Dialysis membrane adsorption during CRRT

Blood Flowrate and Dialysis Adequacy in Patients with Permanent Central Venous Catheters

Vascular access efficiency is a major determinant of an adequate dialytic treatment and reports from literature indicates a growing interest in the field of central venous catheterisation as permanent vascular access for hemodialysis. The main reasons are the continuous improvement in design and biomaterials along with the increased number of patients with failure of their vascular beds. In this paper it is presented and commented a series of negative crucial factors which can reduce the quality of the hemodialysis treatment: the problem of recirculation and the catheter related (and the patient related) causes of inadequate flowrate. Finally the Authors conclude with a short presentation of their clinical experience in the field.

Treatment with echinocandins during continuous renal replacement therapy

Echinocandins are indicated as first-line treatment for invasive candidiasis in moderate to severe illness. As sepsis is the main cause of acute kidney injury, the combination of echinocandin treatment and continuous renal replacement therapy (CRRT) is common. Optimizing antibiotic dosage in critically ill patients receiving CRRT is challenging. The pharmacokinetics of echinocandins have been studied under various clinical conditions; however, data for CRRT patients are scarce. Classically, drugs like echinocandins with high protein binding and predominantly non-renal elimination are not removed by CRRT, indicating that no dosage adjustment is required. However, recent studies report different proportions of echinocandins lost by filter adsorption. Nevertheless, the clinical significance of these findings remains unclear.

Cytokine immunopathogenesis of enterovirus 71 brain stem encephalitis

Enterovirus 71 (EV71) is one of the most important causes of herpangina and hand, foot, and mouth disease. It can also cause severe complications of the central nervous system (CNS). Brain stem encephalitis with pulmonary edema is the severe complication that can lead to death. EV71 replicates in leukocytes, endothelial cells, and dendritic cells resulting in the production of immune and inflammatory mediators that shape innate and acquired immune responses and the complications of disease. Cytokines, as a part of innate immunity, favor the development of antiviral and Th1 immune responses. Cytokines and chemokines play an important role in the pathogenesis EV71 brain stem encephalitis. Both the CNS and the systemic inflammatory responses to infection play important, but distinctly different, roles in the pathogenesis of EV71 pulmonary edema. Administration of intravenous immunoglobulin and milrinone, a phosphodiesterase inhibitor, has been shown to modulate inflammation, to reduce sympathetic overactivity, and to improve survival in patients with EV71 autonomic nervous system dysregulation and pulmonary edema.

Blood purification for hypercytokinemia

Blood purification has been steadily improved in the field of critical care, supported by advances in related biomedical technologies as well as efforts to develop better operating procedures. As it has become clear that hypercytokinemia plays a key role in the pathophysiology of critical pathological conditions, use of various blood purification techniques to control hypercytokinemia has been investigated. Answers to questions concerning the optimal cytokine-removing device (dialyzer/hemofilter/adsorber) as well as operating procedures and conditions of such devices in particular clinical conditions have been obtained in the course of such investigations. The recent success in real-time monitoring of cytokine levels in clinical practice to assess the extent of cytokine network activation may improve the precision and efficacy of blood purification in the treatment of hypercytokinemia. In addition, the recently documented effects of genetic factors on hypercytokinemia suggest that the introduction of tailor-made medicine considering the differences in genetic background among individual patients may improve the efficacy of blood purification as a countermeasure to hypercytokinemia.

Inflammatory response to cardiac bypass in ewe fetuses: effects of steroid administration or continuous hemodiafiltration

OBJECTIVES

We sought to investigate the effectiveness of glucocorticoid administration or continuous venovenous hemodiafiltration on endothelin and corticotropin-releasing factor release or clearance during prolonged fetal cardiac bypass and on the overall performance of fetuses.

METHODS

Circulating endothelin 1, 2, and 3 and corticotropin-releasing factor levels were measured in fetal ewes during a 60-minute cardiac bypass period performed with an inline axial flow pump. Blood samples were collected before, during, and 90 minutes after cardiac bypass. Animals were divided into 4 groups. The betamethasone group (n = 6) received maternal treatment with 12 mg of betamethasone 1 and 2 days before the experiment. The methylprednisolone group (n = 5) received fetal treatment with 40 mg/kg intravenous methylprednisolone at the beginning of cardiac bypass. The continuous venovenous hemodiafiltration group (n = 4) underwent continuous venovenous hemodiafiltration with a 0.3-m(2) polysulfone filter during cardiac bypass. The final group was the control group (n = 4).

