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Biomedical subjects

C Ronco

Publications and source records attributed to C Ronco.

At least 37 records · Page 2Linked to original sources
PubMed1995

Removal of platelet-activating factor in experimental continuous arteriovenous hemofiltration.

OBJECTIVE: There is a positive correlation between the amount of ultrafiltration and the improved survival rate of patients with ischemia or sepsis-induced acute renal failure. Continuous arteriovenous hemofiltration (CAVH) removes vasoactive substances with a molecular weight of < 1000 daltons. This study evaluated the removal of platelet-activating factor, a lipid mediator of endotoxic shock, by CAVH with respect to kinetics, adsorption, and ultrafiltration. DESIGN: Prospective laboratory study. SUBJECTS: Normal human subjects. INTERVENTIONS: Radioactive [3H] or biologically active platelet-activating factor was added to whole blood or washed blood resuspended in Tris-buffered (pH 7.2) physiologic saline with 4% human serum albumin or plasma. Whole or washed blood cells or plasma were recirculated at 100 mL/min through polysulfone hemofilters for 120 mins with ultrafiltration (condition A), without ultrafiltration (condition B), or in a static condition (condition C). Concentrations of albumin, total protein, and radioactive or biologically active platelet-activating factor in samples obtained from the blood and ultrafiltrate compartment were determined. MEASUREMENTS: Biologically active platelet-activating factor was quantified on washed rabbit platelets and results were expressed in ng/mL over a calibration curve obtained with synthetic platelet-activating factor. MAIN RESULTS: [3H]-platelet-activating factor added to recirculated whole blood was ultrafiltered (percent of ultrafiltered platelet-activating factor/min: 0.48 +/- 0.02 [SD]; total platelet-activating factor removed in 120 mins: 15.52%; condition A) at significantly (p < .001) higher amounts than when added to washed blood cells (percent of ultrafiltered platelet-activating factor removed/min: 0.195 +/- 0.06; total platelet-activating factor removed in 120 mins: 7.46%). The highest amounts of [3H]-platelet-activating factor were bound to polysulfone membranes after recirculation with whole blood (44.5 +/- 12.2%) than with washed blood (1.1 +/- 0.3%) or plasma (11.9 +/- 0.7%). Biologically active platelet-activating factor concentrations significantly decreased in both conditions A and B (maximal decrease at 120 mins: 63% and 59%, respectively). No significant reduction could be observed in condition C. CONCLUSIONS: These studies provide experimental evidence for the prompt, efficient removal of platelet-activating factor in CAVH and provide a possible rationale for the beneficial effect of this therapy in the development of multiple organ failure in sepsis.

Adsorption↗
PubMed1995

Treatment of acute renal failure in intensive care patients by continuous arteriovenous hemofiltration (CAVH): two years' experience in two centres.

The study objective was to evaluate the outcome of continuous arteriovenous hemofiltration (CAVH) as a first choice treatment for acute renal failure (ARF) in critically ill intensive care patients in two centres with a long experience in the field of continuous renal replacement therapies. Sixty consecutive intensive-care ARF patients from Uppsala Centre and 71 consecutive ARF patients from Vicenza Centre were included during a period of two years. Their age range was 58 +/- 16 and 52 +/- 15 years in Uppsala and Vicenza, respectively. CAVH was performed in the postdilution form using different types of hemofilters. Three choices of vascular access were utilised in each centre, namely: the Buselmeier shunt, femoral vessel catheter and the Scribner shunt. The pre-treatment serum urea level (mean +/- SD) in the Uppsala patients (30 +/- 14 mmol/l) was significantly higher (p < 0.001) than that of the Vicenza patients (17 +/- 10 mmol/l). The Uppsala patients had a longer treatment duration than the Vicenza patients; 8 +/- 6 vs 5 +/- 5 days (p < 0.05) perhaps because they were much older than the Vicenza patients (p < 0.05) in addition to their multi-organ failure. However, the total outcome of CAVH in the two centers was not significantly different (52 and 58% patient's survival in Uppsala and Vicenza, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1995

Achievements and new directions in continuous renal replacement therapies.

