Trauma to the Great Vessels

	INTRODUCTION

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	TRAUMATIC AORTIC DISRUPTION

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Epidemiology

Blunt aortic injury remains the second leading cause of death from vehicular trauma, representing 15% of motor vehicle–caused deaths.^11–13 Death occurs at the accident scene in 75 to 90% of cases.^1,11–14 Approximately 8% of patients survive more than 4 hours.¹ Those who survive aortic transection typically have two other associated serious injuries, while those who die have four or more serious injuries.^1,13 According to Parmley’s landmark report published in 1958, 42% of patients with lethal aortic rupture had an associated cardiac injury.¹ The short duration of postaccident survival and the high incidence of fatal associated injuries preclude recovery in most of these patients. Recovery of the select few who survive the first few hours after aortic rupture depends on how they are managed in the hospital.

The true incidence of blunt aortic rupture is not known, but based on autopsy series aortic rupture occurs in 12 to 23% of deaths from blunt trauma.^1,15–18 According to national vehicular crash databases in the United States and the United Kingdom, the incidence of thoracic aortic injury among motor vehicle crash victims is 1.5% and 1.9%, respectively.¹⁹ Seventy-three to 92% of all traumatic aortic disruptions involve motor vehicle drivers, passengers, or pedestrians hit by vehicles.^{1,13,15,17,18} Alcohol or other substance abuse is involved in over 40% of these motor vehicle accidents.^15,17 Ejection from a vehicle doubles the risk of aortic rupture, and seat belt restraint reduces mortality risk by a factor of four.¹⁵ Data confirm that active restraints (seat belts) are more effective than passive restraints (air bags) in preventing traumatic aortic injury.²⁰ Aortic rupture of both the ascending and descending aorta has been attributed to the deployment of an air bag, in some cases with cars going less than 10 mph.^21–24 The risk of an aortic injury is at least three times higher among unbelted than belted motor vehicle occupants.¹⁹ Frontal and side impact crashes, regardless of the side of impact, have the highest risk.^14,19 Accidental or suicidal falls, crush injuries, airplane accidents, and rare cave-ins are among the other causes of aortic rupture.^{1,13,16,25–27} Falls causing aortic rupture typically occur from heights greater than 3 meters.^1,25,26,28

Seventy to eighty percent of these injuries occur in males with an average age of 36 to 40 years.^7,13,29,30 Seventy-five percent of patients with traumatic aortic rupture who make it to the hospital alive are initially hemodynamically stable,¹³ but up to 50% die prior to definitive surgery.^29,31 Compared to autopsy series, patients who reach the hospital alive have fewer severe associated injuries.^1,12,13,16 Forty to 92% of patients are transferred from a hospital to a level I trauma center.^13,32,33

Table 57-1 lists the frequency of associated injuries from data accrued throughout the 1970s into the late 1990s.^{13,26,34–37} The most robust database was gathered prospectively from 50 trauma centers throughout the United States and Canada (American Association for the Surgery of Trauma [AAST] trial).¹³ Fifty-one percent of patients have an associated closed head injury. Forty-six percent have multiple rib fractures, and 38% have pulmonary contusions. Compared to older autopsy series, which had demonstrated that the majority of patients have associated cardiac contusion, recent data suggest that the incidence is only 4%.¹³ Orthopedic injuries remain common, occurring in 20 to 35% of cases. Mean injury severity score in the AAST trial was 42.1, which is significantly higher than that seen in older retrospective reports, implying that significantly more patients with these types of serious injuries make it to the hospital and are saved in the modern era.¹³

Aortic disruptions occur in all aortic segments including, rarely, the abdominal aorta, but the most common site among patients who survive is at the aortic isthmus (Fig. 57-1). According to autopsy series, 36 to 54% occur at the aortic isthmus, 8 to 27% involve the ascending aorta, 8 to 18% occur in the arch, and 11 to 21% involve the distal descending aorta.^1,16,38,39 Alternatively, surgical series demonstrate that 84 to 97% of ruptures occur at the isthmus, while 3 to 10% occur in the ascending, arch, or distal descending aorta.^{12,13,32,35,36,40–42} Among patients who survive, it is evident that the periadventitial tissues around the isthmus provide some protection against free rupture that allows for short-term survival and transfer to a hospital. The aorta is typically transected in a transverse fashion involving all three layers of the aortic wall with the edges often separated by several centimeters^1,16 (Fig. 57-2). Non-circumferential and partial aortic wall disruptions do occur and can vary from only a few millimeters to several centimeters.^1,16,43,44 Spiral lacerations or longitudinal extensions are uncommon. Intramural hematomas and focal dissections occur with partialthickness disruptions but not transections.¹ Partial tears tend to occur posteriorly, involving the intima and media. Aortic wall structure at and around the transection does not differ from nearby uninvolved aorta, and atherosclerotic disease is generally not present.^1,15,16 The aortic adventitia provides the majority of its tensile strength, but there is no evidence to suggest that the adventitia at the aortic isthmus is any weaker than any other part of the aorta.^45,46

View larger version (26K): [in this window] [in a new window]   Figure 57-1 Anatomic diagram of the thoracic aorta and itsmobility of the aorta at the isthmus and just distal to it. major branches.

View larger version (117K): [in this window] [in a new window]   Figure 57-2 Photograph of a traumatic aortic disruption at the isthmus. (Reproduced with permission from Strassman.44)

Approximately 2 to 5% of patients with aortic disruptions survive without operation, or even detection, to form chronic false aneurysms.⁴⁹ Little is known of the natural history of these chronic pseudoaneurysms because many go undetected. It is likely that an initial false aneurysm with blood flow partially thromboses and organizes to form a fibrous wall. This wall tends to calcify.^49–51 It can evolve into a saccular or fusiform aneurysm and late expansion or even rupture can occur. Ninety percent involve the aortic isthmus, again presumably reflective of the inherent protection afforded to this area by mediastinal periadventitial tissues around the isthmus.^52–54 The patients who develop chronic pseudoaneurysms have fewer associated injuries at the time of the traumatic event.^52–54 In fact, 35% have no other injuries, and 50% have only one.⁵⁰

