Bartels_Hensley's Practical Approach to Cardiothoracic Anesthesia, 7e

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8. Extracorporeal Membrane Oxygenation for Pulmonary or Cardiac Support

a. A volume- and pressure-limited ventilation strategy is standard of care in ARDS, with a proven mortality benefit over conventional higher volumes and plateau airway pres sures. 2 Other strategies that confer a mortality benefit in ARDS include prone posi tioning and possibly the early use of neuromuscular blockade or high levels of positive end-expiratory pressure (PEEP). b. The largest prospective randomized controlled trial of ECMO in severe, refractory ARDS was the Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome (EOLIA) trial, which demonstrated a nonstatistically significant dif ference in 60-day mortality by intention-to-treat analysis in patients with severe ARDS who received ECMO combined with an ultra-lung-protective ventilation strategy com pared to patients who received optimal conventional management (35% in the ECMO arm vs 46% in the control arm; relative risk [RR] 0.76; 95% CI 0.55-1.04; P = .09). Of note, the trial was terminated early after enrollment of 249 patients based on prespeci fied stopping criteria. Furthermore, 28% of patients in the control arm crossed over to ECMO for indications including refractory hypoxemia, right heart failure, or other clinical worsening, thus biasing results to the null. c. A follow-up Bayesian analysis of the data from the EOLIA trial demonstrated high probability of mortality benefit from ECMO in severe ARDS, with the magnitude of benefit varying by the priors applied. 3 A subsequent systematic review and meta-­ analysis as well as a separate individual patient data meta-analysis using data from the EOLIA trial and a prior randomized controlled trial evaluating the efficacy of ECMO for severe ARDS demonstrated a mortality benefit from ECMO at 60 days (RR 0.73; 95% CI 0.58-0.92; P = .008) 4 and 90 days (RR 0.75; 95% CI 0.6-0.94; P = .013). 5 A network meta-analysis—assessing the impact of multiple interventions—likewise demonstrated a 28-day mortality benefit from ECMO when combined with a lung-protective ven tilation strategy. 6 In sum, the data suggest a clinically significant benefit from ECMO compared to conventional management in patients with severe ARDS when performed at experienced ECMO centers and used in concert with a ventilation strategy incorpo rating volumes and airway pressures below the current standard of care. d. Recommended thresholds to initiate ECMO in ARDS, as defined by the EOLIA trial, as are follows 7 : (1) Partial pressure of arterial oxygen to fraction of inspired oxygen (Pao 2 :Fio 2 ) < 50 mm Hg for > 3 hours or Pao 2 :Fio 2 < 80 mm Hg for > 6 hours, despite an Fio 2 ≥ 0.8 and PEEP ≥ 10 cm H 2 O (2) pH < 7.25 and partial pressure of arterial carbon dioxide (Paco 2 ) ≥ 60 mm Hg for > 6 hours with respiratory rate increased to 35 breaths per minute and mechanical ventilation settings adjusted to keep plateau airway pressure ≤ 32 cm H 2 O 2. COVID-19-related ARDS a. Whereas initial observational studies demonstrated similar survival rates for patients receiving ECMO for COVID-19-related severe ARDS as for patients receiving ECMO for severe ARDS due to other prepandemic etiologies, there has been a trend toward worsening mortality in ECMO-supported patients with COVID-19 later in the pan demic, calling into question the benefit and appropriateness of ECMO in this popula tion, particularly in the context of enormous strain on health care resource. 8,9 b. Despite these observed trends, a registry-based comparative effectiveness study of 7,345 patients with COVID-19-related ARDS found a significant reduction in mortality when a strategy of ECMO was applied to patients with a Pao 2 :Fio 2 < 80 mm Hg, compared to conventional mechanical ventilation alone. 10

Copyright © 2024 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. c. Further investigation is needed to more clearly elucidate the role of ECMO in patients with COVID-19-related ARDS, especially in light of the economic and ethical implica tions of ECMO in the context of a worldwide pandemic.

3. Primary graft dysfunction after lung transplantation: Clinically similar to ARDS, though etiologically thought to be a consequence of ischemia-reperfusion injury, pri mary graft dysfunction (PGD) manifests as acute hypoxemic respiratory failure and