Improvement of Normothermic Ex Vivo Machine Perfusion of Rat Liver Grafts by Dialysis and Kupffer Cell Inhibition With Glycine.

Normothermic ex vivo liver machine perfusion might be a superior preservation strategy for liver grafts from extended criteria donors. However, standardized small animal models are not available for basic research on machine perfusion of liver grafts. A laboratory-scaled perfusion system was developed consisting of a custom-made perfusion chamber, a pressure-controlled roller pump, and an oxygenator. Male Wistar rat livers were perfused via the portal vein for 6 hours using oxygenated culture medium supplemented with rat erythrocytes. A separate circuit was connected via a dialysis membrane to the main circuit for plasma volume expansion. Glycine was added to the flush solution, the perfusate, and the perfusion circuit. Portal pressure and transaminase release were stable over the perfusion period. Dialysis significantly decreased the potassium concentration of the perfusate and led to significantly higher bile and total urea production. Hematoxylin-eosin staining and immunostaining for single-stranded DNA and activated caspase 3 showed less sinusoidal dilatation and tissue damage in livers treated with dialysis and glycine. Although Kupffer cells were preserved, tumor necrosis factor α messenger RNA levels were significantly decreased by both treatments. For proof of concept, the optimized perfusion protocol was tested with donation after circulatory death (DCD) grafts, resulting in significantly lower transaminase release into the perfusate and preserved liver architecture compared with baseline perfusion. In conclusion, our laboratory-scaled normothermic portovenous ex vivo liver perfusion system enables rat liver preservation for 6 hours. Both dialysis and glycine treatment were shown to be synergistic for preservation of the integrity of normal and DCD liver grafts.

Population pharmacokinetics of vancomycin in critically ill patients receiving prolonged intermittent renal replacement therapy.

OBJECTIVES: The aim of this study was to describe the population pharmacokinetics of vancomycin during prolonged intermittent renal replacement therapy (PIRRT) in critically ill patients with acute kidney injury. METHODS: Critically ill patients prescribed vancomycin across two sites had blood samples collected during one to three dosing intervals during which PIRRT was performed. Plasma samples were assayed with a validated immunoassay method. Population pharmacokinetic analysis and Monte Carlo simulations were performed using Pmetrics®. The target vancomycin exposures were the area under the concentration-time curve within a 24-h period (AUC0-24)/minimum inhibitory concentration (MIC) ratio of 400 for efficacy and AUC0-24 700 for toxicity. RESULTS: Eleven critically ill patients (seven male) were enrolled and contributed 192 plasma samples. The patient's mean ± standard deviation (SD) age, weight and body mass index (BMI) were 57 ± 13 years, 98 ± 43 kg and 31 ± 9 kg/m2, respectively. A two-compartment linear model adequately described the data. The mean ± SD population pharmacokinetic parameter estimates were PIRRT clearance (CL) 3.47 ± 1.99 L/h, non-PIRRT CL 2.15 ± 2.07 L/h, volume of distribution of the central compartment (Vc) 41.85 ± 24.33 L, distribution rate constant from central to peripheral compartment 5.97 ± 7.93 per h and from peripheral to central compartment 5.29 ± 6.65 per h. Assuming a MIC of 1 mg/L, vancomycin doses of 25 mg/kg per day are suggested to be efficacious, whilst minimising toxic, exposures. CONCLUSIONS: This is the first population pharmacokinetic study of vancomycin in patients receiving PIRRT and we observed large pharmacokinetic variability. Empirically, weight-based doses that are appropriate for the duration of PIRRT, should be selected and supplemented with therapeutic drug monitoring.

Isonatric dialysis biofeedback in hemodiafiltration with online regeneration of ultrafiltrate (HFR): rationale and study protocol for a randomized controlled study.

Dialysate sodium prescription has major implications for hemodialysis tolerance but also for dialyzed patients' cardiovascular morbidity as a determinant factor of blood pressure. Biofeedback systems have been developed to drive dialysate conductivity in order to reach a prescribed serum sodium concentration, indirectly evaluated by a dialysate or an ultrafiltrate conductivity measurement. A biofeedback system using hemodiafiltration with online regeneration of ultrafiltrate (HFR) has been specially developed with an isonatric mode maintaining an equal serum sodium concentration between start and end of the dialysis session, combined with ultrafiltration and conductivity profiles. We hypothesized that using this biofeedback in an isonatric mode would have a beneficial effect on blood pressure and dialysis tolerance. The study protocol has been approved by our ethics committee and is presented herein.

