INTRODUCTION
There are two main causes of acute respiratory distress syndrome (ARDS) in trauma patients. The first is direct severe lung injury, which progresses to respiratory failure [
1]. The second occurs among patients who receive critical care due to multiple traumatic injuries [
2]. Despite management in the intensive care unit (ICU), severe lung injury with ARDS or cardiopulmonary insufficiency is still associated with high morbidity and mortality [
3,
4]. Extracorporeal membrane oxygenation (ECMO) has been used in patients who have undergone pulmonary transplantation and require additional cardiopulmonary support when the standard means of ventilation are ineffective [
5]. Thus, ECMO might be used as a temporary replacement for the damaged lung to provide sufficient ventilation and oxygenation, to improve hypercapnia, and to allow time for recovery of the lung [
6,
7]. However, due to the possibility of bleeding complications, the use of ECMO at trauma care centers has been limited [
8,
9]. Inadequate research has been conducted on the use of ECMO in trauma patients. South Korea has 17 trauma centers; however, ECMO is rarely used in the management of trauma.
This study retrospectively analyzed the characteristics of trauma patients in whom ECMO was used. Data were obtained from the Korea Trauma Data Bank (KTDB), which was established in 2014. This study aimed to describe the experiences at a single institution with the use of ECMO in trauma patients.
DISCUSSION
In cases where ECMO is used in trauma patients, the causes of severe lung injury include insufficient ventilator care during conservative treatment or ARDS during ICU care for multiple traumas [
1]. ECMO is sometimes selected as a salvage technique in trauma; however, its use is still controversial [
11]. In South Korea, it is considered as an alternative treatment; hence, it is rarely used. Since it is challenging to find data on the use of ECMO in trauma, we analyzed its use in trauma cases.
In total, 25 patients were analyzed, including those who had sustained trauma due to drowning and hanging. Drowning was considered as a direct lung injury, and was included in the group of patients with an AIS 3 score of 5. In the case of hanging, ECMO was applied since ARDS occurred during ICU care for a patient with an AIS 1 score of 5. In this study, VA-ECMO was most frequently applied in patients with injuries caused by hanging and drowning.
There were nine patients in whom heparin was not administered during ECMO application (three survivors [30.0%] and six non-survivors [40.0%]). In patients with multiple traumas, the chances of bleeding are high, making it challenging to use anti-hemostatic agents [
12-
14]. Recent studies have shown that ECMO without the use of heparin has good outcomes if VV-ECMO is applied in cases of trauma with a high risk of bleeding [
11,
12,
15]. Although our study did not compare the group to one in which only VV-ECMO was applied, the administration or non-administration of heparin did not affect survival.
Kidney injury might occur due to complications during ECMO application. Acute kidney injury (AKI) during ECMO is caused by hypoperfusion, loss of autoregulation, hypoxia, nephrotoxic drugs, and systemic inflammation. [
16] Other reasons for which CRRT might be required include acid-base and electrolyte disturbances and fluid overload [
16]. Hamdi and Palmer [
16] reported an AKI incidence of more than 80% with 50% of those patients requiring renal replacement therapy within the first week of ECMO application. Thongprayoon et al. [
17] reported that the mortality in patients who received CRRT was 3.7-fold higher due to AKI progression during ECMO application. In our study, 11 patients (44.0%) with AKI were treated with CRRT, and there was no significant difference in the need for CRRT between survivors and non-survivors; however, CRRT was provided more frequently in non-survivors.
In our study, two cases of indirect lung injury were due to a cervical spine injury; one case was due to electric shock, and one case was due to bowel injury. Five patients had long bone or pelvic bone fractures, and two patients had liver injuries. The reasons for using ECMO were ARDS (four cases), pulmonary thromboembolism occurrence (two cases), post-cardiac arrest (one case), aspiration pneumonia (one case), and asphyxia (one case). Engström et al. [
18] reported that the incidence of respiratory failure was high in ICU-treated patients with pelvic fractures, and the risk factors were the degree of lung contusion and surgery. There were few patients in our study in whom we could not analyze the risk factors that could cause ARDS due to pelvic bone fractures. However, these patients comprised the majority of the indirect lung injury group.
There were significant differences in age and ECMO onset time between the direct and indirect lung injury groups. As for the age difference, since the population was small, it would be inappropriate to conclude that those with a younger age suffered more direct injuries based on these results alone. In cases of direct lung injury, the decision to apply ECMO would have been made more quickly because oxygenation after the injury was unfavorable due to severe lung contusions. In cases of indirect lung injury, the start time of ECMO might have been delayed because ARDS occurred due to complications during ICU care.
The other variables showed no significant differences between the two groups. None of the patients had previous lung disease. In the patients with indirect lung injuries, lung disease occurred acutely, similarly to lung injuries due to trauma, and ECMO was applied in such patients. Compared with traumatic direct lung injuries requiring ECMO, performing ECMO in response to an acute disease pattern in trauma led to no significant differences, so it is worth considering ECMO more actively in patients with severe lung injuries.
The limitations of this study include the fact that it was a retrospective analysis comprising a few patients. Therefore, in this study, patients with hanging and drowning were included, and in these cases, VA-ECMO was applied. Another limitation of our study is that not only trauma patients were analyzed. In addition, serial checks of clinical biomarkers for ECMO monitoring have not been standardized. Furthermore, before ECMO application, ECMO-related factors (positive end expiratory pressure level or the peak flow ratio) could not be analyzed in the study because many values were missing from the medical charts. As a final limitation, there was one case of traumatic brain injury; however, the mean GCS was 6.8. The GCS was recorded in the nursing records upon arrival at the ED. Even a patient has not experienced a brain injury, if there is a loss of consciousness due to hypovolemic shock, the GCS may be evaluated as low. Thus, a limitation is that continuous evaluations of the GCS were required, but not conducted. ECMO has been applied at other South Korea trauma centers in few trauma patients. Therefore, a multicenter analysis is necessary, and we expect that more research will be conducted at other institutions in the future.