Targeting arterial partial pressure of carbon dioxide in acute respiratory distress syndrome patients using extracorporeal carbon dioxide removal.

BACKGROUND: A retrospective analysis of SUPERNOVA trial data showed that reductions in tidal volume to ultraprotective levels without significant increases in arterial partial pressure of carbon dioxide (PaCO2 ) for critically ill, mechanically ventilated patients with acute respiratory distress syndrome (ARDS) depends on the rate of extracorporeal carbon dioxide removal (ECCO2 R). METHODS: We used a whole-body mathematical model of acid-base balance to quantify the effect of altering carbon dioxide (CO2 ) removal rates using different ECCO2 R devices to achieve target PaCO2 levels in ARDS patients. Specifically, we predicted the effect of using a new, larger surface area PrismaLung+ device instead of the original PrismaLung device on the results from two multicenter clinical studies in critically ill, mechanically ventilated ARDS patients. RESULTS: After calibrating model parameters to the clinical study data using the PrismaLung device, model predictions determined optimal extracorporeal blood flow rates for the PrismaLung+ and mechanical ventilation frequencies to obtain target PaCO2 levels of 45 and 50 mm Hg in mild and moderate ARDS patients treated at a tidal volume of 3.98 ml/kg predicted body weight (PW). Comparable model predictions showed that reductions in tidal volumes below 6 ml/kg PBW may be difficult for acidotic highly severe ARDS patients with acute kidney injury and high CO2 production rates using a PrismaLung+ device in-series with a continuous venovenous hemofiltration device. CONCLUSIONS: The described model provides guidance on achieving target PaCO2 levels in mechanically ventilated ARDS patients using protective and ultraprotective tidal volumes when increasing CO2 removal rates from ECCO2 R devices.

Modeling acid-base balance for in-series extracorporeal carbon dioxide removal and continuous venovenous hemofiltration devices.

Patients with acute respiratory distress syndrome and acute kidney injury (AKI) treated by kidney replacement therapy may also require treatment with extracorporeal carbon dioxide removal (ECCO2 R) devices to permit protective or ultraprotective mechanical ventilation. We developed a mathematical model of acid-base balance during extracorporeal therapy using ECCO2 R and continuous venovenous hemofiltration (CVVH) devices applied in series for the treatment of mechanically ventilated AKI patients. Published data from clinical studies of mechanically ventilated AKI patients treated by CVVH at known infusion rates of substitution fluid without ECCO2 R were used to adjust the model parameters to fit plasma levels of arterial partial pressure of carbon dioxide (PaCO2 ), arterial plasma bicarbonate concentration ([HCO3 ]), and plasma pH (as well as certain other unmeasured physiological variables). The effects of applying ECCO2 R at an unchanged and a reduced tidal volume on PaCO2 , [HCO3 ] and plasma pH were then simulated assuming carbon dioxide removal rates from the ECCO2 R device measured in the clinical studies. Agreement of such model predictions with clinical data was good whether the ECCO2 R device was positioned proximal or distal to the CVVH device in the extracorporeal circuit. Although carbon dioxide removal rates from the ECCO2 R device measured in one previous clinical study were higher when it was placed proximal to the CVVH device, suggesting that such in-series positioning was optimal, the current mathematical model demonstrates that proximal positioning of the ECCO2 R device also results in lower bicarbonate (and, therefore, total carbon dioxide) removal from the distal CVVH device. Thus, the removal of total carbon dioxide by such extracorporeal circuits is relatively independent of the position of the in-series devices. It is concluded that the described mathematical model has quantitative accuracy; these results suggest that the overall acid-base balance when using ECCO2 R and CVVH devices in a single extracorporeal circuit will be similar, independent of their in-series position.

Intradialytic kinetics of middle molecules during hemodialysis and hemodiafiltration.

