DIAGNOSIS

The first priority should be to identify and manage life-threatening injuries and treat shock. Except for head injuries, nearly all injuries associated with immediate fatality are related to the cardiovascular system.

Advanced Trauma Life Support (ATLS) guidelines should be followed while proceeding with evaluation and treatment simultaneously. Shock from internal hemorrhage can be differentiated from cardiac compression or injury by a quick glance at neck veins. If neck veins are full, the presumption is cardiac compression from tamponade, tension pneumothorax, or cardiac failure. Collapsed neck veins indicate hypovolemia, and failure of response to fluid therapy dictates immediate operative intervention involving the most likely body cavity. This is usually dictated by an emergency chest x-ray. External hemorrhage is usually obvious and immediate control is essential. Generally, direct pressure is effective for temporary control.

The presence of shock may lead to diminished pulses in the extremities and confusion about the location of vascular injury. Associated fractures and dislocations may compromise vascular patency and should be reduced before any decision about vascular injury is reached.

Prompt resuscitation and identification and management of vascular injuries should be the goals in order to minimize mortality and prevent permanent extremity ischemic damage.

HARD AND SOFT SIGNS OF VASCULAR INJURY

On the basis of history and physical examination, manifestations of vascular injury can be classified into two general prognostic categories, hard signs and soft signs (Table 1).

Table 1 Hard versus Soft Signs of Vascular Injury

Hard signs are strong predictors of the presence of an arterial injury and the need for urgent operative intervention. Obvious examples include bright red pulsatile bleeding or a rapidly expanding hematoma. Evidence of extremity ischemia (manifested by the six P’s—pulselessness, pallor, pain, paralysis, paresthesia, and poikilothermia) and a bruit or thrill are additional examples. For extremity trauma, we also consider an arterial pressure index (API), also known as the ankle-brachial index, of less than 0.90 to be a hard sign. The API is determined by dividing the systolic pressure of the injured limb by the systolic pressure of the noninjured limb. Johansen and colleagues¹ demonstrated 95% sensitivity and 97% specificity for identification of occult arterial injury with an API of less than 0.90. An API of more than 0.90 had a 99% negative predictive value for the presence of an arterial injury. The API is readily determined at bedside, and should be considered an extension of the physical examination. An important caveat is that the API may be normal in nonconduit vessels such as the profunda femoris.

Soft signs are those suggestive of an arterial injury, although with a much decreased likelihood than hard signs (see Table 1). These consist of mild pulse deficits, soft bruits, nonexpanding hematomas, and fractures or wounds in close proximity to major vessels. The actual incidence of arterial injury with these findings varies. For instance, patients with injury in proximity to a major vessel as the only finding are found to have an identifiable injury in less than 10% of cases; further, many of these injuries do not require additional treatment beyond simple observation. Most of the controversy of vascular trauma evaluation revolves around the assessment of patients with soft signs.

ADDITIONAL ANCILLARY TESTS

Ancillary imaging includes plain x-rays, duplex scanning, computed tomography (CT) angiography, and formal arteriography. A chest x-ray and plain x-ray imaging of the site of suspected vascular injury are warranted in essentially all patients. The utility of the remaining modalities are most beneficial when dealing with patients with soft signs, when the location of arterial injury is not obvious, or for assorted injuries, that is, thoracic aorta, where information gained may greatly impact subsequent management. In many patients, the presence of an arterial injury is obvious and the need for surgical intervention clear; these patients are generally best served by prompt operation without additional tests.

A chest x-ray and plain films are readily obtained in the emergency room and should be a part of the initial screening of the injured patient. Radio-opaque markers should be placed on all open wounds suspected to have resulted from a penetrating mechanism. Radiographs should completely cover the injured areas; often this requires imaging overlapping areas of the torso to ensure adequate coverage. Films should be scrutinized for foreign bodies, fractures, and dislocations. The trajectory of the injury is assessed as possible. The number of bullets identified and the number of wounds should sum to an even number. If not, the patient should be evaluated for additional unidentified wounds and films should be obtained to locate additional bullets. An important caveat is the possibility of a foreign body from a prior injury. At times, the bullet may travel as a missile embolism in the vascular system to a site distant from the site of entry. Occasionally, fluoroscopy (or the scout film of the CT scan) will assist in localizing additional bullets. A note should be made if the foreign body appears blurred, as this implies motion and the possibility of close contact with, or location within, a vascular structure.

Duplex ultrasonographic scanning combines two-dimensional imaging to assess anatomic detail and Doppler insonation to assess flow characteristics. Several investigators have demonstrated high sensitivity and specificity in the detection of vascular injury in various anatomic locations.^2–5 Duplex ultrasonography is more sensitive to the presence of vascular injury than the arterial pressure index (API). Importantly, duplex ultrasonography can identify arterial injuries in nonconduit vessels such as the profunda femoris (the API will remain normal). However, duplex ultrasonography is limited, as it is technician dependent and in most centers is not readily available after hours.

Recently, there has been a groundswell of interest in the use of CT angiography as a diagnostic modality for vascular injury in multiple anatomic locations.^6–11 Major advantages include almost universal availability and three-dimensional (3D) detail. Compared with formal angiography, an interventional radiologist does not need to be in attendance at the time of the examination. In general, the examination can be obtained more expeditiously than formal angiography, particularly after hours. Technological advancements in imaging resolution and software have been significant. Arterial anatomy can be reconstructed in 3D detail for easy evaluation. However, the modality is diagnostic only. A subsequent angiogram may be required for therapeutic embolization. Notably, the combined contrast load from both a CT angiogram and a subsequent angiogram can be significant. An additional technical limitation is that CT angiography is compromised by scatter from metallic fragments much more than formal angiography.¹² CT angiography is of particular value when thoracic vascular injury is suspected, and it has proven to be a highly sensitive screening test.¹³ However, mediastinal hematoma alone, without evidence of arterial disruption, may still require arteriography to confirm large vessel injury.¹⁴

Arteriography has long been regarded the gold standard for assessment of arterial injury.¹⁵ It is well tolerated and has a low complication rate. Major complications such as iatrogenic pseudoaneurysm or AV fistulas are very uncommon in the young population typical of most trauma centers. A major advantage of arteriography is the availability of therapeutic options (such as embolization). Further, compared with CT angiography, formal arteriography is not prone to scatter from the presence of metallic fragments. Even in centers that rely on CT imaging as the predominant diagnostic study, formal arteriography still has a diagnostic role in confirming or further delineating the presence of equivocal CT findings. This latter point is particularly applicable in the assessment of carotid injuries where even minor injuries may be of importance. An occasional patient requires urgent operation before availability of formal arteriography or CT angiography. In these patients, an on-table, surgeon-performed arteriogram can be obtained in the operating room. For instance, a femoral artery can be cannulated with an arterial catheter, contrast injected, and images obtained either with plain films or fluoroscopy.^16–19 O’Gorman and colleagues^16,17 have demonstrated that the axillary artery can be visualized by injection of contrast into the brachial artery with distal outflow occlusion with a blood pressure cuff inflated to a level well beyond the systolic arterial blood pressure. A benefit of the recent popularity of endovascular techniques has been increased availability of formal arteriography in the operating room. In fact, some centers have the capability of embolization of pelvic or visceral vessels in the operating room, thereby precluding the need to transport an unstable patient to a radiology suite that may not have the resources of the operating room.