Current role of extracorporeal membrane oxygenation for the management of trauma patients: Indications and results

Abstract

Extracorporeal membrane oxygenation (ECMO) has emerged as a vital circulatory life support measure for patients with critical cardiac or pulmonary conditions unresponsive to conventional therapies. ECMO allows blood to be extracted from a patient and introduced to a machine that oxygenates blood and removes carbon dioxide. This blood is then reintroduced into the patient’s circulatory system. This process makes ECMO essential for treating various medical conditions, both as a standalone therapy and as adjuvant therapy. Veno-venous (VV) ECMO primarily supports respiratory function and indicates respiratory distress. Simultaneously, veno-arterial (VA) ECMO provides hemodynamic and respiratory support and is suitable for cardiac-related complications. This study reviews recent literature to elucidate the evolving role of ECMO in trauma care, considering its procedural intricacies, indications, contraindications, and associated complications. Notably, the use of ECMO in trauma patients, particularly for acute respiratory distress syndrome and cardiogenic shock, has demonstrated promising outcomes despite challenges such as anticoagulation management and complications such as acute kidney injury, bleeding, thrombosis, and hemolysis. Some studies have shown that VV ECMO was associated with significantly higher survival rates than conventional mechanical ventilation, whereas other studies have reported that VA ECMO was associated with lower survival rates than VV ECMO. ECMO plays a critical role in managing trauma patients, particularly those with acute respiratory failure. Further research is necessary to explore the full potential of ECMO in trauma care. Clinicians should have a clear understanding of the indications and contraindications for the use of ECMO to maximize its benefits in treating trauma patients.

Key Words: Extracorporeal membrane oxygenation treatments; Multiple trauma; Respiratory distress syndrome; Cardiogenic shock; Contraindications; Anticoagulants

Core Tip: Extracorporeal membrane oxygenation (ECMO), comprising veno-venous (VV) and veno-arterial (VA) modalities, offers crucial circulatory and respiratory support for trauma patients with severe cardiac or pulmonary conditions. VV ECMO is indicated for respiratory distress, including acute respiratory distress syndrome, whereas VA ECMO aids in cardiogenic shock and cardiac arrest. Anticoagulation poses challenges, particularly in trauma patients; however, tailored approaches mitigate the risks. Complications such as acute kidney injury and bleeding highlight the need for vigilant monitoring. Standardized protocols and ongoing research are pivotal for optimizing ECMO utilization and outcomes in trauma care, warranting multidisciplinary collaboration and individualized patient management.

INTRODUCTION

Extracorporeal membrane oxygenation (ECMO) is a form of circulatory life support that is used in patients with critical cardiac or pulmonary conditions that are unresponsive to more standard therapies such as cardiopulmonary resuscitation[1,2]. The basis of ECMO is the formation of an oxygenation circuit. First, blood is drained from a patient through a cannula and is transferred to a membrane lung that removes carbon dioxide and oxygenates the blood; this blood is subsequently reintroduced into the patient’s circulatory system via a reinfusion cannula[3]. The use of ECMO for trauma patients has dramatically increased in the last decade[4]. Trauma patients experience high mortality rates and develop various grave conditions, such as cardiac arrest, hemorrhagic shock, and cardiopulmonary failure[5]. Therefore, ECMO has become a critical part of the management of trauma patients. ECMO requires a team of specialized healthcare workers with adequate supplies; these requirements may contribute to ECMO’s lack of accessibility in many lower- and middle-income countries[6]. The intricacies associated with the use of ECMO, coupled with its current unavailability in several markets, have blurred the understanding of its application within trauma communities.

Two predominant forms of ECMO are used in clinical practice: Veno-venous (VV) and veno-arterial (VA) ECMO. VV ECMO uses a circuitry that connects a vein to a vein. First, venous blood is drained from the patient (e.g., from the right atrium); the circuitry then removes carbon dioxide and oxygenates the blood; and the blood is then reintroduced into the same venous compartment, allowing complete bypass of the patient’s cardiac output and systemic circulation[3,7]. Therefore, VV ECMO is indicated for use in patients with respiratory complications or failure, such as acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease[8]. The use of VV ECMO allows oxygenated blood from the right atrium to circulate through the pulmonary vasculature, the left side of the heart, and ultimately into systemic circulation; this form of circulatory support requires the heart to be functioning[4]. Therefore, VV ECMO should be used in trauma patients with respiratory distress.

