Vascular Trauma

Chapter 64 Vascular Trauma




Vascular trauma remains one of the most significant challenges in the management of injured patients. The advent of trauma systems and improved prehospital care have resulted in an increasing number of patients with what were previously fatal vascular injuries arriving at trauma centers still alive, but in immediate danger of death.1,2 Vascular trauma is not always obvious and timely recognition may be difficult in patients with multiple injuries.3 The time urgency and high-risk potential in managing these injuries requires an organized approach to deliver appropriate care in a timely fashion. Because so much is at stake, this is a high-risk clinical environment requiring systematic planning, preparation, and the use of practice guidelines for successful early recognition and effective treatment.


This chapter reviews the pathophysiology, clinical presentation, diagnostic workup, management, and outcome of vascular injuries. The educational objectives of this review include the following:







General Approach To Vascular Trauma



Mechanism of Injury


Vascular injury can be produced by a blunt or penetrating mechanism. Penetrating injury tends to be more discrete or focal, whereas blunt injury is more diffuse, with injury not only to the vascular structures but also to the bone, muscle, and nerves. The diffuseness of the blunt injury not only affects the major vascular conduit, but also disrupts smaller vessels that would normally provide collateral flow. As a result, ischemia is worsened or exaggerated. Penetrating injury is generally classified as low velocity (<2500 ft/sec; e.g., stab wound, fragment injury, handgun wound) or high velocity (>2500 ft/sec; e.g., military rifle wound).4 High-velocity weapons produce significantly more tissue damage than low-velocity weapons for three main reasons5,6:





Trauma to a blood vessel (artery or vein) can produce hemorrhage, thrombosis, or spasm, alone or in combination, depending on the magnitude of the force applied to the vessel and on the degree of injury. Hemorrhage is produced when all of the layers, the intima, media, and adventitia, are disrupted or lacerated. If the bleeding is controlled locally, a hematoma is produced, which may or may not be pulsatile. If bleeding is not controlled, exsanguination can occur. Thrombosis occurs if there is damage to the intima exposing the underlying media and causing local thrombus formation, which may propagate and occlude the lumen or embolize distally. In addition, the injured intima can prolapse into the lumen as a result of blood flow dissecting under it, producing partial or complete obstruction. Trauma to surrounding bony structures may cause external compression of the vessel, interrupting flow and producing thrombosis. Spasm occurs if there is external trauma to the vessel, such as stretching or contusion, which can stimulate the release of mediators (e.g., hemoglobin) that cause constriction of the vascular smooth muscle. Spasm, by reducing the cross-sectional area of the vessel, reduces flow.


In addition to the acute pathophysiology produced by hemorrhage and thrombosis, direct trauma can produce subacute, chronic, or occult injuries. The most common are arteriovenous fistula and pseudoaneurysm. An arteriovenous fistula typically occurs after penetrating trauma that causes injury to an artery and vein in close proximity. The high-pressure flow from the artery will follow the path of least vascular resistance into the vein, producing local, regional, and systemic signs and symptoms. These include local tenderness and edema, regional ischemia from steal, and congestive heart failure if the fistula enlarges.7 A pseudoaneurysm is a result of a puncture or laceration of an artery that bleeds into and is controlled by the surrounding tissue. The artery remains patent; blood flows into and out of the pseudoaneurysm, much like flow from the ocean into a tide pool. These can enlarge and produce local compressive symptoms, erode adjacent structures or, rarely, be a source of distal emboli. Initially, they can be clinically occult, but with time become symptomatic.


Not all arterial injuries require operative management. During the past 2 decades, it has been convincingly demonstrated that patients with a normal vascular physical examination and asymptomatic nonocclusive intimal flaps, segmental arterial narrowing, small (<2-cm) false aneurysms, or small arteriovenous fistulas discovered on arterial imaging (i.e., duplex scanning or arteriography) have a benign clinical course.8 Approximately 10% of these minimal injuries will progress to require a surgical or endovascular repair and most within the first week after injury. Thus, it is imperative that these patients have close follow-up with physical examination and duplex imaging, if needed. In rare cases, when a nonocclusive minimal injury increases in size or becomes symptomatic, requiring operative or endovascular repair, morbidity is not increased by the delay.



