Successful treatment of a severely injured soldier from Afghanistan with pumpless extracorporeal lung assist and neurally adjusted ventilatory support

Extracorporeal life support in thoracic emergencies-a narrative review of current evidence

BACKGROUND AND OBJECTIVE

Resuscitative therapies for respiratory and cardiac failure are lifesaving and extended by using extracorporeal life support (ECLS) as mechanical circulatory support (MSC). This review informs the debate to identify the life-threatening thoracic emergencies in which patients may be cannulated for ECLS support.

METHODS

An advanced search was performed in PubMed, Embase, Google Scholar, and references query, assessed in June 2022, identified 761 records. Among them, 74 publications in English were included in the current narrative review.

KEY CONTENT AND FINDINGS

ECLS is an additional tool for organ support in life-threatening thoracic emergencies. It provides bridging to recovery or to decision about destination as definitive therapy, intervention, or surgery. Non-traumatic emergencies include mediastinal mass, acute lung injury (ALI), aspiration, embolisms, acute and chronic heart failure. However, based on the current evidence, trauma, and especially blunt thoracic trauma, is one of the main indications for ECLS use in thoracic emergencies, among others in chest wall fractures, blunt and penetrating lung injuries. ECLS use is always individualized to patient's needs, injury pattern and kind of organ failure, circulatory arrest inclusive, depending on if respiratory or cardiac and circulatory support is needed. Further, ECLS offers the possibility for fast volume resuscitation and rewarming, thus preventing the lethal of trauma: hypothermia, hypoperfusion and acidosis. Anticoagulation may be omitted for some hours or days. Interdisciplinary cooperation between the intensivists, surgeons, anesthesiologists, emergency medical services, an appropriately organized and trained staff, equipment resources and logistical planning are essential for successful outcomes.

CONCLUSIONS

ECLS use in selected life-threatening thoracic emergencies is increasing. The summarized findings appeal to policymakers, and we hope that our summary of recommendations may impact clinical practice and research.

A Case Report of Combat Blast Injury Requiring Combat Casualty Care, Far-Forward ECMO, Air Transport, and All Levels of Military Critical Care

We describe a 34-year-old soldier who sustained a blast injury in Syria resulting in tracheal 5 cm tracheal loss, cervical spine and cord injury with tetraplegia, multiple bilateral rib fractures, esophageal injury, traumatic brain injury, globe evisceration, and multiple extremity soft tissue and musculoskeletal injuries including a left tibia fracture with compartment syndrome. An emergent intubation of the transected trachea was performed in the field, and the patient was resuscitated with whole blood prehospital. During transport to the Role 2, the patient required cardiopulmonary resuscitation for cardiac arrest. On arrival, he underwent a resuscitative thoracotomy and received a massive transfusion exclusively with whole blood. A specialized critical care team transported the patient to the Role 3 hospital in Baghdad, and the DoD extracorporeal membrane oxygenation (ECMO) team was activated secondary to his unstable airway and severe hypoxia secondary to pulmonary blast injury. The casualty was cannulated in Baghdad approximately 40 hours after injury with bifemoral cannulae in a venovenous configuration. He was transported from Iraq to the U.S. Army Institute of Surgical Research Burn Center in San Antonio without issue. Extracorporeal membrane oxygenation support was successfully weaned, and he was decannulated on ECMO day 4. The early and en route use of venovenous ECMO allowed for maintenance of respiratory support during transport and bridge to operative management and demonstrates the feasibility of prolonged ECMO transport in critically ill combat casualties.

The Feasibility of Venovenous ECMO at Role-2 Facilities in Austere Military Environments

INTRODUCTION

Venovenous extracorporeal membrane oxygenation (VV-ECMO) has been gaining use to bridge the recovery from acute respiratory distress syndrome (ARDS) refractory to conventional treatment. However, these interventions are often limited to higher echelons of military care. We present a case of lung salvage from severe ARDS in an Afghani soldier with VV-ECMO at a Role-2 (R2) facility in an austere military environment in Afghanistan.

CASE

A 25-year-old Afghani soldier presented to an R2 facility with blast lung injury and multiple penetrating injuries following an explosion. The patient underwent immediate damage control laparotomy. The abdomen was left open for subsequent washouts and ongoing resuscitation. Due to his ineligibility for evacuation and worsening ARDS, despite 5 d of conventional ventilation strategies, he was started on VV-ECMO. The patient had immediate improvements in oxygenation, which continued for 10 d. Moreover, he underwent three transportations to the operating room without accidental decannulation or disruption of the VV-ECMO device. Despite significant improvements, the patient expired on postoperative day 15, due to an overwhelming intra-abdominal sepsis.

