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71.
The responsiveness of arterial smooth muscle to vasoactive stimuli is enhanced hypertension. It is however, unclear whether this increased reactivity is a generalised property of vascular smooth muscle, involving veins as well. We examined the responses of rings of cephalic veinin vitro taken from 11 dogs with chronic renovascular hypertension and 10 normal dogs. Mean blood pressure was 129 ± 3 mmHg in the hypertensive dogs, 26% above control. Veins from hypertensive dogs had steeper passive circumference-tension relationships than veins from normal dogs, indicating reduced compliance. Sensitivity (defined as location of EC50) to potassium depolarisation was unchanged, but maximal contractile force (Fmax) developed was 35% greater in hypertension when compared with normotensive dogs. With noradrenaline and the selective alpha1-adrenoceptor agonist methoxamine, there was no difference between normotensive and hypertensive dogs in either location of the EC50 or in the Fmax. With the selective alphaz-adrenoceptor agonist UK 14304, there was a tenfold decrease in sensitivity in hypertension when compared with normotensive dogs, but no change in Fmax. There was, however a tenfold increase in sensitivity to serotonin in hypertension when compared to normotensive dogs, and a 22% increase in Fmax. Contractile responses to transmural sympathetic nerve stimulation were similar in the two groups. As desipramine caused equal increases in responses to neural stimulation, there was no demonstrable abnormality of neuronal uptake in hypertension. Morphometric examination showed no change in media thickness, media thickness/radius ratios or media cross sectional area in hypertension. Therefore, veins from dogs with chronic renovascular hypertension are stiffer but not hypertrophied, and exhibit some specific differences in contractile responses to vasoconstrictor agents when compared with veins from normotensive dogs.  相似文献   
72.
Two distinct receptor mechanisms have been identified in relationship to the kidney's release of renin and the subsequent pressor effects of the renin-angiotensin system. One is intravascular, the other tubular. Recent studies have delineated the relative roles and signals perceived by each and have contributed to knowledge of feedback mechanisms as well as of the precise effects of pharmacologic interventions.  相似文献   
73.
《Hospital practice (1995)》2013,41(2):123-140
Chemonucleolysis is the last step in “conservative” care of a patient with disk herniation. In experienced hands, the technique is less traumatic than spinal surgery.  相似文献   
74.
Echocardiography     
Echocardiography occupies a unique place as an investigative tool in cardiology. This introduction to the technique reviews the basic principles and outlines the diagnosis of common cardiac lesions. Being entirely noninvasive, echocardiography can be repeated to ascertain the severity and observe the progression of cardiac lesions.  相似文献   
75.
The success of psychoactive agents in management of psychoses has directed attention to prevention of psychiatric disorders. A number of substances are said to be effective in prophylaxis, but the claims await substantiation in controlled studies and preventive pharmacotherapy in general awaits a clearer understanding of etiology.  相似文献   
76.
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78.
《Annals of medicine》2013,45(7):474-481
Abstract

Inferior vena cava filter (IVCF) use continues to increase in the United States (US) despite questionable clinical benefit and increasing concerns over long-term complications. For this review we comprehensively examine the randomized, prospective data on IVC filter efficacy, compare relative rates of IVCF placement in the US and Europe, compare commonly considered guidelines for IVCF indications, and the current data on IVCF complications. Searches of MEDLINE and Cochrane databases were conducted for randomized prospective IVCF studies. Only three randomized prospective studies for IVCFs were identified. Commonly cited IVCF guidelines were reviewed with attention to their evolution over time. No evidence has shown a survival benefit with IVCF use. Despite this, continued rising utilization, especially for primary prophylactic indications, is concerning, given increasing evidence of long-term filter-related complications. This is particularly noted in the US where IVCF placements for 2012 are projected to be 25 times that of an equivalent population in Europe (224,700 versus 9,070). Pending much-needed randomized controlled trials that also evaluate long-term safety, we support the more stringent American College of Chest Physicians (ACCP) guidelines for IVCF placement indications and advocate a close, structured follow-up of retrievable IVCFs to improve filter retrieval rates.  相似文献   
79.
Summary. During laparoscopic surgery, intra-abdominal pressure is increased by the pneumoperitoneum. This may impede venous return from the legs and so predispose to venous thrombosis. The aim of this study was to investigate femoral venous velocity and femoral venous diameter during pneumoperitoneum, and to assess the reversibility of this effect by use of an intermittent calf compression device. Fourteen patients undergoing laparoscopic cholecystectomy were studied. A duplex scanner was used to assess femoral venous velocity (both with and without use of a calf compression device), and diameter, before, during and after establishment of a pneumoperitoneum. There was a significant reduction in the femoral venous velocity (from 0.15-0.105 m/s, P<0.01) and a significant increase in femoral venous diameter (from 6.55-9.3 mm, P<0.01) during pneumoperitoneum. The use of a calf compression device reversed this effect (augmented velocity of 0.395 m/s during pneumoperitoneum, P<0.01). These results indicate that laparoscopic surgery affects venous haemodynamics and this effect can be reversed with calf compression devices.  相似文献   
80.
Antibiotic lock therapy (ALT) – instillation of high concentrations of anti-microbial agent with or without anti-coagulant into the lumen of central venous catheters – is considered a valid conservative treatment for catheter-related bloodstream infection (CRBSI) in patients highly dependent on maintaining the catheter. Results from randomized controlled studies have indicated that the effectiveness of ALT is moderate, but recent findings from experimental studies and observational case series point to considerable efficacy and safety of this therapy, which is usually associated with concomitant systemic treatment. In this article, the current knowledge about ALT for patients with CRBSI is reviewed and discussed, with emphasis on existing controversies and the results obtained according to the various uses of the catheters and the etiologies of infection.  相似文献   
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