Body mass index does not impact survival in COVID-19 patients requiring veno-venous extracorporeal membrane oxygenation

Should Obesity Be an Exclusion Criterion for Extracorporeal Membrane Oxygenation Support? A Scoping Review

Obesity is often considered a contraindication to extracorporeal membrane oxygenation (ECMO) candidacy due to technical challenges with vascular access, higher cardiac output requirements, and known associations between obesity and overall increased morbidity and mortality due to chronic health conditions. However, a growing body of literature suggests that ECMO may be as safe and efficacious in both obese and nonobese patients. This scoping review provides a synthesis of the available literature on the outcomes of obese patients supported with (1) venovenous (VV)-ECMO in acute respiratory distress syndrome (ARDS) not due to coronavirus disease 2019 (COVID-19), (2) VV-ECMO in ARDS due to COVID-19, (3) venoarterial (VA)-ECMO for all indications, and (4) studies combining data of patients supported with VA- and VV-ECMO. A librarian-assisted search was performed using 4 primary electronic medical databases (PubMed, Web of Science, Excerpta Medica database [Embase], and Cochrane Library) from January 2003 to March 2023. Articles that reported outcomes of obese patients requiring ECMO support were included. Two reviewers independently screened titles, abstracts, and full text of articles to determine eligibility. Data extraction was performed using customized fields established a priori within a systematic review software system. A total of 354 publications were imported for screening on titles and abstracts, and 30 studies were selected for full-text review. A total of 26 publications met the inclusion criteria: 7 on VV-ECMO support in non-COVID-19 ARDS patients, 6 on ECMO in COVID-19 ARDS patients, 8 in patients supported with VA-ECMO, and 5 combining both VA- and VV-ECMO data. Although the included studies are limited to retrospective analyses and display a heterogeneity in definitions of obesity and comparison groups, the currently available literature suggests that outcomes and complications of ECMO therapy are equivalent in obese patients as compared to nonobese patients. Hence, obesity as measured by body mass index alone should not be considered an exclusion criterion in the decision to initiate ECMO.

Specific and Non-specific Aspects and Future Challenges of ICU Care Among COVID-19 Patients with Obesity: A Narrative Review

PURPOSE OF REVIEW

Since the end of 2019, the coronavirus disease 2019 (COVID-19) pandemic has infected nearly 800 million people and caused almost seven million deaths. Obesity was quickly identified as a risk factor for severe COVID-19, ICU admission, acute respiratory distress syndrome, organ support including mechanical ventilation and prolonged length of stay. The relationship among obesity; COVID-19; and respiratory, thrombotic, and renal complications upon admission to the ICU is unclear.

RECENT FINDINGS

The predominant effect of a hyperinflammatory status or a cytokine storm has been suggested in patients with obesity, but more recent studies have challenged this hypothesis. Numerous studies have also shown increased mortality among critically ill patients with obesity and COVID-19, casting doubt on the obesity paradox, with survival advantages with overweight and mild obesity being reported in other ICU syndromes. Finally, it is now clear that the increase in the global prevalence of overweight and obesity is a major public health issue that must be accompanied by a transformation of our ICUs, both in terms of equipment and human resources. Research must also focus more on these patients to improve their care. In this review, we focused on the central role of obesity in critically ill patients during this pandemic, highlighting its specificities during their stay in the ICU, identifying the lessons we have learned, and identifying areas for future research as well as the future challenges for ICU activity.

Impact of obesity on outcomes of extracorporeal membrane oxygenation support: a systematic review and meta-analysis

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is used when standard methods of standard treatment methods are not successful. Obese patients present unique challenges during ECMO due to large body size hindering sufficient flows, difficulties with patient positioning and anatomical landmark identification, and restricted radiology scans. This meta-analysis aims to investigate the impact of obesity on the outcomes of patients undergoing ECMO.

METHODS

Databases (PubMed, Embase, and Scopus databases) were searched to identify relevant studies published until July 2023. Data were reported as odds ratios (OR) with 95% confidence interval (CI), and the descriptive data were reported as standard difference of means (SDM) by a random effects model.

RESULTS

A literature search identified 345 studies. Of them, 18 studies met the inclusion criteria. The findings from the meta-analysis revealed no significant association between obesity and survival outcomes after ECMO (odds ratio (OR): 0.91, 95% confidence interval (CI): 0.70-1.17, p: 0.46). Moreover, no comparative significant differences were found between obese and non-obese individuals on the duration of ECMO procedure (standardized mean difference (SMD): 0.07, -0.03-0.17), length of hospital stay (-0.03, -0.19 to 0.12), and duration of ventilation support (-0.10, -0.44 to 0.24).

CONCLUSION

The meta-analysis findings suggest no significant impact of obesity on the survival outcomes after the ECMO procedure. There was no significant impact of obesity on the duration of ECMO procedures, length of hospital stay, and duration of ventilation support.

