Death occurs immediately after traumatic rupture of the thoracic aorta 75%–90% of the time since bleeding is so severe, and 80–85% of patients die before arriving at a hospital.[2] Though there is a concern that a small, stable tear in the aorta could enlarge and cause complete rupture of the aorta and heavy bleeding, this may be less common than previously believed as long as the patient’s blood pressure does not get too high.[2]
Traumatic aortic rupture is treated with surgery. However, morbidity and mortality rates for surgical repair of the aorta for this condition are among the highest of any cardiovascular surgery.[3] For example, surgery is associated with a high rate of paraplegia,[8] because the spinal cord is very sensitive to ischemia (lack of blood supply), and the nerve tissue can be damaged or killed by the interruption of the blood supply during surgery.
Since a high blood pressure could exacerbate the tear in the aorta or even separate it completely from the heart, which would almost inevitably kill the patient, hospital staff take measures to keep the blood pressure low.[1] Such measures include giving pain medication, keeping the patient calm, and avoiding procedures that could cause gagging or vomiting.[1
The injury is usually caused by high speed impacts such as those that occur in vehicle collisions and serious falls.[1] It may be due to different rates of deceleration of the heart and the aorta, which is in a fixed position.[5]
By far the most common site for tearing in traumatic aortic rupture is the aortic isthmus, near where the left subclavian artery branches off from the aorta.[6][7]
The aorta may also be torn at the point where it is connected to the heart. The aorta may be completely torn apart from the heart, but patients with such injuries very rarely survive for very long after the injury; thus it is much more common for hospital staff to treat patients with partially torn aortas.[1] When the aorta is partially torn, it may form a “pseudoaneurysm”. In patients who do live long enough to be seen in a hospital, a majority have only a partially torn blood vessel, with the layer called the adventitia still intact.[2] In some of these patients, the adventitia and nearby structures within the chest may serve to prevent severe hemorrhage.[2]
The condition is difficult to detect and may go unnoticed, since most patients have no symptoms. However, a minority of patients may be hoarse, find it difficult to breathe or speak, or have shortness of breath, or have chest or upper back pain.[1] Diagnosis is further complicated by the fact that many patients with the injury experienced multiple other serious injuries as well,[4] so the attention of hospital staff may be distracted from the possibility of aortic rupture.
The preferred method of diagnosis is aortography. Though not completely reliable, chest X-rays are used to diagnose the condition.
Traumatic aortic rupture, also called traumatic aortic disruption or transection, is a condition in which the aorta, the largest artery in the body, is torn or ruptured as the result of trauma. The condition is frequently fatal due to the profuse bleeding that results from the rupture. Since the aorta branches directly from the heart to supply blood to the rest of the body, the pressure within it is very great, and blood may be pumped out of a tear in the blood vessel very rapidly. This can quickly result in shock and death. Thus traumatic aortic rupture is a common killer of victims of automotive accidents and other traumas,[1] with up to 18% of deaths that occur in automobile collisions being related to the injury.[2] In fact, aortic disruption due to blunt chest trauma is the second leading cause of injury death (behind traumatic brain injury).[3]
Throughout most of history the mortality rate of TBI was thought to be 100%.[5] However, in 1871 a healed TBI was noted in a duck that had been killed by a hunter, thus demonstrating that the injury could be survived, at least in the general sense.[6] This report, made by Winslow, was the first record in the medical literature of a bronchus injury.[15] In 1873, Seuvre made one of the earliest reports of TBI in the medical literature: a 74-year-old woman whose chest was crushed by a wagon wheel was found on autopsy to have an avulsion of the right bronchus.[15] Long-term survival of the injury was unknown in humans until a report was made of a person who survived in 1927.[5][6] In 1931, a report made by Nissen described successful removal of a lung in a 12-year-old girl who had had narrowing of the bronchus due to the injury.[15] Repair of TBI was probably first attempted in 1945, when the first documented case of a successful suturing of a lacerated bronchus was made.[6] Prior to 1950, the mortality rate was 36%; it had fallen to 9% by 2001;[3][15] this improvement was likely due to improvements in treatments and surgical techniques, including those for injuries commonly associated with TBI.[3]