Pathogenesis of Blunt Aortic Injury

Despite extensive investigation, analysis, and debate, no consensus or unified understanding of the pathogenesis of aortic transection has emerged. Popular opinion has employed the "whiplash" theory posing that a combination of traction, torsion, shear, bending, and bursting forces secondary to differential deceleration of tissues within the mediastinum cause an appropriate stress to rupture the aorta at specific sites—the isthmus being the most common.^{15,45,46,55–62} The ligamentum arteriosum, the left main stem bronchus, and the paired intercostal arteries limit the Experiments have suggested that the aorta can be displaced in a longitudinal (cranial or caudal) direction sufficient to cause traction tears at the isthmus.^57,59 It has also been apparently recognized that deceleration forces can reach several hundred times the force of gravity, producing injury without any direct impact on the chest.^55,56 Alternatively, a "shoveling mechanism" has been postulated to explain cranially directed traction stresses in drivers and front seat passengers in motor vehicle accidents.⁶³

Contrarily, Crass and associates argue that the forces of differential deceleration, torsion, or hydrostatics alone have inadequate magnitude in vehicular accidents to result in aortic tearing given the inherent properties of the aorta.^64–66 Several studies have demonstrated that the gravitational forces of vehicular trauma do not approach the tensile strength of the aorta. Oppenheim and Zehnder showed that a normal aorta can withstand a 2000-mm Hg pressure before bursting.^67,68 Crass proposed a new mechanism he coined "the osseous pinch" based on thoracic compression that he tested in the laboratory. The hypothesis was that anterior thoracic osseous structures (manubrium, first rib, and clavicular heads) rotate posteriorly and inferiorly about the axes of the posterior rib attachments. When the force is large enough these anterior bony structures impact the vertebral column, and the portion of the aorta fixed overlying the spine (the isthmus and proximal descending aorta) is pinched between the bones. This causes a direct shearing of the aorta. Crass’ group demonstrated in a canine model that a blunt force as small as 20,000 N transected the intima and media of the aorta.⁶⁴ In comparison, a 38-mph collision produces a force of 198,000 N in a normal-sized adult.⁶⁴ Some clinical data support the osseous pinch mechanism.⁶⁹

Other forces may be important in ascending aortic injuries. The anterior location of the ascending aorta and the weight and ease of displacement of the heart downward and to the left facilitate traction stress on and above the aortic root.⁵⁹ Hyperextension of the spine and consequent shearing forces may play a role in the distal descending aorta.⁶⁴

It is likely that the majority of victims of motor vehicle accidents experience some combination of differential deceleration forces and thoracic compression forces, causing aortic disruption.⁷⁰ It is clear that many different mechanisms of trauma (i.e., front impact, side impact, falls, crushing injury, and blasts) have caused aortic disruption. Each of these situations affords different circumstances and different forces, making it difficult to isolate a specific mechanism.

Natural History

The natural history of aortic transection in a given patient is dependent on many factors, not the least of which is how quickly a diagnosis is made. Our understanding of survival rates is based on data drawn from autopsy series and operative series. Autopsy studies tend to underestimate the rate of long-term survival, while operative studies tend to overestimate it. Parmley and associates observed that 86% of patients die at the scene, and 11% survive longer than 6 hours.¹ The only survivors in the Parmley series were in fact operated on. Mortality rates in most recent surgical series range from 0 to 50% variably dependent on the size of the series, although the attributable-mortality rates are not clearly defined.^{12,13,25,29–32,71–75}

Several groups have reported selective nonoperative or delayed operative management with aggressive anti-impulse therapy (beta-blockade) in patients deemed unsuitable candidates for surgery or in cases of apparent minimal aortic injury.^{8,29,30,71,76–82} Those initially unsuitable for surgery in these series were elderly and morbid or had too severe associated injuries to tolerate operative repair and thus underwent delayed repair. When surgery has been delayed for stabilization of other injuries, the interim mortality rate prior to definitive repair appears to be between 30 and 50%, with the majority of deaths being attributed to head trauma or other complications.^79,81,83 Delays of up to 4 months prior to repair have been reported.^78,84–90 We conclude that aortic transection can be treated nonoperatively or with operative delay in carefully selected patients with severe associated injuries or significant comorbidities.

Numerous anecdotal reports confirm long-term survival in self-selected patients who were not diagnosed at the time of injury.^{51,54,91–96} A review of the literature by Finkelmeier and colleagues demonstrated that among survivors like these, over 70% survive more than 5 years from the time of the injury.⁵⁰ The inherent survival bias of this group of patients is evident, but it does confirm that some patients can survive long-term without surgery. In Finkelmeier’s review, the 60 patients who did not have operations for chronic traumatic aortic aneurysms had 5-year, 10-year, and 20-year survival rates of 71, 66, and 62%, respectively. Ninety-four percent of chronic traumatic aortic aneurysms were located at the aortic isthmus. Rarely, the arch and ascending aorta were involved.⁵⁰

Clinical Presentation

The presentation of aortic rupture is protean. Aortic rupture itself manifests in the form of specific signs or symptoms in less than 50% of cases.^18,97–100 Patients may develop dyspnea, back pain, or differential hypertension in the lower as compared to the upper extremities.^{66,97,98,100–104} Aortic injuries are more commonly identified in the backdrop of a multi-trauma patient, and the diagnosis is made only if it is suspected. Consequently, aortic injury can easily be missed if patients are not appropriately screened. Identifying the character and mechanism of trauma is the critical first step in making the diagnosis of aortic disruption. If speeds or distances fallen suggest severe impact or significant deceleration forces, the possibility of aortic rupture exists, and it should be ruled out. In all cases of motor vehicle crashes, falls, blasts, crush injuries, or other deceleration forces, aortic rupture should be considered.^{8,11,25,77,105–108}

The initial management of a multitrauma patient is uniform regardless of whether aortic disruption is suspected. The patient’s airway, breathing, and circulation are addressed first. Primary and secondary surveys are completed, and appropriate venous access is obtained concomitant with initial laboratory and radiographic studies. Priority of injury is based largely on the acute lethal potential of an injury. Exsanguinating hemorrhage in any body compartment, perforated viscus, or central neurologic injury take the usual priority. Most patients with aortic disruption also have one or more bone fractures. Fractures should be stabilized but not definitively treated prior to excluding the diagnosis or treating an aortic rupture. There are often clues evident in the initial evaluation of a trauma patient that suggest aortic disruption (Table 57-2). In the majority of trauma cases, a supine chest radiograph is obtained as part of the initial evaluation, and the constellation of grossly widened mediastinum, hemothorax, and transient hemodynamic instability upon arrival appear to be predictive of early in-hospital death from blunt thoracic aortic injury.¹⁰⁹