Clinical Presentation


Vascular injuries can present with a broad spectrum of clinical manifestations, from profound hemorrhagic shock to subtle findings, such as an asymptomatic bruit. Patients who present in hemorrhagic shock must be assumed to have a major vascular injury until proven otherwise. There are five anatomic areas to consider, each with specific considerations. In the head and neck, external hemorrhage is required for vascular injuries to result in shock. Relatively small and tightly organized tissue planes preclude significant internal hemorrhage. In the chest, each hemithorax can accommodate lethal amounts of hemorrhage from cardiac, pulmonary, or great vessel arterial and venous injuries. Abdominal and pelvic vascular injuries can also result in lethal hemorrhage, particularly from the aorta and iliac arteries. Like the head and neck, extremity vascular injuries generally cause hemorrhagic shock only if there is significant external hemorrhage. The patient with hypotension and a lack of chest, abdominal, and pelvic findings may have what appears to be a trivial neck or extremity laceration, but which initially communicated with a major vessel injury. It is important to remember that hemorrhage sufficient to produce hypotension can be followed by thrombosis. It is therefore necessary to obtain a history from the prehospital personnel about the amount of blood at the scene or the initial presence of severe wound hemorrhage. It is also necessary to examine the patient thoroughly for additional wounds and to assess each of them carefully.


Extremity vascular trauma may be immediately apparent on presentation because of external hemorrhage, hematoma, or obvious limb ischemia. A history of penetrating trauma associated with hypotension, pulsatile bleeding, or a large quantity of blood at the scene suggest vascular injury. Blunt trauma is also capable of causing significant vascular injury that can be overlooked when serious head, chest, or abdominal injuries are present. Extremity fractures may result in vascular injury. Supracondylar humerus fractures can be associated with brachial artery injury and knee dislocation carries a significant risk of popliteal artery injury.9 Crush injuries of the extremity without fracture may also result in vascular injury.


A relatively small number of vascular injuries present in a delayed fashion, without initial findings. These are limited to thrombosis of a previously partially disrupted but initially patent vessel, distal emboli from an intimal tear of the arterial wall with formation of platelet debris and, least commonly, rupture or expansion of a pseudoaneurysm that was initially small and contained by the outer arterial wall and local tissue.9 Local signs of hematoma, diminished pulses, and the presence of patterns of associated injuries should indicate the presence of these vascular injuries. A thorough history and physical examination and appropriate adjunctive imaging studies will result in an effective initial diagnosis and result in a decrease in the frequency of these delayed presentations.


Because there is such a broad spectrum of clinical findings associated with vascular trauma, it is best to assume that vascular injury is present until proven otherwise in all patients with hemorrhagic shock and all patients with extremity fractures.



Diagnosis



Physical Examination


Vascular injury can produce systemic symptoms of hypotension, tachycardia, and altered mental status because of hypovolemic shock produced by hemorrhage. As a result, vascular injury can be life-threatening and attention must initially be directed to the primary survey using the principles of advanced trauma life support (ATLS).10 The airway must be assessed, adequate oxygenation and ventilation ensured, and intravenous access achieved. Once this is completed and resuscitation is underway, the secondary survey is undertaken. A thorough history is obtained and careful physical examination is performed. This examination must include a careful inspection of the injured sites and wounds, complete sensory and motor assessment, and pulse examination of each extremity. The presence of a hematoma, bruit, or thrill must be noted. If distal pulses are diminished or absent, ankle or wrist systolic blood pressure should be determined with a continuous wave Doppler device and compared with the uninjured side. A significant difference in systolic blood pressure (>10 mm Hg) between extremities may be an indication of vascular injury. Patients with hard findings of vascular injury (Box 64-1) should be taken directly to the operating room.



In patients without hard findings, but with soft findings (see Box 64-1), vascular imaging can be used to rule out the need for operation. Additionally, patients with hard findings but with multilevel injuries in the same extremity may also need imaging. Catheter arteriography is sensitive and specific for the diagnosis of extremity vascular injuries (Fig. 64-1). Computed tomography angiography (CTA) with the latest generation scanners has proved to be an acceptable alternative to formal arteriography (Fig. 64-2).11,12 Although this imaging technique requires a contrast infusion, it does not require arterial catheterization, is easily performed and is less costly and time-consuming than conventional angiography.




