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

To investigate whether prolonged water immersion (WI) results in reduction of central blood volume and attenuation of renal fluid and electrolyte excretion, these variables were measured in connection with 12 h of immersion. On separate days, nine healthy males were investigated before, during, and after 12 h of WI to the neck or during appropriate control conditions. Central venous pressure, stroke volume, renal sodium (UNaV) and fluid excretion increased on initiation of WI and thereafter gradually declined but were still elevated compared with control values at the 12th h of WI. Atrial natriuretic peptide (ANP) concentration in plasma initially increased threefold during WI and thereafter declined to preimmersion levels, whereas plasma renin activity, plasma aldosterone, and norepinephrine remained constantly suppressed. It is concluded that, compared with the initial increases, central blood volume (central venous pressure and stroke volume) is reduced during prolonged WI and renal fluid and electrolyte excretion is attenuated. UNaV is still increased at the 12th h of WI, whereas renal water excretion returns to control values within 7 h. The WI-induced changes in ANP, plasma renin activity, plasma aldosterone, and norepinephrine may all contribute to the initial increase in UNaV. The results suggest, however, that the attenuation of UNaV during the later stages of WI is due to the decrease in ANP release.
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PMID:Circulation, kidney function, and volume-regulating hormones during prolonged water immersion in humans. 139 77

Ingestion of approximately 30-60 g of carbohydrate during each hour of exercise will generally be sufficient to maintain blood glucose oxidation late in exercise and delay fatigue. Since the average rates of gastric emptying and intestinal absorption exceed 1,250 ml.h-1 for water and solutions containing up to 8% carbohydrate, exercising people can be supplemented with both carbohydrate and fluids at relatively high rates. When cyclists exercise at competitive intensities for 2 h in the heat with a sweat rate of 1,400 ml.h-1, it is clear that the closer that fluid consumption matches sweating rate (at least up to 80% of sweating rate), the better. Increasing dehydration, due to inadequate fluid consumption, directly impairs stroke volume, cardiac output, and skin blood flow, which results in larger increases in body core temperature, heart rate, and ratings of the difficulty of exercise. This same phenomenon probably also applies to running, which argues against the notion that a certain amount of dehydration (i.e., up to 3%) is permissible and without major cardiovascular consequences. However, runners generally drink only 500 ml.h-1 of fluid and thus allow themselves to dehydrate at rates of 500-1,000 ml.h-1. The performance question boils down to "Will the time lost as a result of drinking larger volumes be compensated by the physiological benefits drinking produces and the faster running pace that might be achieved during the last half of the race?" However, if the goal is safety, which means minimizing hyperthermia, there is no question that the closer that the rate of drinking can match the rate of dehydration, the better.
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PMID:Benefits of fluid replacement with carbohydrate during exercise. 140 5

We studied the acute hemodynamic effects of increasing nasal continuous positive airway pressure (CPAP) in 13 patients with acute decompensation of congestive heart failure. Heart rate, respiratory rate, pulmonary capillary wedge pressure, right atrial pressure, systemic blood pressure, and thermodilution cardiac outputs were measured at baseline, during, and after application of nasal CPAP at increasing pressures of 5, 10, and 15 cm H2O. Cardiac index, stroke volume, and oxygen delivery were calculated. Based on a significant change in cardiac output greater than or equal to 400 ml, seven patients were classified as responders, whereas six patients were considered to be nonresponders. In responders, significant increases were noted in cardiac index (2.5 +/- 0.7 to 2.9 +/- 0.9 L/min/m2), stroke volume (49 +/- 15 to 57 +/- 16 ml), and oxygen delivery (10.3 +/- 5.1 to 12.3 +/- 6.0 ml/min/kg) without a change in pulmonary capillary wedge pressure. In contrast, the nonresponders showed no significant change in any of the hemodynamic parameters. Improvement in cardiac output could not be predicted by any of the baseline hemodynamic or clinical variables, nor was it related to random variations since all variables returned to baseline after cessation of CPAP. Increase in stroke volume without a change in pulmonary capillary wedge pressure (preload) suggests either improved inotropic function of the left ventricle or reduced left ventricular afterload with CPAP. Thus, CPAP may offer a new noninvasive adjunct to improving left ventricular function and augmenting cardiac performance in a subset of patients with congestive heart failure.
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PMID:Effect of nasal continuous positive airway pressure on cardiac output and oxygen delivery in patients with congestive heart failure. 142 58

