Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome After Pneumonectomy

The Ventilatory Ratio as a Predictor of Successful Weaning from a Veno-Venous Extracorporeal Membrane Oxygenator

Background: Veno-venous extracorporeal membrane oxygenation (VV-ECMO) is a critical intervention for patients with severe lung failure, especially acute respiratory distress syndrome (ARDS). The weaning process from ECMO relies largely on expert opinion due to a lack of evidence-based guidelines. The ventilatory ratio (VR), which correlates with dead space and mortality in ARDS, is calculated as [minute ventilation (mL/min) x arterial pCO2 (mmHg)]/[predicted body weight × 100 × 37.5]. Objectives: The aim of this study was to determine whether the VR alone can serve as a reliable predictor of safe or unsafe liberation from VV-ECMO in critically ill patients. Methods: A multicenter retrospective analysis was conducted, involving ARDS patients undergoing VV-ECMO weaning at Massachusetts General Hospital (January 2016 - December 2020) and at the University Hospital Aachen (January 2012-December 2021). Safe liberation was defined as no need for ECMO recannulation within 48 h after decannulation. Clinical parameters were obtained for both centers at the same time point: 30 min after the start of the SGOT (sweep gas off trial). Results: Of the patients studied, 83.3% (70/84) were successfully weaned from VV-ECMO. The VR emerged as a significant predictor of unsafe liberation (OR per unit increase: 0.38; CI: 0.17-0.81; p = 0.01). Patients who could not be safely liberated had longer ICU and hospital stays, with a trend towards higher mortality (38% vs. 13%; p = 0.05). Conclusions: The VR may be a valuable predictor for safe liberation from VV-ECMO in ARDS patients, with higher VR values associated with an elevated risk of unsuccessful weaning and adverse clinical outcomes.

Liberation From Venovenous Extracorporeal Membrane Oxygenation for Respiratory Failure: A Scoping Review

BACKGROUND

Safe and timely liberation from venovenous extracorporeal membrane oxygenation (ECMO) would be expected to reduce the duration of ECMO, the risk of complications, and costs. However, how to liberate patients from venovenous ECMO effectively remains understudied.

RESEARCH QUESTION

What is the current state of the evidence on liberation from venovenous ECMO?

STUDY DESIGN AND METHODS

We systematically searched for relevant publications on liberation from venovenous ECMO in Medline and EMBASE. Citations were included if the manuscripts provided any of the following: criteria for readiness for liberation, a liberation protocol, or a definition of successful decannulation or decannulation failure. We included randomized trials, observational trials, narrative reviews, guidelines, editorials, and commentaries. We excluded single case reports and citations where the full text was unavailable.

RESULTS

We screened 1,467 citations to identify 39 key publications on liberation from venovenous ECMO. We then summarized the data into five main topics: current strategies used for liberation, criteria used to define readiness for liberation, conducting liberation trials, criteria used to proceed with decannulation, and parameters used to predict decannulation outcomes.

INTERPRETATION

Practices on liberation from venovenous ECMO are heterogeneous and are influenced strongly by clinician preference. Additional research on liberation thresholds is needed to define optimal liberation strategies and to close existing knowledge gaps in essential topics on liberation from venovenous ECMO.

Physiological adaptations during weaning from veno-venous extracorporeal membrane oxygenation

Veno-venous extracorporeal membrane oxygenation (V-V ECMO) has an established evidence base in acute respiratory distress syndrome (ARDS) and has seen exponential growth in its use over the past decades. However, there is a paucity of evidence regarding the approach to weaning, with variation of practice and outcomes between centres. Preconditions for weaning, management of patients' sedation and mechanical ventilation during this phase, criteria defining success or failure, and the optimal duration of a trial prior to decannulation are all debated subjects. Moreover, there is no prospective evidence demonstrating the superiority of weaning the sweep gas flow (SGF), the extracorporeal blood flow (ECBF) or the fraction of oxygen of the SGF (FdO2), thereby a broad inter-centre variability exists in this regard. Accordingly, the aim of this review is to discuss the required physiological basis to interpret different weaning approaches: first, we will outline the physiological changes in blood gases which should be expected from manipulations of ECBF, SGF and FdO2. Subsequently, we will describe the resulting adaptation of patients' control of breathing, with special reference to the effects of weaning on respiratory effort. Finally, we will discuss pertinent elements of the monitoring and mechanical ventilation of passive and spontaneously breathing patients during a weaning trial. Indeed, to avoid lung injury, invasive monitoring is often required in patients making spontaneous effort, as pressures measured at the airway may not reflect the degree of lung strain. In the absence of evidence, our approach to weaning is driven largely by an understanding of physiology.