Some severely injured patients must be taken to the operating room to treat severe life-threatening associated injuries (e.g., subdural hematoma, ruptured spleen). In such cases, it is not prudent to delay operative therapy to obtain formal vascular imaging. An arteriogram can be obtained in the operating room by cannulating the artery proximal to the suspected vascular injury, injecting 20 to 25 mL of full-strength contrast, and taking an x-ray or using fluoroscopy (Fig. 64-3).13,14 If doubt remains about the presence of a vascular injury and imaging studies and other diagnostic tests are inconclusive, there is a role for operative exploration and direct assessment of the artery. Routine operative exploration in the stable patient with soft signs, however, has a 5% to 30% incidence of morbidity, occasional mortality, and low diagnostic yield.15 These patients are better served with formal vascular imaging.



Duplex color flow imaging is not used for the acute assessment of vascular injury. Wounds, swelling, presence of air in the tissue, and presence of dressings or splints impair the ability to obtain satisfactory images. Duplex imaging does have a role in the follow-up of treated lesions (e.g., to assess patency of bypass grafts or detect luminal stenosis at an anastomosis) or in the follow-up of nonoperative management of minimal vascular injury, such as small pseudoaneurysms or arteriovenous fistulas.



Treatment



Minimal Vascular Injury and Nonoperative Management


The widespread application of arteriography in the evaluation of injured extremities has resulted in the detection of clinically insignificant lesions. There is now an extensive body of experience with lesions that are not clinically significant. These minimal vascular injuries include intimal irregularity, focal spasm with minimal narrowing, and small pseudoaneurysms. They are often asymptomatic and usually do not progress.


A small, nonocclusive intimal flap is the most common clinically insignificant minimal vascular injury. The likelihood that it will progress to cause occlusion or distal embolization is approximately 10% to 15%.8,16 This progression, if it occurs, will be early in the postinjury course. Spasm is another common minimal vascular injury. This finding should resolve promptly after initial discovery. Failure of the return of normal extremity perfusion pressure indicates that a more serious vascular injury is present and intervention is needed. Small pseudoaneurysms are more likely to progress to the point of needing repair and must be actively followed with Duplex color flow imaging. Arteriovenous fistulas always enlarge over time and should be promptly repaired.


Considerable evidence suggests that nonoperative therapy of many asymptomatic lesions is safe and effective. However, successful nonoperative therapy requires continuous surveillance for subsequent progression, occlusion, or hemorrhage. Operative therapy is required for thrombosis, symptoms of chronic ischemia, and failure of small pseudoaneurysms to resolve.



Endovascular Management


The use of endovascular therapy for the treatment of atherosclerotic arterial disease has become widespread. Endoluminal stent deployment for occlusive lesions and stent graft for aortic aneurysms have been used successively in select patients; there is now a strong tendency to generalize from this elective experience in older patients with atherosclerosis to the treatment of younger patients with acute vascular injuries. Most major trauma centers have some experience with endoluminal treatment of acute vascular lesions. However, the evidence to support these approaches is not well developed and there have been problems.1719 A review of available evidence combined with common sense should help identify the appropriate role of endovascular management of traumatic injuries.9,18



Torso Injuries


Endovascular techniques offer various options for hemorrhage control in the torso. Intra-arterial catheter-directed embolization has become a mainstay of the management of solid organ hemorrhage in the abdomen.20,21 Whether used as the sole treatment or in combination with open procedures, this approach has been effective for liver, spleen, and kidney injuries. Less commonly used intra-arterial balloon occlusion for proximal control is a promising adjunct to open repair.22,23 These techniques are quick, accurate, and easily performed. The major obstacle to their widespread popularity has been the reluctance of surgeons to adopt catheter skills or partner with interventional radiologists to bring these techniques to the trauma operating room (OR). It does not require a dedicated endovascular suite to perform these techniques. A digital C arm and the proper catheters transforms any OR to an endovascular-capable room.


The early use of catheter-directed control of hemorrhage associated with pelvic fracture is an effective method of limiting blood loss and improving outcome.24 This approach is well tolerated and has proven superior to open attempts at hemorrhage control by packing in most patients. Unstable patients benefit from an immediate trip to the operating room. If intraoperative endovascular capability is available, a combined approach may offer the best results.


