Longitudinal hemodiafilter performance in modeled continuous renal replacement therapy

Meta-analysis of haematocrit and activated partial thromboplastin time as risk factors for unplanned interruptions in patients undergoing continuous renal replacement therapy

OBJECTIVE

Although continuous renal replacement therapy (CRRT) is common, unplanned interruptions often limit its usefulness. Unplanned interruption refers to the forced interruption of blood purification treatment, the failure to complete blood purification treatment goals or the failure to meet blood purification schedule times. This study aimed to evaluate the effect of haematocrit and activated partial thromboplastin time (APTT) on the incidence of unplanned interruptions in critical patients with CRRT.

METHODS

A systematic review and a meta-analysis were performed by searching the databases of China National Knowledge Infrastructure, Wanfang, VIP, China Biomedical Literature, Cochrane Library, PubMed, Web of Science and Embase from their inception to 31st March 2022 for all studies with a comparator or independent variable relating to the unplanned interruption of CRRT.

RESULTS

Nine studies involving 1165 participants were included. Haematocrit and APTT were independent risk factors for the unplanned interruption of CRRT. The higher the haematocrit level, the greater the risk of unplanned CRRT interruptions (relative risk ratio [RR] = 1.04, 95% confidence interval [CI]: 1.02, 1.07, Z = 4.27, p < 0.001). The prolongation of APPT reduced the risk of unplanned CRRT interruptions (RR = 0.94, 95% CI: 0.92, 0.96, Z = 6.10, p < 0.001).

CONCLUSION

Haematocrit and APTT are the influencing factors on the incidence of unplanned interruptions in critical patients undergoing CRRT.

"CATCH" Study: Correct Antibiotic Therapy in Continuous Hemofiltration in the Critically Ill in Continuous Renal Replacement Therapy: A Prospective Observational Study

The proper posology of antibiotics in the critically ill in CRRT is difficult to assess. We therefore performed a prospective observational cohort study to make clear hints in this topic. Our results reveal a high Sieving Coefficient for all antibiotics, equal to or higher than those described in previous papers. CVVH clearance in relation to total body clearance was significant, (i.e., >than 25% for all classes). A strong correlation between the antibiotic concentrations obtained in plasma and ultrafiltrate was found both at the peak and in the valley, with the determination of two equations that allow a new method for calculating the amount of antibiotic lost in CVVH both for trough levels and peak. Based on the results of our study and considering the limitations we believe that we can extrapolate the following final considerations: (1) it is likely to carry out a loading dose for the main antibiotics (2) subsequent administrations must take into account the daily loss identified by the linear regression equation. This angular coefficient gives the idea that the average daily loss of given antibiotic is about 25%; this implies that on the basis of the linear regression equation that correlates ultrafiltered/plasma antibiotic concentration, the dosage should be increased by 25% every day, while still ensuring a daily plasma TDM of the drug.

Antibiotic Therapy in the Critically Ill with Acute Renal Failure and Renal Replacement Therapy: A Narrative Review

The outcome for critically ill patients is burdened by a double mortality rate and a longer hospital stay in the case of sepsis or septic shock. The adequate use of antibiotics may impact on the outcome since they may affect the pharmacokinetics (Pk) and pharmacodynamics (Pd) of antibiotics in such patients. Acute renal failure (ARF) occurs in about 50% of septic patients, and the consequent need for continuous renal replacement therapy (CRRT) makes the renal elimination rate of most antibiotics highly variable. Antibiotics doses should be reduced in patients experiencing ARF, in accordance with the glomerular filtration rate (GFR), whereas posology should be increased in the case of CRRT. Since different settings of CRRT may be used, identifying a standard dosage of antibiotics is very difficult, because there is a risk of both oversimplification and failing the therapeutic efficacy. Indeed, it has been seen that, in over 25% of cases, the antibiotic therapy does not reach the necessary concentration target mainly due to lack of the proper minimal inhibitory concentration (MIC) achievement. The aim of this narrative review is to clarify whether shared algorithms exist, allowing them to inform the daily practice in the proper antibiotics posology for critically ill patients undergoing CRRT.