BACKGROUND: The kinetics of ß2-microglobulin during hemodialysis and hemodiafiltration is well described by a two-compartment model where clearance by the dialyzer is from a central compartment volume that approximates plasma volume and a total distribution volume that approximates extracellular fluid volume. The kinetics of middle molecules with molecular weights larger than ß2-microglobulin have not been extensively studied. METHODS: Intradialytic plasma concentrations and overall dialyzer clearances of ß2-microglobulin (11.8 kD), myoglobin (16.7 kD) and complement factor D (24.4 kD) were used to estimate three kinetic parameters from a two-compartment model, namely intercompartmental clearance, central compartment volume and total distribution volume, in hemodialysis patients; these data were collected during two clinical trials of medium cut-off dialyzers (with extended middle molecule removal) during hemodialysis and high-flux dialyzers during hemodialysis and hemodiafiltration. In the current exploratory analyses, the kinetic parameters from all dialyzers were combined. Overall dialyzer clearance was evaluated by total mass removed in the dialysate. RESULTS: In total, 345 sets of kinetic parameters from 35 patients were determined. Intercompartmental clearance and central compartment volume for myoglobin and complement factor D were smaller (P < 0.001) than those for ß2-microglobulin. Independent of middle molecule, intercompartmental clearance and central compartment volume were associated with overall dialyzer clearance (P < 0.001), but total distribution volume was not (P = 0.083). CONCLUSIONS: A two-compartment kinetic model can only describe intradialytic kinetics of middle molecules with molecular weights larger than ß2-microglobulin if the central compartment is small and dependent on overall dialyzer clearance.

A Double-Blind Randomized Controlled Trial of High Cutoff Versus Standard Hemofiltration in Critically Ill Patients With Acute Kidney Injury.

OBJECTIVES: In critically ill patients with acute kidney injury receiving vasopressors, high cytokine levels may sustain the shock state. High cutoff hemofiltration achieves greater cytokine removal in ex vivo and in animal models and may reduce the duration of shock but may also increase albumin losses. DESIGN: This was a single-center double-blind randomized controlled trial comparing continuous venovenous hemofiltration-high cutoff to continuous venovenous hemofiltration-standard. SETTING: Tertiary care hospital in Australia. PATIENTS: Vasopressor-dependent patients in acute kidney injury who were admitted to the ICU. INTERVENTIONS: Norepinephrine-free time were calculated in critically ill vasopressor-dependent patients in acute kidney injury, randomized to either continuous venovenous hemofiltration-high cutoff or continuous venovenous hemofiltration-standard. MEASUREMENT AND MAIN RESULTS: A total of 76 patients were randomized with the following characteristics (continuous venovenous hemofiltration-high cutoff vs continuous venovenous hemofiltration-standard); median age of 65 versus 70 year, percentage of males 47% versus 68%, and median Acute Physiology and Chronic Health Evaluation scores of 25 versus 23.5. The median hours of norepinephrine-free time at day 7 were 32 (0-110.8) for continuous venovenous hemofiltration-high cutoff and 56 hours (0-109.3 hr) (p = 0.520) for continuous venovenous hemofiltration-standard. Inhospital mortality was 55.6% with continuous venovenous hemofiltration-high cutoff versus 34.2% with continuous venovenous hemofiltration-standard (adjusted odds ratio, 2.49; 95% CI, 0.81-7.66; p = 0.191). There was no significant difference in time to cessation of norepinephrine (p = 0.358), time to cessation of hemofiltration (p = 0.563), and filter life (p = 0.21). Serum albumin levels (p = 0.192) were similar and the median dose of IV albumin given was 90 grams (20-212 g) for continuous venovenous hemofiltration-high cutoff and 80 grams (15-132 g) for continuous venovenous hemofiltration-standard (p = 0.252). CONCLUSIONS: In critically ill patients with acute kidney injury, continuous venovenous hemofiltration-high cutoff did not reduce the duration of vasopressor support or mortality or change albumin levels compared with continuous venovenous hemofiltration-standard.

Membrane innovation: closer to native kidneys.

Modern methods in analytical biochemistry have established that uraemia is associated with the retention of proteins, both in their native state and post-translationally modified, over a wide range of molecular weights up to 60 kDa. Evidence is accumulating that these higher molecular weight retention solutes are important uraemic toxins, and therapies such as online haemodiafiltration (HDF), which enhance their removal, are associated with improved outcomes. However, HDF has limitations regarding cost, clinical implementation and the need for an external source of sterile substitution solution to maintain fluid balance. New membranes that have a solute removal profile more closely approaching that of the glomerular filtration barrier when used for conventional haemodialysis, while at the same time not allowing the passage of clinically significant amounts of beneficial proteins, are needed to address these limitations. Tighter control of the molecular characteristics of the polymers used for membrane fabrication, along with the introduction of additives and improvements in the manufacturing process, has led to membranes with a tighter pore size distribution that allows the use of an increased absolute pore size without leaking substantial amounts of albumin. At the same time, the wall thickness and internal diameter of membrane fibres have been decreased, enhancing convective transport within the dialyser without the need for an external source of substitution solution. These new expanded range membranes provide a solute removal profile more like that of the native kidney than currently available membranes when used in conventional haemodialysis.