Rupture of the trachea or bronchus is the most common type of blunt injury to the airway.[15] It is difficult to determine the incidence of TBI: in as many as 30–80% of cases, death occurs before the person reaches a hospital, and these people may not be included in studies.[3] On the other hand, some TBIs are so small that they do not cause significant symptoms and are therefore never noticed.[29] In addition, the injury sometimes is not associated with symptoms until complications develop later, further hindering estimation of the true incidence.[6] However, autopsy studies have revealed TBI in 2.5–3.2% of people who died after trauma.[3] Of all neck and chest traumas, including people that died immediately, TBI is estimated to occur in 0.5–2%.[29] An estimated 0.5% of polytrauma patients treated in trauma centers have TBI.[14] The incidence is estimated at 2% in blunt chest and neck trauma and 1–2% in penetrating chest trauma.[14] Laryngotracheal injuries occur in 8% of patients with penetrating injury to the neck, and TBI occurs in 2.8% of blunt chest trauma deaths.[6] In people with blunt trauma who do reach a hospital alive, reports have found incidences of 2.1% and 5.3%.[2] Another study of blunt chest trauma revealed an incidence of only 0.3%, but a mortality rate of 67% (possibly due in part to associated injuries).[6] The incidence of iatrogenic TBI (that caused by medical procedures) is rising, and the risk may be higher for women and the elderly.[30] TBI results about once every 20,000 times someone is intubated through the mouth, but when intubation is performed emergently, the incidence may be as high as 15%.[30]
The death rate (mortality) for people who reach a hospital alive was estimated at 30% in 1966;[2] more recent estimates place this number at 9%.[15] The number of people reaching a hospital alive has increased, perhaps due to improved prehospital care or specialized treatment centers.[14] Of those who reach the hospital alive but then die, most do so within the first two hours of arrival.[17] The sooner a TBI is diagnosed, the higher the mortality rate; this is likely due to other accompanying injuries that prove fatal.[15]
Accompanying injuries often play a key role in the outcome.[14] Injuries that may accompany TBI include pulmonary contusion and laceration; and fractures of the sternum, ribs and clavicles.[2] Spinal cord injury, facial trauma, traumatic aortic injury, injuries to the abdomen, lung, and head are present in 40–100%.[9] The most common accompanying injury is esophageal injury, which occurs in as many as 43% of the penetrating injuries to the neck that cause tracheal injury.[6]
Most people with TBI who die do so within minutes of the injury, due to complications such as pneumothorax and insufficient airway and to other injuries that occurred at the same time.[5] Most late deaths that occur in TBI are attributed to sepsis or multi-organ dysfunction syndrome.[2] If the condition is not recognized and treated early, serious complications are more likely occur; for example,[29] pneumonia and bronchiectasis may occur as late complications.[3] Years can pass before the condition is recognized.[17][29] Some TBIs are so small that they do not have significant clinical manifestations; they may never be noticed or diagnosed and may heal without intervention.[29]
If granulation tissue grows over the injured site, it can cause a stenosis, a narrowing of the airway, after a week to a month.[4] The granulation tissue must be surgically excised.[26] Delayed diagnosis of a bronchial rupture increases risk of infection and lengthens hospital stay.[28] People with a narrowed airway may suffer dyspnea, coughing, wheezing, respiratory infections, and difficulty with clearing secretions.[14] If the bronchiole is completely obstructed, atelectasis occurs: the alveoli of the lung collapse.[4] Lung tissue distal to a completely obstructed bronchiole often does not become infected because it is filled with mucus; this tissue remains functional.[15] When the secretions are removed, the lung is commonly able to function almost normally.[29] However, infection is common in lungs distal to a stenosis,[15] infected lung tissue distal to a stricture can be damaged, and wheezing and coughing may develop due to the narrowing.[13] In addition to pneumonia, the stenosis may cause bronchiectasis, in which bronchi are dilated, to develop.[15] Even after an airway with a stricture is widened back out, the resulting loss of lung function may remain.[15]
Complications may also occur with treatment; for example a granuloma can form at the suture site.[2] Also, the sutured wound can tear again, as occurs when there is excessive pressure in the airways from ventilation.[2] However, for people who do receive surgery soon after the injury to repair the lesion, outcome is usually good; the long-term outcome is good for over 90% of people who have tracheobronchial tears surgically repaired early in treatment.[14] Even when surgery is performed years after the injury, the outlook is good, with low rates of death and disability and good chances of preserving lung function.[29]
