Breathing Life Back Into the Kidney—Continuous Renal Replacement Therapy and Veno-Venous Extracorporeal Membrane Oxygenation

Kidney replacement therapy during extracorporeal membrane oxygenation: pathophysiology, technical considerations, and outcomes

The use of extracorporeal membrane oxygenation has been increasing over time, in part due to the COVID-19 pandemic. Whilst lifesaving, complications that must be managed are also associated with its use. AKI and fluid overload are complications of concern due to their associations with poor outcomes, and ability to be managed by additional interventions such as the use of kidney replacement therapy. Various modalities, timings, and types of kidney replacement therapy are currently being used and outcomes regarding its concurrent use with extracorporeal membranous oxygenation across centers may be mixed. In this review, we discuss the pathophysiology of AKI, methods, modalities and impact of concurrent extracorporeal membrane oxygenation and kidney replacement therapy.

Factors Associated with the Initiation of Renal Replacement Therapy in Patients on VV-ECMO: A Case-Control Study

Acute Kidney Injury (AKI) is a common complication in patients with Acute Respiratory Distress Syndrome (ARDS) receiving VV-ECMO support, carrying a high risk of progression to Renal Replacement Therapy (RRT). Both AKI and RRT are linked to an increased risk of mortality. This study aims to evaluate the risk factors associated with the need for RRT in patients undergoing VV-ECMO. Methods: This is a retrospective case-control study involving patients on VV-ECMO therapy admitted to the intensive care unit (ICU) between 2019 and 2023. Patients on VV ECMO support, with or without RRT, were included and their severity scores and associated mortality were calculated. A multivariate logistic regression analysis was performed to assess the variable RRT using odds ratios (OR) with their corresponding confidence intervals (CI) for the outcome variables. Results: A total of 192 subjects were included, with a mortality rate of 39.6%. Of these, 68.7% were male, with an average ICU stay of 25.1 days and a need for RRT in 19.7% of cases. The multivariate analysis independently associated the use of vasopressors with RRT norepinephrine OR 5.61 (95% CI, 1.64-19.1) and vasopressin OR 4.64 (95% CI, 2.15-10.0)). An increase in creatinine levels before ECMO support is associated with an increased risk OR 2.21 (95% CI 1.54-3.18), and 24 h after ECMO support, the risk rises further adjusted odds ratio (AOR) 3.32 (95% IC 1.55-7.09). The accuracy of severity scores presented weak discrimination and similar behavior, except for DEOx for the primary outcome, with an AUC of 0.79 (95% CI, 0.72-0.87), and APACHE II with an AUC of 0.68 (95% CI, 0.59-0.78). Conclusions: The prediction of RRT in patients on VV-ECMO support was superior for DEOx, which is influenced by the use of vasopressors, creatinine levels, and platelet transfusion prior to cannulation. This could be useful for predicting early interventions in this patient population.

Risk factors for mortality in patients receiving extracorporeal membrane oxygenation

OBJECTIVE

Patients on extracorporeal membrane oxygenation (ECMO) are often complex and have a high mortality rate. Currently, risk assessment and treatment decisions for patients receiving ECMO are controversial. Therefore, we sought to identify risk factors for mortality in patients receiving ECMO and provide a reference for patient management.

METHODS

We retrospectively analyzed the clinical data of 199 patients who received ECMO support from December 2013 to April 2023. Univariate and multivariable logistic regression analyses were used to identify risk factors. The cutoff value was determined by receiver operating characteristic (ROC) curve analysis.

RESULTS

A total of 199 patients were selected for this study, and the mortality rate was 76.38%. More than half of the patients underwent surgery during hospitalization. Multivariable logistic regression analysis revealed that continuous renal replacement therapy (CRRT) implantation (OR = 2.994; 95% CI, 1.405-6.167; p = 0.004) and age (OR = 1.021; 95% CI, 1.002-1.040; p = 0.032) were the independent risk factors for mortality. In the ROC curve analysis, age had the best predictive effect (AUC 0.646, 95% CI 0.559-0.732, p = 0.003) for death when the cutoff value was 48.5 years. Furthermore, in patients receiving combined CRRT and ECMO, lack of congenital heart disease and previous surgical history were the independent risk factors for mortality.

CONCLUSIONS

CRRT implantation and age were independent risk factors for patients with ECMO implantation in a predominantly surgical cohort. In patients receiving a combination of CRRT and ECMO, lack of congenital heart disease and previous surgical history were independent risk factors for mortality.