Modulation of leucocytic angiotensin-converting enzymes expression in patients maintained on high-permeable haemodialysis.

BACKGROUND: High mortality of haemodialysis patients is associated with systemic chronic inflammation and overactivation of the renin-angiotensin system (RAS). Insufficient elimination of pro-inflammatory immune mediators, especially in the molecular weight range of 15-45 kDa, may be one of the reasons for this. Employment of haemodialysis membranes with increased permeability was shown to ameliorate the inflammatory response and might modulate the effects of local RAS. In this study, we tested the impact of high cut-off (HCO), medium cut-off (MCO) and high-flux (HF) dialysis on leucocytic transcripts of angiotensin-converting enzymes (ACE and ACE2). Additionally, the impact of HCO, MCO and HF sera and dialysates on local ACEs and inflammation markers was tested in THP-1 monocytes. METHODS: Patients' leucocytes were obtained from our recent clinical studies comparing HCO and MCO dialysers with HF. The cells were subjected to quantitaive polymerase chain reaction (qPCR) analyses with TaqMan probes specific for ACE, ACE2 and angiotensin II (AngII) and Ang1-7 receptors. Sera and dialysates from the clinical trials as well as samples from in vitro dialysis were tested on THP-1 monocytic cells. The cells were subjected to qPCR analyses with TaqMan probes specific for ACE, ACE2, interleukin-6 and tumour necrosis factor α and immunocytochemistry with ACE and ACE2 antibodies. RESULTS: Leucocytes obtained from patients treated with HCO or MCO demonstrated decreased transcript expression of ACE, while ACE2 was significantly upregulated as compared with HF. Receptors for AngII and Ang1-7 remained unchanged. THP-1 monocytes preconditioned with HCO and MCO patients' or in vitro dialysis sera reflected the same expressional regulation of ACE and ACE2 as those observed in HCO and MCO leucocytes. As a complementary finding, treatment with HCO and MCO in vitro dialysates induced a pro-inflammatory response of the cells as demonstrated by elevated messenger RNA expression of tumour necrosis factor α and interleukin-6, as well as upregulation of ACE and decreased levels of ACE2. CONCLUSIONS: Taken together, these data demonstrate that employment of membranes with high permeability eliminates a spectrum of mediators from circulation that affect the RAS components in leucocytes, especially ACE/ACE2.

Tumour necrosis factor-alpha in uraemic serum promotes osteoblastic transition and calcification of vascular smooth muscle cells via extracellular signal-regulated kinases and activator protein 1/c-FOS-mediated induction of interleukin 6 expression.

Background: Vascular calcification is enhanced in uraemic chronic haemodialysis patients, likely due to the accumulation of midsize uraemic toxins, such as interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-α). Here we have assessed the impact of uraemia on vascular smooth muscle cell (VSMC) calcification and examined the role of IL-6 and TNF-α as possible mediators and, most importantly, its underlying signalling pathway in VSMCs. Methods: VSMCs were incubated with samples of uraemic serum obtained from patients treated with haemodialysis for renal failure in the Permeability Enhancement to Reduce Chronic Inflammation-I clinical trial. The VSMCs were assessed for IL-6 gene regulation and promoter activation in response to uraemic serum and TNF-α with reporter assays and electrophoretic mobility shift assay and for osteoblastic transition, cellular calcification and cell viability upon osteogenic differentiation. Results: Uraemic serum contained higher levels of TNF-α and IL-6 compared with serum from healthy individuals. Exposure of VSMCs to uraemic serum or recombinant TNF-α lead to a strong upregulation of IL-6 mRNA expression and protein secretion, which was mediated by activator protein 1 (AP-1)/c-FOS-pathway signalling. Uraemic serum induced osteoblastic transition and calcification of VSMCs could be strongly attenuated by blocking TNF-α, IL-6 or AP-1/c-FOS signalling, which was accompanied by improved cell viability. Conclusion: These results demonstrate that uraemic serum contains higher levels of uraemic toxins TNF-α and IL-6 and that uraemia promotes vascular calcification through a signalling pathway involving TNF-α, IL-6 and the AP-1/c-FOS cytokine-signalling axis. Thus treatment modalities aiming to reduce systemic TNF-α and IL-6 levels in chronic haemodialysis patients should be evaluated in future clinical trials.

Removal of Cell-Activating Substances Using Dialyzers With Various Permeability Profiles.