Enthusiasm for stent graft management of great vessel injuries in the chest has steadily grown. The success of stent grafts for the treatment of aneurysm disease in the infrarenal aorta has led to the use of similar devices to treat contained thoracic aortic lacerations following blunt trauma. The initial results have been encouraging but are not without complications.18 Lifelong CT imaging is necessary because of the possibility of delayed endoleak and possible loss of device fixation as the aorta enlarges over time. There is a promising role for covered stents in proximal branches of the aorta in the thorax and abdomen. In stable injuries at risk for delayed hemorrhage or thrombosis, carefully placed stents have the potential to lower morbidity compared with open procedures that require extensive operative dissection for exposure and control. Endoluminal management with stent grafts appears most effective in those torso injuries that are surgically inaccessible, with the potential for significant hemorrhage in stable patients (Fig. 64-4). These techniques should only be used in centers with an active elective endovascular practice that has experience in treating trauma patients.




Cerebrovascular Injuries


Endovascular techniques offer advantages in anatomic regions in which direct operative control is difficult or impossible. For example, hemorrhage from a penetrating injury at the base of the skull is extremely difficult to control. Catheter-directed placement of coil, balloon, or hemostatic agent in the injured carotid or vertebral artery could be lifesaving. Initially, stent placement appeared to be less effective than anticoagulation in partially occluded injuries without associated hemorrhage.17,25 However, the role of stents in cerebrovascular trauma has yet to be defined and may prove safe.26 This use of endoluminal interventions, however, requires significant expertise and experience. If such experience does not exist at the receiving hospital, consideration should be given to transferring the patient to a medical center with experience in this mode of therapy.



Extremity Vascular Injury


The use of stent grafts in the extremities is becoming more common 27,28 The long-term results, however, have not been documented and caution should be used when considering this type of treatment. Covered stents can be used to improve intraluminal diameter in partially occluded traumatized vessels with favorable early patency rates; however, they are prone to occlusion and long-term outcomes are as yet unknown. Autologous vein interposition grafts have excellent long-term patency rates and remain the gold standard for vascular repairs in the extremities.


Catheter-directed therapies for controlling hemorrhage from large branch vessels in the extremities are often effective and sufficient to manage these injuries.29 Endoluminal treatment is not advocated for pseudoaneurysms of the extremity arteries. Small pseudoaneurysms are likely to resolve without any intervention and large pseudoaneurysms are best treated with open techniques because the risk of arterial thrombosis or distal embolization is high with this endovascular intervention.




Surgical Treatment



Preparation for Operative Management


Operative procedures to manage vascular injuries should be limited to those surgeons who are capable, experienced, and qualified. Board certification in vascular surgery is not enough to qualify a surgeon as capable of handling these injuries, just as the lack of certification does not necessarily disqualify a surgeon. Many surgeons who perform elective vascular surgery are not sufficiently experienced in the management of vascular trauma. Conversely, there are many trauma surgeons who are skilled in vascular technique by virtue of their interest and experience.


Successful operative management of vascular injuries requires a systematic approach, with careful preparation. This begins with airway control, adequate intravenous access, and availability of blood products. However, these blood products should not be administered before obtaining control of hemorrhage unless the patient is profoundly hypotensive.3032 If the blood pressure (BP) is below approximately 80 to 90 mm Hg, the goal should be to provide adequate volume restoration with O-negative packed cells and type AB fresh-frozen plasma infusion to support transport to the operating room for definitive hemorrhage control without delay. Volume infusion that raises the blood pressure above a systolic pressure of 90 to 100 mm Hg may increase bleeding and negatively affect outcome, particularly if the infusion delays transport to the OR.


Broad-spectrum preoperative antibiotics (and tetanus toxoid, if it is a penetrating wound) should be administered; if there is an isolated extremity injury without significant hemorrhage, an IV bolus of 5000 U of heparin should also be given. Systemic heparinization should be avoided in patients with torso injuries, head injuries, or multiple extremity injuries.


The most commonly omitted step in preparation is a failure to document preoperative extremity neurologic status. The presence of a neurologic deficit after operative vascular repair without knowing the preoperative status presents a difficult management challenge. A new neurologic deficit after vascular repair merits investigation and, possibly, reoperation. Therefore, a thorough preoperative neurologic examination and careful documentation are essential to effective management.