Defining and understanding the "extra-corporeal membrane oxygenation gap" in the veno-venous configuration: Timing and causes of death

In‐hospital mortality of adult veno‐venous extracorporeal membrane oxygenation (V‐V ECMO) patients remains invariably high. However, little is known regarding timing and causes of in‐hospital death, either on‐ECMO or after weaning. The current review aims to investigate the timing and causes of death of adult patients during hospital admittance for V‐V ECMO, and to define the V‐V ECMO gap, which is represented by the patients that are successfully weaned of ECMO but still die during hospital stay. A systematic search was performed using electronic MEDLINE and EMBASE databases through PubMed. Studies reporting on adult V‐V ECMO patients from January 2006 to December 2020 were screened. Studies that did not report on at least on‐ECMO mortality and discharge rate were excluded from analysis as they could not provide the required information regarding the proposed V‐V ECMO‐gap. Mortality rates on‐ECMO and after weaning, as well as weaning and discharge rates, were analyzed as primary outcomes. Secondary outcomes were the causes of death and complications. Initially, 35 studies were finally included in this review. Merely 24 of these studies (comprising 975 patients) reported on prespecified V‐V ECMO outcomes (on‐ECMO mortality and discharge rate). Mortality on V‐V ECMO support was 27.8% (95% confidence interval (CI) 22.5%‐33.2%), whereas mortality after successful weaning was 12.7% (95% CI 8.8%‐16.6%, defining the V‐V ECMO gap). 72.2% of patients (95% CI 66.8%‐77.5%) were weaned successfully from support and 56.8% (95% CI 49.9%‐63.8%) of patients were discharged from hospital. The most common causes of death on ECMO were multiple organ failure, bleeding, and sepsis. Most common causes of death after weaning were multiorgan failure and sepsis. Although the majority of patients are weaned successfully from V‐V ECMO support, a significant proportion of subjects still die during hospital stay, defining the V‐V ECMO gap. Overall, timing and causes of death are poorly reported in current literature. Future studies on V‐V ECMO should describe morbidity and mortality outcomes in more detail in relation to the timing of the events, to improve patient management, due to enhanced understanding of the clinical course.

Esophageal Balloon-Directed Ventilator Management for Postpneumonectomy Acute Respiratory Distress Syndrome

Objective

Postpneumonectomy patients may develop acute respiratory distress syndrome (ARDS). There is a paucity of data regarding the optimal management of mechanical ventilation for postpneumonectomy patients. Esophageal balloon pressure monitoring has been used in traditional ARDS patients to set positive end-expiratory pressure (PEEP) and minimize transpulmonary driving pressure (ΔP_L), but its clinical use has not been previously described nor validated in postpneumonectomy patients. The primary objective of this report was to describe the potential clinical application of esophageal pressure monitoring to manage the postpneumonectomy patient with ARDS.

Design

Case report. Setting. Surgical intensive care unit (ICU) of a university-affiliated teaching hospital. Patient. A 28-year-old patient was involved in a motor vehicle collision, with a right main bronchus injury, that required a right-sided pneumonectomy to stabilize his condition. In the perioperative phase, they subsequently developed ventilator-associated pneumonia, significant cumulative positive fluid balance, and ARDS. Interventions. Prone positioning and neuromuscular blockade were initiated. An esophageal balloon was inserted to direct ventilator management. Measurements and Main Results. V_T was kept around 3.6 mL/kg PBW, ΔP_L at ≤14 cm H₂O, and plateau pressure at ≤30 cm H₂O. Lung compliance was measured to be 37 mL/cm H₂O. PEEP was optimized to maintain end-inspiratory transpulmonary pressure (P_L) < 15 cm H₂O, and end-expiratory P_L between 0 and 5 cm H₂O. The maximal ΔP_L was measured to be 11 cm H₂O during the care of this patient. The patient improved with esophageal balloon-directed ventilator management and was eventually liberated from mechanical ventilation.

Conclusions

The optimal targets for V_T remain unknown in the postpneumonectomy patient. However, postpneumonectomy patients with ARDS may potentially benefit from very low V_T and optimization of PEEP. We demonstrate the application of esophageal balloon pressure monitoring that clinicians could potentially use to limit injurious ventilation and improve outcomes in postpneumonectomy patients with ARDS. However, esophageal balloon pressure monitoring has not been extensively validated in this patient population.

