Patients with blunt ascending aortic injuries rarely survive transportation to the hospital. Operative repair usually requires use of total cardiopulmonary bypass and insertion of a Dacron graft. If the sinus of Valsalva or the aortic valve is involved, aortic root with reimplantation of the coronary ostia may be required.49
Penetrating injuries involving the ascending aorta are uncommon (see Figs. 26-12 and 26-13). Survival rates approach 50% for patients having stable vital signs on arrival at a trauma center.59 When in extremis, these injuries are found during an exploration through a left anterolateral or clamshell incision. For urgent explorations these injuries can be approached via a median sternotomy. Although primary repair of anterior lacerations can be accomplished without adjuncts, cardiopulmonary bypass may be required if there is an additional posterior injury. The possibility of a peripheral bullet embolus must be considered in these patients.
When approaching an injury to the transverse aortic arch, extension of the median sternotomy to the neck is necessary to obtain exposure of the arch and brachiocephalic branches. If necessary, exposure can be further enhanced by division of the innominate vein. When hemorrhage limits exposure, the use of balloon tamponade is useful as a temporary measure. Simple lacerations may be repaired by lateral aortorrhaphy. With difficult lesions, such as posterior lacerations or those with concomitant pulmonary artery injuries, cardiopulmonary bypass may be required. As with injuries to the ascending thoracic aorta, survival rates approaching 50% are possible.59
Median sternotomy is employed for access to innominate artery injuries. A right cervical extension can be used when necessary. Blunt injuries typically involve the proximal innominate artery (Figs. 26-16 and 26-17) and, therefore, actually represent aortic injuries and require obtaining proximal control at the transverse aortic arch. In contrast, penetrating injuries of the innominate artery may occur throughout its course. Exposure is enhanced by division of the innominate vein.
Plain chest x-ray of a patient with a blunt injury of the innominate artery. Note that the hematoma is at the thoracic outlet rather than the aortic isthmus.
Aortogram of the patient in Fig. 26-15 demonstrating the tear involving the proximal innominate artery.
In selected patients with penetrating injuries, a running lateral arteriorrhaphy using 4-0 polypropylene suture is occasionally possible. More often, injuries to the innominate artery require repair via the bypass exclusion technique developed by Mattox et al (Fig. 26-18).60 Bypass grafting is performed from the ascending aorta to the distal innominate artery (immediately proximal to the bifurcation of the subclavian and right carotid arteries) using a Dacron tube graft. The area of injury is avoided until the areas for bypass insertion are exposed. A vascular clamp is placed proximal to the bifurcation of the innominate artery to allow collateral flow to the brain via the right subclavian and carotid arteries. Hypothermia, systemic anticoagulation, and shunting are not required. After the bypass is completed, the area of hematoma is entered, and the injury controlled with a partial occluding clamp (usually at the origin of the innominate artery), and oversewn. If concomitantly injured or previously divided, the innominate vein may be ligated with impunity.
Drawing depicting the bypass exclusion technique employed in patients with innominate artery injuries. (Copyright © Baylor College of Medicine, 1981.)
The treatment of an iatrogenic tracheal-innominate artery fistula deserves special consideration. These fistulae are usually caused by the concave surface of a low riding tracheostomy tube eroding into the innominate artery.
Arteriography during a “stable interval” is generally not helpful in making a precise diagnosis; instead, the possibility of a tracheal-innominate fistula should be evaluated via bronchoscopy. A chest CT, looking for a violated plane between the trachea and innominate artery, can be obtained. With massive bleeding, control is achieved by performing orotracheal intubation, removing the tracheostomy tube, and directly tamponading the bleeding digitally through the tracheotomy during transport to the operating room. Through a median sternotomy with a right neck extension, the innominate artery is ligated at its origin from the aorta and distally just before the division into the carotid and subclavian arteries. Despite a greater than 25% chance of neurologic complications, no attempt should be made at revascularization, since delayed graft infection with its dreaded associated complications inevitably occur. There are sporadic descriptions of the use of endografts to temporize these critical patients.
Descending Thoracic Aorta
Prehospital mortality is 85% for patients with blunt injury to the descending thoracic aorta.61 In patients who arrive at the hospital alive, the majority of blunt aortic injuries are located at the isthmus (Fig. 26-19). Patients presenting with an injury in the mid-descending thoracic aorta or distally, near the diaphragm, are far less common (Fig. 26-20). Multiple blunt aortic injuries are rare, but may occur.
