Obesity does not impact survival following ECMO

Rachael Alexis Jividen, DNP, APRN-CNS, ACCNS-AG, CCRN-CSC-CMC

This meta-analysis suggests no significant impact of obesity on duration of ECMO therapy or survival outcomes after separation from ECMO therapy. BMI may not be a predictor of survival for patients with obesity on ECMO therapy; however, it is a known predictor of all-cause mortality in patients with other comorbidities.

Although patients may survive ECMO therapy, they may not survive until discharge from the ICU or hospital due to complications of comorbidities associated with obesity and prolonged immobilization during ECMO therapy.

These specific data points are collected by the Extracorporeal Life Support Organization (ELSO) through the national data registry, but it is impossible to thoroughly evaluate the data as not all ECMO centers are actively reporting data, limiting researchers to data points reported in the literature to supplement the ELSO registry.

Results of the study may be used to improve care by providing evidence to extinguish biases that patients who are obese experience poorer outcomes during and after ECMO therapy compared with individuals who are not obese. Each facility may have clinical practice guidelines delineating who will receive ECMO therapy — a resource intensive and expensive therapy. Smaller facilities with limited resources may have defined guidelines for ECMO cannulation, and morbid obesity may be listed as a relative contraindication for cannulation. However, the study suggests BMI is a poor predictor of total health rendering BMI an inappropriate contraindication to ECMO therapy. This may expand the total population of patients eligible for ECMO.

After receiving ECMO therapy, patients are generally debilitated and require intensive physical rehabilitation. Aggressive rehabilitation may be difficult for patients with a high BMI who experience additional strain and cardiac demand during mobilization.

Facilities may consider instituting protocols to promote early, progressive mobilization of patients who are obese and receiving ECMO therapy to further reduce duration of ECMO therapy, mechanical ventilation, ICU and hospital length of stay, and complications associated with limited mobility.

Although there is extensive research suggesting obesity does not largely impact outcomes for patients on ECMO, academic medical centers that accept high-risk patients may feel that results of the study do not reflect outcomes at their institutions where patients with obesity have multiple concomitant comorbidities that increase overall morbidity and mortality. Similarly, outcomes for patients who are obese and undergoing high-risk cardiothoracic surgery may have a different clinical trajectory than a patient who is obese and cannulated for respiratory dysfunction in the setting of no health problems.

Gaps in data include ECMO type; there may be differences in outcomes for patients who are obese receiving veno-arterial ECMO as opposed to veno-venous ECMO therapy. Patients receiving veno-venous therapy may have chronic pulmonary disease but few comorbidities, whereas individuals receiving veno-arterial ECMO typically have assorted comorbidities in the setting of cardiopulmonary failure. Mortality is generally higher for patients on veno-arterial ECMO compared with veno-venous ECMO.

Of the studies with ECMO type reported, 545 patients received veno-venous ECMO therapy, and 39 patients received veno-arterial ECMO therapy. Five patients in one study received a hybrid ECMO configuration. Other studies included in the meta-analysis did not report ECMO type, but of the cases specified, veno-arterial ECMO is vastly underrepresented.

Implications for future research include evaluating quality of life of in patients who are obese and successfully decannulated. Quality of life is largely subjective but may include consideration of objective factors such as dependence on mechanical ventilation, intermittent hemodialysis and residence in a long-term acute care facility. It would be helpful for studies to incorporate a patient acuity rating to compare severity of illness before and after ECMO therapy for patients who are obese vs. nonobese.

Future researchers may consider including patient demographics in their data. Additionally, studies should consider reporting 1-year survival rates post cannulation for ECMO in patients who are obese vs. nonobese to illustrate longer term survival and wellness in the post-ECMO rehabilitation period.