Venovenous extracorporeal membrane oxygenation in obese patients

ECMO for the pregnant and peripartum patient: A practical review of indications, unique management considerations, and an approach framework

The use of extracorporeal membrane oxygenation (ECMO) to support the pregnant patient and fetus requires a complex decision-making process. Peripartum ECMO requires coordinated and informed decision-making between an interdisciplinary team of experts, incorporating the unique considerations and, at times, competing physiologic priorities of the pregnant patient. It is often confounded by a scarcity of local relevant experience engendered by its rare occurrence. No event has made the need for an organized approach to the utilization of ECMO in pregnant patients more pressing than the COVID pandemic. The conditions affecting pregnant patients that warrant ECMO consideration are high stakes and, at times, ethically challenging, although outcomes are favourable compared to the general population. This review provides background information and context, followed by a practical approach to the care and specific medical management of patients who are facing life-threatening conditions warranting ECMO while pregnant.

The Association Between Body Mass Index and Mortality Mediated by Medical and Mechanical Complications in Venovenous Extracorporeal Membrane Oxygenation

OBJECTIVES

To estimate the associations between body mass index (BMI) and mortality and between BMI and complications in patients receiving venovenous extracorporeal membrane oxygenation (ECMO) and to estimate if any mortality association was mediated by complications.

DESIGN

Retrospective analysis of an international, multicenter registry.

SETTING

ICUs.

PATIENTS

Adults in the Extracorporeal Life Support Organization database who received venovenous ECMO between January 1, 2015, and December 31, 2021.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Logistic regression with BMI transformed using fractional polynomials was used to estimate the association between BMI and hospital mortality and between BMI and complications. Mediation analysis was used to estimate if the association between BMI and mortality was a direct effect or was mediated by complications. Of the 24,796 patient runs, 10,361 patients died (48%). After adjusting for confounders, we found nonlinear associations between BMI and mortality. Compared with BMI = 25 kg/m2, a BMI = 20 had an 11% higher risk of dying, odds ratio (OR) =1.11 (95% CI, 1.08-1.15); a BMI = 30 had an 8% lower risk, OR = 0.92 (95% CI, 0.90-0.95); and a BMI = 40 kg/m2 had an 18% lower risk of death OR = 0.82 (95% CI, 0.78-0.87). BMI was also associated with mechanical, renal, pulmonary, and neurologic complications. The association between BMI and mortality was both a direct effect and mediated via pulmonary complications, while mechanical, renal replacement therapy, and neurologic complications were suppressors having a negative association with improved mortality in patients with higher BMI.

CONCLUSIONS

We confirmed that patients with higher BMI requiring venovenous ECMO were less likely to die. This finding was partially mediated by pulmonary complications and partially via a direct association between BMI and mortality. BMI was also associated with mechanical, renal replacement therapy, and neurologic complications that acted as suppressing mediators and were associated with increased mortality for increasing BMI despite the overall trend of improved survival.

VV-ECMO in critical COVID-19 obese patients: a cohort study

BACKGROUND

Obesity causes significant difficulties in successful extracorporeal membrane oxygenation (ECMO) support and may interfere with patient outcomes. During the COVID-19 pandemic, we experienced an increased number of obese patients supported with ECMO in our intensive care unit due to severe illness in this population.

METHODS

We designed a single-center retrospective study to identify prognostic factors for 180-day survival in obese critical COVID-19 patients receiving venovenous ECMO (VV-ECMO). We included adult critical COVID-19 patients on VV-ECMO, who were obese and overweight (according to the World Health Organization) and admitted to a tertiary hospital's intensive care unit from April 1, 2020, to May 31, 2022. Univariate logistic regression analysis was performed to assess differences in 180-day mortality.

RESULTS

Forty-one patients were included. The median age was 55 (IQR 45-60) years, and 70.7% of the patients were male. The median body mass index (BMI) was 36 (IQR 31-42.5) kg/m2; 39% of patients had a BMI ≥ 40 kg/m2. The participants had 3 (IQR 1.5-4) days of mechanical ventilation prior to ECMO, and 63.4% were weaned from VV-ECMO support after a median of 19 (IQR 10-34) days. The median ICU length of stay was 31.9 (IQR 17.5-44.5) days. The duration of mechanical ventilation was 30 (IQR 19-49.5) days. The 180-day mortality rate was 41.5%. Univariate logistic regression analysis revealed that a higher BMI was associated with greater 180-day survival (OR 1.157 [1.038-1.291], p = 0.009). Younger age, female sex, less invasive ventilation time before ECMO, and fewer complications at the time of ECMO cannulation were associated with greater 180-day survival [OR 0.858 (0.774-0.953), p 0.004; OR 0.074 (0.008-0.650), p 0.019; OR 0.612 (0.401-0.933), p 0.022; OR 0.13 (0.03-0.740), p 0.022), respectively].