Despite multiple efforts to target an improvement in clinical outcomes of patients with end-stage renal disease, several challenges must still be addressed. Dialysis patients are at a high risk for complications, as reflected by increasing mortality rates. The objective of this study is to assess the impact of the application of dialyzers with varying permeability profiles on the removal of cell-activating substances from the blood of hemodialysis (HD) patients. Dialysate samples were collected using Revaclear 400 (RC) and MCO-Ci400 (MCO-CI). Total protein and solute marker concentrations were determined for the concentrated sample. The response of tubular epithelial cells (TECs) to the dialysate samples was assessed via measurement of interleukin 6, cell viability, and morphology. Proteomic analysis of the dialysate samples was performed using liquid chromatography coupled to tandem mass spectrometry. Treatment of TECs with the MCO-CI dialysate resulted in significantly decreased cell viability compared with the RC dialysate. TECs incubated with samples from MCO-CI lost their typical brick-like shape and cell-cell connections. Proteomic analysis of dialysate samples indicated multiple pro-apoptotic and pro-inflammatory proteins, supporting the observed phenotype. Additionally, application of the MCO-CI dialyzer allowed for more efficient removal of proteins associated with advanced chronic kidney disease stages. Collectively, the use of dialyzer with a higher permeability profile enabled more efficient removal of cell-activating and toxic substances from the blood of HD patients. However, a further large-scale study is needed to address benefits and associated risks for patients.

Expanded Haemodialysis Therapy of Chronic Haemodialysis Patients Prevents Calcification and Apoptosis of Vascular Smooth Muscle Cells in vitro.

BACKGROUND: Vascular calcification is a common phenomenon in patients with chronic kidney disease and strongly associated with increased cardiovascular mortality. Vascular calcification is an active process mediated in part by inflammatory processes in vascular smooth muscle cells (VSMC). These could be modified by the insufficient removal of proinflammatory cytokines through conventional high-flux (HF) membranes. Recent trials demonstrated a reduction of inflammation in VSMC by use of dialysis membranes with a higher and steeper cut-off. These membranes caused significant albumin loss. Therefore, the effect of high retention Onset (HRO) dialysis membranes on vascular calcification and its implications in vitro was evaluated. METHODS: In the PERCI II trial, 48 chronic dialysis patients were dialyzed using HF and HRO dialyzers and serum samples were collected. Calcifying VSMC were incubated with the serum samples. Calcification was determined using alizarin red staining (AZR) and determination of alkaline phosphatase (ALP) activity. Furthermore, apoptosis was evaluated, and release of matrix Gla protein (MGP), osteopontin (OPN) and growth differentiation factor 15 (GDF-15) were measured in cell supernatants. RESULTS: Vascular calcification in vitro was significantly reduced by 24% (ALP) and 36% (AZR) after 4 weeks of HRO dialysis and by 33% (ALP) and 48% (AZR) after 12 weeks of dialysis using HRO membranes compared to HF dialysis. Apoptosis was significantly lower in the HRO group. The concentrations of MGP and OPN were significantly elevated after incubation with HF serum compared to HRO serum and healthy controls. Similarly, GDF-15 release in the supernatant was elevated after incubation with HF serum, an effect significantly ameliorated after treatment with HRO medium. CONCLUSIONS: Expanded haemodialysis therapy reduces the pro-calcific potential of serum from dialysis patients in vitro. With a markedly reduced albumin filtration compared to high cut-off dialysis, use of the HRO dialyzers may possibly provide a treatment option for chronic dialysis patients to reduce the progression of vascular calcification.

In Vitro Dialysis of Cytokine-Rich Plasma With High and Medium Cut-Off Membranes Reduces Its Procalcific Activity.

Recently developed high-flux (HF) dialysis membranes with extended permeability provide better clearance of middle-sized molecules such as interleukins (ILs). Whether this modulation of inflammation influences the procalcific effects of septic plasma on vascular smooth muscle cells (VSMCs) is not known. To assess the effects of high cut-off (HCO) and medium cut-off (MCO) membranes on microinflammation and in vitro vascular calcification we developed a miniature dialysis model. Plasma samples from lipopolysaccharide-spiked blood were dialyzed with HF, HCO, and MCO membranes in an in vitro miniature dialysis model. Afterwards, IL-6 concentrations were determined in dialysate and plasma. Calcifying VSMCs were incubated with dialyzed plasma samples and vascular calcification was assessed. Osteopontin (OPN) and matrix Gla protein (MGP) were measured in VSMC supernatants. IL-6 plasma concentrations were markedly lower with HCO and MCO dialysis. VSMC calcification was significantly lower after incubation with MCO- and HCO-serum compared to HF plasma. MGP and OPN levels in supernatants were significantly lower in the MCO but not in the HCO group compared to HF. In vitro dialysis of cytokine-enriched plasma samples with MCO and HCO membranes reduces IL-6 levels. The induction of vascular calcification by cytokine-enriched plasma is reduced after HCO and MCO dialysis.