Development and Use of an Ex-Vivo In-Vivo Correlation to Predict Antiepileptic Drug Clearance in Patients Undergoing Continuous Renal Replacement Therapy

OBJECTIVES

Results from previous ex-vivo continuous renal replacement therapy (CRRT) models have successfully demonstrated similar extraction coefficients (EC) identified from in-vivo clinical trials. The objectives of this study are to develop an ex-vivo in-vivo correlation (EVIVC) model to predict drug clearance for commonly used antiepileptics and to evaluate similarity in drug extraction across different CRRT modalities to extrapolate dosing recommendations.

METHODS

Levetiracetam, lacosamide, and phenytoin CRRT clearance was evaluated using the Prismaflex CRRT system and M150 hemodiafilters using an albumin containing normal saline (ALB-NS) vehicle with 3 different albumin concentrations (2 g/dL, 3 g/dL, and 4 g/dL) and a human plasma vehicle at 3 different effluent flow rates (1 L/hr, 2 L/hr, and 3 L/hr). Blood and effluent/dialysate concentrations were collected after circuit priming. ECs were calculated for each drug, modality, vehicle, and experimental arm combination.

RESULTS

The calculated average EC for levetiracetam and lacosamide was approximated to the fraction unbound from plasma protein. Human plasma and ALB-NS vehicles demonstrated adequate prediction of in-vivo CRRT clearance. Geometric mean ratios indicated similarity in extraction coefficients when comparing between hemofiltration and hemodiafiltration modalities and between filtration and dialysis modalities at effluent flow rates ≤ 2L/hr. Evaluation of phenytoin provided inconsistent findings with regards to extraction coefficient similarity across different CRRT modalities.

CONCLUSION

The findings indicate that an ex-vivo study can be used as a surrogate to predict in-vivo levetiracetam and lacosamide clearance in patients receiving CRRT.

Contribution of diafiltration and adsorption to vancomycin clearance in a continuous hemodiafiltration circuit model in vitro

BACKGROUND

Vancomycin (VCM) is eliminated mainly by diafiltration under continuous hemodiafiltration (CHDF), but the contribution of adsorption to CHDF clearance (CL_CHDF ) of VCM using a polyacrylonitrile and sodium methallyl sulfonate copolymer membrane coated with polyethylenimine (AN69ST) or a polymethylmethacrylate (PMMA) membrane is unknown. This study sought to investigate the contribution of diafiltration and adsorption to the CL_CHDF of VCM using AN69ST and PMMA membranes in vitro.

METHODS

An in vitro CHDF circuit model was developed. The initial concentration of VCM was 50 μg/mL and human serum albumin (HSA) was prepared at a concentration of 0, 2.5, or 5.0 g/dL. The effluent flow rate (Qe) was set at 800, 1500, or 3000 mL/h. The CL_CHDF , diafiltration rate, and adsorption rate of VCM were calculated.

RESULTS

Total CL_CHDF of VCM using the AN69ST membrane increased and decreased with increasing Qe and HSA concentration, respectively. Diafiltration and adsorption rates were 82.1 ± 9.8% and 12.1 ± 6.1% under all conditions, respectively. Total CL_CHDF using the PMMA membrane increased with increasing Qe. Diafiltration and adsorption rates were 89.2 ± 20.4% and 4.6 ± 17.0% under all conditions, respectively. The observed CL_CHDF values significantly correlated with the predicted CL_CHDF , calculated according to a previous study as the product of Qe and the plasma unbound fraction.

CONCLUSIONS

Diafiltration predominantly contributed to CL_CHDF of VCM using AN69ST and PMMA membranes. When diafiltration rather than adsorption mainly contributes to the CL_CHDF of VCM, the CL_CHDF could be predicted from the Qe and HSA concentration, at least in vitro.