VA ECMO is the other major form of ECMO. It is routinely used in the context of cardiac arrest and cardiogenic shock[9]. Unlike VV ECMO, which mainly provides respiratory support, VA ECMO provides hemodynamic and respiratory support[10]. The fundamentals governing VA ECMO are similar to those governing VV ECMO. First, venous blood is drained (e.g., from the inferior vena cava) and mechanically pumped outside the body where carbon dioxide is removed and the blood is oxygenated before being reintroduced into the arterial system via cannulation (e.g., the femoral artery)[10]. Although VV ECMO allows bypass of the respiratory system[11], VA ECMO allows full bypass of both the cardiac and pulmonary systems[12]. These differences dictate the clinical indications for ECMO. Despite its increased use, ECMO remains misunderstood by trauma communities and requires a standardized set of rules for its clinical use. A deeper scrutiny of its indications, procedural technicalities, risks, and benefits may abridge some of these gaps to allow further adoption of ECMO in various clinical settings.

This study aims to address these gaps by exploring and consolidating the role of ECMO and its use in trauma patients with a focus on the interventions, indications, and appropriate management.

LITERATURE REVIEW

This minireview was conducted to evaluate the current literature on the use of ECMO in trauma patients, with a focus on publications from 2014 to the present.

Several scientific databases, including PubMed, Scopus, and Google Scholar, were systematically searched using the following keywords: “ECMO”, “trauma”, “extracorporeal life support”, and “traumatic injury”. The inclusion criteria were peer-reviewed articles published between January 2014 and the present, written in English, and directly addressing the application of ECMO in trauma patients. Only studies involving adult patients were included, with no restrictions on the type of trauma (blunt or penetrating).

Review articles, clinical trials, case reports, and observational studies were considered; however, non-English articles, animal studies, and publications not directly relevant to ECMO in trauma were excluded. After an initial screening based on the title and abstract, eligible articles underwent a full-text review.

The primary objective of this study was to summarize the clinical outcomes, indications, contraindications, and complications associated with the use of ECMO for trauma. The secondary objectives were to assess trends in ECMO use and identify gaps in the current literature.

INDICATIONS AND CONTRAINDICATIONS OF ECMO

VA ECMO and VV ECMO are the two most commonly used forms of ECMO in clinical practice. Both types abide by similar mechanics: Blood is drained from a vein into a machine containing a membrane that removes carbon dioxide and adds oxygen, and then blood is reintroduced into either a vein (VV ECMO) or an artery (VA ECMO). This is a slight difference in the methodology wherein each ECMO type is indicated in clinical practice. Table 1 presents a summary of the indications for VV ECMO[10,13-15], and Table 2 presents a summary of the indications for VA ECMO. Unfortunately, the contraindications for the use of ECMO were inconsistent because they vary depending on the center and country. However, some overarching similarities were observed regarding accepted VV ECMO contraindications; these are listed in Table 3[10,13,14,16,17]. Many of these contraindications can be grouped into relative or absolute contraindications. Difficulties arise when relative contraindications clash with the possibility of therapeutic benefit because some relative contraindications should be weighed by the clinician more severely than others[17]. Indications for both VV ECMO and VA ECMO vary and are controversial depending on the judgments of clinicians and their institutions. In clinical practice, determining whether a patient is a candidate for VA ECMO or VV ECMO becomes particularly difficult. Therefore, a summary of some of the most common and important indications for both VV ECMO and VA ECMO is presented in the following tables. VA ECMO is primarily used for cardiac-related complications. Table 2 presents the most pertinent indications[9,18-21].

Table 1 Summary of the indications for the use of veno-venous-extracorporeal membrane oxygenation[10,13-15].

