Super High-Flux Continuous Venovenous Hemodialysis Using Regional Citrate Anticoagulation: Long-Term Stability of Middle Molecule Clearance

Change in prefilter pressure as a key determinant in the decision to return blood in continuous renal replacement therapy: An observational study

BACKGROUND

During continuous renal replacement therapy (CRRT), circuit coagulation is an important event that can result in suboptimal outcomes. Nurses must remain alert throughout the treatment and observe machine pressures. Transmembrane pressure (TMP) is commonly used for monitoring but it is sometimes too late to return blood to the patient.

AIM

To compare the capacity of prefilter pressure (FP) versus TMP to predict the risk of circuit coagulation in adult patients with acute renal failure on CRRT.

STUDY DESIGN

An observational, longitudinal, prospective study. This study was carried out in a tertiary referral hospital over 2 years. Data collected included the following variables: TMP, filter or FP, effluent pressure, venous and arterial pressure, filtration fraction, and ultrafiltration constant of each circuit. Means and their trends over time were collected, for both diffusive and convective therapy and for two membrane types.

RESULTS

A total of 151 circuits (24 polysulfone and 127 acrylonitrile) were analysed, from 71 patients (n = 22 [34%] women; mean age, 66.5 [36-84] years). Of the total treatments, 80 were diffusive, and the rest were convective or mixed. In the diffusive circuits, a progressive rise in FP was observed without an increase in TMP and with an increasing trend in effluent pressure. Circuit lifespan was between 2 and 90 h. In 11% (n = 17) of the cases, the blood could not be returned to the patient.

CONCLUSION

These findings allowed the creation of graphs that indicate the appropriate point to return blood to the patient. FP was a major determinant in this decision; in most cases, TMP was not a reliable parameter. Our findings are applicable to convective, diffusive, and mixed treatments as well as both types of membranes used in this acute setting.

RELEVANCE TO CLINICAL PRACTICE

This study provides two clear reference graphs showing risk scales for the assessment of circuit pressures in CRRT. The graphs proposed here can be used to evaluate any machine on the market and the two types of membranes used in this acute setting. Both convective and diffusive circuits can be assessed, allowing safer evaluation in patients who change treatment.

Comparison of diluted vs concentrated regional citrate anticoagulation in continuous renal replacement therapy: A quasi-experimental study

BACKGROUND

The incidence of coagulation of continuous renal replacement therapy circuits remains high. To the best of our knowledge, no scholar has published a protocol to avoid management errors when different types of citrates coexist in the same Intensive Care Unit.

AIM

To assess the safety and efficacy of the unification of two protocols with different concentrations of citrate solution.

STUDY DESING

A prospective, quasi-experimental study was carried out in the intensive care unit of a tertiary referral hospital (in Barcelona, Spain), over 3 years. Consecutive adult patients requiring continuous renal replacement therapy with citrate were included. The sample was divided into two groups, a control group (concentrated citrate) and an intervention group (diluted citrate). The decision to initiate anticoagulation with diluted (18 mmol/L) or concentrated (136 mmol/L) citrate was made based on the machine available and the decision of the doctor responsible for the patient. It was not possible to randomize the sample. Both protocols were matched with a starting citrate dose of 3.5 mmol/L, and a dialysis solution was used. Post-filter replacement was not used, and the citrate solution was the only fluid administered pre-filter.

RESULTS

The analysis included 59 circuits in the concentrated citrate group and 40 circuits in the diluted citrate group. An increased need for electrolyte replacement was observed in the diluted group (p < .001). The concentrated citrate group had a longer filter life (p < .05), and there was a slight trend toward alkalosis.

CONCLUSION

The diluted citrate group had a higher incidence of electrolyte replacement. The concentrated citrate group had longer circuit lifespan and a trend toward metabolic alkalosis, although this was not statistically significant. If these conclusions are considered, the protocol can be unified.

RELEVANCE TO CLINICAL PRACTICE

The present work aims to provide information on the differences in the use of regional anticoagulation with diluted or concentrated citrate. The objective is to pay special attention to aspects that can lead to complications. The unified protocol proposed in this paper could be extrapolated to any machine on the market that uses either of these two types of citrate concentration.