Chest radiograph

A standard supine anteroposterior chest x-ray does not provide the diagnostic sensitivity to rule out aortic injury.^8,10,25,110 Nine to 40% of patients with aortic rupture have chest x-ray findings interpreted as normal at the time of initial evaluation in major trauma centers.^{8,10,25,99,110–117} At least fifteen distinct signs on a standard anteroposterior chest x-ray are associated with blunt aortic injury or rupture (Table 57-3).¹¹⁰ Unfortunately, none of these signs are sufficiently sensitive, specific, or predictive of aortic rupture. In a series of 188 consecutively evaluated multi-trauma patients, 10 blunt aortic injuries were identified, and the sensitivities of these plain radiographic findings ranged from 0 to 90%.¹¹⁰ The specificities ranged from 6 to 93%.¹¹⁰ In lieu of obtaining an upright chest x-ray which is typically not possible in a multitrauma patient, reverse Trendelenburg 45° anteroposterior chest x-rays have been suggested to be more accurate than supine films at evaluating the mediastinum.¹¹⁸

Volumetric helical or spiral computed tomography (CT) has become the standard screening tool to rule out aortic disruption, with sensitivity and negative predictive values of 100%.^{8,10,25,116,119–121} The technology was introduced in the early 1990s, and since that time it has become the screening modality used in most institutions.^{8–10,25,28,76,88,112,116,117,119,121–132} Its advantages over other sophisticated imaging techniques (e.g., transesophageal echocardiography, magnetic resonance imaging, or aortography) include its wide availability, its speed, its sensitivity, its reasonable cost, and its ease of interpretation.

Nonionic contrast media is typically used, and 50 to 150 images with slice thicknesses of 3 to 5 mm are acquired in less than 1.5 minutes.¹⁰ Normal aorta is depicted with homogeneous enhancement. Several findings are indicative of aortic disruption, including wall thickening, extravasation of contrast, filling defects, para-aortic hematoma, intimal flaps, mural thrombi, pseudoaneurysm, or pseudocoarctation (Fig. 57-3).¹⁰

View larger version (94K): [in this window] [in a new window]   Figure 57-3 Helical computed tomography scan of the chest in a 30-year-old male after a high-speed motor vehicle accident. Slice A demonstrates circumferential disruption of the aortic wall just beyond the left subclavian. Slice B demonstrates an intimal flap in the proximal descending thoracic aorta. Both slices demonstrate periaortic hematoma.

Transesophageal echocardiography

The development of multiplanar transesophageal echocardiography (TEE) has revolutionized cardiothoracic surgery such that its use is now necessary to plan and facilitate intraoperative management in most cardiothoracic surgical procedures. Its use in cases of aortic transection is no exception. TEE reliably images the entire thoracic aorta except the distal ascending aorta and proximal aortic arch, which can be obscured by tracheal and bronchial air artifact. Contrarily, transthoracic echocardiography cannot accurately evaluate the descending aorta. The accuracy of TEE for diagnosing aortic injury is operator-dependent. Some report its sensitivity and specificity to be approaching 100%,^120,133,134 while others demonstrate a sensitivity and specificity as low as 63 and 84%, respectively.¹³⁵ A recent prospective comparison of the use of helical CT to TEE in evaluating blunt aortic injury in 110 consecutive patients demonstrated a sensitivity, specificity, negative predictive value, and positive predictive value of 93, 100, 99, and 100%, respectively, for TEE compared to 73, 100, 95, and 100% for helical CT.¹²⁰

A major advantage of TEE is its portability. The hemodynamically unstable patient who is taken to the operating room immediately can undergo exploratory laparotomy or other procedures while simultaneously being evaluated by TEE. The major disadvantage of TEE is that it requires an experienced operator. The risk of TEE is low.^120,133 It is contraindicated in cases of concomitant cervical spine, oropharyngeal, esophageal, or severe maxillofacial injury, or in patients with esophageal or pharyngeal lesions that would impede or complicate passage of the probe.

Multiplanar TEE probes permit acquisition of cross-sectional images at different angles along a single rotational axis (Fig. 57-4). The typical 5- or 7-MHz transducer permits adequate resolution of structures as small as 1 to 2 mm.

View larger version (83K): [in this window] [in a new window]   Figure 57-4 Transesophageal echocardiographic cross-sectional image in the shortaxis with color flow Doppler depicting transection of the aortic isthmus. The transection appears as two distinct lumens, the "double-barrel"sign, and there is flow between the separated aorta. (Courtesy of B. Milas, University of Pennsylvania.)

The most common feature of aortic injury identified by TEE is a mural flap. Thickening of the vessel wall can represent a contained rupture or a mural thrombus. Color Doppler flow mapping can demonstrate alterations in flow patterns including turbulence at the site of injury. Chronic atheromatous changes can produce false-positive signs of intimal disruption. When aortic disruption is suspected on TEE there usually is a surrounding mediastinal hematoma, and its absence should prompt skepticism of the diagnosis.

Aortography

Aortography is the imaging modality by which all other techniques have been previously compared for evaluation of aortic injury. Its technique and role in evaluating aortic injuries or other vascular injuries was established long before any of the other sophisticated imaging methodologies. In experienced hands its sensitivity and specificity both approach 100%.¹³⁶ Its major disadvantages are that its use requires a highly skilled interventional radiology team, and it is time consuming, rendering the patient inaccessible during the time of the study. Rates of exsanguination and death of up to 10% in the angiography suite have been reported.^104,137,138 Complication rates attributed directly to aortography are low. Contrast reactions, renal insufficiency secondary to contrast material and groin hematomas or pseudoaneurysms do occur. In the pre–helical CT era, 85 to 95% of aortograms were negative, calling into question the cost- and time-effectiveness of the technique.^{28,98,104,131,136,138} False-positive studies are usually attributed to atheromata or ductal diverticula. Though now only rarely used for diagnosis, aortography is becoming routine to facilitate endovascular stent grafting (EVSG) for traumatic disruptions (Fig. 57-5).

View larger version (112K): [in this window] [in a new window]   Figure 57-5 Intra-arterial digital subtraction angiogram of an acute traumatic aortic disruption near the isthmus. The left subclavian artery was transposed to the left common carotid artery prior to deployment of a stent graft.