Effects of modified ultrafiltration on coagulation as measured by the thromboelastograph.

Hemodilution during cardiopulmonary bypass (CPB) continues to be a cause of morbidity associated with coagulation dysfunction, bleeding, and allogeneic blood transfusion. Clot formation and strength have been shown to impact bleeding and transfusions. Strategies to reduce hemodilution may be negated based on the course of the cardiac procedure itself. Modified ultrafiltration (MUF) is commonly used in pediatric cardiac surgery; however, it is not well accepted in adult surgery. This study aimed to evaluate clot formation and strength, bleeding, and transfusions in adult subjects undergoing MUF. Nineteen subjects having primary coronary artery bypass, aortic, or mitral valve surgeries were recruited and randomized to having MUF (n = 10) or no-MUF (n = 9) performed after the termination of CPB. Five time points for data collection were designated: T1, baseline/induction; T2, termination CPB; T3, post-MUF; T4, post-protamine; T5, 24 hours postoperative. Subjects randomized to MUF had 1505 +/- 15.8 mL of effluent removed, and no-MUF subjects had the CPB remnants processed with a cell salvage device. There was no statistical difference seen in 24-hour chest tube output, thromboelastograph values, or allogeneic transfusions at any time point between MUF and no-MUF subjects. There was a significant difference between MUF and no-MUF in the number of autologous cell salvage units processed (1.3 +/- .48 vs. 2.9 +/- .78, p = .0013) and end of procedure net fluid balance (+2003 +/- 1211 vs. +4194 +/- 1276 mL, p = .001), respectively. Estimated plasma loss from the cell salvage device was 477.6 mL greater in the no-MUF group. In primary adult cardiac procedures, MUF did not change coagulation values as measured by thromboelastography, number of allogeneic unit transfusions, or chest tube output at 24 hours postoperatively. There was a significant difference in autologous cell salvage units processed and end of procedure net fluid balance that benefited MUF subjects.

[Experiment on the formation and characterizations of anodic alumina membrane for use in hemodialysis].

The correlations between various formation conditions and the membrane pore characterizations of the anodic alumina membrane were investigated for seeking the optimal conditions for the formation of anodic alumina membrane. High purity aluminum foils were used as the starting materials. The anodizations were conducted under three types of electrolytes, 3% sulfuric acid, 5% sulfuric acid and 2.7% oxalic acid, respectively, with different voltages at 0 degrees C for 48 hours. The characterizations of the pore size, the effective porosity and the pore porosity were observed and determined by scanning electron microscopy. The hydraulic conductance of the membranes was measured to confirm that the pores were open and to evaluate the permselectivity of the membranes. The experimental results showed that the ordered pore arrays were obtained for oxidation under our experimental conditions. While the forming voltage was increasing, the pore size and pore porosity increased significantly (P < 0.05), and the effective porosity decreased significantly (P < 0.05). The pore size formed with 3% sulfuric acid or 5% sulfuric acid was much smaller than that with 2.7% oxalic acid as an electrolyte. The hydraulic conductance of anodic alumina membrane that formed under our experimental condition was high than those of the membranes currently available in clinical procedures. The results suggested that the optimal conditions for the formation of anodic alumina membrane to be used in hemodialysis should be 3% or 5% sulfuric acid with 12.5 V to 17.5 V at 0 degrees C for 48 hours.

Sequential hemofiltration-hemodiafiltration technique: all in one?