One Lung Soldier: A Ventilation Conundrum in a Postpneumonectomy Syndrome Complicated by Acute Respiratory Syndrome

Postpneumonectomy syndrome involves mediastinal shift causing dynamic airway obstruction via compression of the main bronchus and distal trachea. A few case reports describe the development of ARDS in patients with postpneumonectomy syndrome. Reeb et al. (2017) describe the mortality of postpneumonectomy ARDS anywhere from 33% to 88%. One may encounter difficulty in intubation and ventilation as parameters based on ideal body weight may not apply. Prone positioning ventilation and ECMO have been successfully used in isolated cases. We present such a case and highlight challenges in management. A 70-year-old male Vietnam veteran with remote history of right pneumonectomy thirty years prior presented with fever, cough, and dyspnea. Physical exam was significant for T 36.3°C, BP 162/73, heart rate 145 BPM, RR 22 breaths/minute, ht. 1.72 m, and wt. 78 kg, with transmitted right lung sounds and rhonchi on the left. Labs showed WBC 23.92/nL and procalcitonin 0.84 ng/mL. CXR showed left infiltrate and opacification of right hemithorax with right mediastinal shift. EKG showed atrial fibrillation. He was started on broad spectrum antibiotics for pneumonia, but deteriorated, and was intubated for respiratory distress from ARDS. Vasopressors were initiated for shock. Given the history of pneumonectomy, he was initially ventilated with lower tidal volumes (320 mL). However, incremental changes were made to tidal volumes, and ETT was repositioned several times for hypoxia. Epoprostenol and cisatracurium were also initiated. Positional changes would lead to sudden desaturation; hence, prone positioning ventilation was not done. He was not considered for ECMO due to his pneumonectomy status. Unfortunately, his condition worsened progressively and he expired. The guidelines for ARDS are well established. However, postpneumonectomy patients are unique as seen in our patient. It is unclear whether an endobronchial tube advanced into the left bronchus could have helped difficult airway management resulting from suspected postpneumonectomy syndrome as suggested by CXR. Higher tidal volumes were also unsuccessful in alleviating hypoxia and led to persistently elevated plateau pressures and driving pressures as high as 23, which was inconsistent with our goal of lung protective ventilation. Few case reports describe the successful use of prone positioning ventilation or ECMO in postpneumonectomy patients with ARDS. Although not well studied, low tidal volumes supported with ECMO may have been a favorable strategy for our patient.

Extracorporeal membrane oxygenation in trauma: A single institution experience and review of the literature

INTRODUCTION:

Limited options exist for cardiovascular support of the trauma patient in extremis. This patient population offers challenges that are often considered insurmountable. This article identifies a heterogeneous group of trauma patients in extremis who may benefit from extracorporeal membrane oxygenation.

METHODS:

Data were sourced from the medical records of all patients placed on extracorporeal membrane oxygenation following trauma at a Level I Trauma Center between 1 December 2016 and 1 December 2017.

RESULTS:

All patients were male (N = 7), mostly with blunt injuries (n = 5), with an average age of 41 years and with an average Injury Severity Scores of 33 (median = 34). Two out of seven patients survived (28.5%). Survivors tended to have a longer duration on extracorporeal membrane oxygenation (13.5 vs 3.8 days), had extracorporeal membrane oxygenation initiated later (15 vs 7.8 days), and had suffered a blunt injury. Two patients were initiated on veno-arterial extracorporeal membrane oxygenation (both non-survivors) and five were initiated on veno-venous extracorporeal membrane oxygenation (two survivors, three non-survivors). Five patients were heparinized immediately (one survivor, four non-survivors), and two patients were heparinized after clotting was noted in the circuit (one survivor, one non-survivor). Three of the seven (42.8%) patients suffered cardiac arrest either prior to, or during, the initiation of extracorporeal membrane oxygenation (all non-survivors).

DISCUSSION:

Extracorporeal membrane oxygenation use in the trauma patient in extremis is not standard; however, this article demonstrates that extracorporeal membrane oxygenation is feasible in a complex, heterogeneous patient population when treated at designated centers.

Extracorporeal membrane oxygenation as a rescue measure after thoracic surgery

Background

Extracorporeal membrane oxygenation is used for many different conditions including respiratory distress, cardiogenic shock, and trauma. In these patient groups, extracorporeal membrane oxygenation has been extensively studied. Recently, it has been used as a rescue measure in patients experiencing acute respiratory distress after thoracic surgery. The goal of our study was to examine the efficacy and cost-effectiveness of extracorporeal membrane oxygenation as a rescue measure after thoracic surgery at a single center.

Methods

We conducted a retrospective review of all patients who received extracorporeal membrane oxygenation after thoracic surgery at the University of Kentucky from January 9, 2012 to January 9, 2017. Eight patients were identified.

Results

The average time on extracorporeal membrane oxygenation was 9.125 days, and the average hospital stay was 65.125 days. Of the 8 patients placed on extracorporeal membrane oxygenation, 3 survived to discharge. Of the 3 patients who survived to discharge, 1 died within 6 months and 2 have been followed up for less than 4 months. The average total charge per patient was calculated to be $1,053,551, and the average charge per day was $16,177. The contribution margin was $109,200 per case.

Conclusions

Extracorporeal membrane oxygenation is a tool that saves lives in many different patient populations but it does not appear to be as effective in patients experiencing acute respiratory distress syndrome after thoracic surgery. Extracorporeal membrane oxygenation in this group also uses a tremendous amount of hospital resources.