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Biomedical subjects

S Chiaramonte

Publications and source records attributed to S Chiaramonte.

At least 19 recordsLinked to original sources
PubMed1992

Hepatitis C virus antibody response in acute and chronic non-A, non-B hepatitis.

Patients with post-transfusion, community-acquired or hemodialysis-acquired non-A, non-B hepatitis (NANBH) were tested for antibody to hepatitis C virus (HCV) during acute-phase and resolving or chronicized illness. HCV appears to be involved in most cases of post-transfusion and hemodialysis-acquired NANBH, but only in 40% of community-acquired NANBH. Second generation HCV antibody assays are more specific and sensitive, favoring early detection of HCV seroconversion and identification of HCV-antibody-positive individuals years after exposure to the virus.

Adult↗
PubMed1992

Dynamic catheterography in the early diagnosis of peritoneal catheter malfunction.

The dynamic catheterography is an image technique that allows to study the peritoneal solution inflow and outflow phases in case of catheter malfunction. The examination is carried out in three subsequent steps: 1) direct examination without contrast media in order to define the position of the catheter inside the abdomen; 2) low speed catheterography by normal injection of 10 ml of hydrosoluble contrast medium to verify the patency of the cannula; 3) high speed catheterography by 30 ml hydrosoluble dye injected with an automateds high pressure system to study the inflow phase, the fluid distribution in the peritoneal cavity and the patency of the catheter holes. Different radiographic patterns can be found: dislocation of the catheter tip, KinKing, one way obstruction, inner lumen obstruction. The procedure is simple, safe and reliable for a correct diagnosis and for the choice of a successful therapeutic approach to peritoneal catheter malfunction.

Catheterization↗
PubMed1990

Paired filtration dialysis: studies on efficiency, flow dynamics and hydraulic properties of the system.

Several strategies have been proposed to increase dialysis efficiency in order to reduce dialysis treatment time. Paired filtration dialysis (two-chamber technique) is a new technique combining the advantages of highly permeable membranes and convective transport with the high depurative efficacy of diffusion. The system operates with two units in series (hemofilter + dialyzer) with membranes of polysulfone and hemophan, respectively. A detailed analysis of the hydraulic properties of the system and its possible optimization in terms of depurative efficiency is reported in this paper. In vitro and in vivo tests provided data sufficient to draw some hypotheses on a new utilization of the system. The system appears to be adequate for operating under conditions of high blood flows, however, some limitations were evidenced during our evaluation: the convective component may be insufficient and further increases are impossible because of the limiting effect of the low surface area of the hemofilter; the configuration in which the weight loss is achieved in the hemofilter exposes to the risk of backfiltration in the dialyzer, reducing the benefits of a highly biocompatible system, and the use of acetate in the dialysate and/or lactate in the substitution fluid may interfere with a satisfactory correction of metabolic acidosis. On the basis of our evaluations, some changes can be proposed such as: (1) increased surface area of the hemofilter; (2) use of blood flows higher than 300 ml/min; (3) use of bicarbonate in the dialysate and in the replacement solution; (4) increased convective component with ultrafiltration rates of 50-60 ml/min and full replacement with substitution fluid in between the two filters, and (5) weight loss achieved in the dialyzer with a constantly positive transmembrane pressure. With such a modification of the operative conditions, paired filtration dialysis can be probably applied as a highly efficient dialysis technique in a large number of patients with a significant reduction of dialysis treatment time.

Blood Flow Velocity↗
PubMed1990

Fluctuation of vasopressin secretion in chronic hypernatremia.

