Biomedical subjects

G Guadagni

Publications and source records attributed to G Guadagni.

10 recordsLinked to original sources

PubMed2004

Clinical evaluation of internal hemodiafiltration (iHDF): a diffusive-convective technique performed with internal filtration enhanced high-flux dialyzers.

AIM: Efficiency in removing middle molecules such as beta2-microglobulin (beta2-MG) is one of the main purposes of modern dialytic therapy. In order to achieve this, techniques requiring complex machines and substitution fluid have been developed over recent years. Alternatively, the internal filtration/back filtration phenomenon can be used. The recent development of a so-called "internal filtration enhanced dialyser" prompted us to compare the removal of beta2-MG together with other small molecules when the dialyser was used either in standard hemodiafiltration (HDF) or internal hemodiafiltration (iHDF). METHODS: Ten stable, anuric, hemodialysis (HD) patients treated by thrice weekly standard bicarbonate HD using low-flux synthetic membrane entered the study. A new high-flux polysulfone dialyser designed with the specific aim of enhancing internal filtration (BS-1.6 UL, 1.6 m2, Toray Industries) was used. Post dilution HDF (2.5 l/hour of substitution fluid, dialysate flow 500 ml/min) was compared with iHDF (dialysate flow 750 ml/min), with blood flow at 300 ml/min. Samples were obtained at the start and at the end of the session in order to measure the % removal of urea, creatinine, uric acid, phosphate and beta2-MG (corrected for total protein concentration). In addition, after 20 min of dialysis the clearances of the same molecules were measured. A mathematical model has been developed for the description of the hydrodynamic phenomena taking place within the dialyser and of fluid filtration across the membrane. RESULTS: No significant differences have been observed in removal rate switching from HDF to iHDF except for beta2-MG removal, which was slightly higher in HDF than in iHDF Phosphate clearance is significantly higher than those obtained with creatinine in both HDF (p<0.005) and iHDF (p<0.01) modalities. The total convection calculated with the model is reduced with respect to HDF only by 24% (4100 ml/h vs. 5400 ml/h on the average). CONCLUSIONS: iHDF is a high flux dialysis method, which, if performed with a dialyser designed to enhance internal filtration, obtains a much higher removal rate in comparison with dialysers in traditional high flux dialysis, as previously reported in the literature. Provided that the dialyser is used on a dialysis machine working with ultra pure dialysate and UF control, this dialyser line can perform reliable internal HDF without the need for replacement solution. Considering the narrow difference in performance observed between iHDF and HDF, and the increasing number (and age) of patients leading to higher dialysis costs, iHDF represents a cost-effective alternative to other diffusive-convective techniques.

Aged↗

PubMed2001

Effects of pulmonary afterload on the hemodynamics after the hemi-Fontan procedure.

A computational fluid dynamics study based on the application of the finite volume method has been performed to investigate the effects of the pulmonary afterload on the hemodynamics after the hemi-Fontan procedure. This operation is generally used as part of a series of staged procedures to treat complex congenital malformations of the heart. It consists of re-directing the superior vena caval flow from the right atrium into the pulmonary arteries, by-passing the right ventricle while excluding the inferior caval flow from the lungs. To reproduce correctly the pulmonary afterload conditions, a simplified lumped-parameter mechanical model of the pulmonary circulation has been developed and linked to the finite volume solver. In addition, the effect of a stenosis in the left pulmonary artery was also examined. In this paper the adopted methodology is presented, together with some of the preliminary results. The model has been used to simulate the local fluid dynamics for different values of the pulmonary arteriolar resistance and lung resistances, allowing a quantitative evaluation of the dissipated energy and the flow distribution into the lungs. The results show that both flow distribution into the lungs and energy dissipation after the hemi-Fontan procedure are only minimally affected by the pulmonary arteriolar resistance.

Biomedical Engineering↗

PubMed2001

Fluid-structure interaction within realistic three-dimensional models of the aneurysmatic aorta as a guidance to assess the risk of rupture of the aneurysm.

Abdominal aortic aneurysm (AAA) disease is a degenerating process whose ultimate event is the rupture of the vessel wall. Rupture occurs when the stresses acting on the wall rise above the strength of the AAA wall tissue. The complex mechanical interaction between blood flow and wall dynamics in a three dimensional custom model of a patient AAA was studied by means of computational coupled fluid-structure interaction analysis. Real 3D AAA geometry is obtained from CT scans image processing. The results provide a quantitative local evaluation of the stresses due to local structural and fluid dynamic conditions. The method accounts for the complex geometry of the aneurysm, the presence of a thrombus and the interaction between solid and fluid. A proven clinical efficacy may promote the method as a tool to determine factual aneurysm risk of rupture and aid the surgeon to refer elective surgery patients.