The evolution of renal replacement therapy has permitted the treatment of critically ill patients with acute renal failure. In intensive care settings, continuous renal replacement therapies have been shown to be better tolerated and clinically useful. Continuous hemofiltration is now performed with blood pumps and double-lumen venous catheters, thus avoiding the complications found in previous arteriovenous treatments. The use of countercurrent dialysate flow has overcome problems related to low treatment efficiency. High clearances can now be obtained during continuous hemodialysis or hemodiafiltration, and adequate blood purification can be achieved even in severely catabolic patients. New replacement solutions allow for a more effective correction of acidosis and electrolyte imbalances. Finally, newly designed machines permit continuous therapies while minimizing staff workload. Continuous therapies are today moving toward newer indications and applications. The ability to remove proinflammatory substances by filtration and/or adsorption has opened a series of potential indications. The concept that renal support and protection take place during hemofiltration suggests that very early use of this technique is desirable, even before the onset of oliguria or azotemia.

Acute Kidney Injury↗
PubMed1995

On-line urea monitoring: a further step towards adequate dialysis prescription and delivery.

The aim of this study is to present a clinical experience carried out with a new device designed to measure on-line Urea Nitrogen concentration in the effluent dialysate. The Biostat 1000 Urea Monitor (Baxter Healthcare, Dirfield, Ill, USA) was utilized in the present study. The monitor is based on the principle that multiple urea measurements in the dialysate effluent from the dialyzer, permit to built a double exponential regression leading to the urea kinetic parameters of the dialysis session. Data obtained with the Urea Monitor were, in the present study, compared with those obtained by direct measurements carried out in blood and dialysate and by the collection of the whole amount of spent dialysate. The monitor provided an accurate value of predialysis BUN without any blood drawing. Urea kinetics were established from multiple dialysate measurements and no blood drawing was necessary. The double pool kinetics were taken into account and Kt/V, PCR and SRI% obtained were comparable to those obtained from direct measurement. Since a projected value of Kt/V can be obtained, the monitor could represent a potential source of information to detect possible filter and machine dysfunction, as well as high rate of recirculation.

Adult↗
PubMed1994

Assessment of adequacy in peritoneal dialysis.

Adequacy of peritoneal dialysis has been less well studied than that of hemodialysis. Fractional urea removal, total creatinine removal, and various indices have been proposed to reflect or predict patient morbidity and mortality. No prospective study has been published in this regard. To evaluate this area further, in addition to reviewing selected literature, 45 continuous ambulatory peritoneal dialysis (CAPD) patients were recruited in two dialysis centers for a prospective study on treatment adequacy. Patients were well rehabilitated and had no peritonitis or hospitalization in the 6 months before the study. Urea and creatinine kinetics were analyzed, as were dietary intake and fluid balance. The weekly Kt/V, calculated to include peritoneal and residual renal clearance (KprT/V), averaged 1.77 with a Kt/V hemodialysis equivalent of 0.59. Patients with residual renal function (58% of the studied population) had an average residual renal clearance of 3.42 mL/min, and had lower steady-state concentrations of urea nitrogen and creatinine in the plasma than patients with no residual renal function. As a consequence, a lower percent excretion of urea and creatinine in the peritoneal fluid was observed in the former patients compared with the latter, where the peritoneal route was the only one for solute excretion. The concentration profiles in blood appear to be the critical factor in achieving the final target of the treatment, ie, the excretion of the overall amount of waste products derived from protein and other metabolic pathways. The constant blood levels in CAPD explain why such a low Kt/V can be adequate whereas, in hemodialysis, a higher Kt/V is required.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
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

On line filtration of dialysate: structural and functional features of an asymmetric polysulfone hollow fiber ultrafilter (Diaclean).

The endotoxin transfer across dialysis membranes has been investigated using specific in vitro circuits. Backdiffusion and backfiltration have been analyzed and most dialysis membranes have shown to be permeable to LAL positive substances. Synthetic membranes however display the better capacity of retention of these products despite their higher porosity and permeability. For such reason synthetic polysulfone ultrafilters are used as pyrogen filters to obtain ultrapure dialysate. We have investigated the characteristics of a polysulfone ultrafilter named Diaclean and manufactured by Amicon Ireland. The capacity of endotoxin retention has been investigated both in filtration and backfiltration modes on new and used ultrafilters. The capacity of endotoxin adsorption was investigated as well. Used ultrafilters appeared to maintain the retention capacity and the adsorption capacity up to 4 months of use. Only slight differences were noted from the baseline values (p = n.s.). The best adsorption capacity is always displayed by the outer layer of the membrane suggesting its best utilization in back filtration mode with tangential flow. No morphological changes were observed in the used membrane analyzed by scanning electron microscopy.

Diffusion↗
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↗