Continuous renal replacement therapy: understanding circuit hemodynamics to improve therapy adequacy

A novel pump-free ultrafiltration rate modulation system for continuous renal replacement therapy applications

Purpose

Extracorporeal ultrafiltration is an attractive alternative to diuretics for removing excess plasma water in critically ill patients suffering from fluid overload. In continuous renal replacement therapy (CRRT), ultrafiltration occurs in isolated form (SCUF) or supplemented by replacement fluid infusion (CVVH) and the net fluid removal rate is controlled by peristaltic pumps. In this work, a pump-free solution for regulating the ultrafiltration rate in CRRT applications is presented.

Methods

The system consists of a motorized clamp on the ultrafiltration line, whose intermittent opening is modulated with a closed-loop control system based on monitoring of ultrafiltrate collected and any replacement fluid infused. The system was tested on two platforms for SCUF and CVVH, with “low-flux” and “high-flux” hemofilter, with various ultrafiltration setpoints and patient net weight loss targets.

Results

In all configurations the set ultrafiltration rate was achieved with a maximum error of 5% and the values recorded were kept within ± 100 ml/h with respect to the setpoint, as recommended by international standard IEC 60601-2-16. The net fluid removal trend was highly correlated with that expected (95%<R2<99%) and the weight loss target was reached in the expected time. For low ultrafiltration rates (60-150 ml/h) the system accuracy was better with the “low-flux” hemofilter.

Conclusion

The developed clamp system represents a valid alternative to state-of-the-art solutions with peristaltic pumps in terms of performance, with potential usability advantages. The compliance with safety requirements given by international standard IEC 60601-2-16 is a prerequisite for clinical use.

Trends, Advantages and Disadvantages in Combined Extracorporeal Lung and Kidney Support From a Technical Point of View

Extracorporeal membrane oxygenation (ECMO) provides pulmonary and/or cardiac support for critically ill patients. Due to their diseases, they are at high risk of developing acute kidney injury. In that case, continuous renal replacement therapy (CRRT) is applied to provide renal support and fluid management. The ECMO and CRRT circuits can be combined by an integrated or parallel approach. So far, all methods used for combined extracorporeal lung and kidney support present serious drawbacks. This includes not only high risks of circuit related complications such as bleeding, thrombus formation, and hemolysis, but also increase in technical workload and health care costs. In this sense, the development of a novel optimized artificial lung device with integrated renal support could offer important treatment benefits. Therefore, we conducted a review to provide technical background on existing techniques for extracorporeal lung and kidney support and give insight on important aspects to be addressed in the development of this novel highly integrated artificial lung device.

Acute kidney injury and renal replacement therapy: terminology standardization

The Department of Acute Kidney Injury (IRA) of the Brazilian Society of Nephrology prepared this document for the purpose of standardizing AKI terminology and dialysis modalities in the Portuguese language for Brazil. Several terms with similar meanings have been used in AKI and its dialysis modalities, causing confusion and disparities among patients, nephrologists, health institutions, private care companies, insurance companies and government entities. These disparities can impact medical care, hospital organization and care, as well as the funding and reimbursement of AKI-related procedures. Thus, consensual nomenclature and definitions were developed, including the definitions of AKI, acute kidney disease (AKD) and chronic kidney disease (CKD). Additionally, we addressed all dialysis modalities and extracorporeal procedures related to AKI, currently approved and available in the country. The Brazilian Society of Nephrology hopes that this Consensus can standardize the terminology and provide technical support to all involved in AKI care in Brazil.

Injúria renal aguda e métodos de suporte: padronização da nomenclatura

Resumo O Departamento de Injúria Renal Aguda (IRA) da Sociedade Brasileira de Nefrologia elaborou o presente documento para fins de padronização da terminologia em IRA e modalidades dialíticas na língua portuguesa para o Brasil. Diversos termos com significados semelhantes têm sido empregados em IRA e suas modalidades dialíticas, causando confusão e disparidades entre pacientes, nefrologistas, instituições de saúde, empresas privadas de assistência, seguradoras e entidades governamentais. Essas disparidades podem impactar a assistência médica, a organização e o atendimento hospitalares, assim como o financiamento e reembolso dos procedimentos relacionados com a IRA. Assim, nomenclatura e definições consensuais foram elaboradas, incluindo-se as definições de IRA, doença renal aguda (DRA) e doença renal crônica (DRC). Adicionalmente, todas as modalidades dialíticas e os procedimentos extracorpóreos relacionados a IRA, atualmente aprovados e disponíveis no país, foram abordados. A Sociedade Brasileira de Nefrologia espera que este Consenso possa padronizar a nomenclatura e prover suporte técnico para todos os atores envolvidos na assistência à IRA no Brasil.