Aortogram demonstrating the classic intimal tear and traumatic pseudoaneurysm of the descending thoracic aorta.
Aortogram in a patient with blunt chest trauma demonstrating an intimal tear of the descending thoracic aorta at the diaphragm.
Injury to the descending thoracic aorta is often accompanied by other organ injuries. If the patient has a stable thoracic hematoma and concomitant abdominal injury, laparotomy should be the initial procedure. For the patient with a rapidly expanding hematoma, however, repair of the thoracic injury should be the primary therapeutic goal. Sequencing is driven by the lesion that is most likely to cause exsanguination.
The current standard technique of repair involves clamping and direct reconstruction (Table 26-8). Three commonly employed adjuncts to this approach are (1) pharmacological agents, (2) temporary, passive bypass shunts, and (3) pump assisted atriofemoral bypass or cardiopulmonary bypass. In the latter approach, two options exist: (1) traditional pump bypass, which requires heparin, and (2) use of centrifugal (heparinless) pump circuits. All three of these adjunctive approaches to the clamp-and-repair principle should be in the armamentarium of the surgeon, who must choose the approach most appropriate to the specific clinical situation.
TABLE 26-8Current Therapeutic Approaches to the Management of Thoracic Aortic Injuries ||Download (.pdf) TABLE 26-8 Current Therapeutic Approaches to the Management of Thoracic Aortic Injuries
Surgical (clamp and direct reconstruction with or without an interposition graft)
Pharmacological control of proximal hypertension
Passive bypass shunts
Traditional cardiopulmonary bypass (with total body heparinization)
Atrio-femoral bypass using centrifugal pump (with/without heparinization)
Nonoperative and/or purposeful delay of operation (with pharmacological treatment and close radiologic surveillance)
Injury to the descending thoracic aorta is approached via a posterolateral thoracotomy through the fourth intercostal space. The injury usually originates at the medial aspect of the aorta at the level of the ligamentum arteriosum; however, one must take care to avoid missing a second injury (usually at the level of the diaphragm).
The initial objective is proximal control. Therefore, the transverse aortic arch is exposed, and umbilical tapes are passed around the arch between the left carotid and subclavian arteries. Similarly, the subclavian artery is encircled with umbilical tape. Care should be taken to avoid injuring the left recurrent laryngeal nerve, though this is often difficult to visualize in the hematoma. If it is suspected that the tear extends to the aortic arch or ascending aorta, cardiopulmonary bypass should be available in the operating room. If the patient has had previous coronary artery bypass surgery with use of the left internal mammary artery as a conduit, repair may require full cardiopulmonary bypass to protect the heart during repair.
Vascular clamps are applied to three locations: proximal aorta, distal aorta, and left subclavian artery. Close communication between anesthesiologist and surgeon is essential to maintain stability of hemodynamic parameters before, during, and after clamping. The use of vasodilators prevents cardiac strain. The hematoma is entered, and back bleeding from intercostal arteries is controlled. Care is taken to avoid indiscriminate ligation of intercostal vessels; only those required for adequate repair of the aorta should be ligated. After defining the injury, the clamps are moved closer, allowing maximal collateral flow. The proximal and distal ends of the aorta are completely transected and dissected away from the esophagus, allowing full-thickness suturing, while minimizing the risk of a secondary aortoesophageal fistula. The injury is then repaired by either end-to-end anastomosis or graft interposition. Graft interposition is utilized in more than 85% of reported cases. Prior to clamp removal, volumes of fluid (blood and crystalloid) may need to be administered to avoid clamp release hypotension.
For patients undergoing repair of blunt descending thoracic aortic injury, the reported mortality ranges from 0 to 55% (average 13%).53,62 As expected in these victims of major blunt trauma, the mortality is primarily associated with multisystem trauma and is ultimately due to head injury, infection, respiratory insufficiency, and renal insufficiency.