Blood cardioplegia is considered by many to be the preferred solution for myocardial protection. Proposed benefits include the ability to deliver oxygen and the ability to maintain metabolic substrate stores. However, the decreased capacity of blood to release oxygen at hypothermic conditions as well as the presence of deleterious leukocytes, platelets, and complement may limit complete functional recovery. Fluosol is an asanguineous solution with the ability to bind and release oxygen linearly at low temperatures. Neonatal piglet hearts (24 to 48 hours old) were excised and supported on an isolated, blood-perfused working heart model. After baseline stroke-work index was determined, hearts were arrested with either normocalcemic blood cardioplegia (group 1, n = 8) or normocalcemic Fluosol cardioplegia (group 2, n = 8). Cold cardioplegia was administered at 45 mm Hg every 20 minutes for 2 hours. Hearts were then reperfused with whole blood. Functional recovery, expressed as percent of control stroke-work index, was determined 60 minutes after reperfusion at left atrial pressures of 3, 6, 9, and 12 mm Hg. Functional recovery at 60 minutes was similar between group 1 (95%, 93%, 93%, 88%) and group 2 (100%, 94%, 94%, 95%) at left atrial pressures of 3, 6, 9, and 12 mm Hg, respectively. Mean lactate consumption 5 minutes after reperfusion was significantly greater (p = 0.0001) in group 1 (31.8 +/- 6.3 micrograms.min-1 x g-1) than in group 2 (-0.59 +/- 0.1 microgram.min-1 x g-1), indicating superior metabolic recovery in the blood cardioplegia hearts. Edema formation, as determined both by water content (group 1, 81.10%; group 2, 81.63%) and by electron microscopy, was not significantly different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Fluosol cardioplegia results in complete functional recovery: a comparison with blood cardioplegia. 144 1

Localized water suppressed proton spectroscopy has opened up a new field of pathophysiological studies of severe brain ischemia. The signals obtained with the pulse sequences used so far are both T1 and T2 weighted. In order to evaluate the extent to which changes in metabolite signals during the course of infarction can be explained by changes in T1 and T2 relaxation times, eight patients with acute stroke were studied. STEAM sequences with varying echo delay times and repetition times were used to measure T1 and T2 of N-acetyl-aspartate (NAA), creatine plus phosphocreatine (Cr+PCr) and choline containing compounds (CHO) in a 27-ml voxel located in the affected area of the brain. Ten healthy volunteers served as controls. We found no difference in T1 or T2 of the metabolites between the patients and the normal controls. The T2 of CHO was longer than that of NAA and Cr+PCr. Our results indicate that spectra obtained in brain infarcts and normal tissue with the same acquisition parameters are directly comparable with respect to relative signal intensities as well as signals scaled with internal and external standards.
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PMID:In vivo relaxation of N-acetyl-aspartate, creatine plus phosphocreatine, and choline containing compounds during the course of brain infarction: a proton MRS study. 146 Oct 96

The laryngeal mask airway (LMA) provides a patent airway when placed 'blindly' into the hypopharynx. At the laryngeal side it is supposed to form a seal surrounding the laryngeal inlet with the epiglottis lying outside the mask aperture. This study is designed to assess the prelaryngeal position of the mask by the fibreoptic technique. METHODS. After approval by the local ethical committee and informed consent, 100 adult patients (ASA groups I and II) undergoing general anaesthesia for extracorporal stroke wave lithotripsy (ESWL, Lithotripter HM 3, Dornier) of the kidney were studied. Anaesthesia was induced with propofol (1.5-2.5 mg.kg-1) and fentanyl (1-1.5 micrograms.kg-1) and maintained with isoflurane and N2O (65% in O2) as clinically indicated. The LMA was left in situ until the patients opened their mouth on command. Monitoring consisted of an ECG (SMV 104-D, Dornier), a pulse oximeter (Nellcor 200, Draeger), and a non-invasive blood pressure monitor (BP 103 N, Hoyer). Clinical assessment of airway patency and fibreoptic laryngoscopy (BF Typ 10, Olympus)--immediately and 20 min following the insertion of the LMA--were performed by two observers. RESULTS. The insertion of the LMA was successful on the first attempt in 89 patients while 5% required two, 4% three and 2% four attempts. 'Blindly' inserted without neuromuscular blockade the LMA provided a clinically sufficient airway in all patients. A central position of the LMA was assessed in only 59% of the cases. In 4 patients the mask was riding on the vocal folds. Positioned at the posterior larynx the cuff produced a compression of the laryngeal orifice when insufflated. Oblique insertion of the LMA or oblique head position during insertion produced a misplacement of the LMA. In 5 cases the LMA followed lateral movements of the head without losing its central position. In 87% the epiglottis was within the lumen of the LMA. Secretions inside the mask lumen or at the anatomic structures were seen in 36%. During manual ventilation with high inspiratory pressure (> 25 cm H2O) the oesophagus opened in 10 cases. CONCLUSIONS. Previous studies have suggested that the LMA takes a 'perfect' position at the laryngeal side when a clinically patent airway is recognized. In contrast, our results demonstrated that a central position of the LMA is achieved in only 59% of the cases. Our results indicate that epiglottic downfolding or left/right side or anterior/posterior misplacement are common but generally provide a satisfactory patent airway. This is consistent with fibreoptic findings in children and radiological observations in adults. The LMA is an essential enrichment to conventional airway management. It provides a better seal than the face mask, especially in bearded or in old patients where the facial contours are often not suited to the mask. Ideal indications seem to be elective operations of intermediate duration (1-2 h). The LMA does not protect against aspiration. For patients who are at risk of regurgitation of gastric contents, use of the LMA is absolutely contraindicated. Relative contraindications are local pathology of the pharynx and situations with low pulmonary compliance and/or high airway resistance (massive obesity, asthma, etc.), especially during controlled ventilation. Further studies are necessary to establish definite indications for the application of the LMA.
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PMID:[Fiberoptic determination of the position of the laryngeal mask]. 148 77