High cut-off dialysis in chronic haemodialysis patients reduces serum procalcific activity.

BACKGROUND: Vascular calcification is enhanced in chronic dialysis patients, possibly due to the insufficient removal of various intermediate molecular weight uraemic toxins such as interleukins with conventional membranes. In this study, we assessed the modulation of in vitro vascular calcification with the use of high cut-off (HCO) membranes in chronic dialysis patients. METHODS: In a PERCI trial, 43 chronic dialysis patients were treated with conventional high-flux and HCO filters for 3 weeks in a randomized order following a 2-period crossover design. After each phase, serum predialysis samples were drawn. Calcifying human coronary vascular smooth muscle cells (VSMCs) were incubated with the patient's serum samples. Calcification was assessed with alkaline phosphatase (ALP) and alizarin red staining. In the clinical trial, HCO dialysis reduced the serum levels of the soluble tumour necrosis factor receptor (sTNFR) 1 and 2, vascular cell adhesion molecule 1 (VCAM-1) and soluble interleukin-2 receptor (sIL2R). We therefore investigated the in vitro effects of these mediators on vascular calcification. RESULTS: VSMCs incubated with HCO dialysis serum showed a 26% reduction of ALP with HCO serum compared with high-flux serum. Alizarin was 43% lower after incubation with the HCO serum compared with the high-flux serum. While sIL2R and sTNFR 1 and 2 showed no effects on VSMC calcification, VCAM-1 caused a dose-dependent enhancement of calcification. CONCLUSIONS: The use of HCO dialysis membranes in chronic dialysis patients reduces the procalcific effects of serum on VSMC in vitro. The mechanisms of the strong effect of HCO on in vitro calcification are not completely understood. One factor may be lower levels of VCAM-1 in HCO serum samples, since VCAM-1 was able to induce vascular calcification in our experiments. Neither sTNFR 1, sTNFR 2 nor sIL2R enhance vascular calcification in vitro. Regardless of the mechanisms, our results encourage further studies of highly permeable filters in chronic dialysis patients.

Soluble urokinase receptor is a biomarker of cardiovascular disease in chronic kidney disease.

Soluble urokinase-type plasminogen activator receptor (suPAR) accumulates in patients with chronic kidney disease (CKD). In various non-CKD populations, suPAR has been proposed as a prognostic marker for mortality and cardiovascular disease. However, it is not known whether suPAR holds prognostic information in patients with mild-to-moderate CKD. In a prospective observational study of 476 patients with mild-to-moderate kidney disease, we examined multivariate associations between suPAR, overall mortality, and cardiovascular events. After a mean follow-up of 57 months, 52 patients died and 76 patients had at least one fatal or nonfatal cardiovascular event. Higher suPAR was directly and significantly associated with both overall mortality (univariate hazard ratio 5.35) and cardiovascular events (univariate hazard ratio 5.06). In multivariate analysis, suPAR remained significantly associated with cardiovascular events (full model, hazard ratio 3.05). Thus, in patients with mild-to-moderate CKD, suPAR concentrations show a clear, direct, and graded association with a higher risk for new-onset cardiovascular disease.

High cut-off dialysis in chronic haemodialysis patients.

BACKGROUND: Haemodialysis patients suffer from chronic systemic inflammation and high incidence of cardiovascular disease. One cause for this may be the failure of diseased kidneys to eliminate immune mediators. Current haemodialysis treatment achieves insufficient elimination of proteins in the molecular weight range 15-45 kD. Thus, high cut-off dialysis might improve the inflammatory state. DESIGN: In this randomized crossover trial, 43 haemodialysis patients were treated for 3 weeks with high cut-off or high-flux dialysis. Inflammatory plasma mediators, monocyte subpopulation distribution and leucocyte gene expression were quantified. RESULTS: High cut-off dialysis supplemented by a low-flux filter did not influence the primary end-point, expression density of CD162 on monocytes. Nevertheless, treatment reduced multiple immune mediators in plasma. Such reduction proved - at least for some markers - to be a sustained effect over the interdialytic interval. Thus, for example, soluble TNF-receptor 1 concentration predialysis was reduced from median 13·3 (IQR 8·9-17·2) to 9·7 (IQR 7·5-13·2) ng/mL with high cut-off while remaining constant with high-flux treatment. The expression profile of multiple proinflammatory genes in leucocytes was significantly dampened. Treatment was well tolerated although albumin losses in high cut-off dialysis would be prohibitive against long-term use. CONCLUSIONS: The study shows for the first time that a dampening effect of high cut-off dialysis on systemic inflammation is achievable. Earlier studies had failed due to short study duration or insufficient dialysis efficacy. Removal of soluble mediators from the circulation influences cellular activation levels in leucocytes. Continued development of less albumin leaky membranes with similar cytokine elimination is justified.

