Conversion From Venovenous to Venoarterial Extracorporeal Membrane Oxygenation Is Associated With Increased Mortality in Children

Safety and feasibility of conversion from venoarterial to venovenous extracorporeal membrane oxygenation in pediatric patients: A case series

INTRODUCTION

In children requiring venoarterial (VA) extracorporeal membrane oxygenation (ECMO) for long durations, conversion to venovenous (VV) support may be advantageous. The purpose of this study was to evaluate the feasibility and safety of conversion from VA to VV ECMO.

METHODS

This is a retrospective review of all children who underwent conversion from VA to VV ECMO at a single institution, from 2015 to 2022. Indications for and methods of conversion were examined as well as adverse events including re-operation, ischemic complications, renal failure, and mortality.

RESULTS

Of 422 pediatric patients on initial VA ECMO, 4 children (0.9%) underwent conversion from VA to VV support. The indications for cannulation were: respiratory failure due to COVID19, respiratory failure due to congenital diaphragmatic hernia, cardiac dysfunction following heart transplant, and sepsis with associated left ventricular dysfunction. The indications for conversion were bleeding from the arterial cannula and ongoing respiratory failure. The median time to conversion was 6.5 days (range 4-54 days) and the median length of ECMO run was 34.5 days. Three patients required renal replacement therapy with two progressing to long-term dialysis. There were no ischemic limb complications although one patient developed a femoral artery pseudoaneurysm that required re-operation. Three patients survived to discharge. One patient was unable to be decannulated after conversion and mechanical support was withdrawn.

CONCLUSIONS

Conversion to VV ECMO from initial VA ECMO cannulation is feasible but a rare event. For patients with cardiac stability but continued need for respiratory support, conversion to VV ECMO can be considered.

Outcomes After Respiratory Extracorporeal Life Support in Teens and Young Adults: An Extracorporeal Life Support Organization Registry Analysis

OBJECTIVES

A recent study from Germany found that survival after respiratory extracorporeal life support (ECLS) was lower among patients 10-20 years old than 20-30 years old. The objective of this study was to compare survival between teenage and young adult patients who receive respiratory ECLS.

DESIGN

Retrospective cohort study.

SETTING

Extracorporeal Life Support Organization registry, an international prospective quality improvement database.

PATIENTS

All patients ages 16-30 years cannulated for respiratory indications from 1990 to 2020 were included. Patients were divided into two groups, teens (16-19 yr old) and young adults (20-30 yr old).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Primary outcome was survival to discharge. Variables were considered for the multivariate logistic regression model if there was both a statistically significant difference (p ≤ 0.05) and a clinically meaningful absolute difference between the groups. A total of 5,751 patients were included, of whom 1,653 (29%) were teens and 4,098 (71%) were young adults. Survival to discharge was higher in young adults than teens, 69% versus 63% (p < 0.001). Severity of illness was higher among teens; however, survival within each stratum defined by Pao2/Fio2 ratio was higher in young adults than in teens. Use of venoarterial ECLS was higher in teens than in young adults, 15% versus 7%, respectively. Teens were more likely to receive high-frequency oscillatory ventilation and this therapy was associated with a longer time from admission to ECLS initiation. After adjusting for variables that differ significantly between the groups, the odds ratio for survival in young adults compared with teens was 1.14 (95% CI, 1.004-1.3).

CONCLUSIONS

In this large multicenter retrospective study, mortality was higher in teens than in young adults who received respiratory ECLS. This difference persisted after adjusting for multiple variables and the mechanism underlying these findings remains unclear.

Neonatal venoarterial and venovenous ECMO

ECMO remains an important support tool in the treatment of neonates with reversible congenital cardiopulmonary diseases. There are specific circumstances that call for either venoarterial (VA) or venovenous (VV) ECMO in neonates. While limited by the infant's the size and gestational age, ECMO can confer exceptional survival rates to a number of neonates who can often develop without devastating complications. However, it remains a labor and time intensive endeavor, which may be impractical or unattainable in resource-limited environments. While adult and pediatric ECMO indications and equipment options have expanded in recent years, neonatal ECMO continues to be a niche subspecialty requiring specific expertise and technical skill, especially considering the ever-changing neonatal physiology in the setting of cardiopulmonary support. It is critical to recognize the unique approaches to cannulation options, imaging, vessel management, anticoagulation, and monitoring protocols to achieve optimal outcomes. Thus, it becomes nearly impossible to separate the role of pediatric surgeons from the continuous involvement with and management of neonatal ECMO patients. This necessitates that pediatric surgeons in ECMO centers continue to hone their expertise and remain heavily involved in neonatal ECMO. This section reviews the most critical current approaches and unresolved controversies in neonatal ECMO with special attention to the practical aspects and decisions a surgeon faces in initiation and termination of neonatal ECMO.

Incidence and predictors of brain infarction in neonatal patients on extracorporeal membrane oxygenation: an observational cohort study

To determine the incidence and identify predictors of brain infarctions (BI) in neonatal patients treated with extracorporeal membrane oxygenation (ECMO). We performed a retrospective cohort study at ECMO Centre Karolinska, Stockholm, Sweden. Logistic regression models were used to identify BI predictors. Neonates (age 0-28 days) treated with veno-arterial (VA) or veno-venous (VV) ECMO between 2010 and 2018. The primary outcome was a computed tomography (CT) verified BI diagnosed during ECMO treatment. In total, 223 patients were included, 102 patients (46%) underwent at least one brain CT and 27 patients (12%) were diagnosed with a BI. BI diagnosis was associated with increased 30-day mortality (48% vs. 18%). High pre-ECMO Pediatric Index of Mortality score, sepsis as the indication for ECMO treatment, VA ECMO, conversion between ECMO modes, use of continuous renal replacement therapy, and extracranial thrombosis were identified as independent predictors of BI development. The incidence of BI in neonatal ECMO patients may be higher than previously understood. Risk factor identification may help initiate steps to lower the risk or facilitate earlier diagnosis of BI in neonates undergoing ECMO treatment.