CONCLUSION

As future advancements are sought, VV-ECMO may become a consideration for casualties with severe ARDS at the point of injury and at lower echelons of military care.

Delayed Cardiac Rupture Induced by Traumatic Myocardial Infarction: Consequence of a 45-Magnum Blast Injury; A Comprehensive Case Review

A penetrating chest trauma, a myocardial contusion or a myocardial infarction can lead to a cardiac rupture, which is linked to an extreme high death rate. Only few cases with delayed perforation of the myocardium have been reported in literature. We report about a penetrating gunshot injury, which led to a myocardial contusion with secondary delayed rupture of the left ventricle and the left inferior lobe of the lung. The leakage of the lesion in the left ventricle could be sealed sufficiently with fibrin-coated collagen fleeces after adapting stitches with Prolene 2-0. For additional stabilization of the vulnerable myocardium area, a bovine patch has been placed on the damaged ventricle. Fibrin fleeces are used successfully in cardiac surgery, as in our case, to seal the leakage of the lesion in the left ventricle. The implantation of a bovine patch in the pericardium could prevent a cardiac compartment syndrome with a fatal pericardial tamponade. To prohibit a thoracic compartment syndrome a modified Bogota bag could be sewed in for temporarily closure of the chest. In most cases penetrating cardiac injuries can be treated without heart-lung-machines. An immediate transfer to a cardio-surgical center is, due to the acute situation, not possible. If a surgeon with thoraco-surgical expertise is present a transfer is not absolutely necessary.

Extracorporeal life support in critically ill adults

Extracorporeal life support (ECLS) has become increasingly popular as a salvage strategy for critically ill adults. Major advances in technology and the severe acute respiratory distress syndrome that characterized the 2009 influenza A(H1N1) pandemic have stimulated renewed interest in the use of venovenous extracorporeal membrane oxygenation (ECMO) and extracorporeal carbon dioxide removal to support the respiratory system. Theoretical advantages of ECLS for respiratory failure include the ability to rest the lungs by avoiding injurious mechanical ventilator settings and the potential to facilitate early mobilization, which may be advantageous for bridging to recovery or to lung transplantation. The use of venoarterial ECMO has been expanded and applied to critically ill adults with hemodynamic compromise from a variety of etiologies, beyond postcardiotomy failure. Although technology and general care of the ECLS patient have evolved, ECLS is not without potentially serious complications and remains unproven as a treatment modality. The therapy is now being tested in clinical trials, although numerous questions remain about the application of ECLS and its impact on outcomes in critically ill adults.

Application of neurally adjusted ventilatory assist in neonates

Neurally adjusted ventilatory assist (NAVA) uses the electrical activity of the diaphragm (Edi) as a neural trigger to synchronize mechanical ventilatory breaths with the patient's neural respiratory drive. Using this signal enables the ventilator to proportionally support the patient's instantaneous drive on a breath-by-breath basis. Synchrony can be achieved even in the presence of significant air leaks, which make this an attractive choice for invasive and non-invasive ventilation of the neonate. This paper describes the Edi signal, neuroventilatory coupling, and patient-ventilator synchrony including the functional concept of NAVA. Safety features, NAVA terminology, and clinical application of NAVA to unload respiratory musculature are presented. The use of the Edi signal as a respiratory vital sign for conventional ventilation is discussed. The results of animal and adult studies are briefly summarized and detailed descriptions of all NAVA-related research in pediatric and neonatal patients are provided. Further studies are needed to determine whether NAVA will have significant impact on the overall outcomes of neonates.

