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Biomedical subjects

L Bragantini

Publications and source records attributed to L Bragantini.

At least 19 recordsLinked to original sources
PubMed1994

Ultrafiltration and clearance studies in human isolated peritoneal vascular loops.

Eight samples of human peritoneal tissue were obtained from patients undergoing hemicholectomy for cancer. An artery and a vein were cannulated and perfused with blood in vitro with a special circuit able to provide different perfusion pressures. Ultrafiltration and clearance studies were performed in these samples. Both ultrafiltration and small-solute clearances linearly correlated with the blood flow, demonstrating a strong dependence on this parameter. The peritoneal capillary showed a typical filtration pressure equilibrium with a constant filtration fraction at different blood flows. The results suggest that the blood flow may be a factor limiting the efficiency of peritoneal dialysis both in terms of mass transfer coefficients and maximal ultrafiltration rates.

Blood↗
PubMed1994

Double pass dialysis: a new method of renal replacement in patients with malfunctioning vascular access.

Several patients undergoing chronic renal replacement therapy present problems related to their vascular access. Low blood flows and high rates of recirculation are common in such patients in which, for this reason, it becomes difficult to apply highly efficient techniques or techniques where diffusion and convection are combined as in hemodiafiltration. In these patients we studied the possibility of partially recirculating the blood in the extracorporeal circuit in order to increase the flow rate per single hollow fiber; we defined our system "double pass dialysis". We evaluated the system's efficiency in 12 patients during 24 dialysis sessions: 12 high flux dialysis sessions (without reinfusion) and 12 hemodiafiltration sessions (9 liters reinfusion). Different surfaces of polyacrylonitrile dialyzers were utilized (1.3-1.7-2.1 sqm) at 250 and 350 ml/min of blood flow with or without 100 ml/min of recirculation. During each dialysis session blood and dialysate samples were taken in order to calculate BUN, Creatinine, Phosphate and Inuline clearances from both the blood and dialysate side. The clearances of low molecular weight solutes were not really influenced by the artificial increase of the blood flow, but on the other hand, the clearances of higher molecular weight solutes increased from 10 to 30% during both high flux dialysis and hemodiafiltration with recirculation. This increase was evident mostly in hemodiafiltration suggesting that the cleaning effect on the membrane has a positive impact on the permeability. The good clinical results obtained with the double pass dialysis show that the system is safe and reliable and may become a valid support in critical situations in order to reach adequate dialysis treatment.

Adult↗
PubMed1994

A new blood module for continuous renal replacement therapies.

A new blood module for continuous renal replacement therapies has been utilized to perform CVVH in critically ill patients. The features of the new module named (HP300 and manufactured by Medica srl (Medolla, Modena) are the easy installation and transportability to the bedside, the simple and safe management and the continuous measurement of the pre and post filter pressure with automatic calculation of the end-to-end pressure drop inside the filter. The last feature permits to detect early malfunctions of the filter due to fibers clotting or due to the internal coating of the hollow fibers by plasma proteins. In both cases the efficiency of the treatment can be reduced because of a significant reduction of the ultrafiltration rates or a remarkable decay of the membrane permeability and solute sieving coefficients. In many cases this reduction is only detected when important effects on solute removal have already occurred. In our experience, the new module permitted the substitution of the filters when early malfunctions were detected and maximal treatment efficiency was therefore guaranteed over extended periods of time.

Hemofiltration↗
PubMed1991

Effect of dialysate and substitution fluid buffer on buffer flux in hemodiafiltration.