A safe and effective protocol for postdilution hemofiltration with regional citrate anticoagulation

BACKGROUND

Regional citrate anticoagulation (RCA) is recommended during continuous renal replacement therapy. Compared to systemic anticoagulation, RCA provides a longer filter lifespan with the risk of metabolic alkalosis and impaired calcium homeostasis. Surprisingly, most RCA protocols are designed for continuous veno-venous hemodialysis or hemodiafiltration. Effective protocols for continuous veno-venous hemofiltration (CVVH) are rare, although CVVH is a standard treatment for high-molecular-weight clearance. Therefore, we evaluated a new RCA protocol for postdilution CVVH.

METHODS

This is a monocentric prospective interventional study to evaluate a new RCA protocol for postdilution CVVH. We recruited surgical patients with stage III acute kidney injury who needed renal replacement therapy. We recorded dialysis and RCA data and hemodynamic and laboratory parameters during treatment sessions of 72 h. The primary endpoint was filter patency at 72 h. The major safety parameters were metabolic alkalosis and severe hypocalcemia at any time.

RESULTS

We included 38 patients who underwent 66 treatment sessions. The mean filter lifespan was 66 ± 12 h, and 44 of 66 (66%) filters were patent at 72 h. After censoring for non-CVVH-related cessation of treatment, 83% of all filters were patent at 72 h. The delivered dialysis dose was 28 ± 5 ml/kgBW/h. The serum levels of creatinine, urea and beta2-microglobulin decreased significantly from day 0 to day 3. Metabolic alkalosis occurred in one patient. An iCa++ below 1.0 mmol/L occurred in four patients. Citrate accumulation did not occur.

CONCLUSIONS

We describe a safe, effective, and easy-to-use RCA protocol for postdilution CVVH. This protocol provides a long and sustained filter lifespan without serious adverse effects. The risk of metabolic alkalosis and hypocalcemia is low. Using this protocol, a recommended dialysis dose can be safely administered with effective clearance of low- and middle-molecular-weight molecules.

TRIAL REGISTRATION

The study was approved by the medical ethics committee of Heinrich-Heine University Duesseldorf (No. 2018-82KFogU). The trial was registered in the local study register of the university (No: 2018044660) on 07/04/2018 and was retrospectively registered at ClinicalTrials.gov (ClinicalTrials.gov Identifier: NCT03969966) on 31/05/2019.

Kinetics of small and middle molecule clearance during continuous hemodialysis

Regional citrate anticoagulation (RCA) enables prolonged continuous kidney replacement therapy (CKRT) filter lifespan. However, membrane diffusive performance might progressively decrease and remain unnoticed. We prospectively evaluated the kinetics of solute clearance and factors associated with decreased membrane performance in 135 consecutive CKRT-RCA circuits (35 patients). We recorded baseline patients' characteristics and clinical signs of decreased membrane performance. We calculated effluent/serum ratios (ESR) as well as respective clearances for urea, creatinine and β2-microglobuline at 12, 24, 48 and 72 h after circuit initiation. Using mixed-effects logistic regression model analyses, we assessed the effect of time on those values and determined independent predictors of decreased membrane performance as defined by an ESR for urea < 0.81. We observed a minor but statistically significant decrease in both ESR and solute clearance across the duration of therapy for all three solutes. We observed decreased membrane performance in 31 (23%) circuits while clinical signs were present in 19 (14.1%). The risk of decreased membrane performance significantly increased over time: 1.8% at T1 (p = 0.16); 7.3% at T2 (p = 0.01); 15.7% at T3 (p = 0.001) and 16.4% at T4 (p < 0.003). Four factors present within 24 h of circuit initiation were independently associated with decreased membrane performance: arterial blood bicarbonate level (OR 1.50; p < 0.001), activated partial thromboplastin time (aPTT; OR = 0.93; p = 0.02), fibrinogen level (OR 6.40; p = 0.03) and Charlson score (OR 0.10; p < 0.01). COVID-19 infection was not associated with increased risk of decreased membrane performance. Regular monitoring of ESR might be appropriate in selected patients undergoing CKRT.

