about 12 ms. Activity can often be correlated with the presence of mucus, which is carried as strands on the tips of the ciliary effective strokes whilst the recovery strokes move beneath the mucus. Coordination of ciliary activity was very variable; local antiplectic metachrony of the recovery strokes could almost always be seen, and on very active epithelia effective strokes were associated with approximately diaplectic waves (either to left or right), but any particular pattern of coordinated activity was transient and quickly transformed to another pattern. Beating and coordination of these short cilia were compared with those of cilia propelling water.
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PMID:Ciliary function of the frog oro-pharyngeal epithelium. 30 Feb 83

The effects of elevated temperatures and the time-temperature combinations for irreversible damage are outlined. Coagulation abnormalities and the effects on the kidney, liver, heart, brain and serum enzymes, the role of electrolytes and water, including salt deficiency and the controversial question of salt supplements, potassium deficiency, changes in other electrolytes and sweat solutes, and rhabdomyolysis (including a discussion of experimental work on dogs) are reviewed. The section ends with a discussion of the effects of drugs and an account of a recent fatal case of heat stroke which may have been triggered by chlorpromazine therapy.
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PMID:Heat illness. II. Pathogenesis. 32 Jul 24

A 1974 showing of more than 200 oils and water colors at the Tate Gallery, London, has led to a revival of interest in the 19th century English painter, Richard Dadd (1817 to 1886). In 1843, Dadd killed his father, cutting his throat, because he believed him to be the devil in human form. On a trip to the Near East, Dadd became deluded that the Egyptian god Osiris was directing him to eliminate the devil's influence. Four months after he returned to London he murdered his father, and was institutionalized for the last 43 years of his life. We advance the hypothesis that one particular painting. 'The Fairy Feller's Master-Stroke,' symbolically re-enacts the murder and makes talion restitution. The painting shows minute attention to detail and altogether occupied the artist for 9 years. He also made a water color copy of it entirely from memory, and wrote a 22-page poem explaining the picture with the title, 'An Elimination.' We suggest that this hints at the same theme of undoing. Some art critics have seen in Dadd's other art works a projection of his inner feelings, especially a series of more than 30 water colors entitled 'Sketches to Illustrate the Passions,' amongthem 'Murder,' 'Anger,' 'Hatred,' 'Grief,' and 'Melancholy.' We construe these to support the thesis of redoing and undoing following the trauma of murder. We also mention Dadd's reminiscing, visible in his art, and its usefulness in reaffirming his self-identity. In the art work of Dadd's last 25 years, violent scenes are remarkably absent. Instead, imaginary landscapes and seascenes--the subject matter of his earliest adolescent art--reflect an inward absorption in and continuity of lifelong interests. We suggest that the long process of painting 'The Fairy Feller's Master-Stroke' recapitulated and made restitution for the murder, encapsulating it so that compulsive expression of violent ideation was largely reduced, allowing other memories and activities to be engaged and expressed.
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PMID:Murder will out. 32 26

The circulatory effects of incremental increases in positive end-expiratory pressure ventilation (PEEP) were assessed on 11 occasions in post-operative cardiac surgical patients by phasic aortic blood flow measurements and high-fidelity pressure recordings from which flow and pressure-flow derivatives of cardiac performance were calculated. At 15 cm H2O PEEP, mean arterial blood pressure was decreased by 10%, stroke volume and cardiac output by 15%, and peak left ventricular power by 21%. Although these indices promptly returned to control levels when PEEP was discontinued, levels of PEEP above 10 cm H2O should be used with caution for this group of patients.
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PMID:Effects of PEEP on cardiovascular dynamics after open-heart surgery: a new postoperative monitoring technique. 32 9

To investigate the effects of sustained positive-pressure breathing (PPB) on the adaptation of respiratory and circulatory functions to exercise, 8 healthy volunteers were exposed to PPB of air at 15 and 30 cm H2O in the supine position at rest and while performing leg exercise at 50% of individual maximal working capacity. PPB was both subjectively and objectively better tolerated when combined with exercise than it was at rest. PPB at 30 cm H2O resulted in marked hyperventilation with alkalosis in the resting condition, but did not significantly affect respiratory minute volume, blood gases or acid-base balance during exercise. Cardiac output and left ventricular work were reduced by about one fifth and one third, respectively, both at rest and during exercise. In contrast to the case at normal airway pressure, exercise-induced increase in cardiac output was accompanied by an increment in stroke volume during PPB. Although mean arterial pressure (relative to atmospheric) was elevated by PPB at rest and during exercise, the driving pressure in systemic circuits (arterial minus central venous pressure) was reduced in both conditions. It is concluded that dynamic exercise counteracts deleterious effects of PPB by normalizing respiratory function and by improving cardiac filling by activation of the leg muscle and the abdominal pumps.
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PMID:Respiratory and circulatory responses to sustained positive-pressure breathing and exercise in man. 36 97

