The importance of adequate prehospital trauma triage for injured patients has been emphasized by previous research [13]. Achieving a shorter time to hemorrhage control following traumatic injury remains a significant challenge in preventing mortality. For rapid hemostasis, the concept of DOR has been proposed long ago, and some institutions have implemented DOR for resuscitating patients with the most severe injuries. In our review, the definition of DOR in most studies was that patients were immediately transported to the trauma OR, bypassing any evaluation in the ER department. The goal of DOR is to minimize any delays to the OR and initiate both resuscitation and surgical interventions [8]. In most studies, the DOR status was determined by the trauma team [5,6,7, 10]. Martin et al. reported that the best predictors of DOR were mechanism, physiology, and pattern of injury, while EMS suspicion was associated with the least need for DOR [11]. Moreover, most patients assigned to DOR required major surgical interventions, including laparotomy, thoracotomy, craniotomy, and neck exploration, and vascular repair and resuscitation procedures, including intubation, surgical airway, needle decompression, chest tube, central venous access, and massive transfusion [5,6,7, 9]. The American College of Surgeons certification does not specify requirements for OR locations. Therefore, each trauma center maintains either a rotation OR, a dedicated OR, or an OR located within the ER department [10]. Studies on DOR using EDOR have also been conducted, which were included in our review. There is not much difference between the system or indications of the DOR and EDOR as EDOR refers to ORs located within ER department. Habarth-Morales et al. mentioned that EDOR has several inherent advantages because it provides an ideal location to facilitate diagnosis and intervention, enabling simultaneous resuscitation and hemorrhage control, but the DOR system has same advantages, as mentioned above. In the case of EDOR, patients are triaged directly to the EDOR by either trauma physicians, ED physicians, or trauma nursing staff, according to institutional policies [10]. As DOR or EDOR are terms coined depending on the location, and the underlying central concept is the same, there is no need to interpret the results of studies on DOR and EDOR differently.

Recently, the concept of hybrid OTs has emerged, which has been implemented by many countries. Hybrid OTs allow for simultaneous interventional radiology and operative procedures, thereby shortening the time to definitive treatment. Recent research, including systematic reviews, has investigated hybrid OTs [12, 14,15,16,17,18,19,20]. In some studies, the procedural time was reduced by introducing hybrid OTs.

In our review, we identified five studies that compared the actual mortality with the predicted mortality using the TRISS [21]. In four of these studies, the overall survival rate was better than the predicted survival rate. Some studies performed subgroup analyses. Two studies showed that the survival rate for penetrating injuries was better, and one study showed that the survival rate for blunt injuries was better than the predicted survival rate. One study compared mortality rates using propensity matching and found no significant difference in the overall mortality. In addition, some studies assessed the time to the start of surgical intervention. In two studies, the time to the start of surgical intervention was shorter in the DOR group. Although no comparison was made in the three remaining studies, the time to surgical intervention was less than 30 min, suggesting that DOR can reduce the time before institution of hemorrhage control.

Identifying patients who may benefit from DOR remains controversial. Moreover, although there were minute differences in the indications for DOR in each study, they were similar in a broader context. The indications for DOR included (1) profound shock; (2) penetration injuries of the neck, chest, abdomen, and pelvis; (3) cardiopulmonary arrest; (4) amputation; and (5) evisceration. Establishing concrete indications for DOR can help its implementation. To the best of our knowledge, this is the first systematic review to compare the results of DOR in patients with trauma. Our study represents the first attempt to systematically summarize the existing literature using a systematic review to identify comparative studies assessment mortality and the incision time. The results encompass practical aspects that can assist individual hospitals in implementing DOR, given the resource and skill set availability. This review also suggests emerging concepts of hybrid OTs that are associated with the timeliness of the intervention.

Although the results of our systematic review were derived from the best available evidence, there were some limitations. First, the studies reviewed were observational cohort studies; therefore, selection bias may have existed. The use of the Newcastle–Ottawa Scale score did not permit qualitative assessment of the methodological quality of the studies. However, it remains one of the best tools for evaluating non-randomized studies. Second, the included studies did not allow for the quantitative summation of results because most studies compared actual mortality with predicted mortality. In addition, only two studies compared the time to surgical intervention. We suggest that future studies should present their results in broad categories, including the comparison of subgroups that derived clear, practical benefits from DOR and efficiency targets such as 24-h mortality, time to surgical intervention, and amount of blood product involved. Realistically, this can only be achieved in a high-volume center, preferably in a clinical trial setting. Finally, most studies reviewed in our study did not mention the manner in which prehospital interventions, such as airway management, decompression of tension pneumothorax, and blood transfusion or fibrinogen and tranexamic acid use, affected the patients’ outcomes. However, until now, high-level evidence on the relationship between prehospital interventions and patient’s outcomes was lacking; moreover, each country or institute has different emergency medical environments (e.g., the role of EMS, whether medical staff is dispatched to the scene), often limiting interventions that can be performed in the prehospital stage. Moreover, as the scene to OR time for definite bleeding control was as short as 25 min in most studies reviewed in our study, it is difficult to confirm whether interventions at the prehospital stage had a profound effect on the patients’ outcomes. We endeavor to demonstrate this through well-designed follow-up studies in the future. We also suggest that future studies should consider incorporating a multicenter design to compare DOR and traditional practice.