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Abstract: Over the past 10 years, extracorporeal membrane oxygenation (ECMO) use in trauma patients has increased significantly. This includes adult and pediatric trauma patients and even combat casualties. Most ECMO applications are in a venovenous (VV ECMO) configuration for acute hypoxemic respiratory failure or anatomic injuries that require pneumonectomy or extreme lung rest in a patient with insufficient respiratory reserve. In this narrative review, we summarize the most common indications for VV ECMO and other forms of ECMO support used in critically injured patients, underscore the importance of early ECMO consultation or regional referral, review the technical aspects of ECMO cannulation and management, and examine the expected outcomes for these patients. In addition, we evaluate the data where it exists to try to debunk some common myths surrounding ECMO management., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Acute respiratory distress syndrome (ARDS) occurs in more than 10% of intensive care unit admissions and in nearly 25% of ventilated patients. Mortality remains high at 40%, and, for patients who survive, recovery continues for months or even years. Early recognition and minimizing further lung injury remain essential to successful management of severe ARDS. Advanced treatment strategies, which complement lung protective ventilation, include short-term neuromuscular blockade, prone positioning, and extracorporeal membrane oxygenation. Alternative ventilator strategies include high-frequency ventilation and airway pressure release ventilation. This article reviews these options in patients with severe ARDS., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: The overall incidence and mortality of acute respiratory distress syndrome (ARDS) in civilian trauma settings have decreased over the past four decades; however, the epidemiology and impact of ARDS on modern combat casualty care are unknown. We sought to determine the incidence, risk factors, resource utilization, and mortality associated with ARDS in current combat casualty care., Methods: This was a retrospective review of mechanically ventilated US combat casualties within the Department of Defense Trauma Registry (formerly the Joint Theater Trauma Registry) during Operation Iraqi Freedom/Enduring Freedom (October 2001 to August 2008) for ARDS development, resource utilization, and mortality., Results: Of 18,329 US Department of Defense Trauma Registry encounters, 4,679 (25.5%) required mechanical ventilation; ARDS was identified in 156 encounters (3.3%). On multivariate logistic regression, ARDS was independently associated with female sex (odds ratio [OR], 2.62; 95% confidence interval [CI], 1.21-5.71; p = 0.02), higher military-specific Injury Severity Score (Mil ISS) (OR, 4.18; 95% CI, 2.61-6.71; p < 0.001 for Mil ISS ≥25 vs. <15), hypotension (admission systolic blood pressure <90 vs. ≥90 mm Hg; OR, 1.76; 95% CI, 1.07-2.88; p = 0.03), and tachycardia (admission heart rate ≥90 vs. <90 beats per minute; OR, 1.53; 95% CI, 1.06-2.22; p = 0.02). Explosion injury was not associated with increased risk of ARDS. Critical care resource utilization was significantly higher in ARDS patients as was all-cause hospital mortality (ARDS vs. no ARDS, 12.8% vs. 5.9%; p = 0.002). After adjustment for age, sex, injury severity, injury mechanism, Mil ISS, hypotension, tachycardia, and admission Glasgow Coma Scale score, ARDS remained an independent risk factor for death (OR, 1.99; 95% CI, 1.12-3.52; p = 0.02)., Conclusions: In this large cohort of modern combat casualties, ARDS risk factors included female sex, higher injury severity, hypotension, and tachycardia, but not explosion injury. Patients with ARDS also required more medical resources and were at greater risk of death compared with patients without ARDS. Thus, ARDS remains a significant complication in current combat casualty care., Level of Evidence: Prognostic/epidemiologic study, level III.

The purpose of this study was to compare the Berlin definition to the American-European Consensus Conference (AECC) definition in determining the prevalence of acute respiratory distress syndrome (ARDS) and associated mortality in the critically ill burn population. Consecutive patients admitted to our institution with burn injury that required mechanical ventilation for more than 24 hours were included for analysis. Included patients (N = 891) were classified by both definitions. The median age, % TBSA burn, and injury severity score (interquartile ranges) were 35 (24-51), 25 (11-45), and 18 (9-26), respectively. Inhalation injury was present in 35.5%. The prevalence of ARDS was 34% using the Berlin definition and 30.5% using the AECC definition (combined acute lung injury and ARDS), with associated mortality rates of 40.9 and 42.9%, respectively. Under the Berlin definition, mortality rose with increased ARDS severity (14.6% no ARDS; 16.7% mild; 44% moderate; and 59.7% severe, P < 0.001). By contrast, under the AECC definition increased mortality was seen only for ARDS category (14.7% no ARDS; 15.1% acute lung injury; and 46.0% ARDS, P < 0.001). The mortality of the 22 subjects meeting the AECC, but not the Berlin definition was not different from patients without ARDS (P = .91). The Berlin definition better stratifies ARDS in terms of severity and correctly excludes those with minimal disease previously captured by the AECC.