CONCLUSION

In this retrospective cohort of critical COVID-19 obese adult patients supported by VV-ECMO, a higher BMI, younger age, and female sex were associated with greater 180-day survival. A shorter invasive ventilation time before ECMO and fewer complications at ECMO cannulation were also associated with increased survival.

Outcomes following additional drainage during veno-venous extracorporeal membrane oxygenation: A single-center retrospective study

Refractory hypoxemia during veno-venous (V-V) extracorporeal membrane oxygenation (ECMO) may require an additional cannula (VV-V ECMO) to improve oxygenation. This intervention includes risk of recirculation and other various adverse events (AEs) such as injury to the lung, cannula malpositioning, bleeding, circuit or cannula thrombosis requiring intervention (i.e., clot), or cerebral injury. During the study period, 23 of 142 V-V ECMO patients were converted to VV-V utilizing two separate cannulas for bi-caval drainage with an additional upper extremity cannula placed for return. Of those, 21 had COVID-19. In the first 24 h after conversion, ECMO flow rates were higher (5.96 vs 5.24 L/min, p = .002) with no significant change in pump speed (3764 vs 3630 revolutions per minute [RPMs], p = .42). Arterial oxygenation (PaO2) increased (87 vs 64 mmHg, p < .0001) with comparable pre-oxygenator venous saturation (61 vs 53.3, p = .12). By day 5, flows were similar to pre-conversion values at lower pump speed but with improved PaO2. Unadjusted survival was similar in those converted to VV-V ECMO compared to V-V ECMO alone (70% [16/23] vs 66.4% [79/119], p = .77). In a mixed effect regression model, any incidence of AEs, demonstrated a negative impact on PaO2 in the first 48 h but not at day 5. VV-V ECMO improved oxygenation with increasing flows without a significant difference in AEs or pump speed. AEs transiently impacted oxygenation. VV-V ECMO is effective and feasible strategy for refractory hypoxemia on VV-ECMO allowing for higher flow rate and unchanged pump speed.

Morbid obesity's impact on COVID-19 patients requiring venovenous extracorporeal membrane oxygenation: The covid-19 critical care consortium database review

Introduction: Obesity is associated with a worse prognosis in COVID-19 patients with acute respiratory distress syndrome (ARDS). Veno-venous (V-V) Extracorporeal Membrane Oxygenation (ECMO) can be a rescue option, however, the direct impact of morbid obesity in this select group of patients remains unclear.Methods: This is an observational study of critically ill adults with COVID-19 and ARDS supported by V-V ECMO. Data are from 82 institutions participating in the COVID-19 Critical Care Consortium international registry. Patients were admitted between 12 January 2020 to 27 April 2021. They were stratified based on Body Mass Index (BMI) at 40 kg/m2. The endpoint was survival to hospital discharge.Results: Complete data available on 354 of 401 patients supported on V-V ECMO. The characteristics of the high BMI (>40 kg/m2) and lower BMI (≤40 kg/m2) groups were statistically similar. However, the 'high BMI' group were comparatively younger and had a lower APACHE II score. Using survival analysis, older age (Hazard Ratio, HR 1.49 per-10-years, CI 1.25-1.79) and higher BMI (HR 1.15 per-5 kg/m2 increase, CI 1.03-1.28) were associated with a decreased patient survival. A safe BMI threshold above which V-V ECMO would be prohibitive was not apparent and instead, the risk of an adverse outcome increased linearly with BMI.Conclusion: In COVID-19 patients with severe ARDS who require V-V ECMO, there is an increased risk of death associated with age and BMI. The risk is linear and there is no BMI threshold beyond which the risk for death greatly increases.

Early Tracheostomy May Be Performed Safely in Obese COVID-19 Patients Supported on VV-ECMO

OBJECTIVE

Obese patients with coronavirus disease 2019 (COVID-19)-associated acute respiratory failure (ARDS) often require prolonged intubation. However, data are sparse regarding optimal tracheostomy timing in obese adults with COVID-19 requiring venovenous extracorporeal membrane oxygenation (VV-ECMO). This study retrospectively describes the course of obese patients with COVID-19 who underwent tracheostomy on VV-ECMO between March 2020 and December 2022.

METHODS

There were 62 participants with a median age of 43 (interquartile range [IQR] 33 to 53) years and a median body mass index of 42 (IQR 34 to 50) kg/m2 who received VV-ECMO for COVID-19-associated ARDS. Of those, 42 underwent tracheostomy on VV-ECMO, and 50% (n = 21) of the 42 patients underwent early (within 14 days of initiated ventilatory support) tracheostomy.