Factors associated with post-hospitalization dialysis dependence in ECMO patients who required continuous renal replacement therapy

OBJECTIVE

This single center retrospective study aimed to describe the variables associated with outpatient dialysis dependence in extracorporeal membrane oxygenation (ECMO) patients who needed continuous renal replacement therapy (CRRT) for acute kidney injury (AKI) during their hospitalization.

METHODS

Retrospective study of patients who required ECMO-CRRT.

RESULTS

Between the years of 2016 and 2022, 202 patients required ECMO-CRRT. One hundred and six patients (52.5%) survived their hospitalization and were followed up for a median of 391 [133, 1005] days. Eighty-one patients (76.5%) recovered kidney function and were dialysis-free before hospital discharge. Twenty-five patients (23.5%) were hemodialysis-dependent after hospitalization. On multivariate regression analysis, hyperlipidemia (odds ratio, OR 6.08 [1.67-22]) and CRRT duration (OR 1.09 [1.03-1.15]) were associated with the need for dialysis post-hospitalization. In this group, 16 patients eventually became dialysis-free, after a median of 49 [34.7, 78.5] days. These patients had a higher median baseline glomerular filtration rate (GFR) compared to those who never recovered renal function (93 mL/min/1.73 m2 [82.4, 104.3] vs. 63.8 mL/min/1.73 m2 [37.9, 83], p = .009). Their follow-up GFR was lower compared to those who recovered renal function before hospital discharge; (87 mL/min/1.73 m2 [68.2, 98.9] vs. 99 mL/min/1.73 m2 [79, 118], p = .07).

CONCLUSIONS

AKI requiring CRRT was associated with high mortality in patients receiving ECMO. Nonetheless, most ECMO survivors became dialysis-free before hospital discharge. Variables associated with the need for outpatient dialysis included hyperlipidemia and prolonged need for CRRT during hospitalization.

Risk factors associated with hospital mortality in non-surgical patients receiving extracorporeal membrane oxygenation and continuous renal replacement treatment: a retrospective analysis

OBJECTIVES

The prognosis-predicting factors for non-surgical patients receiving continuous renal replacement therapy (CRRT) and extracorporeal membrane oxygenation (ECMO) remains limited. In this study, we aim to analyze prognosis-predicting factors in the non-surgical patients receiving these two therapies.

METHODS

We retrospectively analyzed data from non-surgical patients with ECMO treatment from December 2013 until April 2023. Hospital mortality was primary endpoint of this study. The area under the curve and receiver operating characteristic curves were used to assess the sensitivity and specificity of mortality. The independent risk factors were identified by multivariate logistic regression. The prediction model was a nomogram, and decision curve analysis and the calibration plot were used to assess it. Using restricted cubic spline curves and Spearman correlation, the correlation analysis was performed.

RESULTS

The model that incorporated CRRT duration and age surpassed the two variables alone in predicting hospital mortality in non-surgical patients with ECMO therapy (AUC value = 0.868, 95% CI = 0.779-0.956). Older age, CRRT implantation, and duration were independent risk factors for hospital mortality (all p < 0.05). The nomogram predicting outcomes model containing on CRRT implantation and duration was developed, and the consistency between the predicted probability and observed probability and clinical utility of the models were good. CRRT duration was negatively associated with hemoglobin concentration and positively associated with urea nitrogen and serum creatinine levels.

CONCLUSION

Hospital mortality in non-surgical ECMO patients was found to be independently associated with older age, longer CRRT duration, and CRRT implantation.

High protein intake and nitrogen balance in patients receiving venovenous extracorporeal membrane oxygenation: A descriptive cohort study

BACKGROUND

This retrospective cohort study sought to describe the ability of high protein regimens to achieve nitrogen equilibrium in patients receiving venovenous extracorporeal membrane oxygenation (VV ECMO).

METHODS

Patients aged ≥18 years with a documented nitrogen balance study (NB) on VV ECMO between February 2018 and December 2021 were included. Studies with incomplete 24-h urine collections or changes in blood urea nitrogen ≥10 mg/dl were excluded. Data were summarized, correlation between first NB and potentially contributing variables was assessed with Kendall tau. Subanalysis described findings after stratifying for weight class (obese vs nonobese) and duration of VV ECMO at the time of NB.