Venous distensibility in essential hypertension has been reported to be unchanged or decreased; its pathophysiologic role is uncertain. In 27 male hypertensive patients and 21 normotensive control subjects, forearm venous distensibility and capillary filtration rate at 30 cm of H2O distending pressure were measured by strain gauge plethysmography. Plasma renin activity (PRA), plasma volume (PV) by the Evans blue dye dilution technique, mean arterial pressure (MAP) by cuff, and cardiac output (CO) by the CO2 rebreathing method were also measured. Compared to values in normotensive control subjects, forearm venous distensibility in hypertensive subjects was decreased (P less than 0.05); the forearm venous pressure-volume curves (deflation phase) were shifted in the direction of the pressure axis (P less than 0.02); and the capillary filtration rate was increased (P less than 0.05). Venous distensibility changes in hypertensive subjects were unrelated to PRA, MAP, PV, CO, stroke volume, and total peripheral resistance. These findings confirm previous reports of decreased venous distensibility in hypertension and provide direct evidence for increased capillary filtration rate. In view of the lack of significant correlation between venous distensibility and the measured hemodynamic parameters, a patho-physiologic role for venous distensibility in hypertension could not be established.
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PMID:Decreased venous distensibility in essential hypertension: lack of systemic hemodynamic correlates. 37 15

Variable hemodynamic responses to positive end-expiratory pressure (PEEP) with spontaneous ventilation have been reported. To clarify these responses, 15 awake patients were studied using a catheter-tip velocity transducer to record phasic aortic root blood flow continuously before, during and after PEEP (10 cm H2O) applied with a face mask. Central blood volume and effective ventricular filling pressures were measured. Phasic pulmonary artery blood flow was also simultaneously recorded in three of these patients. PEEP produced an acute aortic blood flow reduction, detected within one respiratory cycle. Stroke volume decreased 12%, and since heart rate was unchanged, cardiac output also declined (p less than 0.05). Inspiratory-to-expiratory aortic flow changes were less during PEEP. In contrast, inspiratory-to-expiratory pulmonary artery flow alterations were exaggerated due to a marked flow decline during expiration. Central blood volume and effective left ventricular filling pressure decreased 9% and 19%, respectively (p less than 0.05 in all patients). The decrease in pulmonary artery flow was associated with a decrease in central blood volume in the three patients in whom pulmonary flow was measured. PEEP promptly reduces cardiac output during spontaneous ventilation, related to a decrease in pulmonary flow in expiration.
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PMID:Instantaneous blood flow responses to positive end-expiratory pressure with spontaneous ventilation. 37 24

Acute regional cerebral ischemia was produced in the middle cerebral artery (MCA) territory in monkeys (Macaca mulatta) by selective embolization of the internal carotid (ICA) bifurcation with minimum surgical intervention in the neck under sedated conditions. Two of five hours after embolization, brain water (measurement of dry weight) and tissue concentration of sodium and potassium were determined in the tissues of the sylvian cortex, putamen and subcortical white matter in the affected MCA territory. As early as three hours, initial increase in brain water was detected in the samples of the putament without noticeable change in tissue electrolytes in two of three animals. Gross ischemic swelling of the gray matter, in both the sylvian cortex and putamen, became obvious in six of eight animals after four to five hours. This swollen gray matter showed marked increase in brain water (up to 36% swelling), increase in tissue sodium (up to 100% of the control value), and decrease in tissue potassium (down to 55%). On the other hand, edema in the white matter, if present at all, was minimal without detectable change in tissue electrolytes and was always accompanied by much greater ( greater than two to seven times) edema in the gray matter. Thus, the gray matter edema, in both the deep subcortical structures and the cortex, appeared to play the major role in the development of hemispheric swelling of the brain which may begin within hours of the onset of the MCA stroke in monkeys. Microscopically, the swollen gray matter which showed more than 10% swelling with a definite shift of tissue sodium and potassium content appeared to be dead tissue. However, early edema in the gray matter which showed less than 10% swelling without detectable change in electrolytes might be caused by simple diffusion of water through the dysfunctional capillary wall or cell membrane with or without a permeability gradient between the intravascular cerebrospinal fluid and cerebral tissue compartment and might possibly be reversible.
Stroke
PMID:Experimental regional cerebral ischemia in the middle cerebral artery territory in primates. Part 2: Effects on brain water and electrolytes in the early phase of MCA stroke. 40 42


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