Operational characteristics of continuous renal replacement modalities used for critically ill patients with acute kidney injury

Toward microfluidic integration of respiratory and renal organ support in a single cartridge

BACKGROUND

Extracorporeal organ assist devices provide lifesaving functions for acutely and chronically ill patients suffering from respiratory and renal failure, but their availability and use is severely limited by an extremely high level of operational complexity. While current hollow fiber-based devices provide high-efficiency blood gas transfer and waste removal in extracorporeal membrane oxygenation (ECMO) and hemodialysis, respectively, their impact on blood health is often highly deleterious and difficult to control. Further challenges are encountered when integrating multiple organ support functions, as is often required when ECMO and ultrafiltration (UF) are combined to deal with fluid overload in critically ill patients, necessitating an unwieldy circuit containing two separate cartridges.

METHODS

We report the first laboratory demonstration of simultaneous blood gas oxygenation and fluid removal in single microfluidic circuit, an achievement enabled by the microchannel-based blood flow configuration of the device. Porcine blood is flowed through a stack of two microfluidic layers, one with a non-porous, gas-permeable silicone membrane separating blood and oxygen chambers, and the other containing a porous dialysis membrane separating blood and filtrate compartments.

RESULTS

High levels of oxygen transfer are measured across the oxygenator, while tunable rates of fluid removal, governed by the transmembrane pressure (TMP), are achieved across the UF layer. Key parameters including the blood flow rate, TMP and hematocrit are monitored and compared with computationally predicted performance metrics.

CONCLUSIONS

These results represent a model demonstration of a potential future clinical therapy where respiratory support and fluid removal are both realized through a single monolithic cartridge.

Renal replacement therapy for AKI: When? How much? When to stop?

Severe acute kidney injury (AKI) requiring renal replacement therapy (RRT) is a serious clinical disorder in the intensive care unit (ICU), occurring in a significant proportion of critically ill patients. However, many questions remain about the optimal administration of RRT with regard to several important considerations, including treatment dose, timing of treatment initiation and cessation, therapy mode, type of anticoagulation, and management of fluid overload. While Level 1 evidence exists for RRT dosing in AKI, all the studies contributing to this evidence base employed fixed-dose regimens throughout a patient's continuous RRT (CRRT) course, without regard for the possibility of individualizing treatment dose according to the clinical status of a given patient at a specific time. As opposed to CRRT dose, no consensus about the timing of RRT in critically ill AKI patients exists currently. While numerous clinical trials over the past 40 years have attempted to assess "early" versus "late" initiation of RRT, they have been plagued by a myriad of methodological problems, including their largely observational nature and the widely varying definitions of early and late initiation. Although questions about the appropriate timing of CRRT discontinuation arise very frequently in clinical practice, even less information is available in the literature to guide this important decision. The aim of this review is to provide a comprehensive update on RRT delivery to critically ill AKI patients, with specific attention paid to treatment dose and timing and emphasis on addressing the practical questions that arise in daily clinical practice.

The future of critical care: renal support in 2027

Since its inception four decades ago, both the clinical and technologic aspects of continuous renal replacement therapy (CRRT) have evolved substantially. Devices now specifically designed for critically ill patients with acute kidney injury are widely available and the clinical challenges associated with treating this complex patient population continue to be addressed. However, several important questions remain unanswered, leaving doubts in the minds of many clinicians about therapy prescription/delivery and patient management. Specifically, questions surrounding therapy dosing, timing of initiation and termination, fluid management, anticoagulation, drug dosing, and data analytics may lead to inconsistent delivery of CRRT and even reluctance to prescribe it. In this review, we discuss current limitations of CRRT and potential solutions over the next decade from both a patient management and a technology perspective. We also address the issue of sustainability for CRRT and related therapies beyond 2027 and raise several points for consideration.

