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Biomedical subjects

C Ronco

Publications and source records attributed to C Ronco.

At least 163 records · Page 9Linked to original sources
PubMed1999

Online monitoring in continuous renal replacement therapies.

Technical improvements in dialysis equipment for chronic hemodialysis patients has mirrored improvements in continuous renal replacement therapies (CRRTs) for patients with acute renal failure who are critically ill. This article reviews the available types and importance of online monitors such as urea sensors to provide real-time urea kinetic parameters, temperature sensors to target thermal balance throughout each session, conductivity measurement of sodium balance in the dialysate, blood volume monitoring to aid against cardiovascular instability and treatment-induced hypotension, biofeedback systems, and remote dialysis/teledialysis for efficient use of trained personnel.

Biosensing Techniques↗
PubMed1999

Use of adsorptive mechanisms in continuous renal replacement therapies in the critically ill.

The pathophysiology of sepsis is becoming a more complicated scenario. In sepsis, endotoxin or other gram-positive derived products induce a complex and dynamic cellular response giving rise to several mediators known to be relevant in the pathogenesis of septic shock, such as specific mediators. substances responsible for up- or down-regulation of cytokine receptors and cytokine antagonists, inactivators of nuclear factor-kappaB or signal transduction pathways, and precursor molecules. In this article, we delve into some new concepts stemming from the use of sorbents in continuous plasma filtration. The rationale is based on the assumption that the nonspecific removal of several mediators of the inflammatory cascade and cytokine network may improve outcome in a rabbit model of septic shock and hemodynamics in a pilot clinical study. The importance of looking for innovative treatments specifically targeted for the special needs of the critically ill patients rather than using concepts and technology applied to the treatment of chronic renal failure is underlined.

Animals↗
PubMed1999

Renal replacement therapy in the intensive care unit.

OBJECTIVE: To present an overview of the principles of renal replacement therapy, its application in the critically ill patient, and an update of recent research in this area. DATA SOURCES: Articles and published peer-review abstracts on the beneficial effects of continuous renal replacement therapy (CCRT) in the critically ill patient. SUMMARY OF REVIEW: Renal replacement therapy utilizes dialysers that enable solute and solvent to move across semipermeable membranes in either a convective or diffusive fashion. In the critically ill patient, percutaneous vascular access and improvement in dialysis machines, have facilitated the intensive care unit management of acute renal failure in these patients. Currently, CCRT is most often used to manage the critically ill patient with acute renal failure, as it is less likely to produce hypotension when compared with intermittent haemodialysis. However, CCRT has been expanded to manage critically ill patients with multiple organ failure, with the demonstration that it is able to remove or adsorb putative mediators of organ dysfunction. While there are experimental and uncontrolled clinical data that have suggested that this form of therapy is beneficial, currently there are no prospective randomised, controlled trials that have confirmed this benefit when used in these patients. CONCLUSIONS: Continuous renal replacement therapy has become commonplace in the management of critically ill patients with acute renal failure. It has the advantage of causing less hypotension and a more gradual return of the fluid and electrolyte status, when compared with intermittent haemodialysis. Recent evidence suggests that it may also be a useful immunomodulator and may be beneficial in the management of patients with multiple organ failure.

Journal Article↗
PubMed1998

Enhancement of convective transport by internal filtration in a modified experimental hemodialyzer: technical note.

BACKGROUND: Hemodialysis using high flux membranes today is a commonly used therapy. The primary advantage is the larger spectrum of molecules removed with these membranes, and the mechanism of removal is in part due to a phenomenon of filtration and backfiltration along the length of the hollow fibers. We hypothesized that increasing the filtration and backfiltration fluxes by modifying the structure of the dialyzer could enhance the convective transport of various solutes. METHODS: A modified high flux dialyzer was compared to the standard model in terms of pressure profiles, filtration-backfiltration rates and solute clearances. The modification consisted on the placement of a O-ring around the fiber bundle to create a resistance for the flow of the dialysis solution external to the fibers. The study on filtration fluxes was carried out using a scintigraphic method previously described, and solute clearances were studied during ultrafiltration-controlled hemodialysis sessions. RESULTS: Utilizing a net filtration condition proximal to zero, the rates of proximal filtration and distal backfiltration in the experimental dialyzer were significantly enhanced in comparison with the standard dialyzer. The pressure drop in the dialysate compartment could be increased significantly, thus permitting an increase in the positive transmembrane pressure in the first half of the dialyzer and a parallel increase in the negative transmembrane pressure in the second half of the dialyzer. This resulted in a significant enhancement of the convective transport of middle-large solutes as demonstrated by the increase in vitamin B12 and inulin clearances. CONCLUSIONS: This approach suggests that changes in design of the dialyzer may affect its performance. The use of internal filtration is suggested to improve convection and dialyzer efficiency for larger solutes without the requirement for high volumes of replacement fluid, as is the case for current hemodiafiltration techniques.

