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Biomedical subjects

P Zucchelli

Publications and source records attributed to P Zucchelli.

At least 217 records · Page 12Linked to original sources
PubMedDate not supplied

Automatic control of blood volume trends during hemodialysis.

Dialysis induced hypovolemia plays an important role in triggering intradialytic hypotension. The authors developed an automatic system (BVAC) with feedback changes in the ultrafiltration rate (UFR) and dialysate conductivity (DC) to match blood volume (BV) intradialytic profiles with the desired trajectories. The system consists of three subunits: (1) an optical probe to continuously detect the BV changes derived from hemoglobin changes, and (2) a dialysis machine interfaced with (3), a personal computer in which a time-dependent model is implemented. The model is based on a dynamic regulator that can set the actual BV changes against the corresponding desired values. Any discrepancy is offset by changes in UFR and DC. To verify the efficacy of the BVAC system in reducing intradialytic cardiovascular instability, five hypotension-prone patients were studied during a three period protocol (A1-B-A2) that lasted six sessions per period per patient. During periods A1 and A2, the dialysis procedure was conventional hemodialysis (HD) with linear UFR and constant DC. During period B, both UFR and DC were automatically regulated by the BVAC system. Mean BV reduction and its variability were lower during period B than during periods A1 and A2 (-10.2%, -11.3%, and -11.5, respectively). Episodes of hypotension were significantly (P < 0.05) fewer during period B (n = 1) than during periods A1 (n = 8) and A2 (n = 5). The therapeutic interventions defined as infused milliliters of isotonic and hypertonic solution were fewer during period B compared with periods A1 and A2. Total UF and end-dialysis plasma sodium concentrations did not differ in the three study periods. BVAC was effective in improving cardiovascular tolerance to treatment.

Aged↗
PubMedDate not supplied

The management of hypotension in dialyzed patients.

Acute hypotension is a frequent hemodialysis complication. This intra-treatment vascular instability is a multifactorial process in which procedure-related and patient-related factors may influence the decrease in plasma volume and the impairment of cardiovascular regulatory mechanisms. Identification of the most susceptible patients and of the various risk factors may contribute to significantly improving cardiovascular stability during dialysis. In some high-risk patients, continuous monitoring of the various parameters can predict the appearance of symptomatic hypotension and help to prevent its onset.

Humans↗
PubMedDate not supplied

How to achieve optimal correction of acidosis in end-stage renal failure patients.

Metabolic acidosis appears to be responsible for a variety of detrimental clinical and biological effects in uremic subjects, making its correction with dialysis mandatory. By utilizing the kinetic approach, pre- and post-dialysis target levels to be achieved by dialysis can be defined. Although a clear-cut bicarbonate concentration threshold, below which deleterious effects appear, has not yet been defined, it seems that a time-averaged concentration of 24 mmol/l is the gold standard for an optimal acid-base correction. However, apart from the bicarbonate levels, even the characteristics of the buffer used play a role in optimal, symptom-free acidosis correction. Currently, bicarbonate must be considered the base to be administered during treatment in the majority of patients. Due to the numerous factors affecting the bicarbonate mass balance (both patient related and technique related), the ideal dialytic dose for an individual patient is highly variable. Hence, the use of theoretical models may be very complex and impracticable for the individual patient on routine dialysis. Dedicated statistical models, obtained from in vivo data, are more useful and reliable. They allow us to tailor the bicarbonate prescriptions according to individual needs and differing dialysis methods.

Acetates↗
PubMedDate not supplied

Ischemic nephropathy: diagnosis and treatment.

Recent epidemiologic studies have shown that ischemic nephropathy secondary to stenosis or obstruction of the main renal arteries in the cause of renal insufficiency in a growing number of subjects. The clinicians dealing with renovascular disease need non-invasive diagnostic tools and effective therapeutic measures to successfully face the problem. Duplex ultrasound scanning is a non-invasive, non expensive diagnostic tool and when an experienced, dedicated technologist is available, it should be suggested as the first-step test. Magnetic resonance angiography and spiral CT angiography play an ancillary role in detecting patients with renovascular disease. Captopril-enhanced (CE) scintigraphy when positive indicates the activation of intrarenal renin-angiotensin system and may be useful in detecting patients with renal artery stenosis. Moreover, CE scintigraphy can play an important role in the choice between the revascularization and a wait-and-see approach. As a matter of fact, the presence of an activated intrarenal renin-angiotensin system furnishes theoretical as well practical reasons in favour of the revascularization. In the recent years percutaneous transluminal renal angioplasty has become the cornerstone of therapeutic strategy. The introduction of the metallic stent has dramatically improved its efficacy in ostial stenoses and has reduced the indication for surgical revascularization.