Obesity and Extracorporeal Membrane Oxygenation

Obesity is increasing in prevalence worldwide and carries a theoretical increased risk of morbidity and mortality in critical illness, including hypercoagulability, thrombosis, and renal dysfunction. Obesity has historically been considered a relative contraindication to candidacy for extracorporeal membrane oxygenation (ECMO); however, recent research has suggested that obesity may be associated with improved outcomes in ECMO. This review was conducted to assess and synthesize the existing literature on ECMO outcomes in the obese population. We searched PubMed, Scopus, and CENTRAL databases for obesity and ECMO outcomes, and articles were screened independently by 2 authors. The selection process yielded 29 articles, with one ambispective and 28 retrospective cohort studies. Analyses of these studies show no evidence of globally increased mortality or complications in obesity. Prospective evaluation is needed to further investigate this relationship, but there is currently no evidence to support using body mass index as exclusionary criteria for ECMO.

Obesity and Extracorporeal Membrane Oxygenation (ECMO): Analysis of Outcomes

Traditionally, patients with obesity have been deemed ineligible for extracorporeal life support (ELS) therapies such as extracorporeal membrane oxygenation (ECMO), given the association of obesity with chronic health conditions that contribute to increased morbidity and mortality. Nevertheless, a growing body of literature suggests the feasibility, efficacy, and safety of ECMO in the obese population. This review provides an in-depth analysis of the current literature assessing the effects of obesity on outcomes among patients supported with ECMO (venovenous [VV] ECMO in noncoronavirus disease 2019 and coronavirus disease 2019 acute respiratory distress syndrome, venoarterial [VA] ECMO, and combined VV and VA ECMO), offer a possible explanation of the current findings on the basis of the obesity paradox phenomenon, provides a framework for future studies addressing the use of ELS therapies in the obese patient population, and provides guidance from the literature for many of the challenges related to initiating, maintaining, and weaning ELS therapy in patients with obesity.

Body mass index is not associated with time on veno-venous extracorporeal membrane oxygenation or in-hospital mortality

Morbid obesity, as characterized by BMI, is often utilized as an exclusion criterion for VV-ECMO because of presumed poor prognosis and technically complex cannulation. However, the "obesity paradox" suggests obesity may be protective during critical illness, and BMI does not capture variations in body type, adiposity, or fluid balance. This study examines relationships between BMI and patient outcomes. Adult VV-ECMO patients with BMI ≥ 35 kg/m2 admitted January 2012 to June 2021 were identified from an institutional registry. BMI and outcomes were analyzed with Mann-Whitney U tests and Pearson correlations with Bayesian post-hoc analyses. 116 of 960 ECMO patients met inclusion criteria. Median (Q1, Q3) BMI was 42.3 (37.3, 50.8) and min, max of 35.0, 87.8 with 9.0 (5.0, 15.5) ECMO days. BMI was not significantly correlated with ECMO days (r = -0.102; p = .279). Bayesian analyses showed moderate evidence against BMI correlating with ECMO days. In-hospital mortality (27%) was significantly associated with ECMO days (p = .014) but not BMI (p = .485). In this cohort of high-BMI patients, BMI was not associated with survival or time on ECMO. BMI itself should not be used as an exclusion criterion for VV-ECMO.

Obesity associated with improved mortality of extracorporeal membrane oxygenation for severe COVID-19 pneumonia

INTRODUCTION

Determining a patient's candidacy for extracorporeal membrane oxygenation (ECMO) in severe COVID-19 pneumonia is a critical aspect of efficient healthcare delivery. A body mass index (BMI) ≥40 is considered a relative contraindication for ECMO by the Extracorporeal Life Support Organization (ELSO). We sought to determine the impact of obesity on the survival of patients with COVID-19 on ECMO.

METHODS

This project was a retrospective review of a multicenter US database from January 2020 to December 2021. The primary outcome was in-hospital mortality after ECMO initiation, with a comparison between patients classified into body mass index categories (<30, 30-39.9, and ≥40). Secondary outcomes included ventilator days, intensive care days, and complications.

RESULTS

We completed records review on 359 patients, with 90 patients excluded because of missing data. The overall mortality for the 269 patients was 37.5%. Patients with a BMI <30 had higher odds of mortality compared to all patients with BMI >30 (OR 1.98; p = 0.013), those with BMI 30-39.9 (OR 1.84; p = 0.036), and BMI ≥40 (OR 2.33; p = 0.024). There were no differences between BMI groups for ECMO duration; length of stay (LOS); or rate of bloodstream infection, stroke, or blood transfusion. Age, ECMO duration, and modified-Elixhauser index were not independent risk factors for mortality.

CONCLUSIONS

In patients receiving ECMO for severe COVID-19, neither obesity (BMI >30) nor morbid obesity (BMI >40) were associated with in-hospital mortality. These results are consistent with previous reports and held true after adjusting for age and comorbidities. Our data suggest further examination of the recommendations to withhold ECMO in patients who are obese.

Fundamentals of weaning veno-arterial and veno-venous extracorporeal membrane oxygenation

Recent advances in veno-arterial (VA) and veno-venous (VV) extracorporeal membrane oxygenation (ECMO) technology and management have enabled us to support patients with cardiac and/or pulmonary failure, who may have previously been considered untreatable. VA ECMO and VV ECMO are by definition transient therapies and serve as a bridge to recovery, bridge to decision, bridge to transplant, or bridge to no recovery. Weaning ECMO should be considered for all patients once native cardiac and pulmonary function show signs of recovery. Currently, there are no universally accepted protocols for weaning VA and VV ECMO, and consequently, each individual center follows their own weaning protocols. The aim of this review article is to describe different approaches to safely wean from VA and VV ECMO.