Mechanical ventilation during extracorporeal membrane oxygenation

The timing of extracorporeal membrane oxygenation (ECMO) initiation and its outcome in the management of respiratory and cardiac failure have received considerable attention, but very little attention has been given to mechanical ventilation during ECMO. Mechanical ventilation settings in non-ECMO studies have been shown to have an effect on survival and may also have contributed to a treatment effect in ECMO trials. Protective lung ventilation strategies established for non-ECMO-supported respiratory failure patients may not be optimal for more severe forms of respiratory failure requiring ECMO support. The influence of positive end-expiratory pressure on the reduction of the left ventricular compliance may be a matter of concern for patients receiving ECMO support for cardiac failure. The objectives of this review were to describe potential mechanisms for lung injury during ECMO for respiratory or cardiac failure, to assess the possible benefits from the use of ultra-protective lung ventilation strategies and to review published guidelines and expert opinions available on mechanical ventilation-specific management of patients requiring ECMO, including mode and ventilator settings. Articles were identified through a detailed search of PubMed, Ovid, Cochrane databases and Google Scholar. Additional references were retrieved from the selected studies. Growing evidence suggests that mechanical ventilation settings are important in ECMO patients to minimize further lung damage and improve outcomes. An ultra-protective ventilation strategy may be optimal for mechanical ventilation during ECMO for respiratory failure. The effects of airway pressure on right and left ventricular afterload should be considered during venoarterial ECMO support of cardiac failure. Future studies are needed to better understand the potential impact of invasive mechanical ventilation modes and settings on outcomes.

The UK military experience of thoracic injury in the wars in Iraq and Afghanistan

INTRODUCTION

Thoracic injury during warfare is associated with a high incidence of morbidity and mortality. This study examines the pattern and mortality of thoracic wounding in the counter-insurgency conflicts of Iraq and Afghanistan, and outlines the operative and decision making skills required by the modern military surgeon in the deployed hospital setting to manage these injuries.

METHODS

The UK Joint Theatre Trauma Registry was searched between 2003 and 2011 to identify all patients who sustained battle-related thoracic injuries admitted to a UK Field Hospital (Role 3). All UK soldiers, coalition forces and local civilians were included.

RESULTS

During the study period 7856 patients were admitted because of trauma, 826 (10.5%) of whom had thoracic injury. Thoracic injury-related mortality was 118/826 (14.3%). There were no differences in gender, age, coalition status and mechanism of injury between survivors and non-survivors. Survivors had a significantly higher GCS, Revised Trauma Score and systolic blood pressure on admission to a Role 3 facility. Multivariable regression analysis identified admission systolic blood pressure less than 90, severe head or abdominal injury and cardiac arrest as independent predictors of mortality.

CONCLUSIONS

Blast is the main mechanism of thoracic wounding in the recent conflicts in Iraq and Afghanistan. Thoracic trauma in association with severe head or abdominal injuries are predictors of mortality, rather than thoracic injury alone. Deploying surgeons require training in thoracic surgery in order to be able to manage patients appropriately at Role 3.

Transportable extracorporeal lung support for rescue of severe respiratory failure in combat casualties

BACKGROUND

Advances in oxygenator membrane, vascular cannula, and centrifugal pump technologies led to the miniaturization of extracorporeal lung support (ECLS) and simplified its insertion and use. Support of combat injuries complicated by severe respiratory failure requires critical care resources not sustainable in the deployed environment. In response to this need, a unique international military-civilian partnership was forged to create a transportable ECLS capability to rescue combat casualties experiencing severe respiratory failure.

METHODS

A multidisciplinary training and consultative relationship developed between the US military at Landstuhl Regional Medical Center (LRMC) and the University Hospital Regensburg (UHR), a German regional "lung failure" center with expertise in ECLS. ECLS circuits used were pumpless arteriovenous extracorporeal lung assist (NovaLung iLA) and pump-driven venovenous extracorporeal membrane oxygenation (PLS Quadrox D Membrane Oxygenator with Rotaflow Centrifugal Pump). US casualties supported by ECLS between June 2005 and August 2011 were identified from the LRMC Trauma Program Registry for review.

RESULTS

UHR cared for 10 US casualties supported by ECLS. The initial five patients were cannulated with arteriovenous circuits (pumpless arteriovenous extracorporeal lung assist), and the remaining five were cannulated with pump-driven venovenous circuits (extracorporeal membrane oxygenation). Four patients were cannulated in the war zone, and six patients were cannulated at LRMC after evacuation to Germany. All patients were transferred to UHR for continued management (mean, 9.6 ECLS days). In all cases, both hypoxemia and hypercapnia improved, allowing for decreased airway pressures. Nine patients were weaned from ECLS and extubated. One soldier died from progressive multiple-organ failure.

CONCLUSION

ECLS should be considered in the management of trauma complicated by severe respiratory failure. Modern ECLS technology allows these therapies to be transported for initiation outside of specialized centers even in austere settings. Close collaboration with established centers potentially allows both military and civilian hospitals with infrequent ECLS requirements to use it for initial patient stabilization before transfer for continued care.