Flummoxed by flux: the indeterminate principles of haemodialysis

In haemodialysis (HD), unwanted substances (uraemic retention solutes or ‘uraemic toxins’) that accumulate in uraemia are removed from blood by transport across the semipermeable membrane. Like all membrane separation processes, the transport requires driving forces to facilitate the transfer of molecules across the membrane. The magnitude of the transport is quantified by the phenomenon of ‘flux’, a finite parameter defined as the volume of fluid (or permeate) transferred per unit area of membrane surface per unit time. In HD, as transmembrane pressure is applied to facilitate fluid flow or flux across the membrane to enhance solute removal, flux is defined by the ultrafiltration coefficient (KUF; mL/h/mmHg) reflecting the hydraulic permeability of the membrane. However, in HD, the designation of flux has come to be used in a much broader sense and the term is commonly used interchangeably and erroneously with other measures of membrane separation processes, resulting in considerable confusion. Increased flux is perceived to reflect more ‘porous’ membranes having ‘larger’ pores, even though other membrane and therapy attributes determine the magnitude of flux achieved during HD. Adjectival designations of flux (low-, mid-, high-, super-, ultra-) have found indiscriminate usage in the scientific literature to qualify a parameter that influences clinical decision making and prescription of therapy modalities (low-flux or high-flux HD). Over the years the concept and definition of flux has undergone arbitrary and periodic adjustment and redefinition by authors in publications, regulatory bodies (US Food and Drug Administration) and professional association guidelines (European Renal Association, Kidney Disease Outcomes Quality Initiative), with little consensus. Industry has stretched the boundaries of flux to derive marketing advantages, justify increased reimbursement or contrive new classes of therapy modalities when in fact flux is just one of several specifications that determine membrane or dialyser performance. Membranes considered as high-flux previously are today at the lower end of the flux spectrum. Further, additional parameters unrelated to the rate of diffusive or convective transport (flux) are used in conjunction with or in place of KUF to allude to flux: clearance (mL/min, e.g. of β₂-microglobulin) or sieving coefficients (dimensionless). Considering that clinical trials in nephrology, designed to make therapy recommendations and guide policy with economic repercussions, are based on the parameter flux they merit clarification—by regulatory authorities and scientists alike—to avoid further misappropriation.

Effect of Dynamic Circuit Pressures Monitoring on the Lifespan of Extracorporeal Circuit and the Efficiency of Solute Removal During Continuous Renal Replacement Therapy

Objective: To observe the effects of dynamic pressure monitoring on the lifespan of the extracorporeal circuit and the efficiency of solute removal during continuous renal replacement therapy (CRRT).

Materials and Methods: A prospective observational study was performed at the West China Hospital of Sichuan University in the ICU. Analyses of the downloaded pressure data recorded by CRRT machines and the solute removal efficiencies, calculated by 2^*Ce/(Cpre+Cpost), where Ce, Cpre, and Cpost are the concentrations of the effluent, pre-filter blood, and post-filter blood, respectively, were performed. Samples were collected at 0, 2, 6, 12, and 24 h when continuous veno-venous hemodiafiltration (CVVHDF) was used after the initiation of CRRT. Measurements in concentrations of creatinine, blood urea nitrogen, and β2-microglobulin in the plasma and effluent were recorded.

Results: Extracorporeal circuits characterized by moderate-to-severe (M–S) access outflow dysfunction (AOD) events, defined as access outflow pressure less than or equal to −200 mmHg for more than 5 min, had shorter median lifespans with no anticoagulation (32.3 vs. 10.90 h, P = 0.001) compared with the no M–S AOD events group. The significant outcome also existed in regional citrate anticoagulation (RCA) (72 vs. 42.47 h, P = 0.02). Moreover, Cox regression analysis revealed that the lack of M–S AOD events, RCA, or CVVHDF independently prolonged the circuit lifespan. All tested solutes removal efficiencies started to decline at 12 h. Furthermore, efficiencies of all solutes removal dropped obviously at 24 h when TMP ≥ 150 mmHg.