Captopril↗
PubMedDate not supplied

A prospective randomised European multicentre study of medium-long run mortality and morbidity comparing acetate-free biofiltration and bicarbonate dialysis.

In recent years, the progressive increase in the mean age of the population entering chronic dialysis treatment has been responsible, on the one hand, for the growing number of patients undergoing regular dialysis, and on the other, for the high number of "critical" patients, both as a result of their age and the presence of concomitant morbidity. Thus, dialysis treatment today is not only aimed at waste removal and water-electrolyte homeostasis, but also at a reduction in morbidity and mortality, and at improving the patients' quality of life, thanks to the use of biocompatible materials and the achievement of good cardiovascular tolerance to treatment. Consequently, diffusive-convective dialysis procedures have been on the increase, since they combine better depuration with the use of biocompatible high-flux membranes. Acetate-free biofiltration (AFB) is a diffusive-convective dialysis procedure which utilises a high-flux membrane, AN69, post-dilution infusion of a sodium bicarbonate solution (NaHCO3), and a dialysate which is completely free of any buffer, and thus also free of acetate, which may have various negative effects on the patient. A number of studies have already shown the better hemodynamic stability and the reduction of intradialytic side-effects during AFB. All these, however, were short-term studies. To verify the beneficial effects of AFB in the long run, a three year multicentre randomised European trial has been proposed to compare bicarbonate hemodialysis (BD), a technique used in nearly 80% of the world's dialysis population, and AFB. The specific aim of the investigation is to verify, in a large number of patients, the results of hemodialysis treatment in terms of morbidity, mortality and quality of life. The study involves 80 hemodialysis units across Italy, France, Germany, Spain, Slovenia and Croatia, with enrollment of about 400 patients considered "critical" for at least one of the following reasons: age, diabetes, dialysis cardiovascular instability. Fifty percent of the patients are to undergo AFB with the AN69 membrane and bicarbonate solution infusion (NaHCO3 145 or 167 mEq/lt), and the other fifty percent are to be treated by BD, with any membrane except the nonmodified cellulosic one. Biochemical, cardiological, and nutritional parameters will be considered throughout the study. Mortality, morbidity both in terms of intra- and interdialysis symptoms - and hospitalisation rate, as well as the patients' quality of life, evaluated by the SF36 questionnaire, will be analysed.

Aged↗
PubMedDate not supplied

Ischemic nephropathy.

Ischemic nephropathy, involving stenotic lesions in the renal arteries, associated with renal insufficiency, is now recognized as a frequent disease. It may be responsible for a significant proportion of end stage renal disease, at least in the Caucasian population. Some non-invasive but reliable techniques such as echo-color-Doppler, gadolinium-enhanced magnetic resonance and spiral CT angiography are now available for diagnosis. Revascularization with either angioplasty, stent or surgery improves renal function in many patients. In the near future systemic and/or local medical therapy will provide better answers for renovascular disease.

Animals↗
PubMedDate not supplied

3 R study: renal outcome in renal ischemia: revascularisation or medical treatment.

Ischemic nephropathy refers to the kidney damage following stenosis or an obstructive lesion in the main kidney arteries. This disorder has been overlooked in the past and a more rational and specific use of clinical criteria, and the development of not very invasive techniques with a good diagnostic accuracy such as spiral CT angiography, NMR angiography and echo-colour-Doppler have improved our ability to identify these patients. It is therefore likely that, in the next few years, we will find ourselves treating an increasing number of patients with renovascular ischemic disorders. Transluminal angioplasty and, more recently, the use of endovascular stents, have led to a marked improvement in the treatment of stenoses and, together with vascular surgery, allow to treat almost all patients with this disorder. There is, however, a lack of prospective and controlled studies, which demonstrate the long term benefit of revascularization treatment, as compared with optimum conservative treatment in reducing cardiovascular mortality, cardiovascular events and preserving renal function. The Ischemic Nephropathy Study Group of the Italian Society of Nephrology has organized a prospective, controlled study over a period of three years, aimed at comparing the effect of revascularization versus medical therapy in 300 patients with renal artery stenosis, ranging between 50 and 90 per cent, who will be randomly assigned to the two treatments. End point will be cardiovascular mortality and morbidity and need for renal replacement therapy.