Hemodiafiltration↗
PubMed1998

Chronic renal replacement therapy in children: which index is best for adequacy?

BACKGROUND: The dialysis dose, Kt/V, and Solute Removal Index (SRI) have been proposed as tools to measure and compare adequacy of different renal replacement therapies in adults. The aim of our study was to elucidate whether the Kt/V and SRI could be appropriate parameters to compare different treatments and define adequacy targets in children. METHODS: Twenty-two pediatric chronic dialysis patients (2 to 17 years) were prospectively studied. Six patients were on continuous ambulatory peritoneal dialysis (CAPD), 7 patients were on automatic nightly peritoneal dialysis (ANPD), and 9 were on hemodialysis (HD). Patients had no peritonitis and were not hospitalized during the previous two months and, as proved by growth and subjective well being, were in steady state condition at the initiation of the protocol. As a consequence, the treatment delivered was assumed to be adequate and the prospective analysis was carried out within one month. Urea levels in dialysate, plasma and urine were measured to determine urea kinetics and measure adequacy parameters. RESULTS: Instantaneous urea clearance was much higher when hemodialysis was used (124.67 +/- 32.04 ml/min) compared to CAPD (2.79 +/- 0.29 ml/min) and ANPD (6.60 +/- 1.42 ml/min), as expected. The Urea dialytic clearance per week was greater in HD (67320 +/- 17299 ml) than in CAPD(28144 +/- 2895 ml) and ANPD (29910 +/- 4234 ml). Residual renal function contributed to the overall weekly clearance by 47% in CAPD, while it was only by 19% in HD and 26% in ANPD. The overall weekly clearance was therefore 79,842 ml/week in HD, 53,340 ml/week in CAPD and 41,012 ml/week in ANPD. Weekly dialytic Kt/V results were much higher in HD (3.75) than in CAPD (1.78) and ANPD (2.37). To these values, the renal Kt/V was added, reaching the values of overall (dialytic + renal) weekly Kt/V of 4.53 in HD, 3.41 in CAPD and 3.41 in ANPD. Although higher Kt/V values were observed in HD, when the SRI % was considered, HD appeared to be less efficient compared with the other two techniques. Since postdialytic rebound in HD patients averaged 22.5%, we may speculate that hemodialysis in children is less efficient than continuous or daily peritoneal dialysis because of a remarkable cardipulmonary recirculation and solute sequestration. CONCLUSION: In the global evaluation, dialysis SRI% appears to be more reliable as an index of adequacy compared to Kt/V in children. At least an integration between the two indices is strongly recommended.

Adolescent↗
PubMed1998

Removal of cytokines and activated complement components in an experimental model of continuous plasma filtration coupled with sorbent adsorption.