Conclusion: RCA and CVVHDF predicted a longer circuit lifespan. M–S AOD events were associated with a shorter circuit lifespan when RCA or no anticoagulant was used. Replacement of extracorporeal circuit could be considered when running time of filter lasted up to 24 h with TMP ≥ 150 mmHg.

Elimination of fosfomycin during dialysis with the Genius system in septic patients

To assess fosfomycin (FOS) elimination in patients with sepsis and acute kidney injury (AKI) undergoing slow-extended daily dialysis (SLEDD) with the Genius system in a prospective observational study. After ethics committee approval ten patients with sepsis and AKI stage 3 underwent daily SLEDD sessions of eight hours. FOS was applied i.v. at doses of 3 × 5 g per day. FOS serum levels were measured pre- and post hemofilter before, during, and after SLEDD sessions, and instantaneous clearance was calculated. In five of the patients, we analyzed FOS levels after the first dose, in the other five patients serum levels were measured during ongoing therapy. FOS was eliminated rapidly via the hemofilter. FOS clearance decreased from 152 ± 10 mL/min (start of SLEED session) to 43 ± 38 mL/min (end of SLEDD session). In 3/5 first-dose patients after 4–6 h of SLEDD the FOS serum level fell below the EUCAST breakpoint of 32 mg/L for Enterobacterales and Staphylococcus species. In all patients with ongoing fosfomycin therapy serum levels were high and above the breakpoint at all times. FOS toxicity or adverse effects were not observed. FOS serum concentrations exhibit wide variability in critically ill patients with sepsis and AKI. FOS is eliminated rapidly during SLEDD. A loading dose of 5 g is not sufficient to achieve serum levels above the EUCAST breakpoint for common bacteria in all patients, considering that T > MIC > 70% of the dosing interval indicates sufficient plasma levels. We thus recommend a loading dose of 8 g followed by a maintenance dose of 5 g after a SLEDD session in anuric patients. We strongly recommend therapeutic drug monitoring of FOS levels in critically ill patients with AKI and dialysis therapy.

Myoglobin clearance with continuous veno-venous hemodialysis using high cutoff dialyzer versus continuous veno-venous hemodiafiltration using high-flux dialyzer: a prospective randomized controlled trial

Background

Myoglobin clearance in acute kidney injury requiring renal replacement therapy is important because myoglobin has direct renal toxic effects. Clinical data comparing different modalities of renal replacement therapy addressing myoglobin clearance are limited. This study aimed to compare two renal replacement modalities regarding myoglobin clearance.

Methods

In this prospective, randomized, single-blinded, single-center trial, 70 critically ill patients requiring renal replacement therapy were randomized 1:1 into an intervention arm using continuous veno-venous hemodialysis with high cutoff dialyzer and a control arm using continuous veno-venous hemodiafiltration postdilution with high-flux dialyzer. Regional citrate anticoagulation was used in both groups to maintain the extracorporeal circuit. The concentrations of myoglobin, urea, creatinine, β2-microglobulin, interleukin-6 and albumin were measured before and after the dialyzer at 1 h, 6 h, 12 h, 24 h and 48 h after initiating continuous renal replacement therapy.

Results

Thirty-three patients were allocated to the control arm (CVVHDF with high-flux dialyzer) and 35 patients to the intervention arm (CVVHD with high cutoff dialyzer). Myoglobin clearance, as a primary endpoint, was significantly better in the intervention arm than in the control arm throughout the whole study period. The clearance values for urea and creatinine were higher in the control arm. There was no measurable albumin clearance in both arms. The clearance data for β₂-microglobulin and interleukin-6 were non-inferior in the intervention arm compared to those for the control arm. Dialyzer lifespan was 57.0 [38.0, 72.0] hours in the control arm and 70.0 [56.75, 72.0] hours in the intervention arm (p = 0.029).

Conclusions

Myoglobin clearance using continuous veno-venous hemodialysis with high cutoff dialyzer and regional citrate anticoagulation is better than that with continuous veno-venous hemodiafiltration with regional citrate anticoagulation.

