In the USA, trauma represents the leading cause of death between the ages of 1 and
46 years and contributed to 192,000 deaths in 2014.
1
Major trauma is also responsible for significant disabilities and increased hospital
length of stay (LOS), and represents a huge financial burden. Acute respiratory failure
(ARF) is multifactorial in trauma patients with diverse underlying pathophysiological
mechanisms. In a blunt thoracic injury, all the chest compartments can be affected
and are directly responsible for mortality of 20–25%.
2
Two main mechanisms contribute to pulmonary injury; the first mechanism is a direct
trauma leading to contusion, intra-alveolar hemorrhage, and aspiration pneumonia.
Some of the mechanical injuries to the chest (pneumothorax, hemothorax, airways injury)
are reversible by various interventions (pleural drains, surgical airway repair, etc.).
The second mechanism is an indirect immunological lung injury, which may result from
extrapulmonary trauma and/or the required management of trauma patients (massive transfusion,
fluid overload, ventilator lung induced injury, etc.) leading to acute respiratory
distress syndrome (ARDS). Extracorporeal membrane oxygenation (ECMO) is an attractive
therapy in ARF. In 1972, the first successful use of ECMO was in a 24-year-old polytrauma
patient who developed a “shock lung syndrome”.
3
However, subsequent results in the next two to three decades were disappointing. The
H1N1 influenza epidemic with a high number of young patients with severe respiratory
failure led to resurgence of ECMO use. ECMO has been successfully used in severe ARDS
secondary to the influenza A (H1N1) epidemic in 2009 with acceptable outcomes. A large
multicenter trial (CESAR trial) in the UK showed that referral and transfer of patients
to severe respiratory failure centers with ECMO capabilities reduced mortality in
severe ARDS patients.
4
Despite these encouraging results and use of ECMO worldwide for severe ARDS, use of
ECMO in trauma patient is poorly studied. Severe ARF requiring mechanical ventilation
(MV) in trauma patients is associated with high mortality and increased hospital LOS.
In patients with severe impaired gas exchange despite optimized MV, ECMO is proposed
to avoid injurious lung ventilation. It is prudent to start ECMO at an earlier stage
to avoid irreversible MV-induced pulmonary injury in these cases. In severe thoracic
trauma cases requiring lung resection or progressive lung fibrosis with severely limited
reserve, ECMO may prove to be the main therapy as a bridge to lung transplant. The
heterogeneity and complexity of trauma patients make ECMO use challenging in trauma
cases with uncertain benefit/risk balance and multidisciplinary decision-making becomes
extremely important on a case-by-case basis. Among trauma patients with ARF, those
with a traumatic brain injury represent a specific group as their prognosis is mainly
dependent on neurological recovery. These patients may require earlier ECMO support
compared with non-brain-injured patients, to prevent secondary neurological injury
from severe hypoxemia, hypercapnic acidosis, and worsening cerebral edema from fluid
overload. Indeed, the combination of gas exchange alteration from respiratory failure
and intracerebral pathology leads to a difficult challenge in ventilatory management
of these patients. The usual dilemma of lung-protective versus neuroprotective ventilation
creates contradictory goals. A high PEEP strategy, permissive hypercapnia, and permissive
hypoxemia are well-accepted strategies for ARDS management, but may lead to secondary
neurological insult in brain-injured patients. Munoz-Bendix and colleagues showed
in their study that intracerebral pressure can be decreased by the PaCO2 control with
ECMO support in trauma patients, which is a major goal of neuroprotective ventilation
in these patients.
5
ECMO in brain-injured patient is an attractive option as it allows the combination
of neuroprotective and lung-protective ventilator strategies at the same time. The
goal of ECMO is to support the patients who have good functional prognosis from their
neurological injury. Unfortunately, this prognostication is not easy in brain-injured
patients at the time when they are in need of ECMO. Better prognostic predictors in
brain-injured patients may help the healthcare teams to improve the selection of patients
who will benefit from ECMO.
ECMO use is limited in trauma patients, particularly those with traumatic brain injury,
complicated pelvic fractures, or major vascular injuries in view of fear of serious
bleeding during systemic anticoagulation. However, with improved ECMO circuit technology
(newer pump systems, reduced circuit area, newer biocompatible circuit material, heparin
coating etc.), and a relatively high blood flow during veno-venous (VV) ECMO, thrombotic
complications during heparin-free ECMO runs are relatively uncommon. In the literature,
there are many reports of prolonged heparin-free ECMO use in patients with trauma
as well as other pathologies with high risk of bleeding complications with excellent
outcomes and no serious thrombotic complications.
6–9
Recently, a systematic review of the literature with an aggregated total of 215 trauma
patients showed an overall survival to discharge ranging from 50 to 79%;
10
however, this work suffered from various limitations. All studies included were retrospective
and included a maximum of five patients per year per center. Most of the studies with
a high number of patients were performed over many years making definitive conclusions
difficult to formulate as the ECMO management and techniques and ICU approaches have
evolved over the years. An interesting cohort study using data from two American centers
compared 76 trauma patients on MV and 26 who required VV extracorporeal life support
(ECLS).
11
There were no differences between the two groups regarding ventilator days, intensive
care unit LOS, and hospital LOS. However, when ECLS patients were severity matched
to patients on MV, a better survival was demonstrated in the ECLS group. These are
very encouraging results, but there were multiple limitations, and lot of questions
remained unanswered. Further studies are needed to define the appropriate time to
initiate ECMO, proper patient selection, and outcome data beyond survival to hospital
discharge, including functional and psychosocial outcomes, particularly in brain-injured
patients. The holy grail of ECMO use in trauma patients is the optimal timing to initiate
this therapy. ECMO is a complex treatment modality, which involves a multiprofessional
team of clinicians, and financial and physical resources for its optimal implementation.
The use of ECMO in inappropriate patient at an inappropriate time may lead to poor
outcomes with wastage of precious healthcare resources. Unfortunately, several large
ECMO centers do not have a level 3 trauma center and, at the same time, multiple trauma
centers do not have any ECMO service. Therefore, studies from centers with combined
trauma and ECMO services are really needed to demonstrate their complementary positive
impact on the care of trauma patients. Trauma patients should be considered as a genuine
group to benefit from ECMO support. Beside the encouragement of centers to publish
their individual experiences, a multidisciplinary task force under the aegis of ELSO
may be a reasonable approach to conduct studies to answer the unresolved questions
of ECMO use in trauma patients. A reasonable first phase towards this goal would be
to create a specific registry for interested centers with experience in trauma care
as well as ECMO capabilities. The management of these patients is complex and needs
a multidisciplinary team approach with experience of trauma teams as well as intensivists
and an ECMO team with a reasonable patient volume. The specific pathways created by
collaboration of ECMO specialists, perfusionists, intensivists, emergency room physicians,
trauma surgeons, and interventional radiologists will lead to improved patient care
as well as valuable data to optimize the care of these patients in the future. The
time has come not to deny the lifesaving ECMO therapy to trauma patient based on our
perceived notions and prejudices. Indeed, the decision to start ECMO in trauma patients
is not easy and straightforward and needs input from multidisciplinary team members
but should be considered for each patient on an individual basis and may lead to very
satisfying outcome in these mostly young patients. The need for more data and more
outcome-based well-designed studies are needed to better define the role of ECMO in
the care of trauma patients. The ECMO community should work in harmony to achieve
this goal. The future of ECMO in trauma patients may prove to be bright after all.