Treatment of TBI varies based on the location and severity of injury and whether the patient is stable or having trouble breathing,[2] but ensuring that the airway is patent so that the patient can breathe is always of paramount importance.[14] Ensuring an open airway and adequate ventilation may be difficult in people with TBI.[3] Intubation, one method to secure the airway, can be used to bypass the tear in the airway in order to send air to the lungs.[3] If necessary, a tube can be placed into the uninjured bronchus, and a single lung can be ventilated.[3] If there is a penetrating injury to the neck through which air is escaping, the patient may be intubated through the wound.[14] Multiple unsuccessful attempts to intubate may threaten the airway, so techniques that allow healthcare providers to visualize the airway may be used to facilitate intubation.[14] Clinicians can visualize the airway with a bronchoscope, and a fiberoptic endotracheal tube can also be used.[14] If the upper trachea is injured, an incision can be made in the trachea (tracheostomy) or the cricothyroid membrane (cricothyroidotomy) in order to ensure an open airway.[6] However, cricothyroidotomy may not be useful if the trachea is torn distal to (below) the site of the artificial airway.[14] Tracheostomy is used sparingly because it can cause complications such as infections and narrowing of the trachea and larynx.[26] When it is impossible to establish a sufficient airway, or when complicated surgery must be performed, cardiopulmonary bypass may be used—blood is pumped out of the body, oxygenated by a machine, and pumped back in.[26] If a pneumothorax occurs, a chest tube may be inserted into the pleural cavity to remove the air.[19]
A left main bronchus laceration, resulting in pneumothorax. Air is evacuated from the chest cavity with a chest tube.
People with TBI are provided with supplemental oxygen and may need mechanical ventilation.[20] Positive end expiratory pressure, ventilation at higher-than-normal pressures, may be helpful in maintaining adequate oxygenation.[3] However, it can increase leakage of air through a tear, and can stress the sutures in a tear that has been surgically repaired; therefore healthcare providers use the lowest possible airway pressures that still maintain oxygenation.[3] Mechanical ventilation can also cause barotrauma to the lung when high pressure is required to ventilate the patient.[3] Techniques such as pulmonary toilet (removal of secretions), fluid management, and treatment of pneumonia are employed to improve pulmonary compliance (the elasticity of the lungs).[26]
While TBI may be managed without surgery, surgical repair of the tear is considered standard in the treatment of most TBI.[3][27] It is required if a tear interferes with ventilation; if mediastinitis (inflammation of the tissues in the mid-chest) occurs; or if subcutaneous or mediastinal emphysema progresses rapidly;[3] or if air leak or large pneumothorax is persistent despite chest tube placement.[19] Other indications for surgery are a tear more than one third the circumference of the airway, tears with loss of tissue, and a need for positive pressure ventilation.[26] Damaged tissue around a rupture (e.g. torn or scarred tissue) may be removed in order to obtain clean edges that can be surgically repaired.[15] Debridement of damaged tissue can shorten the trachea by as much as 50%.[28] Repair of extensive tears can include sewing a flap of tissue taken from the membranes surrounding the heart or lungs (the pericardium and pleura, respectively) over the sutures to protect them.[2] When lung tissue is destroyed as a result of TBI complications, pneumonectomy or lobectomy (removal of a lung or of one lobe, respectively) may be required.[29] Pneumonectomy is avoided whenever possible due to the high rate of death associated with the procedure.[3] Surgery to repair a tear in the tracheobronchial tree can be successful even when it is performed months after the trauma, as can occur if the diagnosis of TBI is delayed.[3] When a stenosis (narrowing) in the airways results after delayed diagnosis, surgery is similar to that performed after early diagnosis: the stenotic section is removed and the cut airway is repaired.[28]
Vehicle occupants who wear seat belts have a lower incidence of tracheobronchial injury after a motor vehicle accident.[25] However if the strap is situated across the front of the neck (instead of the chest), this increases the risk of tracheal injury.[14] Design of medical instruments can be modified to prevent iatrogenic TBI, and medical practitioners can use techniques that reduce the risk of injury with procedures such as tracheostomy.[22]