Magnetic resonance angiography

Magnetic resonance angiography provides excellent images of vascular structures, particularly the thoracic aorta, and its utility in the diagnosis and follow-up of complex aortic disease including aortic dissections and aneurysms is firmly established.^139–142 However, its use in the acute trauma patient has not been broadly justified. The time required to attain images and the confining nature of the scanners preclude its use in this patient population. If in the future magnetic resonance data acquisition time decreases and patient accessibility within a scanner increases, there may be a role for magnetic resonance angiography in acute trauma settings. Alternatively, it is reasonable to use magnetic resonance angiography for posttherapeutic surveillance of traumatic aortic injuries, particularly in those patients with minimal aortic injury who are treated nonoperatively.

Patient Assessment

Initial evaluation

Ninety-five percent of patients with aortic disruption have associated injuries, and consequently it is imperative that a comprehensive trauma evaluation occur prior to definitive imaging to rule out aortic injury.^12,13,77 However, the leading cause of death in patients with aortic injury who make it to the hospital remains exsanguinating aortic rupture, which occurs in at least 20% of patients.¹³ Among patients who present hemodynamically stable with aortic injury, 4% die in the hospital of aortic rupture prior to surgical repair.¹³ These data emphasize that a careful, planned, and expeditious team approach is mandatory in order to save as many of these patients as possible. The first steps include primary and secondary physical examinations with control of the airway, respiration, and hemodynamics. Intubation, cardiovascular resuscitation, chest x-ray, insertion of thoracostomy tubes, and identification and stabilization of head injuries take priority. Patients with nonlethal associated injuries who are hemodynamically stable should be diverted toward exclusion of aortic injury, and patients who are unstable require immediate direction toward life-saving operative intervention (e.g., laparotomy or thoracotomy), bypassing all time-consuming tests, in order to achieve the best chance of survival.

After initial trauma evaluation, a head CT should be obtained prior to any planned aortic operation in all patients with signs of an open- or closed-head injury. Relief of intracranial space-occupying lesions takes priority over nonbleeding aortic injuries. Hemodynamically unstable patients with signs of exsanguinating hemorrhage should go directly to the operating room for control of hemorrhage, and TEE should be used to evaluate for aortic injury. Identification of blunt aortic injuries in hemodynamically stable patients should be done in the most efficient manner for a given institution, depending on availability of experienced imaging diagnosticians and equipment, and should be coordinated with the evaluation of other life-threatening injuries. The usual scenario of a hemodynamically stable blunt trauma patient dictates leaving the emergency department to undergo head and abdominopelvic CT scan for identification of closed head injury and intra-abdominal injury. Patients with either an abnormal chest x-ray or a mechanism of injury that poses significant risk of aortic injury (e.g., falls greater than 3 m, motor vehicle crashes of greater than 50 km/h, or pedestrians hit by automobiles) should undergo simultaneous helical chest CT at the time of head and/or abdominopelvic CT. In most institutions, aortography is now reserved for use in patients with equivocal helical CT or TEE results or in patients with complex aortic injuries which cannot be accurately defined by these other imaging techniques. Occasionally thoracoscopy has been used to evaluate traumatic hemothoraces.¹⁴³ However, there is little role for thoracoscopy in the diagnosis of aortic disruption, because in experienced hands, the sensitivity and specificity of intraoperative TEE is so good.

In the preoperative period, patients with aortic injury should receive anti-impulse therapy for control of aortic wall tension and blood pressure.^8,77 Reduction of the change in pressure over the change in time (P/t) reduces wall stress significantly.¹⁴⁴ These measures have been shown to reduce in-hospital aortic rupture rates without adversely affecting the outcome of other injuries.⁸ These control measures should be employed in patients going to the operating room and in patients undergoing delayed aortic repair for the treatment of other life-threatening injuries.

Timing of operation

Immediate aortic repair is recommended once the diagnosis of aortic injury is made in hemodynamically stable patients without severe associated injuries that require emergent laparotomy, craniotomy, or pelvic stabilization. Intracranial bleeding causing mass effect, and significant thoracic, abdominal, pelvic, or retroperitoneal hemorrhage should all be addressed prior to thoracotomy or stent grafting for contained aortic injury.^84,145 Contained aortic injuries should be aggressively managed with anti-impulse therapy if delayed aortic management is planned in order to address other life-threatening injuries. Delayed management may be appropriate in carefully selected patients with severe associated injuries or severe comorbidity.^{29–31,71,79-83,146} Presentation of aortic disruption with ongoing aortic bleeding or signs of impending rupture requires immediate surgical intervention. Aortic injuries should be monitored by TEE during the surgical treatment of intracranial, thoracic, or abdominopelvic injuries. Treatment of all non–life-threatening injuries should be delayed until after definitive aortic repair.

Hemodynamically unstable patients should be taken to the operating room immediately, prior to definitive testing. Laparotomy or even thoracotomy may be required to locate and control ongoing hemorrhage. Patients with instability secondary to associated trauma who require laparotomy or thoracotomy for damage control to establish hemodynamic stability may be better served by subsequent immediate transfer to the intensive care unit for further resuscitation prior to definitive repair of contained aortic rupture until complete resuscitation and hemodynamic stability are achieved. Once stabilized, anti-impulse therapy with short-acting beta-blockade should be instituted and aggressively applied to reduce aortic wall stress.⁸ Determining the optimal extent of delay for definitive aortic repair in patients with severe associated injuries is not clear. In rare cases, particularly extremely comorbid patients, nonoperative management has been extended for long periods of time with acceptable mortality.^82,83

Operative Strategies

Conventional open repair of traumatic aortic disruption via interposition grafting for replacement of the injured segment is safe, effective, and durable. Historically, open repair via thoracotomy is the standard to which all other management strategies must be compared. However, as endovascular strategies for treating abdominal and more recently thoracic aortic pathology have evolved, there is growing enthusiasm for endovascular stent grafting (EVSG) of traumatic disruption because of its relative ease, reduced operative time required, and potentially reduced complication rate compared to conventional open repair. Consequently, but despite a lack of prospective clinical trials, recent trends around the world demonstrate a more liberal use of EVSG for acute traumatic aortic disruption, particularly for complicated cases with severe associated injuries. Retrospective reviews of single institutional experiences have demonstrated favorable short-term outcomes with endovascular strategies; however, the reported series are small, ranging from 5 to 29 cases per report.^{29,30,72,73,80,147–151} Currently there are ongoing clinical trials of the use of new EVSG repair for traumatic aortic disruption, but these trials are not randomizing patients to open repair. An important limitation of the use of EVSG for traumatic transection is that the currently available thoracic aortic stent grafts were designed to treat aneurysmal disease, not traumatic disruption. Unlike aneurysms, aortic transection typically occurs in younger patients (average age 36 to 40 years)^7,29,30,152 with normal-caliber descending aortas in the range of 18 to 24 mm. The currently available stent grafts are not optimally suited for this size thoracic aorta. Consequently, groups have often resorted to the use of homemade or improvised materials that were originally designed for other purposes like extension cuffs of abdominal stent grafts. The long-term durability of these rudimentary, rigged devices or even the newest available devices designed for the thoracic aorta is not known. Despite these limitations, it is becoming clearer that EVSG can safely be used in a significant percentage of trauma patients. In many cases, simply bridging a patient with a stent graft to a more stable, chronic pseudoaneurysm may have an advantage over thoracotomy in a multitrauma patient. Because EVSG techniques continue to evolve and are not uniformly applicable, surgeons treating thoracic aortic disruption must be comfortable with conventional open repair techniques.