Background: The objective of this report was to compare the prevalence of acute respiratory distress syndrome (ARDS) and associated mortality between military service members with burns sustained during or in support of combat operations and civilian burn patients treated at a single burn center., Methods: Demographic and physiologic data were collected retrospectively on mechanically ventilated military and civilian patients admitted to our burn intensive care unit between January 2003 and December 2011. Patients with ARDS were identified and categorized as mild, moderate, or severe using the Berlin criteria. Demographics and clinical outcomes were compared. After initial comparison, propensity matching was performed and mortality compared., Results: A total of 891 burn patients required mechanical ventilation during the study period; 291 military and 600 civilian. The prevalence of ARDS was 34% (n=304) for the entire cohort, 33% (n=96) for military, and 35% (n=208) for civilians (p=0.55). For the entire cohort, despite more severe injury burden, military patients had a significantly lower overall mortality (17% vs. 28%; p=0.0002) as well as ARDS mortality (33 vs. 48%, p=0.02) when compared to civilians. This difference was not significant after propensity matching based on age., Conclusion: In a retrospective cohort study, burned military patients on mechanical ventilation had a significantly lower overall and ARDS mortality despite larger burns and more severe injury when compared to civilian burn patients. This difference appears to be largely because of age., (Reprint & Copyright © 2015 Association of Military Surgeons of the U.S.)

Background: Recently, automated alerts have been used to identify patients with respiratory failure based on set criteria, which can be gleaned from the electronic medical record (EMR). Such an approach may also be useful for identifying patients with severe adult respiratory distress syndrome (ARDS) who may benefit from extracorporeal membrane oxygenation (ECMO). Inhaled nitric oxide (iNO) is a common rescue therapy for severe ARDS which can be easily tracked in the EMR, and some patients started on iNO may have indications for initiating ECMO. This case series summarizes our experience with using automated electronic alerts for ECMO team activation focused particularly on an alert triggered by the initiation of iNO., Methods: After a brief trial evaluation, our Smart Alert system generated an automated page and e-mail alert to ECMO team members whenever a nonzero value for iNO appeared in the respiratory care section of our EMR. If iNO was initiated for severe respiratory failure, a detailed evaluation by the ECMO team determined if ECMO was indicated. For those patients managed with ECMO, we tabulated baseline characteristics, indication for ECMO, and outcomes., Results: From September 2012 to July 2013, 45 iNO alerts were generated on 42 unique patients. Six patients (14%) met criteria for ECMO. Of these, four were identified exclusively by the iNO alert. At the time of the alert, the median PaO₂-to-FIO₂ ratio was 64 mm Hg (range, 55-107 mm Hg), the median age-adjusted oxygenation index was 73 (range, 51-96), and the median Murray score was 3.4 (range, 3-3.75), indicating severe respiratory failure. Median time from iNO alert to ECMO initiation was 81 hours (range, -2-292 hours). Survival to hospital discharge was 83% in those managed with ECMO., Conclusion: Automated alerts may be useful for identifying patients with severe ARDS who may be ECMO candidates., Level of Evidence: Diagnostic test, level V.

Background: Venovenous extracorporeal life support (VV ECLS) has been reported in adult trauma patients with severe respiratory failure; however, ECLS is not available in many trauma centers, few trauma surgeons have experience initiating ECLS and managing ECLS patients, and there is currently little evidence supporting its use in severely injured patients. This study seeks to determine if VV ECLS improves survival in such patients., Methods: Data from two American College of Surgeons-verified Level 1 trauma centers, which maintain detailed records of patients with acute hypoxemic respiratory failure (AHRF), were evaluated retrospectively. The study population included trauma patients between 16 years and 55 years of age treated for AHRF between January 2001 and December 2009. These patients were divided into two cohorts as follows: patients who received VV ECLS after an incomplete or no response to other rescue therapies (ECLS) versus patients who were managed with mechanical ventilation (CONV). The primary outcome was survival to discharge, and secondary outcomes were intensive care unit and hospital length of stay (LOS), total ventilator days, and rate of complications requiring intervention., Results: Twenty-six ECLS patients and 76 CONV patients were compared. Adjusted survival was greater in the ECLS group (adjusted odds ratio, 0.193; 95% confidence interval, 0.042-0.884; p = 0.034). Ventilator days, intensive care unit LOS, and hospital LOS did not differ between the groups. ECLS patients received more blood transfusions and had more bleeding complications, while the CONV patients had more pulmonary complications. A cohort of 17 ECLS and 17 CONV patients matched for age and lung injury severity also demonstrated a significantly greater survival in the ECLS group (adjusted odds ratio, 0.038; 95% confidence interval, 0.004-0.407; p = 0.007)., Conclusion: VV ECLS is independently associated with survival in adult trauma patients with AHRF. ECLS should be considered in trauma patients with AHRF when conventional therapies prove ineffective; if ECLS is not readily available, transfer to an ECLS center should be pursued., Level of Evidence: Therapeutic study, level III.