Aorta, Abdominal↗

PubMed2001

A computational study of the hemodynamics after "edge-to-edge" mitral valve repair.

Edge-to-edge mitral valve repair consists in suturing the free edge of the leaflets to re-establish coaptation in prolapsing valves. The leaflets are frequently sutured at the middle and a double orifice valve is created. In order to study the hemodynamic implications, a parametric model of the left heart has been developed. Different valve areas and shapes have been investigated. Results show that the simplified Bernoulli formula provides a good estimation of the pressure drop and that the pressure drop may be predicted on the basis of the pre-operative geometric and hemodynamics data by means of customized models.

Blood Flow Velocity↗

PubMed1999

Endobronchial granular cell tumour.

Granular cell tumour of the lung is a rare benign tumour. We report a case of endobronchial granular cell tumour which occurred in a 70-yr-old male with haemoptysis. Because of the size of the tumour (greater than 8 mm) and the associated pseudoepitheliomatous hyperplasia with marked atypia, surgical resection was performed. No neoplastic relapse has been observed in nearly 4 yrs of follow-up.

Aged↗

PubMed1977

[Valvular insufficiency after venous thrombosis. Experimental study].

Venous thrombosis can produce lesions of valvular cusps which are generally ascribe to the phase of thrombus organization. Valvular lesions hold a very important role in the genesis of the post phlebitic chronic venous insufficiency. Experimental thrombosis had been induced in dogs with electrical stimulation of femoral veins to study morphological aspects of valvular cusps in various evolutive phases of thrombosis. Results emphasize too early onset and quick evolution of valvular damage. It can contribute to explain frequent failures of attempted therapy about prevention of post phlebitic syndromes.

Animals↗

PubMedDate not supplied

[Experimental observations on posttraumatic venous thrombosis].

Venous thrombosis had been experimentally induced in dogs by two different ways of trauma: contusion of whole venous wall and stripping of intimal layer. Both ways produced thrombosis in 33% of cases. The Authors describent histological findings of venous wall and thrombi with attention to genesis and evolution of these post-traumatic venous thrombosis.

Animals↗

PubMedDate not supplied

[Experimental venous thrombosis induced in dogs by electric stimulation of venous wall (author's transl)].

The Authors describe an experimental method to induce venous thrombosis in dogs by venous walls electric stimulation. The aspects of thrombogenesis, the evolution of thrombus and venous wall lesions at level of primary thrombus as well as extensive thrombosis, are studied. These studies based on histological findings at different steps from electric stimulation.

Adenosine Triphosphate↗

PubMedDate not supplied

Cytologic features of a functioning parathyroid carcinoma: a case report.

The cytologic findings in a fine needle aspirate of a functioning parathyroid carcinoma are presented. The smears were highly cellular. The most peculiar feature was the large number of dissociated cells scattered as free elements, with scanty or no cytoplasm and characterized by a marked variation in nuclear size. Several giant nuclei with multiple enlarged nucleoli were present. Clusters of atypical cells with moderate variation in nuclear size and chromatin content were mixed with groups of clear cells with abundant vacuolated cytoplasm and poorly outlined cellular borders. Clear cells were often seen palisading along fibrous vascular septa. The differential diagnosis is discussed.

Biopsy, Needle↗

PubMedDate not supplied

[Non-invasive nasal ventilation in a a case of hypercapnic coma].

Noninvasive positive pressure ventilation (NPPV) via nasal mask is well known to be effective in the treatment of acute respiratory failure (ARF) secondary to chronic obstructive pulmonary disease (COPD). A case of ARF with hypercapnic coma due to exacerbation of COPD is described. Six hours of conservative therapy with oxygen and medical treatment did not show any result. As endotracheal intubation (ET) was avoided on the basis of advanced age, poor life expectancy of the patient and family wish, NPPV was set up using a pressure triggered ventilator. After 61 hours of uninterrupted NPPV, the acid-base alteration and the lethargic status was fully reversed. The conclusions is drawn that NPPV may be useful also in the treatment of patients affected by severe decompensated hypercapnic respiratory failure in whom ET is not indicated.

Aged↗