RESULTS

Among patients who received tracheostomies, the combined respiratory tract and lung parenchymal bleeding rate was 29% (n = 12), but only 7% required surgical intervention for bleeding from the tracheostomy site (n = 3). The hospital length of stay (LOS) was 42 (IQR 36 to 57) days, and mortality rate was 38% (n = 16). Tracheostomy timing was not associated with differences in respiratory tract bleeding, mechanical ventilatory support duration, VV-ECMO support duration, intensive care unit LOS, hospital LOS, mortality, or survival probability.

CONCLUSIONS

Although an individualized and holistic approach to clinical decision making continues to be necessary, the findings of this study suggest that early tracheostomy may be performed safely in obese patients with COVID-19 on VV-ECMO.

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

INTRODUCTION

With the increased demand for veno-venous extracorporeal membrane oxygenation (VV ECMO) during the COVID-19 pandemic, guidelines for patient candidacy have often limited this modality for patients with a body mass index (BMI) less than 40 kg/m2. We hypothesize that COVID-19 VV ECMO patients with at least class III obesity (BMI ≥ 40) have decreased in-hospital mortality when compared to non-COVID-19 and non-class III obese COVID-19 VV ECMO populations.

METHODS

This is a single-center retrospective study of COVID-19 VV ECMO patients from January 1, 2014, to November 30, 2021. Our institution used BMI ≥ 40 as part of a multi-disciplinary VV ECMO candidate screening process in COVID-19 patients. BMI criteria were not considered for exclusion criteria in non-COVID-19 patients. Univariate and multivariable analyses were performed to assess in-hospital mortality differences.

RESULTS

A total of 380 patients were included in our analysis: The COVID-19 group had a lower survival rate that was not statistically significant (65.7% vs.74.9%, p = .07). The median BMI between BMI ≥ 40 COVID-19 and non-COVID-19 patients was not different (44.5 vs 45.5, p = .2). There was no difference in survival between the groups (73.3% vs. 78.5%, p = .58), nor was there a difference in survival between the COVID-19 BMI ≥ 40 and BMI < 40 patients (73.3, 62.7, p= .29). Multivariable logistic regression with the outcome of in-hospital mortality was performed and BMI was not found to be significant (OR 0.99, 95% CI 0.89, 1.01; p = .92).

CONCLUSION

BMI ≥ 40 was not an independent risk factor for decreased in-hospital survival in this cohort of VV ECMO patients at a high-volume center. BMI should not be the sole factor when deciding VV ECMO candidacy in patients with COVID-19.

Complications Associated With Venovenous Extracorporeal Membrane Oxygenation-What Can Go Wrong?

OBJECTIVES

Despite increasing use and promising outcomes, venovenous extracorporeal membrane oxygenation (V-V ECMO) introduces the risk of a number of complications across the spectrum of ECMO care. This narrative review describes the variety of short- and long-term complications that can occur during treatment with ECMO and how patient selection and management decisions may influence the risk of these complications.

DATA SOURCES

English language articles were identified in PubMed using phrases related to V-V ECMO, acute respiratory distress syndrome, severe respiratory failure, and complications.

STUDY SELECTION

Original research, review articles, commentaries, and published guidelines from the Extracorporeal Life support Organization were considered.

DATA EXTRACTION

Data from relevant literature were identified, reviewed, and integrated into a concise narrative review.

DATA SYNTHESIS

Selecting patients for V-V ECMO exposes the patient to a number of complications. Adequate knowledge of these risks is needed to weigh them against the anticipated benefit of treatment. Timing of ECMO initiation and transfer to centers capable of providing ECMO affect patient outcomes. Choosing a configuration that insufficiently addresses the patient's physiologic deficit leads to consequences of inadequate physiologic support. Suboptimal mechanical ventilator management during ECMO may lead to worsening lung injury, delayed lung recovery, or ventilator-associated pneumonia. Premature decannulation from ECMO as lungs recover can lead to clinical worsening, and delayed decannulation can prolong exposure to complications unnecessarily. Short-term complications include bleeding, thrombosis, and hemolysis, renal and neurologic injury, concomitant infections, and technical and mechanical problems. Long-term complications reflect the physical, functional, and neurologic sequelae of critical illness. ECMO can introduce ethical and emotional challenges, particularly when bridging strategies fail.

CONCLUSIONS

V-V ECMO is associated with a number of complications. ECMO selection, timing of initiation, and management decisions impact the presence and severity of these potential harms.