Follow-Up Studies↗
PubMedDate not supplied

Continuous urea monitoring in hemodialysis: a model approach to forecast dialytic performance. Results of a multicenter study.

BACKGROUND: A urea biosensor, inserted into the ultrafiltrate collection-line of paired filtration dialysis (PFD), not only allows on-line dialysis quantification, but also forecasts final (Cend) and 30 min equilibrated urea concentration (Ceq), the most reliable value for calculating dialysis efficiency. The urea biosensor processes plasma ultrafiltrate continuously, delivering a large amount of data to the computer, which estimates the parameters by a mathematical model, thus predicting the whole urea profile with rebound. METHODS: A multicenter randomized trial on 41 patients was conducted to ascertain the ability of a two-pool variable-volume urea model to forecast Cend and Ceq at 60 and 90 min after the start of dialysis. Two alternative dialytic treatments, A or B, were chosen, the latter being more efficient. Each treatment included six serial PFD. The accuracy of forecasting was evaluated through four indices based on forecast errors, calculated as the difference between observed and forecasted urea values: mean percent error (MPE) (%), mean absolute deviation (MAD) (mg/dl), mean absolute percent error (MAPE) (%) and root mean squared error (RMSE) (mg/dl). RESULTS: Forecasted urea concentrations were lower than those measured by the biosensor. MPE for Cend was negligible in A (+1.2%) and much higher in B (+7.2%); both values improved at 90 min, +1.0% and +5.8%, respectively. MAD for Cend was similar in both treatments and improved slightly at 90 min, ranging from 4.9 to 5.9 mg/dl. MPE for Ceq was +4% in A and and more than doubled in B (+11.5%); both values improved at 90 min, +3.7% and +9.7%, respectively. MAD for Ceq was 7.5 mg/dl in A and 8.5 mg/dl in B; both improved at 90 min, 6.7 and 7.4 m g/dl, respectively. The other indices, MAPE and RMSE, showed similar results. Comparison between the errors of the two treatments with analysis of variance (ANOVA) for repeated measures gave no significant results. CONCLUSIONS: Our model forecasts of urea concentrations were overall lower than the measured ones: the bias was negligible for A-Cend, greater for the A-Ceq and when the more efficient treatment B was used. The 60 min predictions improved at 90 min. The comparison between the prediction errors in the two treatments were not statistically significant. The recirculation measurement would probably reduce the bias if it were properly incorporated into the model.

Filtration↗
PubMedDate not supplied

Prompt plasma-exchange treatment and coma reversibility in two patients with thrombotic thrombocytopenic purpura.

We report on the cases of two women with acute thrombotic thrombocytopenic purpura (TTP) whose clinical courses were characterized by the onset of a coma state. Prompt commencement of plasma-exchange (PE) treatment led to complete hematological and neurological remission, which can still be observed without any maintenance therapy. No CNS abnormalities were observed in either patient using brain CT and NMR scans.

Adult↗
PubMedDate not supplied

Ticlopidine in the treatment of thrombotic thrombocytopenic purpura: report of two cases.

The observation of two clinical cases make possible an evaluation of the potential therapeutic activity of platelet function inhibitors in thrombotic thrombocytopenic purpura (TTP). In particular, the clinical and hematological effects of ticlopidine (TC), employed alone in two TTP patients, are reported. The mechanism of action of this peculiar antiplatelet drug is mainly represented by the inhibition of fibrinogen binding on the platelet surface. In the first patient, a 45-year-old female in whom plasma-exchange (PE) and corticosteroids (C) led to a partial remission (platelets 80 x 10(9)/l), treatment with TC at a dose of 750 mg/day was carried out, and after 6 weeks a normal platelet count was observed. A complete remission was maintained for 31+ months, even after reduction of the TC dose to 250 mg/day. In the second patient, an 18-year-old female affected by relapsing TTP, a complete remission obtained with PE and C was maintained for 19 months in concomitance with TC treatment, started at a dose of 750 mg/day and lowered to 250 mg/day. After 11 months of treatment at this low dosage there was a relapse (platelets 20 x 10(9)/l), but the increase of the TC dose to 750 mg/day in a few weeks induced a complete remission again. These data, in accord with a few other recent preliminary reports, suggest that TC, even alone, may play an interesting role in the management of TTP patients.

Adolescent↗