A Clinician's Guide to Dosing Analgesics, Anticonvulsants, and Psychotropic Medications in Continuous Renal Replacement Therapy

Acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT) is a common complication in critical illness and has a significant impact on pharmacokinetic factors determining drug exposure, including absorption, distribution, transport, metabolism, and clearance. In this review, we provide a practical guide to drug dosing considerations in critically ill patients undergoing CRRT, focusing on the most commonly used analgesic, anticonvulsant, and psychotropic medications in the clinical care of critically ill patients. A literature search was conducted to identify articles in which drug dosing was evaluated in adult patients receiving CRRT between the years 1980 and 2020. We included articles with pharmacokinetic/pharmacodynamic analyses and those that described medication clearance via CRRT. A summary of the data focused on practical pharmacokinetic and pharmacodynamic principles is presented, with recommendations for drug dosing of analgesics, anticonvulsants, and psychotropic medications. Pharmacokinetic and pharmacodynamic studies to guide drug dosing of analgesics, anticonvulsants, and psychotropic medications in critically ill patients receiving CRRT are sparse. Considering the widespread use of these medications, narrow therapeutic index of these drug classes, and risks of over- and underdosing, additional studies in patients receiving CRRT are needed to inform drug dosing.

A Guide to Understanding Antimicrobial Drug Dosing in Critically Ill Patients on Renal Replacement Therapy

A careful management of antimicrobials is essential in the critically ill with acute kidney injury, especially if renal replacement therapy is required. Acute kidney injury may lead per se to clinically significant modifications of drugs' pharmacokinetic parameters, and the need for renal replacement therapy represents a further variable that should be considered to avoid inappropriate antimicrobial therapy. The most important pharmacokinetic parameters, useful to determine the significance of extracorporeal removal of a given drug, are molecular weight, protein binding, and distribution volume. In many cases, the extracorporeal removal of antimicrobials can be relevant, with a consistent risk of underdosing-related treatment failure and/or potential onset of bacterial resistance. It should also be taken into account that renal replacement therapies are often not standardized in critically ill patients, and their impact on plasma drug concentrations may substantially vary in relation to membrane characteristics, treatment modality, and delivered dialysis dose. Thus, in this clinical scenario, the knowledge of the pharmacokinetic and pharmacodynamic properties of different antimicrobial classes is crucial to tailor maintenance dose and/or time interval according to clinical needs. Finally, especially for antimicrobials known for a tight therapeutic range, therapeutic drug monitoring is strongly suggested to guide dosing adjustment in complex clinical settings, such as septic patients with acute kidney injury undergoing renal replacement therapy.

A mode of CVVH with regional citrate anticoagulation compared to no anticoagulation for acute kidney injury patients at high risk of bleeding

The study was designed to assess a practical mode of postdilution continuous venovenous hemofiltration (CVVH) with regional citrate anticoagulation (RCA) using a calcium-containing replacement solution, and to compare it with a CVVH mode with no anticoagulation (NA). Both methods were employed in our center for acute kidney injury (AKI) patients at high risk of bleeding. Fifty-six patients were equally allocated into the RCA-CVVH group and the NA-CVVH group. The study displayed no significant differences between groups involving baseline characteristics, severity level, blood gas analysis, hepatic/renal/coagulative functions, electrolytes, hemoglobin concentration, and platelet counts before or after continuous renal replacement therapy (CRRT). Compared to the NA-CVVH group, the RCA-CVVH group had a lower level of transfused packed red blood cells and platelet as well as a longer filter lifespan. The result showed no substantial differences between groups in terms of the mean supporting time and cost involving CRRT per person, the length of ICU and hospital stays, and the ICU survival. Homeostasis was basically preserved at a target range during the RCA post-CVVH procedure. Serious complications did not arise during the RCA process. RCA postdilutional CVVH is a safe and effective mode for application in AKI patients with a high risk of bleeding, and it can extend the filter lifespan and decrease blood loss, compared with the NA mode for CRRT. Further studies are needed to evaluate this mode for CRRT. (Retrospective Registration number ChiCTR1800016462, Registration date 2/6/2018)

Renal replacement therapy: a practical update

Acute kidney injury (AKI) is defined as an abrupt decrease in kidney function, with the most severe form requiring some method of renal replacement therapy (RRT). The use of RRT is required in 5-10% of critically ill patients who develop severe AKI. Renal replacement therapy can be provided as either intermittent hemodialysis or one of the various modes of continuous renal replacement therapy (CRRT), with CRRT potentially conferring an advantage with respect to renal recovery and dialysis independence. There is no difference in mortality when comparing low (< 25 mL·kg^-1·hr^-1) vs high (> 40 mL·kg^-1·hr^-1) RRT dosing. Continuous renal replacement therapy may be run in different modes of increasing complexity depending on a given patient's clinical needs. Regional citrate anticoagulation is recommended as the therapy of choice for the majority of critically ill patients requiring CRRT.