The operative management of extremity vascular injuries must be carefully orchestrated with the overall care of the patient. The choice between definitive repair and damage control should be made as soon as possible in patients with life-threatening torso injuries or severe head injuries. This includes coordinating two surgical teams to work simultaneously to care for the torso injury and extremity vascular injury at the same time. Associated injuries to the soft tissue and bone require a coordinated assessment and treatment with orthopedic and plastic surgery consultants. These specialists should be involved as early as possible to facilitate any additional imaging or diagnostic procedures prior to proceeding to the OR. The conduct of the operation should also be discussed with these colleagues.32 For example, the use of damage control procedures with shunt placement, followed by orthopedic stabilization, can remove the sense of urgency to restore blood flow. Extensive soft tissue injuries may compromise the proper coverage of vascular repairs and fracture fixation. The advice and assistance of a plastic and reconstructive surgeon can be helpful in obtaining coverage of exposed grafts and fractures.



Vascular Exposure and Control


A generous sterile field should be prepared to allow for the adequate exposure of vessels to obtain proximal and distal control. In torso injuries, this includes prepping the chest and abdomen to the table laterally on both sides and both legs in case distal access or an autologous conduit is needed. For proximal vascular injuries of the extremities, at the groin crease or axilla, the chest or abdomen should be prepared to obtain proximal control out of the zone of injury. An uninjured leg should be also prepared for harvesting of autologous venous conduit.


Proximal control is the first priority in the exposure of vascular injuries.33 In the torso, chest injuries with life-threatening hemorrhage are best approached through a fourth intercostal space anterolateral thoracotomy that can be extended across the sternum into the third intercostal space of the right chest to create a clamshell incision. Thoracic outlet and proximal neck vascular injuries may require median sternotomy, with extension above the clavicle, up along the ipsilateral sternocleidomastoid muscle. For abdominal vascular injuries, a generous xiphoid to pubis incision is needed for adequate exposure. Proximal control for aortic injuries can be obtained just below the aortic hiatus of the diaphragm or may require a left anterolateral thoracotomy to clamp the distal thoracic aorta.


In proximal extremity injuries with active hemorrhage, the first incision site is chosen to give the fastest exposure of inflow vessels for clamping; this may include incisions over the infraclavicular region of the chest to expose the axillary artery. For injuries in the groin, prepare to enter the lower quadrant of the abdomen for access to the external iliac vessels. In mid and distal extremity vascular injuries associated with active hemorrhage, tourniquets can rapidly obtain control in the trauma resuscitation room. In the operating room, have one team member compress the bleeding site precisely with a gloved hand and a sponge, remove the tourniquet, and prepare the extremity. A 5000-U heparin bolus is then given, if appropriate, the extremity is prepared and draped, and a sterile tourniquet is placed proximal to the wound and inflated. The injury site can then be explored in a controlled fashion and clamps or vessel loops placed above and below the vascular injury.


Incisions used to manage vascular injuries are the same as those used to mange elective cases, but are generally more generous. The use of smaller incisions may lead to errors in identifying the extent of vascular injury, adequately controlling branch vessel hemorrhage, and identifying associated venous lacerations. This is particularly true for popliteal artery and vein injuries. A limited approach with separate medial above- and below-knee incisions will not expose the site of injury adequately. A medial incision from the proximal popliteal space to the distal popliteal space, with division of the medial head of the gastrocnemius, semimembranosus, and semitendinosus muscles, with full exposure of the popliteal artery and vein and tibial nerve, provides adequate exposure. This ensures adequate vascular control and the opportunity for successful repair. Closure of the wound to include approximation of the divided muscles yields an excellent functional result. Dividing the inguinal ligament in the groin, dividing the pectoralis major in the axilla, and removing the midclavicle may rarely be necessary. In the presence of life-threatening hemorrhage that cannot be controlled by any other approach, these structures should not stand in the way of adequate exposure and control.


There are various adjunctive measures that can obtain temporary control. In the resuscitation bay, insertion and inflation of a Foley catheter in a wound in the neck or extremities with active hemorrhage can obtain temporary control and allow for safe transfer to the operating room.30 In the OR, insertion of Fogarty balloon tip catheters under direct vision at sites in the artery above or below the injury also serves to gain control in difficult to reach anatomic areas.

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Aug 1, 2016 | Posted by in CARDIAC SURGERY | Comments Off on Vascular Trauma
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