Open repair

The technical aspects of repairing aortic disruptions are straightforward. Although no one method of repair of aortic transection has been proven superior, standards are established. There remains some controversy surrounding the issue of spinal cord protection and what means of protection are optimal.^{12,13,32,36,40,42,66,77,86,88,99,108,115,153–161} There are two general perspectives: (1) that "clamp-and-sew" techniques are sufficiently safe, and (2) that some form of lower body perfusion provides added spinal cord and visceral protection against the ischemia of the aortic cross-clamp. Paraplegia has historically occurred at an overall rate of approximately 10%.^{12,40,42,99,152,162} More recently, data from multiple institutions demonstrate a marked reduction in paraplegia rates with the use of adjuvant perfusion techniques.^{8,13,25,77,163}

SPINAL CORD PROTECTION: The spinal cord is supplied blood flow by anterior and posterior spinal arteries that consist of anatomic vascular chains that run the length of the cord.¹⁶⁴ The anterior spinal artery supplies the anterior two-thirds of the cord and is well developed in the upper thorax. Collateral arterial vessels also feed off of the left subclavian artery, including the vertebral artery, and consequently its occlusion during repair may have added implications toward a heightened risk of spinal cord ischemia. In the lower thorax and upper abdomen the anterior spinal artery is less developed and relies on segmental branches from intercostal and lumbar arteries. The anterior artery is supplied by 7 to 10 unpaired anterior medullary branches that vary in location along the cord (Fig. 57-6). Usually at least two anterior medullary vessels supply the cervical cord, two or three supply the thoracic cord, and two supply the lumbar cord. At the level of the first lumbar vertebra (variations T8 to L4) the anterior spinal artery receives the arteria radicularis magna (or artery of Adamkiewicz), which is essential for cord blood supply in this zone in at least 25% of patients.^164,165

View larger version (116K): [in this window] [in a new window]   Figure 57-6 Cross-sectional diagram showing a medullary (radicular) arterial branch to the anterior spinal artery.

View larger version (19K): [in this window] [in a new window]   Figure 57-7 Probability of paraplegia in relation to aortic cross-clamp time with and without lower body perfusion in patients with traumatic aortic disruption at the isthmus. (Reproduced with permission from Katz et al.166)

Based on the currently available data from the surgical community as a whole, it appears that cross-clamp times exceeding 30 minutes and utilization of the "clamp-and-sew" technique alone yield higher rates of paraplegia than techniques that include extracorporeal lower body perfusion (Tables 57-4 and 57-5).^152,162,163 Certainly there are groups that have had success with low paraplegia rates using exclusively a simple cross-clamping technique,^12,32 but these results have not been reproducible throughout many institutions, and their results rely on short cross-clamp times (average 20 to 25 minutes) with little margin for difficult cases. Recent data suggest that the paraplegia rate approaches zero when cross-clamp times are short (less than 30 minutes) and lower body perfusion techniques are employed.^13,156,162 We have employed some form of lower body perfusion, typically left heart bypass, during aortic cross-clamping for these injuries since 1994. In our experience, there have been no cases of paraplegia with open repair since this strategy was implemented (over 50 patients, unpublished data).

When aortic cross-clamp times are less than 25 to 30 minutes, low paraplegia rates have been achieved.^12,13,32 However, the average cross-clamp time reported in the literature is 41.0 minutes.⁴⁰ Many cases of aortic transection require more than 30 minutes to repair because of extravasated blood, fragility of the aorta, and difficulty in identifying local anatomy within a large hematoma. This is especially true if the tear extends proximally to involve the orifice of the left subclavian artery. These patients require clamping the aorta proximal to the left subclavian artery, which may increase the incidence of paraplegia in the absence of distal aortic perfusion.

ADJUVANT PERFUSION METHODS: Optimally, both right radial and femoral arterial catheters should be in place to allow for monitoring of upper and lower body perfusion. Both active and passive shunting systems have been successful with both full systemic heparinization and no heparinization.^{13,32,34,36,108,153–155,157,158,160,169,183–185} Despite the theoretical risk of bleeding with heparinization in the trauma setting, most groups, including our own, that employ active partial left heart bypass techniques use full systemic heparinization and have not seen bleeding complications.^8,13,75 Pulmonary venous cannulation near its confluence with the left atrium has a lower complication rate than cannulation of the left atrial appendage.¹⁸⁶ It is important to be well versed in the various lower body perfusion systems because distinct circumstances may require alterations in routine practice.

The system used by any one group should be simply applied, and reliable and routine for that group. Distal perfusion pressure should be maintained at 60 to 70 mm Hg.¹⁵⁸ Full heparinization is relatively contraindicated in cases of intracranial hemorrhage and severe lung injury, but is otherwise safely used by many groups.^{12,13,40,75,99,158,183,187} Use of a centrifugal pump with heparin-bonded tubing and active partial left heart bypass or use of a heparin-bonded passive shunt is an option that does not require systemic heparinization.^{154,158,185,187} It is helpful to employ the use of a heat exchanger within extracorporeal circuits in order to maintain core temperatures above 35°C in these patients that cool quickly.

PARTIAL LEFT HEART BYPASS: A small single- or dual-stage cannula is placed into the left atrium through the left inferior pulmonary vein to provide inflow to the pump (Fig. 57-8). Arterial cannulation size is determined by body size and site of cannulation. We preferably use a high-flow, atraumatic, aortic cannula in the distal descending aorta or less commonly place a femoral arterial cannula. Distal aortic cannulation has the advantage of convenience and speed. Partial left heart bypass serves several purposes: (1) to unload the left heart and control proximal hypertension at the time of cross-clamping, (2) to maintain lower body perfusion, (3) to allow rapid infusion of volume, and (4) to control (remove) intravascular volume. The lower body is perfused at a flow rate of 2 to 3 L/min with lower body mean arterial pressure of 60 to 70 mm Hg while maintaining an upper body mean arterial pressure of 70 to 80 mm Hg. All field blood is returned to the circuit via a pump reservoir or is accumulated and returned by cell saver.