RESULTS

A total of 68 NBs in 30 patients were included; 47% of the cohort had obesity. The number of NBs per patient was 2.2 ± 1.1, which were completed on a median of 31.5 (interquartile range: 16, 53.8) days receiving ECMO. Nitrogen equilibrium or positive balance was achieved in 72% of studies despite elevated nitrogen excretion. Patients received 87.9 ± 16.8% of prescribed protein on NB days for average intakes of 2.4 ± 0.4 g/kg of actual weight per day and 2.4 ± 0.5 g/kg of ideal weight per day in patients without and with obesity. Median NB in patients without obesity was -1.46 (-8.96, 2.98) g/day and -0.21 (-10.58, 4.04) g/day in patients with obesity. A difference in median NB after stratification for timing was observed (P = 0.029).

CONCLUSION

Nitrogen equilibrium can be achieved with high protein intake in adults receiving VV ECMO. NB monitoring is one tool to individualize protein prescriptions throughout the course of VV ECMO.

COVID-19 outcomes of venovenous extracorporeal membrane oxygenation for acute respiratory failure vs historical cohort of non-COVID-19 viral infections

INTRODUCTION

Veno-venous extracorporeal membrane oxygenation (VV ECMO) has become a support modality for patients with acute respiratory failure refractory to standard therapies. VV ECMO has been increasingly used during the current COVID-19 pandemic for patients with refractory respiratory failure. The object of this study was to evaluate the outcomes of VV ECMO in patients with COVID-19 compared to patients with non-COVID-19 viral infections.

METHODS

We retrospectively reviewed all patients supported with VV ECMO between 8/2014 and 8/2020 whose etiology of illness was a viral pulmonary infection. The primary outcome of this study was to evaluate in-hospital mortality. The secondary outcomes included length of ECMO course, ventilator duration, hospital length of stay, incidence of adverse events through ECMO course.

RESULTS

Eighty-nine patients were included (35 COVID-19 vs 54 non-COVID-19). Forty (74%) of the non-COVID-19 patients had influenza virus. Prior to cannulation, COVID-19 patients had longer ventilator duration (3 vs 1 day, p = .003), higher PaCO2 (64 vs 53 mmHg, p = .012), and white blood cell count (14 vs 9 ×103/μL, p = .004). Overall in-hospital mortality was 33.7% (n = 30). COVID-19 patients had a higher mortality (49% vs. 24%, p = .017) when compared to non-COVID-19 patients. COVID-19 survivors had longer median time on ECMO than non-COVID-19 survivors (24.4 vs 16.5 days p = .03) but had a similar hospital length of stay (HLOS) (41 vs 48 Extracorporeal Membrane Oxygenationdays p = .33).

CONCLUSION

COVID-19 patients supported with VV ECMO have a higher mortality than non-COVID-19 patients. While COVID-19 survivors had significantly longer VV ECMO runs than non-COVID-19 survivors, HLOS was similar. This data add to a growing body of literature supporting the use of ECMO for potentially reversible causes of respiratory failure.

VA-ECMO Cardiac Support During Liver Transplant: A Case Report

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for cardiovascular collapse during and after liver transplantation (LT). According to the most recent guidelines, patients with severe cardiomyopathy are excluded from LT because of high-mortality risk during surgery. Intraoperative ECMO support could give these patients the opportunity to undergo LT by reducing the risk of heart failure and reperfusion syndrome. In this case report, we present a case of veno-arterial ECMO (VA-ECMO) support started before LT surgery in a patient with severe pulmonary hypertension, mitral valve steno-insufficiency, and right heart dysfunction. The presence of severe heart disease would have contraindicated LT, but simultaneous liver cirrhosis contraindicated mitral valve surgery, leaving the patient locked in a "Catch-22" state. The best solution was to perform LT with VA-ECMO support before, during, and after the surgery to reduce cardiac load and possible heart failure. LT was performed with good hemodynamic stability and the patient was successfully weaned from ECMO a few hours after surgery. At the 6 month follow-up, normal liver and kidney functions were recorded as well as an overall improvement of heart function; the patient successfully underwent mitral valve replacement and tricuspid annuloplasty 10 months after transplant and is now in good condition.