No.	Indication
1	Primary indication: Severe, acute respiratory failure refractory to conventional respiratory and medical therapy; including one or more of hypoxemic respiratory failure, hypercapnic respiratory failure, and ventilation support for those awaiting lung transplantation or those dealing with primary graft dysfunction after lung transplantation
2	Acute respiratory distress syndrome
3	Bronchopleural fistulas and pulmonary air leaks
4	Complicated airway management
5	Bacterial/viral/atypical pneumonia
6	Interstitial pneumonitis
7	Airway obstruction
8	Pulmonary hemorrhage

Table 2 Common indications for veno-arterial-extracorporeal membrane oxygenation use[9,18-21].

Generally accepted indications	Indications under consideration
Cardiogenic shock (due to, e.g., acute myocardial infarction, heart failure, fulminant myocarditis, etc)	Massive pulmonary embolism
Cardiac arrest in the setting of extracorporeal cardiopulmonary resuscitation	Sepsis-associated cardiomyopathy
Post-cardiotomy cardiac failure	Pulmonary hypertension
Bridging therapy tool

Table 3 Contraindications for the use of veno-venous-extracorporeal membrane oxygenation[10,13,14,16,17].

Relative contraindications	Absolute contraindications
Advanced age (typically > 70 years of age)	Non-recovery anticipation with no plan for viable de-cannulation (possibly due to multi-organ failure)
Immunocompromised	Cardiogenic failure (vital in VV-ECMO)
Ventilation of patients for an extended period (typically > 7 days)	Patient compliance and autonomy
BMI (differs from center to center)	Disseminated advanced-stage malignancy
Anticoagulation contraindication	Cerebral hemorrhage/cerebral herniation/intractable intracranial hypertension
Central nervous system injury

VV-ECMO: Veno-venous-extracorporeal membrane oxygenation.

Similar to VV ECMO, VA ECMO has its own set of contraindications that can help guide clinicians on the appropriate course of action for patients with indications for VA ECMO. There remains controversy regarding the contraindications to VA ECMO; however, the most widely and generally agreed-upon contraindications are shown in Table 4[9,21-23]. In the literature, there are varying inconsistencies between what is deemed an absolute and a relative contraindication. These inconsistencies add to the difficulties in selecting VA ECMO in clinical practice. When these situations arise, we suggest a personalized multidisciplinary approach that fully scrutinizes and weighs the risks and advantages of ECMO while incorporating the shared decision-making model of patient care.

Table 4 Contraindications for veno-arterial-extracorporeal membrane oxygenation[9,21-23].

Absolute contraindications	Relative contraindications
Unrecoverable cardiac condition	Contraindication to anticoagulation
Short life expectancy (generally less than 1 year)	Aortic dissection
Preexisting conditions with significant mortality rates and/or those that are incompatible with adequate recovery	Aortic regurgitation
Chronic aortic insufficiency (inconsistencies within the literature regarding this contraindication)	Morbid obesity
Incompatibilities with patient’s goal of care	Peripheral vascular disease
	Advanced age (inconsistencies within the literature regarding this contraindication)

MECHANISM OF ECMO

All ECMO circuits incorporate four main parts: Two cannulas (one for drainage and the other for return), a pump, and a gas exchanger[1]. The drainage cannula is usually placed in a vein to allow blood to flow out of the body and into the ECMO circuit. The blood flow is aided by a pump that creates a driving force by generating negative pressure for the blood to move through the oxygenator; the pump can be either afterload dependent or independent[1]. The blood then moves to a gas exchanger that plays the role of the lungs, allowing carbon dioxide and oxygen exchange; thus, the blood becomes oxygenated[1]. The oxygenated blood then moves through the return cannula into the body; the return cannula can be placed in a vein or an artery depending on the indication of the patient[1].

In VV ECMO, drainage and return of blood can be performed using one double-lumen cannula or multiple cannulas. When using a double-lumen cannula, the tip is advanced from the insertion point at the right internal jugular vein into the right atrium and further into the inferior vena cava[1,14]. This allows the drainage ports to sit in the inferior and superior venae cavae, whereas the return port sits in the right atrium[14]. When using multiple cannulas, the drainage cannula is usually placed in either the superior vena cava, inferior vena cava, or femoral vein[1,10,14]. The return cannula is usually placed in the femoral vein or at the junction between the superior vena cava and atrium[1,10,14].