Trial registration

German Clinical Trials Registry (DRKS00012407); date of registration 23/05/2017. https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00012407.

Continuous hemodiafiltration as a rescue therapy for patients with cardiopulmonary failure caused by enterovirus-71: a retrospective observational study in a PICU

Background

Hand, foot and mouth disease (HFMD) remains a burdensome health issue in mainland China. Enterovirus71 (EV-A71) is the main pathogen of severe HFMD. Continuous hemofiltration improves fluid overload, restores kidney function and alleviates inflammatory reactions. The aim of the present study was to evaluate the effects of continuous veno-venous hemodiafiltration (CVVHDF) on severe HFMD caused by EV-A71(EV-A71-HFMD) in a pediatric intensive care unit (PICU).

Methods

A retrospective observational study was performed in a tertiary university PICU from January 2012 to December 2016. Children with severe EV-A71-HFMD complicated by cardiopulmonary failure were included. The patients were divided into a CVVHDF group and a conventional therapy (control) group (non-CVVHDF). The demographics, characteristics, and outcomes between the groups were collected and analyzed.

Results

Twenty-nine patients with severe EV-A71-HFMD were enrolled. The 28-day mortality was 17.6% (3/17) in the CVVHDF group and 33.3% (4/12) in the non-CVVHDF group, with no statistical significance between the two groups (P = 0.403). The median interval between CVVHDF initiation and PICU admission was 6 (4,8.5) hrs, and the median duration of CVVHDF was 48 (36, 64) hrs. The left ventricular ejection fraction (LVEF) and cardiac index (CI) in the CVVHDF group were improved after treatment. The plasma levels of catecholamines and renin-angiotensin-aldosterone system (RAAS) substances in the CVVHDF group were significantly decreased after treatment. The decreased catecholamines and RAAS substances included adrenalin (169.8 [145.5, 244.6] vs. 148.0 [109.0, 208.1] ng/L, P = 0.033), dopamine (152.7 [97.0, 191.1] vs. 96.0 [68.0, 160.9] ng/L, P = 0.026), angiotensin II (185.9 [125.2, 800.0] vs. 106.0 [90.8, 232.5] ng/L, P = 0.047), aldosterone (165.7 [94.0, 353.3] vs. 103.3 [84.3, 144.3] ng/L, P = 0.033), and renin (1.12 [0.74, 3.45] vs. 0.79 [0.52, 1.25] μg/L/h, P = 0.029),

Conclusions

CVVHDF reduced the levels of catecholamines and RAAS substances and improved cardiovascular function. Continuous hemodiafiltration may represent a potential therapy in patients with severe EV-A71-HFMD complicated with cardiopulmonary failure.

Comparison of Blood Compatibility in Various Membrane Materials for Continuous Renal Replacement Therapy

Because hemofilters used for continuous renal replacement therapy contact with blood over a prolonged period during treatments, platelet activation may occur stronger. The purpose of this study is to clarify the blood compatibility in three hemofilters mostly used in Japan. We compared the blood compatibility of the two polysulfone (AEF: Asahi Kasei Medical Co., Tokyo, Japan and SHG: Toray Medical Co., Ltd., Tokyo, Japan) and one polymethylmethacrylate membranes (CH: Toray Medical Co., Ltd.). First, test blood was collected from healthy volunteers. Subsequently, the blood was circulated by a roller pump at the rate of 100 mL/min. We measured the platelet counts and platelet factor 4 (PF4). The platelet counts at 48 h in polymethylmethacrylate membrane were significantly less than that in polysulfone membranes. Levels of the PF4 after the circulation were 978.5 ± 200.0 ng/dL with AEF, 863.0 ± 233.9 ng/dL with SHG and 1780.0 ± 465.1 ng/dL with CH, respectively. Hemofilters with polysulfone membranes showed less platelet activation. It was inferred that the amount of PVP, the smoothness of the membrane surface, and the inner diameter of the hollow fiber affect the blood compatibility in the hemofilter.