Lactate clearance is associated with mortality in septic patients with acute kidney injury requiring continuous renal replacement therapy: A cohort study

The aim of the study was to assess the clinical utility of lactate measured at different time points to predict mortality at 48 hours and 28 days in septic patients with acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT).Consecutive critically ill patients with septic AKI requiring CRRT were prospectively studied. Variables were collected at initiation of CRRT and 24 hours later.In total, 186 patients were analyzed. Overall mortality at 48 hours was 28% and at 28 days was 69%. Initial lactate, lactate at 24 hours and the proportion of patients with a lactate clearance superior to 10% were different between survivors at 28 days [2.0 mmol/L, 1.95 mmol/L and 18/45 (40%)] and nonsurvivors [3.46 mmol, 4.66 mmol, and 18/94 (19%)]. Multivariate analysis demonstrated that lactate at 24 hours and lactate clearance, but not initial lactate, were independently associated to mortality. Area under the ROC curves for 28-day mortality was 0.635 for initial lactate; 0.828 for lactate at 24 hours and 0.701 for lactate clearance.Lactate clearance and lactate after 24 hours of CRRT, but not initial lactate, were independently associated with mortality in septic AKI patients undergoing CRRT. Serial lactate measurements may be useful prognostic markers than initial lactate in these patients.

Compliance with Antibiotic Dosing Guidelines in Critically Ill Patients Receiving Renal Replacement Therapy

Background:

Compliance with antibiotic dosing guidelines and achievement of target serum concentrations in patients with infection who are on renal replacement therapy (RRT) is complex, essential for supportive care, and not well studied.

Objective:

To determine adherence rates to antibiotic dosing guidelines in the setting of RRT in the intensive care unit (ICU).

Methods:

We conducted a retrospective, single-center, cohort study evaluating antibiotic dosing in all patients in the ICU receiving RRT between July 2007 and June 2009. Appropriate dosing was determined by comparing dose administered with established guidelines. Dosing was denoted as accurate if adjustment occurred prior to the third administered dose or, if appropriate dosing is every 12 hours or more, within 24 hours. We compared rates according to modality of RRT (intermittent hemodialysis [IHD] vs continuous veno-venous hemodialysis [CVVHD]), indication for RRT (acute kidney injury [AKI] vs end-stage renal disease [ESRD]), and presence of a clinical pharmacist on rounds.

Results:

Adherence rates of 546 patients receiving RRT, with 1761 individual antibiotic prescriptions, were analyzed. Dosing errors were more common in the group receiving CVVHD than in the IHD group (58.1% vs 49.5%; p < 0.001). Frequency of dosing errors did not differ significantly between patients receiving RRT for AKI versus those with ESRD (55.4% vs 51.3%; p = 0.24) or in ICUs with or without a pharmacist on rounds (53.0% vs 54.6%; p = 0.67). Underdosing occurred less frequently with a clinical pharmacist on rounds (18.7% vs 31.3%; p < 0.001). However, in-hospital mortality was not significantly different in underdosed individuals compared with the rest of the cohort (52.3% vs 51.6%; p = 0.92).

Conclusions:

Antibiotic underdosing is common. Increased awareness of dose adjustment guidelines for CVVHD and having a clinical pharmacist on rounds may improve rates of underdosing.

Drug dosing consideration in patients with acute and chronic kidney disease-a clinical update from Kidney Disease: Improving Global Outcomes (KDIGO)

Drug dosage adjustment for patients with acute or chronic kidney disease is an accepted standard of practice. The challenge is how to accurately estimate a patient's kidney function in both acute and chronic kidney disease and determine the influence of renal replacement therapies on drug disposition. Kidney Disease: Improving Global Outcomes (KDIGO) held a conference to investigate these issues and propose recommendations for practitioners, researchers, and those involved in the drug development and regulatory arenas. The conference attendees discussed the major challenges facing drug dosage adjustment for patients with kidney disease. In particular, although glomerular filtration rate is the metric used to guide dose adjustment, kidney disease does affect nonrenal clearances, and this is not adequately considered in most pharmacokinetic studies. There are also inadequate studies in patients receiving all forms of renal replacement therapy and in the pediatric population. The conference generated 37 recommendations for clinical practice, 32 recommendations for future research directions, and 24 recommendations for regulatory agencies (US Food and Drug Administration and European Medicines Agency) to enhance the quality of pharmacokinetic and pharmacodynamic information available to clinicians. The KDIGO Conference highlighted the gaps and focused on crafting paths to the future that will stimulate research and improve the global outcomes of patients with acute and chronic kidney disease.