In VA ECMO, cannulation can be performed either centrally or peripherally. In central cannulation, a drainage cannula is inserted in either the right atrium or superior vena cava, and a return cannula is inserted in the aorta allowing blood to be drained directly into the arterial system[10,21]. In contrast, peripheral cannulation can be performed in multiple configurations, some of which are the femoral-femoral, where the drainage cannula is placed in the femoral vein and the return cannula is placed in the femoral artery[10,21]. Another configuration is the femoral-axillary, where the drainage cannula is placed in the femoral vein and the return cannula is placed in the axillary artery[10,21]. The major difference between the two cannulation approaches is the level of invasiveness. The central cannulation approach is more invasive, and an operating room is required for cannula placement[21]. Peripheral cannulation is less invasive and can sometimes be performed as a bedside procedure in intensive care units[21].

CLINICAL USE OF ECMO IN TRAUMA PATIENTS

In trauma patients, the most common indication for ECMO is the development of ARDS, which causes refractory respiratory failure[4]. With ARDS, the most common ECMO configuration used is VV ECMO[4]. A meta-analysis in 2023 that included 36 reviews revealed that VV ECMO showed a survival rate of 64.7% compared with the use of conventional mechanical ventilation, which showed a survival rate of 23.5% in patients with hypoxic respiratory failure[5]. Furthermore, 20.0%-30.0% of patients with traumatic brain injury (TBI) develop ARDS, and ECMO plays a crucial role in their management[5]. In patients with TBI who develop ARDS, conventional approaches, such as prone positioning, permissive hypercapnia, and high positive end-expiratory pressure may increase intracranial pressure and worsen the injury; thus, ECMO is necessary in these cases[5]. VA ECMO can also be used in trauma patients with cardiogenic shock; however, the survival rate of patients on VA ECMO is lower than that of patients on VV ECMO; this is mainly attributed to the inclusion of patients with traumatic cardiac arrest when conducting studies[5].

CHALLENGES AND COMPLICATIONS OF ECMO

Anticoagulation is one of the major challenges of using ECMO in trauma patients. Any patient on ECMO will need anticoagulation; however, putting trauma patients on anticoagulation is thought to put them at a higher risk of bleeding, particularly in cases of TBI and hemorrhagic shock[4,5]. This was first observed when using cardiopulmonary bypass (CPB), in which anticoagulation is mandatory; however, ECMO requires lower anticoagulation doses than CPB[4]. Some institutions have stopped the use of anticoagulation on patients on ECMO, unless required, and one of the institutions has reported significantly lower complications in the group that was not coagulated than in the coagulation group[4]. Furthermore, the new approaches for patients with anticoagulation, such as the advancement of low-dose heparin and the delayed anticoagulation approach, make this decision case-specific and not an absolute contraindication as it was before[5].

Many complications are associated with the use of ECMO; one of the most common is acute kidney injury, with an incidence of 72%[14]. Patients may require renal replacement therapy; however, this depends on the guidelines set by the center[14]. Another complication is bleeding, which can occur at different sites in the body, such as the cannulation site, across the gastrointestinal tract, and even body cavities, including the thoracic and abdominal cavities[24]. Thrombosis is also a complication very commonly observed in patients on ECMO and mostly occurs by the formation of a clot in the ECMO circuit, usually in the oxygenator rather than the body[24,25]. Clot formation in arterial cannulas increases the risk of microembolism[24]. A combination of monitoring tests is used to monitor hemostasis once patients are initiated on anticoagulation; tests include but are not limited to prothrombin time, activated partial thromboplastin time, D-dimer, platelet count, and antithrombin[24]. Hemolysis is also seen in patients on ECMO, and it is attributed to shear stress caused by the pump on the erythrocytes[24,25]. To monitor hemolysis, a plasma-free hemoglobin test should be performed twice per day[25].

CONCLUSION

This study emphasizes the expanding use of ECMO in trauma care, highlighting its efficacy in managing complex cardiac and pulmonary conditions. Although ECMO offers a lifeline for critically ill trauma patients, its optimal application requires a nuanced understanding of patient selection, procedural considerations, and complication management. Further research and standardized protocols are necessary to enhance the accessibility and efficacy of ECMO in diverse clinical settings, thereby ensuring improved outcomes for trauma patients worldwide.