Renal Replacement Therapy for Patients Requiring Extracorporeal Membrane Oxygenation: A Multicenter International Survey

INTRODUCTION

Patients receiving extracorporeal membrane oxygenation (ECMO) often require renal replacement therapy (RRT). The challenge of inserting a dialysis catheter (DC) could be solved by direct connection of RRT lines on an ECMO circuit (DCRE) without published guidelines. This study aimed to describe the practice of RRT in patients on ECMO, including the DCRE as well as the perception and concerns related to this technique.

METHODS

An international survey was worldwide sent via email to professionals involved in the management of ECMO. Respondents always or often performing RRT via the ECMO circuit were classified in the ECMO group, and those using a DC were classified in the DC group.

RESULTS

From March 2019 to October 2019, 298 participants answered the questionnaire from 46 different countries. Only 28% were working in pediatric departments. Among the 165 participants commonly performing RRT in patients on ECMO, 100 (61%) performed mainly RRT via the ECMO circuit, and 65 (39%) performed RRT via DC. Pediatric practice and a longer experience were the only noticeable characteristics of the ECMO group. The most reported concern regarding DCRE was the risk of air embolism (n = 84, 28%), but the most encountered problem was unmanageable pressure alarms in RRT devices.

CONCLUSION

The present study showed significant heterogeneity in RRT practices in patients on ECMO. The lower experience of the DC group, the high rates of concerns toward DCRE, and pressure alarm issues suggested that protocols and training may overcome reluctance and technical difficulties.

Review of Anticoagulation in Continuous Renal Replacement Therapy

Continuous renal replacement therapy is an important, yet challenging, treatment of critically ill patients with kidney dysfunction. Clotting within the dialysis filter or circuit leads to time off therapy and impaired delivery of prescribed treatment. Anticoagulation can be used to prevent this complication; however, doing so introduces risk for unintended complications such as bleeding or metabolic derangements in patients who are already critically ill. A thorough understanding of indications, therapeutic options, and monitoring principles is necessary for safe and effective use of this strategy. This review provides clinicians important information regarding when to anticoagulate, differences in pharmacologic agents, recommended doses, routes of drug delivery, and appropriate laboratory monitoring for patients receiving anticoagulation to support continuous renal replacement therapy.

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.

Effect of Blood Flow Rate on the Accuracy of Central Venous Pressure Measurement during Continuous Renal Replacement Therapy

BACKGROUND

The objective of this study was to study the influence of extracorporeal blood flow rate (BFR) on the accuracy of central venous pressure (CVP) measurement during continuous renal replacement therapy (CRRT).

METHODS

Eligible patients were randomly divided into 3 groups based on the location of catheters used for their CRRT and CVP measurement. CVP levels measured at increased extracorporeal BFR (from 0 to 300 mL/min) in the normal and reverse positions of inlet and outlet lines connected to the CV catheter (CVC) in the course of the CRRT session were collected.

RESULTS

CVP levels measured at different extracorporeal BFRs did not significantly differ between and among the 3 groups. Inversion of inlet and outlet lines connected to the catheters did not affect the accuracy of CVP measurement. BFR had a negative correlation with inflow/access pressure but a positive correlation with outflow/return pressure. Neither inflow pressure nor outflow pressure was correlated with CVP.

CONCLUSIONS

Extracorporeal BFR has no influence on the accuracy of CVP measurement during CRRT with the net machine balance adjusted to zero regardless of the location of the catheter and the connection method between catheters and CRRT lines. Thus, CRRT does not need to be discontinued to obtain an accurate CVP measurement.

Vascular access, membranes and circuit for CRRT

The advances in the technology for providing continuous renal replacement therapy (CRRT) have led to an increase in its utilization throughout the world. However, circuit life continues to be a major problem. It leads not only to decreased delivery of dialysis but also causes blood loss, waste of disposables, alters dose delivery of medications and nutrition, and increases nurse workload, all of which increases healthcare cost. Premature circuit failure can be caused by numerous factors that can be difficult to dissect out. The first component is the vascular access; without a well-placed, functioning access, delivery of CRRT becomes very difficult. This is usually accomplished by placing a short-term dialysis catheter into either the right internal jugular or femoral vein. The tips should be located at the caval atrial junction or inferior vena cava. In addition to establishing suitable vascular access, a comprehensive understanding of the circuit facilitates the development of a methodical approach in providing efficient CRRT characterized by optimal circuit life. Moreover, it aids in determining the cause of circuit failure in patients experiencing recurrent episodes. This review therefore summarizes the essential points that guide providers in establishing optimal vascular access. We then provide an overview of the main components of the CRRT circuit including the blood and fluid pumps, the hemofilter, and pressure sensors, which will assist in identifying the key mechanisms contributing to premature failure of the CRRT circuit.