Antibiotic dosing in critically ill patients with acute kidney injury

A common cause of acute kidney injury (AKI) is sepsis, which makes appropriate dosing of antibiotics in these patients essential. Drug dosing in critically ill patients with AKI, however, can be complicated. Critical illness and AKI can both substantially alter pharmacokinetic parameters as compared with healthy individuals or patients with end-stage renal disease. Furthermore, drug pharmacokinetic parameters are highly variable within the critically ill population. The volume of distribution of hydrophilic agents can increase as a result of fluid overload and decreased binding of the drug to serum proteins, and antibiotic loading doses must be adjusted upwards to account for these changes. Although renal elimination of drugs is decreased in patients with AKI, residual renal function in conjunction with renal replacement therapies (RRTs) result in enhanced drug clearance, and maintenance doses must reflect this situation. Antibiotic dosing decisions should be individualized to take into account patient-related, RRT-related, and drug-related factors. Efforts must also be made to optimize the attainment of antibiotic pharmacodynamic goals in this population.

First experience with the Prismaflex HF 20 set in four infants

PURPOSE

Renal replacement therapy (RRT) in infants is challenging due to a lack of widely available technology that is specific to this patient population. We present our initial experience with the newly developed Prismaflex HF20 disposable set used on the Prismaflex device in infants with renal failure.

PATIENTS

Four infants, age 5 to 24 months, were enrolled. Overall 120 treatment sessions were performed over 300 patient-days. Treatment monitoring included patient weight change and fluid balance, treatment efficacy, number of interventions, and alarms.

RESULTS

Desired fluid balance according to the prescribed weight loss was achieved in all patients (R²=0.86, p<0.0001). Treatment efficacy was monitored by blood urea nitrogen (BUN) and serum creatinine values at the start of RRT (59 ± 17 mg/dL and 5.1 ± 1.1 mg/dL) and their decrease after 4 hours of RRT (23 ± 7 mg/dL and 2.2 ± 0.6 mg/dL). Measured urea and creatinine clearances for the HF20 filter were 23 ± 7 ml/min and 19 ± 4 ml/min, respectively. No complications occurred.

CONCLUSION

This is the first report on the use of the Prismaflex HF20 set in infants. No adverse events were observed, treatments were well tolerated in all patients, and flow rate adaptability to infants' needs was good.

Continuous renal replacement therapy for patients with acute kidney injury caused by melamine-related urolithiasis

BACKGROUND

In 2008 there was an epidemic of renal disease affecting infants after consumption of melamine-tainted milk products. Most of the infected children were asymptomatic or with mild symptoms, and a few suffered from acute obstructive kidney injury secondary to melamine-contained renal stones (8 of 15,577 children screened at our hospital for urolithiasis). This study was intended to retrospectively review the management of acute kidney injury using continuous renal replacement therapy (CRRT) in the 8 children with acute kidney injury.

METHODS

The 8 infants with acute kidney injury caused by melamine-related urolithiasis were referred to the pediatric intensive care unit at the hospital in late 2008. CRRT was given to treat their kidney injuries. Medical records of the infants were reviewed for demographic features, diagnosis, CRRT treatment, and outcomes.

RESULTS

Before CRRT, hypertension was found in 6 of the 8 children. Varying degrees of oliguria, anuria, elevated levels of blood urea nitrogen (BUN) (13.11-35.6 mmol/L) and creatinine (Cr) (238.8-773.7 mumol/L) were observed in these patients. After CRRT, the levels of BUN, Cr and electrolytes decreased. Urine output and edema were improved clinically.

CONCLUSION

CRRT can rapidly improve renal function, avoiding such surgical interventions as lithotripsy, percutaneous nephrolithotomy, and ureteroscopy. It is an efficient modality to treat acute kidney injury caused by melamine-related urolithiasis.

Dialysis dose in acute kidney injury: no time for therapeutic nihilism--a critical appraisal of the Acute Renal Failure Trial Network study

The optimal dialysis dose for acute kidney injury is a matter of great controversy. Clinical trials, predominantly single-center studies, have shown conflicting results. The Acute Renal Failure Trial Network (ATN) Study was designed to compare clinical outcomes between patients allocated to an intensive dose versus a less-intensive dose of renal replacement therapy. Recently, the results of this large randomized controlled multicenter study were published. The present article will discuss certain aspects of this trial: the overall design, the baseline patient characteristics, and comparison of the results with earlier studies. Finally, the article will address the implications of the ATN Study results for clinical practice.