The soluble urokinase receptor is not a clinical marker for focal segmental glomerulosclerosis.

The soluble urokinase receptor (suPAR) promotes proteinuria and induces focal segmental glomerulosclerosis (FSGS)-like lesions in mice. A serum suPAR concentration cutoff of 3000 pg/ml has been proposed as a clinical biomarker for patients with FSGS. Interestingly, several studies in patients with glomerulopathy found an inverse correlation between the estimated glomerular filtration rate (eGFR) and suPAR. As patients with FSGS present at different eGFRs, we studied the relationship between eGFR and suPAR in a cohort of 476 non-FSGS patients and 54 patients with biopsy-proven idiopathic FSGS. In the non-FSGS patients, eGFR was the strongest significant determinant of suPAR. The proposed cutoff for suPAR in FSGS patients was exceeded in 17%, 39%, and 88% in patients with eGFRs of more than 60, 45-60, and 30-45 ml/min per 1.73 m(2), respectively. In patients with eGFR of <30 ml/min per 1.73 m(2), suPAR exceeded the cutoff in 95% of patients. Levels of suPAR in patients with idiopathic FSGS overlapped with non-FSGS controls and for any given eGFR did not discriminate FSGS cases from non-FSGS controls. In the overall cohort, there was a negative association between idiopathic FSGS and suPAR, and idiopathic FSGS was not an independent predictor of FSGS concentration over 3000 pg/ml. Thus, this study does not support an absolute, eGFR-independent, suPAR concentration cutoff as a biomarker for underlying FSGS pathology and questions the validity of relative, eGFR-dependent suPAR cutoff values.

Clearance of drugs for multiple myeloma therapy during in vitro high-cutoff hemodialysis.

Current chemotherapy for multiple myeloma is based on bortezomib (BOR), dexamethasone (DEX), and thalidomide (THA). The purpose of the present study was to examine their clearance during high-cutoff (HCO) hemodialysis and to accordingly apply the results to the dialytic removal of protein-bound substances in general. During in vitro hemodialysis with human blood (blood, dialysate, and ultrafiltration flow rates 250, 500 and 5 mL/min, respectively) comparing a highly permeable HCO dialyzer (Theralite, 2.1 m(2) ) to a high-flux dialyzer (PFX; 2.1 m(2) ), ultrafiltered volume was replaced by saline containing 30 g/L urea. After recirculation for equilibration, BOR was injected, and arterial and venous samples were drawn after 10, 11, and 12 min to measure the plasma clearance (K) of both urea and BOR. The same procedure was performed with THA and DEX. By mathematical simulation, the influence of varying plasma albumin concentrations (CHSA ) on the protein-bound drug fraction (PBF) and K was assessed. Plasma K values of HCO and PFX for THA, BOR, and DEX were about 40% (80 ± 7 vs. 65 ± 6 mL/min; P < 0.05), 70% (40 ± 8 vs. 33 ± 4 mL/min; P < 0.05), and 65% (47 ± 11 vs. 38 ± 7 mL/min; P < 0.05), respectively-lower (P < 0.0001) compared with urea (125 ± 7 vs. 122 ± 5 mL/min). K was highest (P < 0.0001) for THA. K was negatively correlated with CHSA (THA, r(2) = 0.58, P < 0.001; BOR, r(2) = 0.24, P < 0.05; DEX, r(2) = 0.22, P < 0.05). CHSA continually decreased (P < 0.05) over time only with HCO, resulting in lower calculated PBF. Compared with BOR and DEX (minimum 72 and 56%, respectively), the PBF of THA (37%) was significantly lower (P < 0.001). A mathematical simulation based on the K values of urea and the drugs reliably estimated PBF (r(2) = 0.886, P < 0.001). Drugs for multiple myeloma therapy are significantly removed with both HCO and PFX, with important implications for the dosing and timing of administration, particularly in patients with cast nephropathy receiving extended dialysis. If the Kurea of a dialyzer and the PBF of any given drug are known, Kdrug can be reliably estimated by mathematical simulation.