View larger version (54K): [in this window] [in a new window]   Figure 57-8 Diagram showing a typical setup for partial left heart bypass in a patient with aortic disruption at the isthmus.

FULL OR PARTIAL CARDIOPULMONARY BYPASS: Direct right atrial cannulation at the inferior vena cava–right atrial junction from a left thoracotomy by simple, transverse, inferior pericardiotomy below the left phrenic nerve is straightforward and provides excellent venous drainage. Alternatively, a long venous catheter with multiple side holes via the left common femoral vein into the right atrium can be placed with a guidewire. Right atrial–femoral arterial bypass has been used with or without an oxygenator like partial left heart bypass. When no oxygenator is used blood is returned with a partial arterial oxygen pressure of approximately 40 mm Hg (saturation 45 to 65%), and this has been shown to be adequate for lower body tissue oxygen needs provided the hemoglobin concentration is maintained above 10 g/dL.^169,188 Full cardiopulmonary bypass support is most useful in cases in which the aortic arch is involved in the injury to allow for systemic cooling.^189,190

Right femoral venous to arterial bypass has the distinct advantage of allowing for establishment of partial or complete bypass prior to entering the chest. This technique may be preferred when there is concomitant right lung contusion in order to ensure adequate tissue oxygenation during repair. Rarely, there may be a need to perform a proximal anastomosis under deep hypothermic circulatory arrest (HCA) because an injury involves the mid-aortic arch. In cases of aortic arch transection in proximity to the innominate or left common carotid, anterior exposure via sternotomy or thoracosternotomy may offer better exposure for total arch replacement.^189,190 Use of HCA in trauma patients should proceed with caution and only after other serious associated injuries have been addressed to avoid bleeding complications. If HCA is required, it is essential to confirm the lack of significant aortic valvular insufficiency. When HCA is utilized within the left chest, the left ventricle should be vented, and we typically do this via the left atrium.

PASSIVE (GOTT) SHUNT: Of predominantly historical interest, this technique shunts blood from the proximal aorta to the distal aorta with a tapered, heparin-coated polyvinyl tube.¹⁵⁴ The proximal end is placed in the ascending or arch of the aorta or the left subclavian artery and the distal end is placed in the descending aorta or femoral artery. Ventricular cannulation had been used in the past; however, it was abandoned due to a high rate of ventricular dysrhythmias, reduced shunt flows, and a higher rate of paraplegia.^{34,154,155,184,191,192} The diameter of the shunt is obviously fixed, and therefore flow is passive, unmonitored, and dependent on a pressure gradient. Femoral arterial monitoring, as with all of these techniques, is recommended.¹⁸⁴ The Gott shunt is easy to use, although it requires a more extensive dissection of either the aortic arch or ascending aorta. It offers no left ventricular unloading or loading advantage that partial bypass systems do, and therefore blood pressure control is left to pharmacology alone.

OPERATIVE TECHNIQUES: A standard fourth interspace posterolateral thoracotomy with or without fifth rib notching usually provides excellent exposure to the aortic isthmus and proximal descending aorta. The incision should be long enough to facilitate dissection of the descending aorta below the level of the inferior pulmonary vein and dissection of the arch of the aorta between the left common carotid and left subclavian arteries. Dissection near the isthmus or tear should be avoided until both proximal and distal aortic control is established. Depending on the stability of the patient, lower body perfusion can be established prior to aortic exposure by gaining access to the left groin.

If cannulation is planned in the chest, proximal and distal aortic control is established first. The left inferior pulmonary vein–left atrial junction is dissected after gaining aortic control when using left heart bypass. Excessive compression or traction of the lung should be avoided, particularly when dissecting out the aortic arch, because the left pulmonary artery may be easily disrupted at this location (see Fig. 57-8).

The mediastinal pleura is incised along the anterior surface of the proximal left subclavian artery. The subclavian artery is isolated. The pleura overlying the distal aortic arch is incised lateral to the vagus nerve. Great care is taken to avoid injury to either the phrenic or vagus nerves as they pass over the aortic arch, which can be difficult since they are often obscured by the hematoma. They should be reflected off the aorta with the overlying pleura and retracted medially by attaching stay sutures to the pleura just lateral to the vagus nerve. Loops around the nerves themselves should be avoided, as even stretch of these nerves can result in paresis. This reflection exposes the arch of the aorta between the left common carotid and left subclavian arteries, which is the point needed for proximal aortic control in the majority of cases. Inferiorly, the vagus nerve and its branching left recurrent laryngeal nerve are reflected medially as well. This exposes the ligamentum arteriosum which can be sharply divided. The aortic arch between the left carotid and subclavian artery superiorly and medial to the ligamentum inferiorly is encircled with a tape after establishing a plane between the posterior arch and the trachea using a combination of sharp and gentle finger dissection. There should be no dissection distal to either the left subclavian or the ligamentum in order to avoid free disruption of the hematoma.

Distal aortic control is established at an adequate distance from the aortic injury to facilitate repair. The overlying pleura is incised, and the aorta isolated. The left inferior pulmonary vein is dissected out anteriorly. Opening the pericardium just anterior to the vein allows better exposure and a better site of pulmonary venous cannulation. Heparin, if employed, is given. We establish arterial cannulation first. Distal aortic purse-string sutures are fashioned below the distal clamp site, or the femoral artery is cannulated by Seldinger technique with serial dilatation to the desired cannula size. The inferior pulmonary vein is then cannulated with a dual-stage catheter. The circuit for left heart bypass is de-aired and connected. Lower body perfusion is initiated, and once systemic blood pressure is stabilized the left subclavian artery is clamped followed by the proximal aorta, then the distal aorta. We prefer to always clamp the proximal aorta between the left common carotid artery and the left subclavian artery because the tear frequently extends quite close to the ostium of the left subclavian artery. Upper and lower body pressures are stabilized with the bypass circuit to maintain upper body mean arterial pressures of 70 to 80 mm Hg and a lower body pressure of 60 to 70 mm Hg with flows of 2 to 3 L/min (see Fig. 57-8).

The periaortic hematoma is then entered, and the edges of the transected aorta identified. Usually the aorta is completely transected, and the edges are separated by 2 to 4 cm.^1,16 Less frequently the transection is partial. Some authors advocate primary repair at this point;^34,193 however, we advocate placing a short interposition graft after débridement of the torn edges.^{12,13,32,35,42,103,155,157,159–161} Collagencoated woven polyester grafts or gelatin-impregnated grafts are used most commonly. Use of intraluminal prostheses has been abandoned by most groups.¹⁹⁴ Grafts are sewn using a running polypropylene suture with the proximal anastomosis performed first, followed by the distal. Generous amounts of adventitial tissue are included in each bite. If the proximal anastomosis is done under HCA, cardiopulmonary bypass and reperfusion of the arch should be reinstituted immediately after completion of the proximal anastomosis for optimal neurocerebral protection. This requires cannulation of the graft just beyond the proximal anastomosis, and then the distal anastomosis is completed using a dual arterial-inflow perfusion setup perfusing the arch and lower body simultaneously. The left subclavian can either be incorporated into the proximal anastomosis or grafted separately as appropriate.

If the aorta is already ruptured with bleeding into the hemithorax, proximal aortic dissection between the left carotid and subclavian arteries is rapidly performed, and a cross-clamp quickly applied. The descending aorta is then clamped below the injury, and the hematoma opened. No attempt is made to establish lower body perfusion, but every attempt is made at maintaining adequate mean arterial pressure during clamping. The aortic repair is done as expeditiously as possible to minimize clamp time. Repair sutures are placed accordingly after clamps are removed. Hemostasis is achieved after continuity of the aorta is reestablished.

SPECIAL CONSIDERATIONS

PREVIOUS LEFT THORACOTOMY: Emergency department thoracotomies are usually done in haste by inexperienced nonthoracic surgeons and are often placed at sites too inferior to effectively repair an aortic transection. Given this situation it is usually best to enter the chest through a fourth interspace thoracotomy even if this means creating a second intercostal incision (using the same skin incision). When a patient with a history of prior left thoracotomy presents with an aortic injury the associated scarring offers both an advantage and disadvantage to the patient. The adhesions between the lung and mediastinum help contain the rupture making it less likely to exsanguinate, but the adhesions also make the dissection considerably more difficult and time consuming. Optimally, dissection in these cases should be done prior to heparinization.

EXTENSION OF THE TEAR INTO THE LEFT SUBCLAVIAN ARTERY: Traumatic aortic disruptions that occur in close proximity (<1 cm) from the left subclavian artery portend a higher mortality risk and greater operative difficulty than injuries further away from the left subclavian ostium.¹⁹⁵ We recommend routinely placing the proximal aortic clamp proximal to the left subclavian artery since most aortic ruptures tear close to it. This allows for an easier, more precise proximal anastomosis. The subclavian should also be controlled by encircling it with a tape just distal to its origin. Occasionally, the aortic tear will extend into the left subclavian orifice, and in this case the proximal clamp may have to partially or totally occlude the left common carotid. The left subclavian can then be completely detached from the aorta, the proximal anastomosis completed, and the clamp then moved distally onto the graft. The left subclavian is then reattached to the aortic graft with an interposition graft after completing the distal aortic anastomosis. The left common carotid artery will usually tolerate occlusion for 10 to 15 minutes without sequelae. The left subclavian interposition graft is fashioned with an end-to-end anastomosis distally and an end-to-side anastomosis proximally.

Endovascular stent grafting (EVSG)

There are now many reports of the efficacy of EVSG in the setting of acute traumatic aortic disruption.^{29–31,72,73,80,147–151,196–199} Most groups placing EVS grafts for aortic disruption are doing so selectively based on the prediction of higher risk with conventional repair due to severity of illness, age, comorbidity, or associated injuries. Open- or closed-head injury, bleeding abdominal visceral injury, retroperitoneal bleeding, and pulmonary contusions are commonly cited factors that may favor an EVSG approach.^{29–31,72,73,80,149}

EVSG for traumatic aortic disruption should be performed in either a hybrid operating room/angiosuite with a fluoroscopy unit designed for endovascular surgery or a conventional operating room with a portable C-arm fluoroscopy unit. The rate of conversion from EVSG to open repair is higher with management of aortic disruption than aneurysms,⁷² and the operative team involved must be ready and capable of making the conversion immediately. General anesthesia is used most commonly. Aortic access is retrograde via either the femoral or iliac artery. Percutaneous and femoral arterial cutdown or direct iliac arterial puncture or iliac access via a silo graft sewn to the iliac artery have all been used. One theoretical advantage of an endovascular approach may be the use of a very low dose or no heparin in trauma patients. A floppy J-tipped wire is advanced under fluoroscopic and/or TEE guidance, and an aortogram is performed using steep anterior oblique projection with a marked catheter to accurately assess and measure the aortic arch anatomy relative to the site of transection. Diameter of the prosthesis used should be based on aortic measurements obtained preoperatively by CT angiography. Length of graft coverage should be based on intraoperative angiographic measurements. Intravascular ultrasound is likely to improve our ability to accurately determine the extent of coverage and the size of grafts needed in the operating room.^200,201 Based on the proximity to the aortic injury, the left subclavian artery may need to be covered, and if covered, it may need to be embolized and bypassed or transposed to the left common carotid artery in order to ensure a proximal EVS graft seal and avoid problems of ischemia to the left arm or vertebrobasilar system (see Fig. 57-5).^202–205

Stent graft collapse is a problem that can occur in nearly any setting, but EVSG for transection may be particularly prone because of the fact that the available grafts may be relatively oversized for the normal-sized aorta adjacent to an injured segment. There are several unpublished reports of EVS graft collapse during or immediately after deployment for transection including events from our own institutions. Idu and colleagues reported a case of delayed EVS graft collapse that was identified on CT angiogram 3 months after repair of a traumatic transection.²⁰⁶

There is little doubt that as devices are designed better and more suitably for aortic transection, EVSG will become part of the standard of care. Currently we employ a selective strategy whereby most patients that are young and have limited associated injuries are treated by conventional open grafting, recognizing the durability of this approach. Alternatively, elderly, comorbid patients or those with severe associated injuries are treated with EVSG.