The most feared complication of great vessel injury is paraplegia. Utilization of protective adjuncts when repairing descending thoracic aortic injuries remains a topic of considerable debate. There have been proponents of the use of passive shunts and cardiopulmonary bypass, with and without heparinization. The mortality rate with the use of routine cardiopulmonary bypass is probably secondary to the massive cerebral, abdominal, or fracture site hemorrhage that occurs in these victims of multisystem trauma. Recent experience using centrifugal pumps for left heart bypass without heparinization has provided an attractive alternative for those who wish to use controlled flow bypass without systemic anticoagulation. This also allows unloading of the left heart during clamping, which can be helpful in patients with cardiac disease. The use of bypass systems, however, is not without complications. In the trauma patient, difficulty inserting cannulae may occur due to patient position, the presence of periaortic hematoma, and time constraints imposed by an expanding, pulsatile, uncontrolled hematoma. Intraoperative and postoperative complications include bleeding at the cannulation sites and false aneurysm formation.
Use of simple clamp-and-repair for injuries to the descending thoracic aorta (without the use of systemic anticoagulation or shunts) is a technique that continues to be used with excellent results. Sweeney, in 1992, reported using simple clamp-repair in 75 patients, only one of whom developed postoperative paraplegia.63
Ultimately, the determinants of postoperative paraplegia are multifactorial (Table 26-9); therefore the precise causes cannot be precisely identified in an individual patient. Paraplegia has been associated with perioperative hypotension, injury or ligation of the intercostal arteries, and duration of clamp occlusion during repair.64 However, there are reports of patients surviving surgery without paraplegia, despite having long segments of aorta replaced, as well as ligation of multiple intercostal arteries.
TABLE 26-9Possible Contributing Factors Related to the Multifactorial Development of Paraplegia Following Operations for Thoracic Great Vessel Injury ||Download (.pdf) TABLE 26-9 Possible Contributing Factors Related to the Multifactorial Development of Paraplegia Following Operations for Thoracic Great Vessel Injury
|Injury factors ||Direct segmental artery injury |
|Direct radicular artery injury |
|Direct spinal artery injury |
|Spinal cord contusion/concussion |
|Spinal canal compartment syndrome |
|Severity of aortic injury |
|Specific anatomic location of aortic injury |
|Patient factors ||Location of arteri radicularis magna |
|Continuity of anterior spinal artery |
|Caliber of individual segmental radicular arteries |
|Congenital narrowing of spinal canal |
|(?) Increased blood alcohol levels |
|Total perispinal collateral blood supply |
|Operative Factors ||Required occlusion of segmental arteries |
|Pharmacological agents required |
|(?) Declamping hypotension |
|(?) Required cross clamp times (in combination with anatomic and injury factors cited in this table); length of required interposition grafting or required exclusion |
|(?) Level of systolic (or mean) proximal aortic blood pressure |
|(?) Level of distal aortic mean blood pressure |
|(?) “Flow” in the aorta distal to clamp |
|Postoperative factors ||Progressive swelling of the spinal cord |
|Spinal canal compartment syndrome |
|Delayed or secondary occlusion of injured or contused segmental, radicular, or spinal arteries |
|Pharmacological induced spasm of spinal cord nutrient arteries |
The length of cross-clamp time does not directly correlate with occurrence of paraplegia. A cross-clamp time less than 30 minutes has been argued to provide a safe margin against paraplegia, and shunting techniques have been recommended when longer cross-clamp times are necessary.64 The use of a shunt, however, does not offer protection for the area of the spinal cord supplied by the arteries between the clamps. Furthermore, patients requiring longer clamp time or interposition grafts have more extensive injuries than those requiring shorter clamp times or end-to-end anastomoses. Thus, it is likely that an increased incidence of paraplegia associated with longer clamp times is secondary to more extensive disruption of intercostal arteries and other flow to the anterior spinal artery caused by the original injury.
Various monitoring techniques are available to assess the effect of aortic occlusion on the spinal cord, including the measurement of somatosensory and motor-evoked potentials. Although correlation appears to exist with loss of somatosensory-evoked potentials, duration of loss of conduction, and postoperative paraplegia, the use of this modality is not common to all trauma centers. The interpretation of results is still being debated, and actual positive applicability requires further delineation. Regardless of the technique used, paraplegia occurs in approximately 10% of these patients (range 0–22%).53,62 No prospective, randomized trial has identified the superiority of any single method. Therefore, the choice of operative technique does not infer legal liability when paraplegia occurs.
Even with potential selection bias in favor of endografts, the low mortality and almost nonexistent paraplegia rate make the use of endografting very compelling. The reported complications of graft migration, enfolding, compression, occlusion of the subclavian artery, and problems at the entry site are all technical and engineering challenges that may potentially be solved by new commercial devices.
Subclavian vascular injuries can involve any combination of the following regions: intrathoracic, thoracic outlet, cervical (zone 1), and axillary/upper extremity. Preoperative arteriography allows for planning appropriate incision(s) to obtain adequate exposure and control.
A cervical extension of the median sternotomy is employed for exposure of right-sided subclavian injuries. For left subclavian artery injuries, proximal control is obtained through an anterolateral thoracotomy (above the nipple, second or third intercostal space), while a separate supraclavicular incision provides distal control. Although these incisions can be connected to create a formal “book” thoracotomy, this results in a high incidence of postoperative “causalgia” type neurologic complications and its use should be limited to highly selected left-sided subclavian artery injuries. The endovascular placement of a balloon for proximal control may obviate the need for a thoracic incision.
In obtaining exposure, it is important to avoid injuring the phrenic nerve (anterior to the scalenus anticus muscle). In subclavian vascular trauma, a high associated rate of brachial plexus injury is seen; thus, documentation of preoperative neurologic status is important.
In most instances, repair requires either lateral arteriorrhaphy or graft interposition. It is unusual that an end-to-end anastomosis can be employed. Associated injuries to the lung should be managed with stapled wedge resection or pulmonary tractotomy.58 One pitfall in subclavian injuries is failure to anticipate the exposure necessary for proximal control. When approaching the subclavian/axillary artery via the deltopectoral groove without proximal control, exsanguination may occur. Resection of the clavicle may aid in proximal control. Combination supra- and infraclavicular incisions may be used to avoid the morbidity of clavicular resection. A mortality rate of 4.7% for patients with subclavian artery injuries has been reported, but death is often due to associated injuries.
With the density of vascular structures in the thoracic outlet and the morbidity of the thoracic incisions needed for proximal control, it would seem that endovascular techniques to address subclavian artery injuries would be advantageous. There are increasing numbers of reports of endovascular approaches to the subclavian artery in both stable and unstable patients.65 If diagnostic arteriography is performed in the OR, a balloon catheter can be left in the proximal left subclavian artery for proximal control. Even in a hypotensive patient, Gilani’s description of using the snare technique to cross even totally transected subclavian arteries often can permit an expeditious endovascular repair.66 This is most applicable in centers where acute vascular imaging for trauma is available in the operating room, and arteriography/covered stent placement can be performed by the trauma/cardiovascular surgeon.
With a vascular imaging capable bed, a C-arm with vascular capability, and a simplified set of endovascular tools, even an unstable trauma patient can be brought to the operating room where resuscitation, imaging, diagnosis and control of bleeding with both open and endovascular techniques can occur.
The operative approach for injuries of the left carotid artery mirrors that used for an innominate artery injury: a median sternotomy with a left cervical extension added, when necessary. As with other great vessel injuries, neither shunts nor pumps are employed. With transection at the left carotid origin, bypass graft repair is preferred over end-to-end anastomosis. Intraoperatively, a carotid shunt can be used to temporize these until resources/assistants can be gathered in the OR.
The intrapericardial pulmonary arteries are approached via median sternotomy. Minimal dissection is needed to expose the main and proximal left pulmonary arteries.67 Exposure of the intrapericardial right pulmonary artery is achieved by dissecting between the superior vena cava and ascending aorta. Although anterior injuries can be repaired primarily without adjuncts, repair of a posterior injury usually requires cardiopulmonary bypass. Mortality rates for injury to the central pulmonary arteries or veins are greater than 70%.32
Distal pulmonary artery injuries present with massive hemothorax and are repaired through an ipsilateral posterolateral thoracotomy. When there is a major hilar injury, rapid pneumonectomy may be a lifesaving maneuver. The use of a hilar clamp or a large tamponading balloon catheter may control exsanguinating hemorrhage.
The internal mammary artery in a young patient is capable of flows in excess of 300 mL/min. Injuries to this artery can produce extensive hemothorax or even pericardial tamponade, simulating a cardiac injury. Such injuries are usually serendipitously discovered at the time of thoracotomy for suspected great vessel or heart injury.
Persistent hemothorax can be caused by simple lacerations of the intercostal arteries. Because of difficulty in exposure, precise ligature can be difficult. At times, control must be achieved by circumferential ligatures around the rib on either side of the intercostal vessel injury.