Objectives: Venovenous extracorporeal gas exchange is increasingly used in awake, spontaneously breathing patients as a bridge to lung transplantation. Limited data are available on a similar use of extracorporeal gas exchange in patients with acute respiratory distress syndrome. The aim of this study was to investigate the use of extracorporeal gas exchange in awake, spontaneously breathing sheep with healthy lungs and with acute respiratory distress syndrome and describe the interactions between the native lung (healthy and diseased) and the artificial lung (extracorporeal gas exchange) in this setting., Design: Laboratory investigation., Setting: Animal ICU of a governmental laboratory., Subjects: Eleven awake, spontaneously breathing sheep on extracorporeal gas exchange., Interventions: Sheep were studied before (healthy lungs) and after the induction of acute respiratory distress syndrome via IV injection of oleic acid. Six gas flow settings (1-10 L/min), resulting in different amounts of extracorporeal CO2 removal (20-100% of total CO2 production), were tested in each animal before and after the injury., Measurements and Main Results: Respiratory variables and gas exchange were measured for every gas flow setting. Both healthy and injured sheep reduced minute ventilation according to the amount of extracorporeal CO2 removal, up to complete apnea. However, compared with healthy sheep, sheep with acute respiratory distress syndrome presented significantly increased esophageal pressure variations (25 ± 9 vs 6 ± 3 cm H2O; p < 0.001), which could be reduced only with very high amounts of CO2 removal (> 80% of total CO2 production)., Conclusions: Spontaneous ventilation of both healthy sheep and sheep with acute respiratory distress syndrome can be controlled via extracorporeal gas exchange. If this holds true in humans, extracorporeal gas exchange could be used in awake, spontaneously breathing patients with acute respiratory distress syndrome to support gas exchange. A deeper understanding of the pathophysiology of spontaneous breathing during acute respiratory distress syndrome is however warranted in order to be able to propose extracorporeal gas exchange as a safe and valuable alternative to mechanical ventilation for the treatment of patients with acute respiratory distress syndrome.

Background: Acute respiratory distress syndrome (ARDS) prevalence and related outcomes in burned military casualties from Iraq and Afghanistan have not been described previously. The objective of this article was to report ARDS prevalence and its associated in-hospital mortality in military burn patients., Methods: Demographic and physiologic data were collected retrospectively on mechanically ventilated military casualties admitted to our burn intensive care unit from January 2003 to December 2011. Patients with ARDS were identified in accordance with the new Berlin definition of ARDS. Subjects were categorized as having mild, moderate, or severe ARDS. Multivariate logistic regression identified independent risk factors for developing moderate-to-severe ARDS. The main outcome measure was the prevalence of ARDS in a cohort of patients burned as a result of recent combat operations., Results: A total of 876 burned military casualties presented during the study period, of whom 291 (33.2%) required mechanical ventilation. Prevalence of ARDS in this cohort was 32.6%, with a crude overall mortality of 16.5%. Mortality increased significantly with ARDS severity: mild (11.1%), moderate (36.1%), and severe (43.8%) compared with no ARDS (8.7%) (p < 0.001). Predictors for the development of moderate or severe ARDS were inhalation injury (odds ratio [OR], 1.90; 95% confidence interval [CI], 1.01-3.54; p = 0.046), Injury Severity Score (ISS) (OR, 1.04; 95% CI, 1.01-1.07; p = 0.0021), pneumonia (OR, 198; 95% CI, 1.07-3.66; p = 0.03), and transfusion of fresh frozen plasma (OR, 1.32; 95% CI, 1.01-1.72; p = 0.04). Size of burn was associated with moderate or severe ARDS by univariate analysis but was not an independent predictor of ARDS by multivariate logistic regression (p > 0.05). Age, size of burn, and moderate or severe ARDS were independent predictors of mortality., Conclusion: In this cohort of military casualties with thermal injuries, nearly a third required mechanical ventilation; of those, nearly one third developed ARDS, and nearly one third of patients with ARDS did not survive. Moderate and severe ARDS increased the odds of death by more than fourfold and ninefold, respectively., Level of Evidence: Epidemiologic/prognostic study, level III.