Antibiotic Dosing in Continuous Renal Replacement Therapy

Appropriate antibiotic dosing is critical to improve outcomes in critically ill patients with sepsis. The addition of continuous renal replacement therapy makes achieving appropriate antibiotic dosing more difficult. The lack of continuous renal replacement therapy standardization results in treatment variability between patients and may influence whether appropriate antibiotic exposure is achieved. The aim of this study was to determine if continuous renal replacement therapy effluent flow rate impacts attaining appropriate antibiotic concentrations when conventional continuous renal replacement therapy antibiotic doses were used. This study used Monte Carlo simulations to evaluate the effect of effluent flow rate variance on pharmacodynamic target attainment for cefepime, ceftazidime, levofloxacin, meropenem, piperacillin, and tazobactam. Published demographic and pharmacokinetic parameters for each antibiotic were used to develop a pharmacokinetic model. Monte Carlo simulations of 5000 patients were evaluated for each antibiotic dosing regimen at the extremes of Kidney Disease: Improving Global Outcomes guidelines recommended effluent flow rates (20 and 35 mL/kg/h). The probability of target attainment was calculated using antibiotic-specific pharmacodynamic targets assessed over the first 72 hours of therapy. Most conventional published antibiotic dosing recommendations, except for levofloxacin, reach acceptable probability of target attainment rates when effluent rates of 20 or 35 mL/kg/h are used.

Clinical Validation of Therapeutic Drug Monitoring of Imipenem in Spent Effluent in Critically Ill Patients Receiving Continuous Renal Replacement Therapy: A Pilot Study

Objectives

The primary objective of this pilot study was to investigate whether the therapeutic drug monitoring of imipenem could be performed with spent effluent instead of blood sampling collected from critically ill patients under continuous renal replacement therapy.

Methods

A prospective open-label study was conducted in a real clinical setting. Both blood and effluent samples were collected pairwise before imipenem administration and 0.5, 1, 1.5, 2, 3, 4, 6, and 8 h after imipenem administration. Plasma and effluent imipenem concentrations were determined by reversed-phase high-performance liquid chromatography with ultraviolet detection. Pharmacokinetic and pharmacodynamic parameters of blood and effluent samples were calculated.

Results

Eighty-three paired plasma and effluent samples were obtained from 10 patients. The Pearson correlation coefficient of the imipenem concentrations in plasma and effluent was 0.950 (P<0.0001). The average plasma-to-effluent imipenem concentration ratio was 1.044 (95% confidence interval, 0.975 to 1.114) with Bland-Altman analysis. No statistically significant difference was found in the pharmacokinetic and pharmacodynamic parameters tested in paired plasma and effluent samples with Wilcoxon test.

Conclusion

Spent effluent of continuous renal replacement therapy could be used for therapeutic drug monitoring of imipenem instead of blood sampling in critically ill patients.

Renal Replacement Therapy

Renal replacement therapy (RRT) is a cornerstone in the clinical management of patients with acute kidney injury. Results from different studies agree that early renal support therapy (aimed to support the residual kidney function during early phases of organ dysfunction) may reduce mortality with respect to late RRT (aimed to substitute the complete loss of function during the advanced kidney insufficiency). Although it seems plausible that a timely initiation of RRT may be associated with improved renal and nonrenal outcomes in these patients, there is scarce evidence in literature to exactly identify the most adequate onset timing for RRT.

Iohexol transmembrane clearance during modeled continuous renal replacement therapy

BACKGROUND/AIMS

Urea clearance during continuous renal replacement therapy (CRRT) is not representative of middle molecular weight solute clearances. We aimed to characterize iohexol, molecular weight 821 Da, clearance during continuous hemofiltration (CH) and continuous hemodialysis (CHD).