Venoarterial to venovenous extracorporeal life support conversion in pediatric acute respiratory distress syndrome

In patients with pediatric acute respiratory distress syndrome (PARDS) and hemodynamic compromise who need venoarterial (VA) extracorporeal life support (ECLS), we have adopted a strategy to promote early VA-to-venovenous (VV) conversion since 2018. A single-center retrospective review was performed of all 22 patients who underwent ECLS for PARDS from 2008 to 2019. Variables were analyzed to determine factors affecting initial cannulation mode and in-hospital mortality. Outcomes were compared between before and after 2018. Of the 22 patients, 9 patients underwent initial VA-support. Small patient size and severe cardiopulmonary compromise prior to ECLS favored initial VA- over VV-support. Lactate level and vasoactive inotrope score at 24 hours post-ECLS initiation predicted in-hospital mortality. After 2018, all five patients with initial VA-support were converted to VV-support at 4.4 ± 1.3 days post-ECLS initiation without complications. In-hospital mortality decreased after 2018 (3/9) compared with before (10/13) (p = 0.041) despite longer ECLS run time (723.4 ± 384.2 vs 286.5 ± 235.1 hours, p = 0.003). The number of ECLS-related complications per ECLS 1000 run hours decreased after 2018 (7.2 ± 4.2 vs 46.9 ± 66.5, p = 0.063). Our strategy to promote early VA-to-VV conversion may be worth further evaluation in larger cohort studies.

Conversion from Venovenous to Venoarterial Extracorporeal Membrane Oxygenation in Adults

No major study has been performed on the conversion from venovenous (VV) to venoarterial (VA) extracorporeal membrane oxygenation (ECMO) in adults. This single-center retrospective cohort study aimed to investigate the incidence, indication, and outcome in patients who converted from VV to VA ECMO. All adult patients (≥18 years) who commenced VV ECMO at our center between 2005 and 2018 were screened. Of 219 VV ECMO patients, 21% (n = 46) were converted to VA ECMO. The indications for conversion were right ventricular failure (RVF) (65%), cardiogenic shock (26%), and other (9%). In the converted patients, there was a significant increase in Sequential Organ Failure Assessment (SOFA) scores between admission 12 (9-13) and conversion 15 (13-17, p < 0.001). Compared to non-converted patients, converted patients also had a higher mortality rate (62% vs. 16%, p < 0.001) and a lower admission Respiratory Extracorporeal Membrane Oxygenation Survival Prediction (RESP) score (p < 0.001). Outcomes were especially unfavorable in those converted due to RVF. These results indicate that VA ECMO, as opposed to VV ECMO, should be considered as the first mode of choice in patients with respiratory failure and signs of circulatory impairment, especially in those with impaired RV function. For the remaining patients, Pre-admission RESP score, daily echocardiography, and SOFA score trajectories may help in the early identification of those where conversion from VV to VA ECMO is warranted. Multi-centric studies are warranted to validate these findings.

Morbidity of conversion from venovenous to venoarterial ECMO in neonates with meconium aspiration or persistent pulmonary hypertension

BACKGROUND

Outcomes in neonates receiving extracorporeal membrane oxygenation (ECMO) for meconium aspiration syndrome (MAS) and/or persistent pulmonary hypertension (PPHN) are favorable. Infants with preserved perfusion are often offered venovenous (VV) support to spare morbidities of venoarterial (VA) ECMO. Worsening perfusion or circuit complications can prompt conversion from VV-to-VA support. We examined whether outcomes in infants requiring VA ECMO for MAS/PPHN differed if they underwent VA support initially versus converting to VA after a VV trial, and what factors predicted conversion.

METHODS

We reviewed the Extracorporeal Life Support Organization registry from 2007 to 2017 for neonates with primary diagnoses of MAS/PPHN. Propensity score analysis matched VA single-runs (controls) 4:1 against VV-to-VA conversions based on age, pre-ECMO pH, and precannulation arrests. Primary outcomes were complications and survival. Data were analyzed using Mann-Whitney U and Fisher's exact testing. Multivariate regression identified independent predictors of conversion for VV patients.

RESULTS

3831 neonates underwent ECMO for MAS/PPHN, including 2129 (55%) initially requiring VA support. Of 1702 patients placed on VV ECMO, 98 (5.8%) required VV-to-VA conversion. Compared with 364 propensity-matched isolated VA controls, conversion runs were longer (190 vs. 127 h, P < 0.001), were associated with more complications, and decreased survival to discharge (70% vs. 83%, P = 0.01). On multivariate regression, conversion was more likely if neonates on VV ECMO did not receive surfactant (OR = 1.7;95%CI = 1.1-2.7;P = 0.03) or required high-frequency ventilation (OR = 1.9;95%CI = 1.2-3.3;P = 0.01) before ECMO.

CONCLUSION

Conversion from VV-to-VA ECMO in infants with MAS/PPHN conveys increased morbidity and mortality compared to similar patients placed initially onto VA ECMO. VV patients not receiving surfactant or requiring high-frequency ventilation before cannulation may have increased risk of conversion. While conversions remain rare, decisions to offer VV ECMO for MAS/PPHN must be informed by inferior outcomes observed should conversion be required.

LEVEL OF EVIDENCE

Level of evidence 3 Retrospective comparative study.