High cut-off hemofiltration versus standard hemofiltration: a pilot assessment of effects on indices of apoptosis.

OBJECTIVES: To measure plasma pro-apoptotic and pro-necrotic activity in severe acute kidney injury (AKI) patients within a randomized controlled trial of continuous veno-venous hemofiltration with high cut-off filters (CVVH-HCO) versus standard filters (CVVH-Std). METHODS: We measured pro-apoptotic and pro-necrotic plasma activity by trypan blue exclusion cell viability assay, detection of DNA fragmentation, and by determination of caspase-3 activity and annexin V-based apoptosis and necrosis detection assay. RESULTS: Compared to no apoptosis or necrosis after incubation with healthy plasma, 14-18% of cells showed apoptosis and 4-8% showed necrosis after incubation with plasma from AKI patients. When comparing different measures of pro-apoptotic or pro-necrotic activity, CVVH-HCO and CVVH-Std showed no differential effects on such activity, which remained high over the first 3 days of treatment. However, using annexin V-FITC, there was a significant drop in pro-apoptotic activity across the filter for the CVVH-HCO group (p = 0.043) but not for the CVVH-Std group (p = 0.327) and a significant difference between the two groups (CVVH-HCO vs. CVVH-Std p = 0.006). CONCLUSIONS: Patients with severe AKI have increased pro-apoptotic and pro-necrotic activity. Although on single-pass effect assessment, CVVH-HCO was superior to CVVH-Std in decreasing annexin V-FITC-assessed pro-apoptotic activity, there was no overall attenuation of such activity during the first 3 days of treatment.

Experimental hemodialysis in diet-induced ketosis and the potential use of dialysis as an adjuvant cancer treatment.

Numerous in vivo studies on the ketogenic diet, a diet that can induce metabolic conditions resembling those following extended starvation, demonstrate strong outcomes on cancer survival, particularly when combined with chemo-, radio- or immunological treatments. However, the therapeutic application of ketogenic diets requires strict dietary adherence from well-informed and motivated patients, and it has recently been proposed that hemodialysis might be utilized to boost ketosis and further destabilize the environment for cancer cells. Yet, plasma ketones may be lost in the dialysate-lowering blood ketone levels. Here we performed a single 180-min experimental hemodialysis (HD) session in six anesthetized Sprague-Dawley rats given ketogenic diet for five days. Median blood ketone levels pre-dialysis were 3.5 mmol/L (IQR 2.2 to 5.6) and 3.8 mmol/L (IQR 2.2 to 5.1) after 180 min HD, p = 0.54 (95% CI - 0.6 to 1.2). Plasma glucose levels were reduced by 36% (- 4.5 mmol/L), p < 0.05 (95% CI - 6.7 to - 2.5). Standard base excess was increased from - 3.5 mmol/L (IQR - 4 to - 2) to 0.5 mmol/L (IQR - 1 to 3), p < 0.01 (95% CI 2.0 to 5.0). A theoretical model was applied confirming that intra-dialytic glucose levels decrease, and ketone levels slightly increase since hepatic ketone production far exceeds dialytic removal. Our experimental data and in-silico modeling indicate that elevated blood ketone levels during ketosis are maintained during hemodialysis despite dialytic removal.

Randomized controlled pilot study of 2 weeks' treatment with high cutoff membrane for hemodialysis patients with elevated C-reactive protein.

Chronic inflammation in hemodialysis (HD) patients is associated with cardiovascular complications and mortality. Circulating immune active proteins in the molecular range 15-45 kD that cannot be efficiently cleared by high-flux (HF) dialysis may be causally involved. We intended to test the feasibility of using a high cutoff (HCO) dialyzer in chronic HD patients and its influence on inflammation and monocyte activation. The Gambro HCO1100 dialyzer was compared to a conventional HF membrane in a randomized double-blind crossover trial in 19 chronic HD patients selected for the presence of elevated serum C-reactive protein levels. Patients were treated for six consecutive dialysis sessions (2 weeks) with each membrane. Safety analysis recorded adverse events and albumin losses through the protein-leaking membranes. Efficacy analysis observed reductions in the number of proinflammatory (CD14+CD16+) monocyte subpopulations in circulating blood. Treatment with the HCO membrane was well tolerated, although the number of adverse events was slightly higher. Despite significant serum albumin loss (from 34.1 ± 2.7 to 29.6 ± 3.0 g/L; P < 0.01), there was no need to supplement albumin, and rising activity of cholinesterase during HCO treatment indicated compensation by enhanced hepatic synthesis. The HCO membrane cleared high amounts of proinflammatory cytokines, but did not reduce predialysis inflammatory monocytes and markers. Although the time of HD session was extended, the study was hampered by a lower Kt/V in the HCO compared to the HF period. Treatment of chronic HD patients with this HCO dialyzer for 2 weeks is tolerable in terms of albumin loss and able to clear proinflammatory cytokines; however, this was not sufficient to decrease monocyte activation. Therefore, a more selective, less albumin-leaking membrane is desirable to allow prolonged high-efficient dialysis with more effective cytokine clearance.