RESULTS

Maternal steroid pretreatment failed to decrease endothelin or corticotropin-releasing factor production when compared with levels in the control animals. Fetal treatment with methylprednisolone produced a significant decrease in endothelin 2 production during cardiac bypass (P <.02) and endothelin 1 production at the end of the experiment (P <.02). Continuous venovenous hemodiafiltration blocked completely the increase of endothelin and corticotropin-releasing factor levels during cardiac bypass (P <.02), which was maintained 90 minutes after cardiac bypass. Acid-base balance was preserved during cardiac bypass by the continuous venovenous hemodiafiltration but worsened after disconnection of the extracorporeal circuit, whereas animals treated with methylprednisolone had better pH, Paco(2), and bicarbonate levels by the end of the experiment. The overall tolerance of the procedure was better in the continuous venovenous hemodiafiltration group during cardiac bypass and in the methylprednisolone group at the end of the experiment.

CONCLUSIONS

Continuous venovenous hemodiafiltration provides sustained stability of endothelin levels during fetal cardiac bypass. This technique might help, in association with fetal steroid treatment, to contain the inflammatory response leading to postbypass placental dysfunction.

The Acute Dialysis Quality Initiative--part IV: membranes for CRRT

The extracorporeal membrane used in a continuous renal replacement therapy (CRRT) for the treatment of a critically ill patient with acute renal failure (ARF) is vitally important for several reasons, including its influence on biocompatibility and filter performance. The clinical relevance of membrane-related biocompatibility markers traditionally used in chronic hemodialysis remains unclear in CRRT. Numerous approaches may be used to assess membrane and filter performance in CRRT, but no specific methodology is accepted widely at present. Although a potential benefit of certain membranes used for CRRT is adsorptive removal of inflammatory mediators, this issue has not been assessed carefully in well-designed clinical trials. These and other issues should be the subject of future clinical research efforts.

New empiric expressions to calculate single pool Kt/V and equilibriated Kt/V

Most formulae used for Kt/V computations are cumbersome and require variables that are not always available. Even the simplest models involve urea distribution volume or patient postdialysis weight. Calculating urea reduction ratio (URR) is easier and does not require additional variables, but it fails to account for residual renal function or for the removal of urea when urea levels do not change, e.g., during ultrafiltration. The goal of this study was to derive new expressions to calculate Kt/V based on URR using bivariate and multivariate linear and nonlinear models, with the URR adjusted for ultrafiltration volume and time on dialysis. Models were derived from a database of 598 dialysis records with a mean spKt/V of 1.6 (range 0.74-2.8). Models were validated on the same dataset that they were derived from and a separate dataset consisting of 17,190 dialysis records. The validation was made by comparing the empirically derived models with the Gotch and Daugirdas formulae. Among our empirically derived expressions, the closest approximation of the "gold standard," Kt/V, is the multivariate linear model of URR adjusted for ultrafiltration volume. When information about ultrafiltration is not available, the bivariate exponential formula can be successfully used to estimate Kt/V.

Effects of heat/citric acid reprocessing on high-flux polysulfone dialyzers

The surface features, morphology, and tensile properties of fibers obtained from pristine, reprocessed, and reused Fresenius Polysulfone High-Flux (Hemoflow F80A) hemodialyzers have been studied. Scanning electron microscopy of the dialyzer fibers revealed a dense skin layer on the inner surface of the membrane and a relatively thick porous layer on the outer surface. Transmission electron microscopy and atomic force microscopy showed an alteration in membrane morphology due to reprocessing and reuse, or to a deposition of blood-borne material on the membrane that is not removed with reprocessing. Fluorescent microscopy images also showed that a fluorescent material not removed by heat/citric acid reprocessing builds up with continued use of the dialyzers. The tensile properties of the dialyzer fibers were not affected by the heat/citric acid reprocessing procedure. The protein layers formed on pristine and reused hemodialyzer membranes during clinical use were also studied using sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting. A considerable amount of protein was found on the blood side of single and multiple use dialyzers. Proteins adsorbed on the dialysate side of the membrane were predominantly in the molecular weight region below 30 kDa. Little protein was detected on the membranes of reprocessed hemodialyzers.

Acute renal failure in the intensive care unit. Therapy overview, patient risk stratification, complications of renal replacement, and special circumstances

This article provides a basic definition of severity scoring among patients with acute renal failure and extends the definition into the types of dialysis support that are generally used in intensive care unit acute renal failure. Acute dialysis dosing and the problems that create a difference between chronic renal failure and acute renal failure support are described, the dialytic techniques and side effects and complications of each are compared, and nonrenal-based special situations in which extracorporeal therapy has been found to be helpful are defined.