Sequential dialysis techniques (i.e. pure ultrafiltration followed by dialysis) have been used in the past, due to their capability to remove large volumes of fluids without inducing hemodynamic instability. The disadvantages of the inadequate dialysis and the lack of technology lead to the decline such methods. Hemofiltration (HF) and hemodiafiltration (HDF) are recently being utilized in a greater proportion thanks to the on line fluid preparation systems. Each process (HF and HDF) has its own benefits in the removal of small, medium and high-molecular weight substances and in the hemodynamic stability. Sequential hemofiltration/ hemodiafiltration (SHF/HDF), may combine the benefits and eliminate the disadvantages of each method. Furthermore they can be easily applied nowadays, due to the development of new high technological hemodialysis machines. In order to evaluate the feasibility and the effects of SHF/HDF we studied 7 chronic hemodialysis patients (6 months of treatment with SHF/HDF switched to 6 months of SHDF/HF), using the same machine (AK200 ULTRA), with on line fluid preparation system and the same type of dialyzer (Polyflux 210). The feasibility of such techniques (SHF/HDF or vice versa) resulted excellent. All sessions left the patients in a condition of well-being making fulltime work. No difference was observed between the different period of treatment, but a reduction in pre value was observed in calcium-phosphorous product, C-reactive protein and beta2-microglobulin, at the end of the sequential techniques. SHF/HDF therapy is a very promising technique. Further studies are needed to better explore the potential of such a therapeutic approach in the quality of life, the hemodialysis adequacy and the hemodynamic stability of our patients.

Homocysteine as a cardiovascular risk factor.

UNLABELLED: Hyperhomocysteinemia (HH), a known risk factor for vascular diseases, is a frequent condition in hemodialysis (HD) patients. HH induces an oxidant stress to the vascular endothelium, causing a failure of vasodilation and an impairment of the antithrombotic properties. Vitamins B(6), B(12) and folic acid are important cofactors for the enzymes in the catabolism of homocysteine (Hcy). Failure of Hcy catabolism forces the cell to export Hcy into the plasma. The kidney is an important metabolic site for removal (up to 70%) of plasma Hcy (P-Hcy). HD lowers the P-Hcy concentration by 29 and 41% with cellulosic and noncellulosic membranes, respectively, yet values return to normal in only a few patients. Clearly, we must decrease the dangerous high levels of Hcy in different ways. Vitamin Supplementation: Vitamins B(6), B(12) and folic acid decreased the basal level of Hcy by about 40%, starting from the sixth month. Membranes: Some membranes performed better than the others. TECHNIQUES: On the chronic basis, in our 1-year experience, paired filtration dialyis led to the best results, when compared to bicarbonate dialysis and acetate-free biofiltration. Finally, as in HD patients no one type of treatment can normalize the P-Hcy concentration, we should try other, different strategies such as absorption, the use of liposomes and new types of supplementation.

Novel online infusate-assisted dialysis system performs microbiologically safely.

Administration of adequate amounts of commercial infusion fluids renders modern convective dialysis modalities, such as hemodiafiltration, labor-intensive and costly. Preparation of infusate by cold sterilization of dialysis fluid, which is abundantly available, and its immediate (online) use, in contrast, enables a large volume fluid exchange in a cost-effective manner. Recent developments aimed at more hygienic and user-friendly online systems with increased operational flexibility. As a result the novel ONLINEplus system does not only provide online prepared infusate for convective dialysis therapy, but also for priming and rinsing of the extracorporeal blood circuit, for intradialytic bolus administration, and for re-infusion of patients' blood as well. Production of infusate from potentially impure dialysis fluid containing endotoxins and other pyrogens raises severe concerns of affecting the patients' well-being. To assess its safety, the online system was challenged with microbially contaminated dialysis fluid. Despite high levels of microbial counts (7.5 x 104 +/- 105 CFU/ml), endotoxin concentration (14.1 +/- 7.7 IU/ml and 9.265 +/- 3.000 IU/ml, as measured turbidimetrically and chromogenically, respectively) and cytokine-inducing activity (20,827 +/- 3,082 pg IL-1Ra/Mio WBC), we failed to detect contaminants in the final infusate during a 5 week laboratory testing period. In addition, infusate samples complied consistently with the European Pharmacopeia test for sterility. The present online system is comprehensive, operates user-friendly, and provides microbiologically safe infusate in large quantities. In this way, both patients and dialysis staff will benefit from improved dialysis therapy and reduced treatment-related labor burden, respectively. Moreover, convective dialysis modalities will become less expensive.