METHODS

Using an in vitro model, iohexol sieving coefficients (SC) and saturation coefficients (SA) were determined with the M100 membrane at ultrafiltration/dialysate rates of 1, 2, 3, 4, and 6 l/h. Iohexol transmembrane clearance was calculated using the measured SC and SA.

RESULTS

During CH, the value of iohexol SC remained approximately 1 at all ultrafiltration rates studied. In contrast, during CHD iohexol the mean SA was 1.02 ± 0.05 at a dialysate rate 1 l/h and decreased significantly with higher dialysate rates to a mean SA of 0.57 ± 0.12 at a dialysate rate of 6 l/h.

CONCLUSIONS

At higher effluent flow rates, CH was more effective in removing iohexol than CHD. CH transmembrane clearance of iohexol appears to approximate the ultrafiltration rate.

Antibiotic Dosing in Patients With Acute Kidney Injury: "Enough But Not Too Much"

Increasing evidence suggests that antibiotic dosing in critically ill patients with acute kidney injury (AKI) often does not achieve pharmacodynamic goals, and the continued high mortality rate due to infectious causes appears to confirm these findings. Although there are compelling reasons why clinicians should use more aggressive antibiotic dosing, particularly in patients receiving aggressive renal replacement therapies, concerns for toxicity associated with higher doses are real. The presence of multisystem organ failure and polypharmacy predispose these patients to drug toxicity. This article examines the pharmacokinetic and pharmacodynamic consequences of critical illness, AKI, and renal replacement therapy and describes potential solutions to help clinicians give "enough but not too much" in these very complicated patients.

Principles and operational parameters to optimize poison removal with extracorporeal treatments

A role for nephrologists in the management of a poisoned patient involves evaluating the indications for, and methods of, enhancing the elimination of a poison. Nephrologists are familiar with the various extracorporeal treatments (ECTRs) used in the management of impaired kidney function, and their respective advantages and disadvantages. However, these same skills and knowledge may not always be considered, or applicable, when prescribing ECTR for the treatment of a poisoned patient. Maximizing solute elimination is a key aim of such treatments, perhaps more so than in the treatment of uremia, because ECTR has the potential to reverse clinical toxicity and shorten the duration of poisoning. This manuscript reviews the various principles that govern poison elimination by ECTR (diffusion, convection, adsorption, and centrifugation) and how components of the ECTR can be adjusted to maximize clearance. Data supporting these recommendations will be presented, whenever available.

Vibration enhances clearance of solutes with varying molecular weights during in vitro hemodialysis

This proof of concept pilot study was performed to determine whether vibration can increase solute clearance when applied to an in vitro dialysis model. Urea, creatinine, gentamicin, and vancomycin transmembrane clearances were calculated at a blood flow rate of 200 ml/min, dialysate flow rates of 2 and 8 L/hr, and no concurrent ultrafiltration at various vibration intensities. Dialyzer integrity was determined by measuring transmembrane pressure, filter drop pressure, and albumin clearance, and by visually inspecting the dialysate. Comparing the highest vibration modality with no vibration, the median percentage increase in urea, creatinine, gentamicin, and vancomycin clearance was 18% (all p < 0.005). The transmembrane clearance of albumin was negligible for all experiments. When measuring transmembrane pressure and filter drop pressure, no significant differences were found between nonvibration and vibration dialysis. The addition of vibration during dialysis increased transmembrane clearance for solutes with molecular weights of 60-1450 Daltons.

Use of an in vitro model of renal replacement therapy systems to estimate extracorporeal drug removal

The use of in vitro modeling to predict in vivo drug and solute clearance during renal replacement therapy has evolved to reflect the different dialytic therapies available in clinical practice. This area of renal replacement therapy research is representative of translational research that demonstrates a correlation from bench to bedside where results generated in the laboratory can assist with clinical decisions in the absence of in vivo studies. This review describes in vitro renal replacement therapy models and compares the findings of several in vitro and in vivo studies.