Background: Damage-control resuscitation (DCR) has been advocated to reduce mortality in military and civilian settings. However, DCR and excessive crystalloid resuscitation may be associated with a higher incidence of acute respiratory distress syndrome (ARDS). We sought to examine the impact of resuscitation strategies on ARDS development in combat casualty care., Methods: A retrospective review of Joint Theater Trauma Registry data on US combat casualties who received at least 1 U of blood product within the first 24 hours of care was performed, cross-referenced with the cohort receiving mechanical ventilation (n = 1,475). Massive transfusion (MT, ≥10 red blood cells [RBCs] and/or whole blood in 24 hours) and volume/ratios of plasma/RBC, platelet/RBC, and crystalloid/RBC (C/RBC, crystalloid liters/RBC units) were examined using bivariate/multivariate logistic regression and local regression analyses as ARDS risk factors, controlling for age, injury severity, admission systolic blood pressure, and Glasgow Coma Scale (GCS) score., Results: ARDS was identified in 95 cases (6.4%). MT was required in 550 (37.3%) of the analysis cohort. ARDS was more common in MT (46 of 550, 8.4%) versus no-MT cohort (49 of 925, 5.3%), but mortality was not different (17.4% MT vs. 16.3% no-MT). ARDS patients received significantly increased crystalloid of blood product volumes. Increased crystalloid resuscitation (C/RBC ratio > 1.5) occurred in 479 (32.7%) of 1,464 patients. Unadjusted mortality was significantly increased in the cohort with C/RBC ratio of 1.5 or less compared with those with greater than 1.5 (19.1% vs. 6.3%, p < 0.0001), but no difference in ARDS (6.5% vs. 6.6%) was identified. Platelet/RBC ratio did not impact on ARDS. Increasing plasma (odds ratio, 1.07; p = 0.0062) and crystalloid (odds ratio, 1.04; p = 0.041) volumes were confirmed as independent ARDS risk factors., Conclusion: In modern combat casualty care, increased plasma and crystalloid infusion were identified as independent risk factors for ARDS. These findings support a practice of decreased plasma/crystalloid transfusion in trauma resuscitation once hemorrhage control is established to achieve the mortality benefit of DCR and ARDS prevention.

Background: Prone positioning (PP) improves oxygenation and may provide a benefit in patients with acute respiratory distress syndrome (ARDS). This approach adds significant challenges to patients in intensive care by limiting access to the endotracheal or tracheostomy tube and vascular access. PP also significantly complicates burn care by making skin protection and wound care more difficult. We hypothesize that PP improves oxygenation and can be performed safely in burn patients with ARDS., Methods: PP was implemented in a burn intensive care unit for 18 patients with severe refractory ARDS. The characteristics of these patients were retrospectively reviewed to evaluate the impact of PP on Pao2:FiO2 ratio (PFR) during the first 48 hours of therapy. Each patient was considered his or her own control before initiation of PP, and trends in PFR were evaluated with one-way analysis of variance. Secondary measures of complications and mortality were also evaluated., Results: Mean PFR before PP was 87 (± 38) with a mean sequential organ failure assessment score of 11 (± 4). PFR improved during 48 hours in 12 of 14 survivors (p < 0.05). Mean PFR was 133 (± 77) immediately after PP, 165 (± 118) at 6 hours, 170 (± 115) at 12 hours, 214 (± 126) at 24 hours, 236 (± 137) at 36 hours, and 210 (± 97) at 48 hours. At each measured time interval except the last, PFR significantly improved. There were no unintended extubations. Facial pressure ulcers developed in four patients (22%). Overall, 14 survived 48 hours (78%), 12 survived 28 days (67%), and six survived to hospital discharge (33%)., Conclusions: PP improves oxygenation in burn patients with severe ARDS and was safely implemented in a burn intensive care unit. Mortality in this population remains high, warranting investigation into additional complementary rescue therapies., Level of Evidence: Therapeutic study, level IV., (Copyright © 2012 by Lippincott Williams & Wilkins.)