In vitro characterization of PrismaLung+: a novel ECCO2R device.

BACKGROUND: Invasive mechanical ventilation is lifesaving in the setting of severe acute respiratory failure but can cause ventilation-induced lung injury. Advances in extracorporeal CO2 removal (ECCO2R) technologies may facilitate more protective lung ventilation in acute respiratory distress syndrome, and enable earlier weaning and/or avoid invasive mechanical ventilation entirely in chronic obstructive pulmonary disease exacerbations. We evaluated the in vitro CO2 removal capacity of the novel PrismaLung+ ECCO2R device compared with two existing gas exchangers. METHODS: The in vitro CO2 removal capacity of the PrismaLung+ (surface area 0.8 m2, Baxter) was compared with the PrismaLung (surface area 0.35 m2, Baxter) and A.L.ONE (surface area 1.35 m2, Eurosets) devices, using a closed-loop bovine blood-perfused extracorporeal circuit. The efficacy of each device was measured at varying pCO2 inlet (pinCO2) levels (45, 60, and 80 mmHg) and blood flow rates (QB) of 200-450 mL/min; the PrismaLung+ and A.L.ONE devices were also tested at a QB of 600 mL/min. The amount of CO2 removed by each device was assessed by measurement of the CO2 infused to maintain circuit equilibrium (CO2 infusion method) and compared with measured CO2 concentrations in the inlet and outlet of the CO2 removal device (blood gas analysis method). RESULTS: The PrismaLung+ device performed similarly to the A.L.ONE device, with both devices demonstrating CO2 removal rates ~ 50% greater than the PrismaLung device. CO2 removal rates were 73 ± 4.0, 44 ± 2.5, and 72 ± 1.9 mL/min, for PrismaLung+, PrismaLung, and A.L.ONE, respectively, at QB 300 mL/min and pinCO2 45 mmHg. A Bland-Altman plot demonstrated that the CO2 infusion method was comparable to the blood gas analysis method for calculating CO2 removal. The resistance to blood flow across the test device, as measured by pressure drop, varied as a function of blood flow rate, and was greatest for PrismaLung and lowest for the A.L.ONE device. CONCLUSIONS: The newly developed PrismaLung+ performed more effectively than PrismaLung, with performance of CO2 removal comparable to A.L.ONE at the flow rates tested, despite the smaller membrane surface area of PrismaLung+ versus A.L.ONE. Clinical testing of PrismaLung+ is warranted to further characterize its performance.

Retention of beneficial molecules and coagulation factors during haemodialysis and haemodiafiltration.

Middle molecules (MMs) are associated with the pathology of uraemia, and are not effectively removed by standard extracorporeal treatments. Increased convection used in haemodiafiltration (HDF) can enhance the removal of MMs; however, high-volume HDF is not available to all patients. The new medium cut-off (MCO) membrane has been developed to allow increased removal of MMs using standard haemodialysis (HD). Improved removal of MMs has been shown with the MCO membrane compared with standard high-flux dialysers, but it is not known whether the increased pore size affects the retention of commonly used medications or that of coagulation factors in dialysis patients. Using an in vitro model, the retention of erythropoietin, heparin, insulin, vancomycin and several coagulation factors (Factors II, VII and X, protein C and antithrombin III) was investigated with the MCO membrane dialyser, compared with high-flux dialysers with polysulfone (in HDF) or polyethersulfone membranes (in HD and HDF). The retention of all molecules investigated was comparable between the MCO membrane and the high-flux dialysers. Results from the in vitro studies suggest that switching from a high-flux dialyser to the MCO membrane should not require changes to the medication dosing or anti-coagulation protocols of dialysis patients.