Bartels_Hensley's Practical Approach to Cardiothoracic Anesthesia, 7e

185

8. Extracorporeal Membrane Oxygenation for Pulmonary or Cardiac Support

VI. Extracorporeal Membrane Oxygenation Management A. Invasive Mechanical Ventilation Practices

1. VILI is believed to be the main determinant of poor outcomes in ARDS, explaining why a volume- and pressure-limited ventilation strategy has such a significant impact on survival. 2. Several studies have demonstrated that tidal volumes and plateau pressures below the cur rent standard of care could further reduce VILI. However, reductions in tidal volumes, airway pressures, and respiratory rates with conventional invasive mechanical ventilation alone are often limited by intolerable levels of respiratory acidosis that come with marked reductions in minute ventilation. 3. ECCO 2 R can facilitate even lower tidal volumes and airway pressures by managing the concomitant hypercapnia and acidemia, to the point where, in select cases, mechanical ventilation may be discontinued, and patients could be endotracheally extubated while on ECMO. 4. In cases of severe ARDS in which ECMO is initiated for refractory gas exchange abnormali ties or excess plateau airway pressures, a strategy of very low tidal volumes, airway pres sures, and respiratory rates, while maintaining a moderate amount of PEEP to minimize alveolar collapse, is recommended based on the results of the EOLIA trial. Occasionally, in select patients, mechanical ventilation can be discontinued altogether. 5. An ultra-lung-protective ventilation strategy may ultimately prove beneficial in less se vere forms of ARDS, where oxygenation is better preserved and an approach target ing CO 2 removal alone with lower blood flows and smaller cannulae (ie, ECCO 2 R) is sufficient. a. A phase 2 prospective, multicenter trial demonstrated the feasibility of ECCO 2 R to fa cilitate ultra-lung-protective ventilation, defined as tidal volumes < 4 mL/kg predicted body weight and plateau airway pressure ≤ 25 cm H 2 O, in patients with moderate ARDS. 20 b. A subsequent randomized, open-label, pragmatic clinical trial found no mortality dif ference in patients with acute hypoxemic respiratory failure treated with ECCO 2 R to facilitate ultraprotective ventilation (goal tidal volume < 3 mL/kg) versus conventional low tidal volume ventilation. Factors that may have contributed to the negative result in clude early termination of the trial and subsequent lack of power to detect a difference, time-limited use of ECCO 2 R in the intervention arm, patient population not restricted to ARDS nor those most likely to benefit from the strategy, high rates of adverse events in the intervention arm, and inability to achieve the target tidal volume of < 3 mL/kg in many patients in the intervention arm. 21 c. Further investigation is necessary to determine whether there is, in fact, a clinical benefit that outweighs the potential risks of extracorporeal support for this potential indication. CLINICAL PEARL The use of extracorporeal support for respiratory failure in mechanically ventilated patients may reduce VILI by permitting the use of tidal volumes and plateau airway pressures below the current standard of care. B. Anticoagulation and Transfusion Strategies 1. Continuous systemic anticoagulation is generally needed to maintain ECMO circuit pa tency and minimize thrombotic risk to the patient. The degree of anticoagulation must be balanced with the risk of hemorrhagic complications. There are no universally accepted an ticoagulation standards for ECMO, nor is there a consensus on how anticoagulation should be monitored, with activated clotting time, activated partial thromboplastin time (aPTT), and thromboelastography, among others, having been reported.

Copyright © 2024 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited.