Purpose-To evaluate the use of pulsed high-intensity focused ultrasound exposures to improve tissue plasminogen activator (tPA)-mediated thrombolysis in an in vitro model. Materials and Methods-All experimental work was compliant with institutional guidelines andHIPAA. Clots were formed by placing 1 mL of human blood in closed-off sections of pediatric Penrose tubes. Four experimental groups were evaluated: control (nontreated) clots, clots treated with pulsed high-intensity focused ultrasound only, clots treated with tPA only, and clots treated with pulsed high-intensity focused ultrasound plus tPA. The focused ultrasound exposures (real or sham) were followed by incubations of the clots in tPA with saline or in saline only. Thrombolysis was measured as the relative reduction in the mass of the clot. D-Dimer assays also were performed. Two additional experiments were performed and yielded dose-response curves for two exposure parameters: number of pulses per raster point and total acoustic power. Radiation force-induced displacements caused by focused ultrasound exposures were simulated in the clots. A Tukey-Kramer honestly significant difference test was performed for comparisons between all pairs of experimental groups.Results-The clots treated with focused ultrasound alone did not show significant increases in thrombolysis compared with the control clots. The clots treated with focused ultrasound plus tPA showed a 50% ([30.2/20.1]/20.1) increase in the degree of thrombolysis compared with the clots treated with tPA only (P < .001), further corroborating the D-dimer assay results (P < .001). Additional experiments revealed how increasing both the number of pulses per raster point and the total acoustic power yielded corresponding increases in the thrombolysis rate. In the latter experiment, simulations performed at a range of power settings revealed a direct correlation between increased displacement and observed thrombolysis rate.Conclusion-The rate of tPA-mediated thrombolysis can be enhanced by using pulsed highintensity focused ultrasound exposure in vitro.Venous thromboembolism, which includes deep venous thrombosis and pulmonary embolism, accounts for about 250 000 hospitalizations per year in the United States (1). Venous Address correspondence to V.F. (e-mail: vfrenkel@cc.nih.gov For decades patients with venous thrombosis have been treated primarily with anticoagulation, which is usually effective at slowing further thrombus formation. However, anticoagulation is often inadequate for eliminating the source of subsequent emboli, alleviating the hemodynamic disturbances, preventing subsequent valvular damage, and preventing permanent impairment to the pulmonary vascular bed (3). For this reason, more aggressive therapy, such as thrombolysis or thrombectomy, is sometimes used.Ultrasound has been studied as a treatment adjunct to thrombolytic drugs for thrombolysis, as well as an independent treatment method in various models (4-9). Catheter-based systems have been used with oscillating wires to ...
Regular brief light-intensity activity bouts can attenuate glycemic responses during television viewing time following a high-energy evening meal in overweight/obese adults.
Significant direct and scatter radiation doses to patient and physician may result from routine interventional radiology practice. A lead-free disposable tungsten antimony shielding pad was tested in phantom patients during simulated diagnostic angiography procedures. Although the exact risk of low doses of ionizing radiation is unknown, dramatic dose reductions can be seen with routine use of this simple, sterile pad made from lightweighttungsten antimony material.THE increasing use of imaging to guide procedures has been accompanied by public health concerns about radiation exposure to patients and health care personnel (1). Whenever a medical image is obtained, a compromise must be made between the quality of the image and the radiation dose used to make that image. Certainly, the lowest dose that can produce a diagnostic image is ideal, which leads to the ALARA principle ("As Low As Reasonably Achievable") (2). This concept is paramount with the use of fluoroscopy because of continuous x-ray production and real-time imaging.Interventional radiology procedures may expose the patient and physician to the effects of direct and scatter radiation (3). Patient exposure is usually mostly direct radiation,whereas physician exposure may be mostly scatter radiation (4). Biologic effects of ionizing radiation can be categorized as acute or delayed. Although the acute effects of radiation are not commonly a problem, the delayed effects remain a poorly quantifiable concern. Because the delayed effects may take years or decades to appear, they are difficult to distinguish from effects caused by other sources. For this reason, they are considered stochastic rather than deterministic effects. The likelihood of a stochasticeffect is directly related to the radiation dose, but its severity is not related to the total dose received. Examples of stochastic effects include carcinogenesis and genetic mutation. This type of effect is of particular concern because it may occur at any dose and there is no threshold dose at which it occurs. However, the lower the dose received, the lower the incidence of consequences that will develop. The principle of ALARA is based on this concept. The deterministic effects do have a threshold dose, and beyond this threshold, the severity is directly related to the dose (ie, cataracts, skin burns) (5,6).In fluoroscopy, the exposure to ionizing radiation can be diminished in several ways, including judicious use of fluoroscopy, use of intermittent or pulsed fluoroscopy, holding of the last image, reduction of field size (ie, collimation), and minimization of fieldoverlap (3). The use of intermittent fluoroscopy can diminish the radiation by 20%-70% (7). Additional methods described include minimization of the distance between the patient and the intensifier, maximization of the distance between the patient and the operator, choice of appropriate parameters to operate the machine, and use of movable lead surface shields (8,9) and shielded gloves (10,11 NIH-PA Author ManuscriptNIH-PA Author M...
Conclusion:A conservative strategy of fluid management in patients with acute lung injury shortens duration of mechanical ventilation without increasing nonpulmonary organ failure.Summary: There is debate about optimal fluid management of patients with acute lung injury. Limiting fluids or inducing diuresis may improve lung function but at the expense of impaired perfusion of other organs. In this randomized study, a conservative or liberal strategy of fluid management in patients with acute lung injuries was used. The protocol was applied for 7 days in 1000 patients with acute lung injury. The primary end point was death at 60 days. Ventilator-free days and organ-failure-free days and measures of lung physiology were secondary end points. There was no difference between the two groups in the primary end point at 60 days. In the conservative strategy group, 25.5% of the patients died, and 28.4% of the patients died in the liberal strategy group (P Ͻ .30; 95% confidence interval for a difference, Ϫ2.6% to 8.4%). The cumulative fluid balance in the first 7 days in the conservative strategy group was Ϫ136 Ϯ 491 mL. The cumulative fluid balance in the first 7 days in the liberal strategy group was ϩ6992 Ϯ 502 mL (P Ͻ .001). The conservative strategy group had an improved oxygenation index, lung injury score, and an increased number of ventilatorfree days (14.6 Ϯ 0.5 vs 12.1 Ϯ 0.5, P Ͻ .001) vs the liberal strategy group. The conservative strategy group also had more days not spent in the intensive care unit (13.4 Ϯ 0.4 vs 11.2 Ϯ 0.4, P Ͻ .001) during the first 28 days. There was no difference between the conservative and liberal strategy groups with respect to prevalence of shock during the course of the study or the use of dialysis during the first 60 days (10% vs 14%, P Ͻ .06).Comment: A conservative fluid management strategy did not decrease death at 60 days vs a liberal fluid management strategy in patients with acute respiratory distress syndrome. However, intensive care unit days were reduced and lung function was improved with the conservative fluid management posture. The results are consistent with other recent reports suggesting improved overall patient outcome with conservative fluid management in acute respiratory distress syndrome. The days of essentially drowning patients with acute lung injury to preserve distal organ perfusion should be over.
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