Water self-diffusion, a recently discovered source of contrast on MR images, has already shown promise for some clinical applications. Most studies have been of the brain, essentially for technical reasons. Diffusion is useful in distinguishing the different components of brain tumors (cystic regions, edema, necrosis) from the tumor core itself. Recent studies have shown that diffusion is anisotropic in brain white matter (i.e., dependent on the fiber tract's orientation in space), offering new insights into myelin disorders. Diffusion is also dramatically altered in the minutes following ischemic injury in the cat brain, which may have tremendous impact for the diagnosis and management of hyperacute stroke. With ultrafast acquisition schemes, diffusion imaging has also been used outside the CNS, for instance, in the eye and kidney. Future applications include diffusion-localized spectroscopy and temperature imaging. This article reviews recent progress in this field and suggests potential applications.
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PMID:Diffusion MR imaging: clinical applications. 150 32

Rapid MRI of the molecular diffusion of water demonstrated cerebral infarcts in 32 patients. We studied these patients at various times following the onset of ischemic symptoms and found that diffusion-weighted imaging revealed the infarcts sooner than conventional T2-weighted spin-echo imaging did; four hyperacute infarcts were shown only by diffusion-weighted imaging. Acute infarcts had lower apparent diffusion coefficients (ADCs) than noninfarcted regions did. This relative difference in ADC reached a nadir in the first 24 hours and rose progressively thereafter. Chronic infarcts showed a relative increase in diffusion and were readily distinguishable from acute infarcts. The technique takes less than 2 minutes to apply using a standard 1.5-tesla scanner in the clinical setting. Diffusion-weighted imaging has the potential to play a role in improving the early anatomic diagnosis of stroke and therefore in the development and implementation of early stroke interventions.
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PMID:Fast magnetic resonance diffusion-weighted imaging of acute human stroke. 151 59

The effect of positive end-expiratory pressure (PEEP) on right ventricular (RV) function in humans is complex. Previous studies have been limited in their interpretation by not defining either pericardial pressure (Ppc) or RV volumes. Accordingly, we measured RV volumes and pressures and Ppc as PEEP was increased from zero to 15 cm H2O in 12 patients after thoracotomy, using a pulmonary arterial catheter equipped with a rapid responding thermistor that allowed measurement of RV ejection fraction (ef), while Ppc was measured via a pericardial balloon catheter. RV end-diastolic volume (EDV) was estimated as the ratio of stroke volume (SV) to RVef, whereas RV end-systolic volume (ESV) was estimated as RV EDV-SV. Right atrial pressure (Pra) was defined as end-diastolic pressure, and pulmonary arterial pressures (Ppa), both peak and mean, were used as end-systolic pressures. PEEP increased Ppc, Pra, and lung compliance (Cl). Cardiac output also decreased but not significantly. Neither mean nor peak systolic Ppa, nor RVef was significantly altered by PEEP. There was no relation between either RV filling pressure (Pra-Ppc) and EDV or the change in RV filling pressure and EDV, although EDV varied significantly as PEEP varied for individuals (p less than 0.05). Similarly, there was no relation between Ppa and ESV when either mean or peak Ppa values relative to Ppc were used. The relations between EDV and both SV and RVef were weak (r = 0.54 and 0.55, respectively). RVef varied inversely with ESV (r = -0.77), although it showed no relation to transmural peak Ppa (r = 0.28).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of positive end-expiratory pressure on right ventricular function in humans. 151 48

The middle cerebral artery was severed bilaterally (bMCA) in adult rats, and controls experienced sham operations. Tactile sensorimotor and gross locomotor functions, measured by the tape test and a rod walking test, were initially impaired in the injured animals. However, these deficits had resolved within 9 and 30 days respectively. The animals were trained in a multiple T water maze task to find the location of a hidden escape platform at the rate of one trial per day for 30 days. Analyses of the number of errors committed and latency to find the escape platform revealed that the bMCA injured rats suffered deficient reference memory, but no decline in working memory. These data support further the use of the bMCA preparation as a model of stroke.
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PMID:A behavioral study of bilateral middle cerebral artery hemorrhagic ischemia in rats. 152 Aug 64


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