Nonisthmic Aortic/Arterial Disruptions

The incidence of acute rupture of the ascending aorta among motor vehicular or other trauma patients is not known, as most of these patients do not survive beyond the site of the accident. However, there are reports of successful repairs of these injuries.^22,33,207 Most commonly the proximal ascending aorta at or just above the sinotubular junction is involved.³³ There are a few case reports of ascending aortic ruptures associated with the deployment of air bags.^22,23 Ascending aortic ruptures require full heparinization and cardiopulmonary bypass for repair. These injuries are approached through a median sternotomy. The survival among cases reported in the literature of those undergoing repair is about 85%.³³ They have been repaired either primarily or with an interposition graft. Rarely, a concomitant aortic valve replacement is required.³³

Lacerations to the base of the innominate or left common carotid arteries should be approached through a median sternotomy and may require cardiopulmonary bypass depending on the degree of aortic involvement.⁴⁷ Extension of the incision into the right or left neck including detachment of the sternocleidomastoid from the sternum is usually helpful in obtaining adequate exposure. When the base of the left carotid or innominate is injured, the safest option is to oversew the base and create an interposition graft to the ascending aorta in an end-to-side fashion.^108,208,209 Injury to the base of the left subclavian artery can be approached either by sternotomy or left posterolateral thoracotomy, the latter of which typically provides better exposure.²⁰⁸ Alternatively, when injuries extend out onto either the left or right subclavian artery a thoracosternotomy, cervicosternotomy, or cervicosternothoracotomy "trap door" incision provides good exposure depending on the level of the injury.⁵ Finally, the transverse anterior thoracosternotomy, "clam-shell" incision provides good exposure to the mediastinal structures and both hemithoraces when multiple injuries require repair.⁵

Aortic injuries of the descending aorta distal to the isthmus to the level of T8 should be approached through a posterolateral thoracotomy in the fourth, fifth, or sixth interspace, depending on the level of injury. These types of aortic injuries from blunt trauma are rare. More commonly, this segment of aorta is injured by penetrating trauma. These patients rarely make it to the hospital alive. When the distal thoracoabdominal aorta is injured below T8, it should be approached by thoracoabdominal incision. This can be done either retroperitoneally or intraperitoneally. An intraperitoneal approach offers the advantage of allowing for abdominal exploration; however, retraction of the abdominal contents with a thoracoabdominal incision and a violated peritoneum can be cumbersome. We use partial left heart bypass with left atrial to femoral arterial or distal aortic cannulation for all thoracoabdominal aortic procedures unless active bleeding precludes its setup, or there is an absolute contraindication to heparinization.

Postoperative Care

Postoperative care after aortic repair is similar to that given patients who have other major cardiothoracic surgery. Immediately following aortic repair in the operating room, patients should undergo flexible bronchoscopy for evacuation of bloody secretions to avoid plugging and atelectasis of the left lung. Respiratory function, ventricular filling pressures, blood pressure, cardiac output, renal function, chest tube output, nasogastric drainage, body temperature, neurologic status, and coagulation function should be monitored closely. Pulmonary toilet is extraordinarily important, and once clinically stable an epidural catheter may be advantageous to facilitate good pulmonary recovery. Antibiotics are given in a standard prophylactic fashion. Patients are extubated as soon as is clinically indicated. Chest tubes are removed when any air leak has stopped and drainage is less than 150 to 200 mL of serous fluid per day.

Complications

Complications after aortic repair occur at a rate of 40 to 50%.^{13,34,36,42,108} Pneumonia is the most common complication and occurs at a rate of 17 to 34%.^{13,34,36,42,108} Other complications include bacteremia, renal insufficiency, and paraplegia. Rates of frequency for several series are listed in Table 57-6.^{13,34,36,42,108} Left vocal cord paralysis has been reported to occur at a rate of 4 to 14% percent, although recurrent nerve injuries are probably underreported. Late complications are rare in these patients. Aortobronchial fistula following repair of transection has been reported.^210,211

Results

The mortality rate of patients with aortic rupture who reach the hospital ranges from 7 to 65% depending on whether or not the injury is repaired.^{12,13,29–32,40} The large discrepancy is likely due to underreporting of patients who make it to the hospital but not to the operating room, as most series only report operative results. Among hemodynamically stable patients undergoing open repair or EVSG repair, the hospital mortality rate ranges from 0 to 20% in the modern era (Tables 57-6 and 57-7).^{13,29,30,80,163} The mortality rate of nonoperative patients with associated injuries precluding initial aortic repair was 55% in the AAST trial.¹³ All patients who either presented in extremis or with free rupture died of aortic rupture. A few small series have demonstrated acceptable survival rates of 67 to 72% in select, high-risk patients treated nonoperatively.^82,83 In his meta-analysis of 1492 patients, Von Opell reported an average of 7.8% of patients dying during aortic repair, and 13.5% dying in the postoperative period.⁴⁰

	NONAORTIC GREAT VESSEL INJURY

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The majority of injuries to the great venous structures and the pulmonary arteries are a result of penetrating trauma. Blunt trauma to these structures is rare, presumably because of their distensibility and low pressure. The incidence of injury to the nonaortic great vessels among cases of penetrating thoracic trauma is not known; however, the overall incidence of great vessel injury with thoracic gunshot wounds is approximately 5% and with stab wounds is 2%.²¹² Wounds penetrating the thoracic "box" bordered by the midclavicular lines, the thoracic outlet, and xiphoid process should be explored operatively. Chest tubes should be inserted as a diagnostic and therapeutic measure, and an echocardiogram or a subxiphoid pericardial window performed to rule out hemopericardium. Patients with a high index of suspicion of mediastinal great vessel injury or with a confirmed hemopericardium should undergo sternotomy. Patients with central venous or pulmonary arterial rupture will decompensate from pericardial tamponade. Expeditious pericardial decompression will often provide enough stability to facilitate definitive repair. Exsanguination from a venous or pulmonary arterial injury into one of the hemithoraces requires immediate massive volume resuscitation and transfer to the operating room. Choice of incision should be made based on clinical suspicion of site of injury or objective data (arteriography, chest radiograph, or bleeding site). When the site of injury is not clear, median sternotomy provides excellent access to the heart and great vessels, and it can be extended across a hemithorax or up the neck along either sternocleidomastoid to facilitate exposure of any vascular structure in the chest. Most venous injuries and pulmonary arterial injuries when localized and simple can be repaired without cardiopulmonary bypass. Large or complex venous, and particularly pulmonary arterial, injuries are often more easily repaired on full cardiopulmonary bypass with a decompressed heart. When repairing pulmonary venous injuries it is important to safeguard against air embolus, the result of which can be devastating. Therefore, complex pulmonary venous injury may require aortic cross-clamping with cardioplegia to prevent embolus to the brain.