Less death in patients with asthma exacerbations, respiratory failure treated with ECMO
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Key takeaways:
- Patients with asthma exacerbations with respiratory failure receiving ECMO vs. usual care had reduced mortality.
- ECMO in these patients came with elevated hospital costs.
Patients with refractory asthma exacerbations with respiratory failure treated with extracorporeal membrane oxygenation had decreased odds for death compared with standard care, according to study results published in CHEST.
“On the basis of 11.2% mortality for the total cohort, reported mortality for ventilated patients with asthma exacerbations with respiratory failure [AERF] ranging from 7% to 15%, and the percentage of no ECMO patients treated with continuous neuromuscular blockade (ie, 10.6%), up to 15% of patients with AERF may be eligible for ECMO each year,” Jonathan K. Zakrajsek, MS, of the division of pulmonary sciences and critical care medicine at the University of Colorado, and colleagues wrote. “These results may also be relevant for low-flow, extracorporeal [carbon dioxide] removal (ECCO2R) systems that use smaller catheters and lower blood flow rates, and can be added to renal replacement therapy systems.”
In a retrospective, epidemiologic and observational cohort study, Zakrajsek and colleagues evaluated 13,714 adults with refractory AERF in ECMO-capable hospitals between 2010 and 2020 to determine if there is a link between ECMO and reduced odds for mortality.
To be included, patients had to be hospitalized with an asthma exacerbation and had to receive short-acting bronchodilators, systemic corticosteroids and invasive ventilation as treatment, according to researchers.
Researchers evaluated odds for hospital mortality of patients treated with ECMO against those treated with standard care in a covariate-adjusted model, a propensity score-adjusted model and a propensity score-matched model.
In addition to mortality, researchers looked for differences in ICU length of stay, hospital length of stay, invasive ventilation duration, overall hospital costs and safety outcomes between the two treatment groups.
Of the total cohort, 127 patients (mean age, 38 years; 54.3% women) received ECMO treatment, whereas 13,587 (mean age, 46 years; 64.2% women) did not receive ECMO. Most patients treated with ECMO received venovenous ECMO (n = 105) with less patients receiving venoarterial ECMO (n = 8) or a combination of the two (n = 14). After being admitted, the average start day of ECMO was day 2.5 (range, 1-19 days), and the mean duration of the treatment was 4 days (range, 1-49 days).
Mortality
During the study period, 1,540 patients (11.2%) died.
In each of the three models, researchers observed a significant relationship between decreased odds for mortality and those receiving ECMO compared with those receiving standard care: covariate-adjusted (OR = 0.33; 95% CI, 0.17-0.64), propensity score-adjusted (OR = 0.36; 95% CI, 0.16-0.81), and propensity score-matched models (OR = 0.48; 95% CI, 0.24-0.98).
Lower odds for mortality with ECMO treatment were further demonstrated in a sensitivity analysis of those treated with ECMO within 7 days of hospitalization (n = 120), but the only significant result was found in the covariate-adjusted model (OR = 0.48; 95% CI, 0.23-0.98).
Additionally, researchers found a significant link between ECMO and a reduction in death in two models when evaluating patients from 499 ECMO-capable hospitals and 377 hospitals not capable of providing ECMO (covariate-adjusted model, OR = 0.35; 95% CI, 0.19-0.67; propensity score-adjusted model, OR = 0.39; 95% CI, 0.18-0.87).
Secondary outcomes, adverse events
In terms of secondary outcomes, researchers did not find a link between ECMO and shorter ICU stays, hospital stays or invasive ventilation durations. However, each of the models showed a significant rise in mean hospital costs with ECMO than without ECMO: co-variate-adjusted (1.5; 95% CI, 1.31-1.71), propensity score-adjusted (1.79; 95% CI, 1.49-2.14) and propensity score-matched models (1.59; 95% CI, 1.32-1.91). Based on the propensity score-matched model, overall hospital costs went up by $113,789 (95% CI, $65,968-$161,611; P < .0001) for each patient treated with ECMO vs. standard care, according to researchers.
When evaluating adverse events between patients receiving ECMO (n = 82) and patients not receiving ECMO (n = 164) in the propensity score matched sample, researchers only observed two major differences. More ECMO patients had hemorrhage than patients not on ECMO (9 patients vs. 2 patients), but more patients not receiving ECMO experienced brain death (8 patients vs. 0 patients).
Importantly, Zakrajsek and colleagues write that their findings need further confirmation in additional studies.
“We wish to emphasize that although this is the largest controlled study to address the impact of ECMO for people with AERF, the results may still be subject to bias [...], and therefore should only be considered hypothesis generating,” Zakrajsek and colleagues wrote. “A randomized clinical trial would be necessary to definitively determine the efficacy of ECMO for AERF requiring mechanical ventilation. Needless to say, any clinical trial would need to optimize standard and adjunctive therapies for AERF before enrollment, including permissive hypercapnia.”
This study by Zakrajsek and colleagues provides a start to understanding ECMO treatment in patients with AERF; however, just as the researchers suggest, more information needs to be captured on the specific patients who may benefit from this option, according to an accompanying editorial by Orlando Garner, MD, intensivist at Midland Memorial Hospital, and Nicola A. Hanania, MD, FCCP, professor in the section of pulmonary and critical care medicine at Baylor College of Medicine.
“Patients with life-threatening asthma exacerbations [LTAE] who required mechanical ventilation were identified using ICD-9 and ICD-10 codes; however, information about their ventilatory settings and pressures as well as their acid-base status was lacking,” Garner and Hanania wrote. “The use of ECMO was a rare event in this study, and detailed information about the selection of patients who underwent cannulation is unknown. This is very important if such strategy is to be implemented on a larger scale in patients with LTAE in the future. One can assume that patients who may benefit from such an intervention are those who are at high risk for ventilator-induced lung injury and those who have reached refractory hypoxemia and hypercarbia limited by high ventilatory pressures.”