Herein we will describe a case of chronic hypernatremic-hyperosmolar syndrome with cerebral localization of systemic sarcoidosis. Several determinations of plasma arginine vasopressin (p-AVP) at various plasma sodium levels were carried out in this patient. During the study p-AVP values varied between 2.6 and 9.5 pg/ml. A high percentage of them was related to plasma osmolality, pointing out that p-AVP secretion was osmotically mediated. This behavior is in contrast with the tendency of hypernatremic patients previously reported in the literature, in whom p-AVP values were inappropriately low for the corresponding degree of plasma osmolality, suggesting that vasopressin secretion was not influenced by osmotic stimulation. Furthermore, our case, unlike those previously described, showed high values of urinary osmolality. In conclusion, our patient represents, in essence, the 'middle' of the spectrum of the hypodipsic-hypernatremic syndrome, because she is to be inserted between the majority of patients who have little or no osmotically mediated AVP release and the case of a child, recently described, who had completely normal AVP secretion.

Arginine Vasopressin↗
PubMed1990

Pathophysiology of ultrafiltration in peritoneal dialysis.

Pathophysiology of peritoneal ultrafiltration is analyzed in the present study. Peritoneal equilibration test is the easiest procedure to study in detail the possible causes of failure to control the ultrafiltration rate in patients undergoing peritoneal dialysis. Membrane failure, reduction in peritoneal blood flow, excessive lymphatic reabsorption catheter malposition, and fluid sequestration are the most common causes of ultrafiltration loss. Pharmacologic manipulation of peritoneal membrane, correction of mechanical inconvenients, reduction in peritonitis rate and in the level of immunostimulation of the mesothelial macrophages, together with a careful policy in terms of glucose concentration in the dialysate and dwell times may contribute not only to treat different forms of ultrafiltration loss but also to prevent their incidence.

Algorithms↗
PubMed1989

Acid base correction in bicarbonate CAPD patients.

Bicarbonate has been proposed as buffer in CAPD solutions in recent years instead of lactate and acetate. The present study is designed to evaluate peritoneal bicarbonate kinetics using bicarbonate solutions. Seventy kinetic studies have been performed in 7 patients treated with 2 CAPD solutions containing 35 mmol/l (A) and 27 mmol/l (B) of bicarbonate. The changes in dialysate bicarbonate concentration at different dwell times were correlated with bicarbonate blood levels. Furthermore after 2 hours of dwell time and at subsequent observations, no differences in dialysate bicarbonate concentration were found between A and B solutions at the same bicarbonatemia. Thus a feedback between bicarbonate absorption and bicarbonate blood concentration was observed. If the amount of bicarbonate transferred to the patient is over the metabolic acid production, bicarbonatemia will rise: consequently bicarbonate dialysate absorption will decrease. After a few days, an equilibrium point will be reached. In this condition the bicarbonate absorption is equal to metabolic acid production and, in stable clinical conditions, a stable acid base status will be maintained by the patient. Our studies empirically demonstrated that the equilibrium is reached when a difference of 5 mmols between blood and inlet dialysate bicarbonate concentration is observed. Consequently to achieve 25 mmol/l of bicarbonatemia, the bicarbonate concentration of CAPD solution should be about 30 mmol/l.

Acetates↗
PubMed1989

Technical and clinical evaluation of a new synthetic low flux polysulphon membrane for hemodialysis.

New synthetic membranes have been developed to reduce the ultrafiltration coefficient (Kf) maintaining an adequate permeability to medium-large solutes and a good biocompatibility. The new Fresenius F6 Low Flux Polysulphon Membrane is studied in this paper as far as hydraulic and permeability properties are concerned. For this purpose in vitro and in vivo tests have been carried out in a series of different conditions. In vitro sieving coefficients were near 1 for solutes with molecular weight up to 5000 Daltons. The ultrafiltration coefficient of the device was 5.4 ml/h/mmHg while the value of Kf normalized per square meter was lower than 5 ml/h/mmHg. The geometry of the blood path was adequate even operating at high blood flows without excessive resistance and obligate filtration. This resulted in vivo in a good performance during short dialysis schedules with good clearances of small and large molecules and with no risks of backfiltration. In fact, the low permeability to water permits constant operation with positive transmembrane pressures without excessive ultrafiltration rates. The biocompatibility of the membrane was excellent and high capacity of adsorption for beta-2 microglobulin was demonstrated. These results suggest that these membranes seem to be able to join the advantages of the traditional cellulosic membranes and of the newer synthetic membranes reducing their relative disadvantages.