LEVEL OF EVIDENCE

Therapeutic/care management study, level V.

Extracorporeal lung support in trauma patients with severe chest injury and acute lung failure: a 10-year institutional experience

Introduction

Severe trauma with concomitant chest injury is frequently associated with acute lung failure (ALF). This report summarizes our experience with extracorporeal lung support (ELS) in thoracic trauma patients treated at the University Medical Center Regensburg.

Methods

A retrospective, observational analysis of prospectively collected data (Regensburg ECMO Registry database) was performed for all consecutive trauma patients with acute pulmonary failure requiring ELS during a 10-year interval.

Results

Between April 2002 and April 2012, 52 patients (49 male, three female) with severe thoracic trauma and ALF refractory to conventional therapy required ELS. The mean age was 32 ± 14 years (range, 16 to 72 years). Major traffic accident (73%) was the most common trauma, followed by blast injury (17%), deep fall (8%) and blunt trauma (2%). The mean Injury Severity Score was 58.9 ± 10.5, the mean lung injury score was 3.3 ± 0.6 and the Sequential Organ Failure Assessment score was 10.5 ± 3. Twenty-six patients required pumpless extracorporeal lung assist (PECLA) and 26 patients required veno-venous extracorporeal membrane oxygenation (vv-ECMO) for primary post-traumatic respiratory failure. The mean time to ELS support was 5.2 ± 7.7 days (range, <24 hours to 38 days) and the mean ELS duration was 6.9 ± 3.6 days (range, <24 hours to 19 days). In 24 cases (48%) ELS implantation was performed in an external facility, and cannulation was done percutaneously by Seldinger's technique in 98% of patients. Cannula-related complications occurred in 15% of patients (PECLA, 19% (n = 5); vv-ECMO, 12% (n = 3)). Surgery was performed in 44 patients, with 16 patients under ELS prevention. Eight patients (15%) died during ELS support and three patients (6%) died after ELS weaning. The overall survival rate was 79% compared with the proposed Injury Severity Score-related mortality (59%).

Conclusion

Pumpless and pump-driven ELS systems are an excellent treatment option in severe thoracic trauma patients with ALF and facilitate survival in an experienced trauma center with an interdisciplinary treatment approach. We encourage the use of vv-ECMO due to reduced complication rates, better oxygenation and best short-term outcome.

Synchronized mechanical ventilation using electrical activity of the diaphragm in neonates

The electrical activity of the diaphragm (Edi) is measured by a specialized nasogastric/orogastric tube positioned in the esophagus at the level of the crural diaphragm. Neurally adjusted ventilatory assist (NAVA) uses the Edi signal as a neural trigger and intrabreath controller to synchronize mechanical ventilatory breaths with the patient's respiratory drive and to proportionally support the patient's respiratory efforts on a breath-by-breath basis. NAVA improves patient-ventilator interaction and synchrony even in the presence of large air leaks, and might therefore be an optimal option for noninvasive ventilation in neonates.

Emerging modes of ventilation in the intensive care unit

Potentially harmful effects of positive pressure mechanical ventilation have been recognized since its inception in the 1950s. Since then, the risk factors for and mechanisms of ventilator-induced lung injury (VILI) have been further characterized. Publication of the ARDSnet tidal volume trial in 2000 demonstrated that a ventilator strategy limiting tidal volumes and plateau pressure in patients with acute respiratory distress syndrome was associated with a 22% reduction in mortality. Since then, a variety of ventilator modes have emerged seeking to improve gas exchange, reduce injurious effects of ventilation, and improve weaning from the ventilator. We review here emerging ventilator modes in the intensive care unit (ICU). Airway pressure release ventilation seeks to optimize alveolar recruitment and maintain spontaneous ventilatory effort. It is associated with improved indices of respiratory and cardiovascular physiology, but data to support outcome benefit are lacking. High-frequency oscillatory ventilation is associated with improvements in gas exchange, but outcome data are conflicting. Extracorporeal modes of ventilation continue to evolve, and extra-corporeal CO₂ removal is a technique that could be used in non-specialist ICUs. Proportional-assist ventilation and neutrally adjusted ventilator assist are modes that vary level of assistance with patient ventilatory effort. They result in greater patient-ventilator synchrony, but at present there is no evidence of a reduction in the duration of mechanical ventilation or outcome benefit. Although the use of many of these modes is likely to increase in intensive care units, further evidence of a beneficial effect is desirable before they are recommended.