Extracorporeal Membrane Oxygenation During Pregnancy

In the last 2 decades, the use of venovenous (VV) and venoarterial (VA) extracorporeal membrane oxygenation (ECMO) during pregnancy and the postpartum period has increased, mirroring the increased utilization in nonpregnant individuals worldwide. VV ECMO provides respiratory support for patients with acute respiratory distress syndrome (ARDS) who fail conventional mechanical ventilation. With the COVID-19 pandemic, the use of VV ECMO has increased dramatically and data during pregnancy and the postpartum period are overall reassuring. In contrast, VA ECMO provides both respiratory and cardiovascular support. Data on the use of VA ECMO during pregnancy are extremely limited.

A descriptive evaluation of causes of death in venovenous extracorporeal membrane oxygenation

Veno-venous extracorporeal membrane oxygenation (VV ECMO) has become an important support modality for patients with acute respiratory failure refractory to optimal medical therapy, such as low tidal volume mechanical ventilator support, early paralytic infusion, and early prone positioning. The objective of this cohort study was to investigate the causes and timing of in-hospital mortality in patients on VV ECMO. All patients, excluding trauma and bridge to lung transplant, admitted 8/2014-6/2019 to a specialty ICU for VV ECMO were reviewed. Two hundred twenty-five patients were included. In-hospital mortality was 24.4% (n = 55). Most non-survivors (46/55, 84%) died prior to lung recovery and decannulation from VV ECMO. Most common cause of death (COD) for patients who died on VV ECMO was removal of life sustaining therapy (LST) in setting of multisystem organ failure (MSOF) (n = 24). Nine patients died a median of 9 days [6, 11] after decannulation. Most common COD in these patients was palliative withdrawal of LST due to poor prognosis (n = 3). Non-survivors were older and had worse predictive mortality scores than survivors. We found that death in patients supported with VV ECMO in our study most often occurs prior to decannulation and lung recovery. This study demonstrated that the most common cause of death in patients supported with VV ECMO was removal of LST due MSOF. Acute hemorrhage (systemic or intracranial) was not found to be a common cause of death in our patient population.

Long-term outcomes in patients who received veno-venous extracorporeal membrane oxygenation and renal replacement therapy: a retrospective cohort study

Background

Acute kidney injury (AKI) is a frequent complication in patients with severe respiratory failure receiving extracorporeal membrane oxygenation (ECMO). However, little is known of long-term kidney function in ECMO survivors. We aimed to assess the long-term mortality and kidney outcomes in adult patients treated with veno-venous ECMO (VV-ECMO).

Methods

This was a single-centre retrospective study of adult patients (≥ 18 years old) who were treated with VV-ECMO at a commissioned ECMO centre in the UK between 1st September 2010, and 30th November 2016. AKI was defined and staged using the serum creatinine and urine output criteria of the Kidney Diseases: Improving Global Outcomes (KDIGO) classification. The primary outcome was 1-year mortality. Secondary outcomes were long-term mortality (up to March 2020), 1-year incidence of end-stage kidney disease (ESKD) or chronic kidney disease (CKD) among AKI patients who received renal replacement therapy (AKI-RRT), AKI patients who did not receive RRT (AKI-no RRT) and patients without AKI (non-AKI).

Results

A total of 300 patients [57% male; median age 44.5; interquartile range (IQR) 34–54] were included in the final analysis. Past medical histories included diabetes (12%), hypertension (17%), and CKD (2.3%). The main cause of severe respiratory failure was pulmonary infection (72%). AKI occurred in 230 patients (76.7%) and 59.3% received renal replacement therapy (RRT). One-year mortality was 32% in AKI-RRT patients vs. 21.4% in non-AKI patients (p = 0.014). The median follow-up time was 4.35 years. Patients who received RRT had a higher risk of 1-year mortality than those who did not receive RRT (adjusted HR 1.80, 95% CI 1.06, 3.06; p = 0.029). ESKD occurred in 3 patients, all of whom were in the AKI-RRT group. At 1-year, 41.2% of survivors had serum creatinine results available. Among these, CKD was prevalent in 33.3% of AKI-RRT patients vs. 4.3% in non-AKI patients (p = 0.004).

Conclusions

VV-EMCO patients with AKI-RRT had high long-term mortality. Monitoring of kidney function after hospital discharge was poor. In patients with follow-up creatinine results available, the CKD prevalence was high at 1 year, especially in AKI-RRT patients. More awareness about this serious long-term complication and appropriate follow-up interventions are required.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01046-0.