Biocompatible Materials↗
PubMed1989

New method of extracorporeal concentration of ascitic fluid as a treatment of refractory ascites.

A new piece of equipment for the treatment of ascites is described. Ascitic fluid is drained by gravity in a unit consisting of an Amicon D-30 ultrafilter and a bag used as transit reservoir placed below the patient. When the bag is full, it is raised to a height sufficient to let the fluid flow back through the filter to the peritoneal cavity. Mainly during this step ultrafiltration of ascitic fluid occurs through the membrane of the filter. Ultrafiltration is enhanced by the negative pressure created in the filtrate compartment due to the height difference between filter unit and filtrate drainage bag placed at the bottom of the machine. Proteins in the ascitic fluid are retained and returned to the abdominal cavity. The machine cycle is automatically repeated as many times as necessary to achieve the scheduled patient weight loss. 17 patients have been treated for a total of 1.94 sessions/patient with reinfusion of the fluid in the abdominal cavity. In all patients a significant reduction of the amount of ascitic fluid and of its rate of formation have been achieved. The treatment was well tolerated and no side effects were observed. After treatment the diuresis and the sodium excretion increased significantly in all patients. The system is safe and reliable for the treatment of refractory ascites without major complications.

Adult↗
PubMed1989

Different buffers for hemodiafiltration: a controlled study.

Hemodiafiltration (HDF) is usually performed using a dialytic solution (D) containing acetate (A) or bicarbonate (B) and a replacement fluid (RF) containing lactate (L). To clarify the role of buffers in HDF, 11 patients underwent different study periods, each three months long: bicarbonate hemodialysis (BHD = Baseline period); HDF with (A) in D and (L) in RF (first period of HDF); HDF with (A) in D and (B) in RF (second HDF); HDF with (B) in D and (L) in RF (third HDF); HDF with (B) in D and (B) in RF (fourth HDF = BHDF). HDF achieved: 1) an increase in dialytic efficiency (kt/V, 1.28), reducing the time-session (197 min); 2) an improvement in acid-base status (pre-dialytic values in BHDF: pH 7.36; pCO2 39.8 mmHg; HCO3- 21.8 mM/L); 3) better "dry weight" gain (reached in 92.8% of HDF and in 81% of BHD sessions); 4) a significant decrease, in dialytic side-effects (mainly during the third and fourth periods). On the whole, BHDF (HDF done using only bicarbonate buffer) represents an easy and safe technique, leading to better cardiovascular stability than BHD and HDF without bicarbonate buffer.

Acetates↗
PubMed1988

High-flux haemodialysis with 1.5 m2 modified cuprammonium rayon membrane: technical and clinical evaluation.

The feasibility and reliability of a short dialysis technique performed with standard dialysis equipment and a modified cuprammonium rayon hollow-fibre filter has been studied. The hydraulic response of the filter and membrane to high blood flows and transmembrane pressures were tested in vitro and the maximal clearances of different solutes achievable during high-flux bicarbonate dialysis were studied in vivo. Clinical studies were undertaken to evaluate the long-term effects of the short, highly efficient dialysis therapy. Six patients were treated for more than a year with single-pass bicarbonate dialysis with a blood flow of 500 ml/min, dialysate flow of 700 ml/min, and average duration of 150 min/session three times weekly. The treatment showed an adequate efficiency with an average KT/V greater than 1. All patients obtained an average blood urea nitrogen during the study of less than 80 mg/dl and an average protein catabolic rate of 0.9 g/kg per 24 h. The treatment was well tolerated by all patients and, on echocardiography, no significant changes in myocardial function were detected after one year of therapy. The treatment is efficient, well tolerated, simple to monitor and does not require the use of synthetic membranes or machines with advanced technology. Thus the reduction of dialysis treatment time is feasible in all centres at a relatively low cost.

Adult↗