Thoracic aortic rupture due to airbag deployment

Michal Plodr, Miroslav Safr, Ivo Novak

1 Department of Emergency Medicine and Military General Medicine, Faculty of Military Health Sciences, University of Defence, Hradec Kralove 50001, Czech Republic

2 Emergency Medical Services of the Hradec Kralove Region, Hradec Kralove 50002, Czech Republic

3 Department of Forensic Medicine, University Hospital Hradec Kralove, Hradec Kralove 50005, Czech Republic

Dear editor,

Airbags are an example of passive preventive measures reducing the risk of severe injury or death from a motor vehicle accident. However, airbags have also been described as a source of injuries related to airbag deployment. Typical airbag-related injuries are eye injuries, cervical spine injuries, rib fractures, cardiac injuries, extremity injuries, and thoracic aortic rupture (TAR).[1-3]Approximately one-third of patients with TAR who survive till hospital admission die before surgical treatment.[4]We present a patient with TAR after a lowspeed motor vehicle accident with rapidly deteriorating vital signs and subsequent death on the scene.

CASE

A 40-year-old woman sitting in the right-front passenger position of a small car was involved in a lowspeed (35-45 km/hour) front-impact road traffic accident with an estate car during a local severe snowstorm. The patient was unrestrained by a seat belt and the collision resulted in the deployment of the front airbags. There was not any deformation of the dashboard into the inner space of the car and the patient was not wedged in place.

During the initial assessment on the scene, there were no signs of massive external bleeding, Glasgow Coma Scale (GCS) was 13, and the patient respired spontaneously but with severe respiratory distress. The head was without any signs of injury. Airbag powder was found on the face and the front side of the chest. Instability with crepitation on the left side of the chest was found, with signs of superficial contusion and weak breath sounds, predominantly on the left side of chest. The abdomen was without distension or signs of contusion, and the extremities were without deformity. The pulse during the initial assessment was palpable on the radial artery, 128 beats per minute, capillary refill time ＞2 seconds, saturation 75%-78%, and anemic color. Further steps involved with manual in-line cervical spine (C-spine) stabilization and the application of a mouth mask with O2(12 L/minute). Because of increased respiratory distress and bilateral diminished breathing sounds, a bilateral needle thoracocentesis laterally to the nipple line was done to exclude tension pneumothorax, but was without an air leak. On the left side, blood was aspirated into the syringe during the procedure. During a couple of minutes, the patient’s status rapidly worsened, GCS dropped to 7-8 with bradycardia 35-40 per minute, and there was no pulse on the periphery. Cardiopulmonary resuscitation was started immediately. According to analysis, the pulseless electrical activity (PEA) was initial rhythm, which changed in time to asystole. Resuscitation attempts were ceased after 40 minutes with exitus.

Autopsy proved widened hemomediastinum, rib fracture (4th-6th) on the left side, left side hemothorax, and compression fracture of the 8ththoracic vertebra. A main finding was the complete (full layer) transection of the proximal descending aorta in a typical location— aortic isthmus. The main cause of death was traumatichemorrhagic shock.

DISCUSSION

Automobile airbags have shown that they significantly reduce morbidity and mortality resulting mainly from a frontal collision. It has been estimated that seat belts reduce the risk of fatal injuries from motor vehicle accidents by 45% and serious injuries by 50%. Airbag deployment has shown a reduction of occupants’ mortality by 63%. The combined use of airbag and seat belt reduces occupants’ mortality by more than 80%.[5]

On the other hand, airbag deployment after collision is an example of the high-speed counter attack against the torso. A fully infl ated airbag has a volume of 50-60 liters and is propelled out of its compartment at a speed of 160-320 km/hour.[2]

The high lethal ratio of patients, who suffer from thoracic aortic rupture as a result of the blunt thoracic aortic injury (BTAI), is caused by uncontrolled bleeding from intimal tears located typically at the aortic isthmus (incidence 54%-65%).[6]The traumatic rupture of thoracic aorta occurs in 1.5%-2.0% of deaths due to the blunt thoracic trauma and is linked with 3%-12% of all motor vehicle fatalities.[2,7]The thoracic aortic rupture can be complete (full layer) or incomplete (partial layer). Death is often inevitable in the first case, which was the situation of the presented patient. When the rupture is incomplete, blood collects between different layers of arterial wall, and a chance of recovery after surgical treatment, open surgery, or currently preferred thoracic endovascular aortic repair (TEVAR) exists.[8]

The presented case report was from the first quarter of 2015. We are aware of the fact that previous guidelines described the possible use of bilateral thoracostomy in the case of traumatic cardiac arrest. This procedure is reported as likely to be more eff ective than needle thoracostomy in the presence of positive pressure ventilation.[9]According to our knowledge, this procedure had not been widely used in most European countries. When the current guidelines were launched in autumn 2015, the bilateral thoracostomy procedure was clearly emphasized, and since that time the procedure has been routinely used.[10]The guidelines for providing bilateral resuscitative thoracotomy in a pre-hospital environment remain guarded about recommending such procedure in patients with blunt trauma, as there are few neurological survivors and the overall survival appears to be poor.[11,12]However, the 2015 European Resus Council Guidelines do off er strict criteria and four prerequisites: (1) appropriate expertise should be readily available; (2) equipment is available to carry out the procedure and deal with the intrathoracic fi ndings; (3) the environment allows appropriate access to the patient; and (4) less than 10 minutes have elapsed since the loss of vital signs.[10]Resuscitative endovascular balloon occlusion of the aorta (REBOA) is the next currently described method for the management of non-compressible torso hemorrhage (NCTH) in a patient with abdominal, pelvic, or junctional extremity hemorrhage. Nevertheless, in a pre-hospital situation this method has not been widely adopted, although promising results presented in case reports from civil and military sectors are at disposal.[13,14]With rising knowledge and experience, it can be expected that this pre-hospital adjunct will be introduced.[15]

The aim of the presented lethal case is to contribute to the complex issue of blunt thoracic trauma, including a demonstration of real autopsy fi ndings. At the same time, we perceive this case report as pointing out the use of all recommended restraint systems as the highest protection for passengers.

CONCLUSIONS

Thoracic aortic rupture is a real life-threatening emergency. Complete aortic wall rupture is associated with uncontrolled bleeding, and prehospital ambulance teams should be aware of the severity of the condition and possible lethal consequences, even if life-saving procedures and resuscitation are performed.

Funding:The work was supported by a long-term organization development plan—clinical branches (Faculty of Military Health Sciences, University of Defence).

Ethical approval:Not needed.

Confl icts of interests:Authors have no fi nancial or other confl icts of interest related to this submission.

Contributors:All authors had substantial contributions to the acquisition, analysis, or interpretation of data for the work. All authors have read and approved the fi nal version of the submitted manuscript.