BACKGROUND: Sepsis is associated with enhanced cytokine production. Here, we examined the in vitro removal of plasma cytokines during continuous plasmafiltration coupled with sorbent adsorption. METHODS: Proinflammatory (tumour necrosis factor-alpha, interleukins-1, -8) and anti-inflammatory (interleukin 1 receptor antagonist, soluble tumour necrosis factor receptor type I and II) cytokines in whole blood spiked with Escherichia coli endotoxin were determined during 2-h recirculation in the ultrafiltrate (condition A), plasma filtrate (condition B), before and after different sorbents (of the Amberlite-, Amberchrome- Ambersorb -type and charcoal). We studied the maximal adsorbing capacity, the 1% leakage test for cytokines and C3a des Arg and the adsorption of complement-dependent leukocyte chemiluminescence. Plasma proteins eluted from the resins were examined by sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblotting with an anti-human alpha2-macroglobulin. RESULTS: In condition B, we observed a 40- and 121-fold % increase (vs condition A) in the removed mass and clearance of tumour necrosis factor-alpha. For all other cytokines, the removed mass and the clearance increased from 2.3- up to 6-fold. The Amberchrome but not the Amberlite or Ambersorb resins could remove the highest amount of cytokines and could reduce complement-dependent chemiluminescence. Two protein bands of approximately 400,000 D and 200,000 D were eluted only from Amberchrome resins and immunoprecipitated by anti-human alpha2-macroglobulin and anti-human C3c antibodies, respectively. CONCLUSIONS: These studies suggest an efficient removal of cytokines in continuous plasmafiltration with sorbent adsorption. The binding of alpha2-macroglobulin, a carrier of cytokines in plasma, might be a additional mechanism in the removal of cytokines from plasma.

Adsorption↗
PubMed1998

Hemodynamic support and the role of dopamine.

The armamentarium of the critical care nephrologist contains several vasoactive and inotropic drugs with powerful effects on the systemic circulation. The physiologically logical use of these drug can be life-saving and have important beneficial effects on renal function. Such drug use must absolutely not be based on a "fixed dosage," but must instead be goal-directed with the aim of achieving those physiological states associated with hemodynamic stability and adequate vital organ perfusion. The achievement and maintenance of these goals must be prompt and guided by appropriate invasive hemodynamic monitoring and may require frequent changes in dosage. When these measures are adhered to, renal protection and clinical success are a much more likely outcome than when stereotyped approaches are followed.

Acute Kidney Injury↗
PubMed1998

Indications and criteria for initiating renal replacement therapy in the intensive care unit.

The decision to initiate renal replacement therapy is usually based on a careful assessment of conflicting priorities in the care of critically ill patients. It is particularly difficult because of the lack of information on what are the optimal criteria and indications for the application of renal replacement therapy (RRT) in the intensive care unit (ICU). As we will discuss in this paper, even though there are several time-honored indications for initiating dialytic therapy in patients with near end-stage renal failure, such indications may not apply to the management of acute renal failure (ARF). In fact, there are several reasons why a more aggressive approach and an earlier intervention may be justified in the ICU.

Acidosis↗
PubMed1998

Renal replacement therapy in acute renal failure: solute removal mechanisms and dose quantification.

Based on numerous studies demonstrating a direct relationship between survival and delivered hemodialysis (HD) dose in end-stage renal disease (ESRD), quantification of delivered HD is now routinely performed in this setting. Recently, investigators have also begun applying kinetic modeling principles to quantify delivered dialysis dose in patients with acute renal failure (ARF). One purpose of this article is to review these ARF studies. However, a broader objective is to provide an overview of the solute removal capabilities of both intermittent and continuous therapies used in ARF. To achieve this goal, the dialytic removal mechanisms for solutes over a wide molecular weight spectrum are discussed.

Acute Kidney Injury↗
PubMed1998

Continuous renal replacement therapy: evolution in technology and current nomenclature.

The evolution of technology and biomaterials has permitted a parallel development of renal replacement therapies in the acute, critically ill patient. From the original description of continuous arteriovenous hemofiltration (CAVH), new techniques such as continuous venous venous hemofiltration (CVVH), hemodiafiltration (HDF) and high flux dialysis (HFD) have been developed and clinically utilized. A parallel improvement in efficiency has been achieved with daily clearances of urea as high as 50 liters or more. The use of special highly permeable dialyzers has also permitted increases in the clearances of larger solutes, thus leading to significant removals of chemical substances involved the acute inflammation and sepsis. In this field, recent observations have suggested the use of hemofiltration with high volumes of fluid exchange. The hardware and software of the newer continuous renal replacement therapy (CRRT) systems are certainly the key points in achieving these results and in safely performing such challenging techniques.

Acute Kidney Injury↗