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to a CT room or for CT examination to be used to identify sites of bleeding35). However, it is important for hemostasis to be immediately achieved at hemorrhaging sites in patients with unstable circu-lation. The number of patients with severe trauma has been decreasing year by year, and the number of experienced trauma surgeons in Japan has declined36). The fact that the diagnostic studies included as part of the initial ATLS® trauma survey are not well equipped to diagnose such a fatal vascular injury37). In addition, recent studies showed the efficacy of evaluation using whole CT during resuscitation in the hybrid ER, for even trauma patients with unstable circulation, in order to detect sites of hemorrhaging and facilitate the immediate performance procedures to obtain hemostasis38-41). Accordingly, to increase the survival rate of patients with fatal vascular injuries, such as blunt azygos injury, the early recognition of the site of hemorrhaging using CT and the immediate execu-tion of surgical hemostasis in an appropriate posi-tion for modern surgeons (less experienced in the management of severe trauma) may be required, even when initial fluid resuscitation fails and unstable circulation remains.Regarding what measures should be taken by young physicians in a standard hospital without a hybrid ER to obtain a survival outcome in patients with fatal azygos injury and unstable circulation until veteran surgeons arrive. Aside from the ATLS® protocol, a 1:1:1 ratio of packed red blood cells, fresh plasma, and platelets with minimal crys-talloids is the preferred resuscitative strategy to avoid diluted coagulopathy by crystalloid fluid resuscitation42). Recently, in patients experiencing hemorrhagic shock, whole-blood transfusion was reported to be associated with both an improved survival and decreased overall blood utilization43). If a patient does not obtain stable circulation even after massive transfusion, they should be intubated to secure the airway35). After definitively securing the airway, a CT examination should be consid-ered, although the proper timing of CT remains controversial44). A chest drain is usually inserted to drain the hemothorax and evaluate the volume in order to decide the timing of radical operation. Tentative drain clamping may be effective for achieving hemostasis at the bleeding source or reducing the total hemorrhaging volume by the 402hematoma tamponade effect, based on our personal experience and evidence from total knee arthro-plasty45). However, it should be noted that drain clamping may result in hemorrhagic death or fatal tension hemothorax. Intensive hypotensive resusci-tation is recommended, as it is safe and has a lower mortality rate than normotensive resuscitation in hemorrhagic shock patients. There is also less blood loss, hemodilution, ischemia, and hypoxia in tissues with such an approach46). If young physi-cians aggressively attempt damage control inter-vention using right thoracotomy but fail to identify the bleeding source, hilar clamping or twisting may be attempted to detect the bleeding source47, 48). If the bleeding cannot be stopped with these proce-dures, the bleeding source likely lies outside of the pulmonary artery and venous system. In addition, in cases with an unknown bleeding source, a large amount of gauze should be packed blindly in order to achieve hemostasis49). Alternatively, clam-shell thoracotomy may be useful for identifying the bleeding source, even in the supine position50).We presented a fatal case of blunt azygos injury and the results of an analysis of the relevant litera-ture. ER physicians must consider azygos vein injury as a possible cause of right hemothorax in patients with blunt chest trauma if the individual shows persistent hypotension. In addition, the early recognition of the site of hemorrhaging using CT may be required, even if the patient’s circulation remains unstable after initial fluid resuscitation. Not applicable.This work was supported in part by a Grant-in-Aid for Special Research in Subsidies for ordi-nary expenses of private schools from The Promo-tion and Mutual Aid Corporation for Private Schools of Japan.KM was a major contributor in writing the manuscript. KJ, SH and YY were editing the manu-script. All authors read and approved the final manuscript.ConclusionAcknowledgmentsFundingAuthor contributions