Extracorporeal Membrane Oxygenation for Pregnant and Postpartum Patients

Extracorporeal membrane oxygenation (ECMO) has seen increasing use for critically ill pregnant and postpartum patients over the past decade. Growing experience continues to demonstrate the feasibility of ECMO in obstetric patients and attest to its favorable outcomes. However, the interaction of pregnancy physiology with ECMO life support requires careful planning and adaptation for success. Additionally, the maintenance of fetal oxygenation and perfusion is essential for safely continuing pregnancy during ECMO support. This review summarizes the considerations for use of ECMO in obstetric patients and how to address these concerns.

Acute kidney injury in ECMO patients

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2021. Other selected articles can be found online at  https://www.biomedcentral.com/collections/annualupdate2021 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from  https://link.springer.com/bookseries/8901 .

Acute Kidney Injury and Extracorporeal Membrane Oxygenation: Review on Multiple Organ Support Options

Extracorporeal membrane oxygenation (ECMO) is a temporary life support system used to assist patients with life-threatening severe cardiac and/or respiratory insufficiency. Patients requiring ECMO can be considered the sickest patients admitted to the intensive care unit (ICU). Acute kidney injury (AKI) represents a frequent complication during ECMO, affecting up to 70% of patients, with multifactorial pathophysiology and an independent risk factor for mortality. Severe AKI requiring Continuous Renal Replacement Therapy (CRRT) occurs in 20% of ECMO patients, but multiple indications and different timing may imply a significantly higher application rate in different centers. CRRT can be run in parallel to ECMO through different vascular access, or it can be conducted in series by connecting the circuits. Anticoagulation of ECMO is typically managed with systemic heparin, but several approaches can be applied for the CRRT circuit, from no anticoagulation to the addition of intra-filter heparin or regional citrate anticoagulation. The combination of CRRT and ECMO can be considered a form of multiple organ support therapy, but this approach still requires optimization in timing, set-up, anticoagulation, prescription and delivery. The aim of this report is to review the pathophysiology of AKI, the CRRT delivery, anticoagulation strategies and outcomes of patients with AKI treated with ECMO.

Continuous renal replacement therapy in patients treated with extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a life‐saving therapy utilized for patients with severe life‐threatening cardiorespiratory failure. Patients treated with ECMO are among the most severely ill encountered in critical care and are at high‐risk of developing multiple organ dysfunction, including acute kidney injury (AKI) and fluid overload. Continuous renal replacement therapy (CRRT) is increasingly utilized inpatients on ECMO to manage AKI and treat fluid overload. The indications for renal replacement therapy for patients on ECMO are similar to those of other critically ill populations; however, there is wide practice variation in how renal supportive therapies are utilized during ECMO. For patients requiring both CRRT and ECMO, CRRT may be connected directly to the ECMO circuit, or CRRT and ECMO may be performed independently. This review will summarize current knowledge of the epidemiology of AKI, indications and timing of CRRT, delivery of CRRT, and the outcomes of patients requiring CRRT with ECMO.

Concurrent Use of Renal Replacement Therapy during Extracorporeal Membrane Oxygenation Support: A Systematic Review and Meta-Analysis

Patients supported with extracorporeal membrane oxygenation (ECMO) often receive renal replacement therapy (RRT). We conducted this systematic review and meta-analysis (between January 2000 and September 2020) to assess outcomes in patients who received RRT on ECMO. Random-effects meta-analyses were performed using R 3.6.1 and certainty of evidence was rated using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach. The primary outcome was pooled mortality. The duration of ECMO support and ICU/hospital lengths of stay were also investigated. Meta-regression analyses identified factors associated with mortality. A total of 5896 adult patients (from 24 observational studies and 1 randomised controlled trial) were included in this review. Overall pooled mortality due to concurrent use of RRT while on ECMO from observational studies was 63.0% (95% CI: 56.0–69.6%). In patients receiving RRT, mortality decreased by 20% in the last five years; the mean duration of ECMO support and ICU and hospital lengths of stay were 9.33 days (95% CI: 7.74–10.92), 15.76 days (95% CI: 12.83–18.69) and 28.47 days (95% CI: 22.13–34.81), respectively, with an 81% increased risk of death (RR: 1.81, 95% CI: 1.56–2.08, p < 0.001). RRT on ECMO was associated with higher mortality rates and a longer ICU/hospital stay compared to those without RRT. Future research should focus on minimizing renal dysfunction in ECMO patients and define the optimal timing of RRT initiation.