The effect of differing dialysate and substitution fluid buffer types and concentrations on acid-base balance have not been assessed in patients treated with hemodiafiltration for ESRD. To determine bicarbonate, acetate, lactate and total buffer flux, mass balance studies were performed in patients treated with hemodiafiltration using four different combinations of dialysate and substitution fluids. Driving force for bicarbonate flux was assessed in all treatments. Bicarbonate flux depended on bicarbonate driving force and ultrafiltration rate. Bicarbonate flux was negative in all treatment combinations, even when the driving force was positive. Acetate flux was positive in all treatment combinations, but the net magnitude was small. Lactate flux, when lactate containing substitution fluid was used, varied with dialysate buffer employed during treatment. Overall buffer flux depended on the bicarbonate driving force, ultrafiltration rate, and varied with the type of substitution and dialysate buffer employed. The types and concentrations of buffer used in dialysate and substitution fluid have important effects on the acid-base balance of patients treated with hemodiafiltration. The long-term implications of different therapeutical choices in these patients is unknown.

Acetates↗
PubMed1991

A multicenter, selection-adjusted comparison of patient and technique survivals on CAPD and hemodialysis.

Four hundred and eighty CAPD and 373 HD patients started regular dialysis treatment between 1981 and 1987 in 6 dialysis centers. The CAPD patients were 6 years older, on average, than the HD patients and had more complicating conditions (43.3% with 3 or more coexisting risk factors versus 28.9% with coexisting complications). The 7-year patient survival rate was not significantly different. Cox's proportional hazards regression showed that age, cardiovascular disease, cerebrovascular disease, peripheral vascular disease, diabetes, malignancy and multisystem disease had significant adverse effects on patient survival. After correcting for the influence of these factors, no significant differences in patient survival were seen. However, after 53.5 years of age, the increase in the risk of death was significantly higher in HD than in CAPD patients. Technique survival was significantly different in the 6 centers and was better for HD than for CAPD. There was no statistically significant difference between CAPD and HD technique survival when peritonitis was eliminated as a cause of failure. Based on this 7 year analysis, CAPD would appear to be an excellent alternative to HD.

Female↗
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

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

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↗
PubMed1988

Renal functional reserve in pregnancy.

Creatinine clearance has been evaluated under baseline conditions and after acute protein load in five normal and 29 pregnant women at different stages of pregnancy without evidence of renal disease. After a 3-h period in which creatinine clearance was measured hourly (resting GFR), a meal containing 80 g of proteins was administered and creatinine clearance was measured hourly for 4 h (test GFR). Resting GFR in normal subjects averaged 104 +/- 22.5 ml/min per 1.73 m2, the wide variation being due to different dietary, protein intake (from 0.3 to 1.2 g of protein per kg body weight). In the pregnant women the resting GFR increased progressively from the first month (99.8 +/- 12.8 ml/min per 1.73 m2) to the last month of gestation (149.6 +/- 12.5 ml/min per 1.73 m2). All subjects showed a significant increase of GFR after protein load although the greatest difference between the resting and the test GFR was detected in the first trimester. Inulin clearance was also measured in seven subjects after protein loading to compare creatinine and inulin clearance values. The two clearance values did not differ significantly, showing that creatinine can be safely used as a reliable marker for measuring GFR. Test GFR averaged 163.3 +/- 4.1 ml/min per 1.73 in normal subjects and 163.8 +/- 6.5 ml/min per 1.73 m2 in pregnant women without any relationship with the stage of pregnancy. The identity of test GFR both in normal subjects and in pregnant women suggests that this parameter is likely to be related to the functioning renal mass, and represents the filtration capacity of the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Technical and clinical evaluation of a new polyamide hollow fiber hemofilter for CAVH.

We carried out an in-vivo and in-vitro evaluation of a new polyamide hollow fiber hemofilter especially designed to operate under conditions of low pressure and low blood flow, such as in continuous arteriovenous hemofiltration (CAVH). The results obtained suggest that this filter is a prototype of a new generation of hemofilters especially designed for CAVH. Its low resistance permits its use even in patients with severe hypotension. The high blood flows achieved at a given pressure reduce the risk of clotting and increase the ultrafiltration rate. When an average ultrafiltration of 20-25 ml/min is achieved in 24 hours CAVH becomes very efficient, and alternative techniques to increase its efficiency are no longer required.

Acute Kidney Injury↗