THE DIAGNOSIS OF VASCULAR TRAUMA

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CHAPTER 63 THE DIAGNOSIS OF VASCULAR TRAUMA

The diagnosis of vascular trauma is usually not a problem, as most injuries manifest overt blood loss, shock, or loss of critical pulses. However, in certain instances, the lesion may not be recognized initially, only to manifest itself later by sudden secondary hemorrhage or the development of critical organ or extremity ischemia.

Most of the vascular injuries of immediate concern to the clinician are those related to arteries. The reason for this is that venous hemorrhage is usually well controlled by the adjacent soft tissues, and excellent collateral flow compensates for occlusive lesions. Late progression of thrombosis and pulmonary embolism are the primary complications related to venous injury.

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.

History

Prehospital personnel should be questioned about bleeding at the scene and the presence or absence of shock. The need for resuscitation and the volume of fluid administered should be solicited. The use and duration of application of a tourniquet should be determined, and the amount and character of blood loss at the accident scene ascertained. A history of bright red pulsatile bleeding suggests arterial injury, while dark blood suggests venous origin. In many instances, bleeding may have ceased by the time the patient reaches the emergency room, leading to a false sense of security. In this type of patient, particularly one with an arterial injury, secondary hemorrhage is possible at any time.

Both the patient and prehospital personnel should be questioned about the mechanism of injury. Most civilian penetrating trauma results from low-velocity mechanisms such as knives or handguns. Arterial injuries in these cases are typically the result of direct injury, that is, from the knife or bullet. Information should be collected to aid in determining the trajectory of injury and potential structures injured. This could include the knife type and length, the number and direction of bullets, and the body position at the time of injury. Vascular injury from blunt mechanisms is often the result of stretching or compression from associated fractures or dislocations. Evidence of extremity fracture, dislocation, or altered perfusion should be elucidated. Additionally, specific mechanisms such as “car bumper” injuries or posterior knee dislocations are often associated with vascular injury and should be sought as appropriate.

Information about neurologic symptoms including sensory and motor deficits should be obtained. Potential confounding factors such as pre-existing peripheral vascular disease, diabetes, or neuropathies should be elicited.

Physical Examination

The patient should be undressed and thoroughly examined. The skin folds of the axilla or perineum and buttocks should not be neglected, as wounds resulting from penetrating trauma may be missed in these areas. Deformity resulting from fracture or dislocation should be identified. In the case of penetrating trauma, the location and number of wounds should be noted in an attempt to identify the trajectory of the wounding object (particularly with reference to major arteries).

Evidence of active bleeding or hematoma formation should be sought. The character of the bleeding, pulsatile bright red blood, or a steady ooze of dark blood should be noted. A tense or expanding hematoma indicates the presence of an arterial injury with bleeding contained by surrounding soft tissues. The opposite uninjured extremity should be evaluated as a comparison. Chronic peripheral vascular disease is generally symmetric. Absent pulses in the noninjured leg would support a diagnosis of pre-existing peripheral vascular disease.

The examination should include palpation of pulses proximal and distal to the injury. Perfusion and tissue viability can be further assessed with skin temperature and capillary refill distal to the injury and determination of motor function. Alterations in any of these parameters warrant further assessment. Conversely, an apparent “normal” pulse does not exclude the possibility of vascular injury. Pulses may be palpable and assessed as normal in up to ⅓ of patients with later proven vascular injury. Again, the opposite noninjured extremity serves as a useful comparison.

Arteriovenous (AV) fistulas may occasionally be identified by auscultation of a bruit over the involved arterial segment. Generally the AV fistulas progress over time—often a bruit is not apparent early postinjury. A glove should be placed over the bell of the stethoscope to keep the stethoscope free of blood when there is an open injury.

A thorough neurologic examination should be documented. Anatomically, the blood vessels and nerves are located in close proximity to each other. A neurologic deficit may hint toward the presence of an associated vascular injury. Further, the examination is of prognostic importance, as functional outcome is very dependent on intact sensation and motor function. A “stocking glove” deficit frequently indicates neurologic dysfunction resulting from ischemia—peripheral nerves are susceptible to ischemia because of a high metabolic rate and low glycogen stores. Blood flow should promptly be re-established to prevent development of muscle death and gangrene.

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 Soft Signs
Active arterial bleeding Neurologic injury in proximity to vessel
Pulselessness/evidence of ischemia Small- to moderate-sized hematoma
Expanding pulsatile hematoma Unexplained hypotension
Bruit or thrill Large blood loss at scene
Arterial pressure index <0.90 pulse deficit Injury (due to penetrating mechanism, fracture, or dislocation) in proximity to major vessel

From Anderson JT, Blaisdell FW: Diagnosis of vascular trauma. In Rich N, Mattox KL, Hirshberg A, editors: Vascular Trauma, 2nd ed. Philadelphia, Elsevier/Saunders, 2004.

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.25 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.611 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.1619 O’Gorman and colleagues16,17 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.

SPECIFIC AREAS OF INJURY

Each of the major anatomical areas presents some unique symptoms or requirements for diagnostic screening for vascular injury. These areas are the neck, chest, abdomen, and extremities.

Cervical vascular trauma may be manifested by initial signs of external hemorrhage, expanding hematoma16 or ipsilateral hemispheric ischemic symptoms, including hemiplegia, hemiparesis, or monocular blindness. The latter neurologic symptoms must be assumed to result from carotid artery interruption or thrombosis until proven otherwise. Deficits resulting from cranial nerves IX, X, XI, and/or XII suggest the possibility of vascular injury because of their immediate proximity to the carotid artery and the jugular vein. Penetrating trauma is associated with hemorrhage or false aneurysms, whereas blunt trauma invariably produces symptoms through thrombosis. This can be either immediate or delayed. In cases of major neck trauma, duplex scanning has greatly facilitated screening for intimal disruption or dissection, and some institutions use it liberally. CT angiography has recently been established as a viable alternative to formal angiography in the screening of blunt carotid injury as well as in the assessment of penetrating neck injury.8,9,11, Formal angiography should still be considered the gold standard, and is required in equivocal cases as well as the occasional patient who requires embolization of a disrupted vertebral artery.

Thoracic great vessel injuries are those to the arteries at the base of the neck and the thoracic aorta. As is true of all penetrating trauma, massive hemorrhage is the usual manifestation of injury to any one or more of these vessels. In this instance, immediate operation is indicated, with location based on the presumed path of the missile, location of the stab wound, and/or chest x-ray. Because of the significance of delayed diagnosis, most patients who are stable and have penetrating injuries of the base of the neck should be evaluated with arteriography. CT angiography is an appropriate alternative in centers with late-generation multidetector/high-resolution CT scanners, and where appropriate radiologic expertise is readily available. Blunt trauma, particularly from deceleration injuries, is associated with traumatic rupture. As opposed to smaller vessels, subclavian, innominate, and aortic injuries are rarely associated with thrombotic symptoms, even though there has been intimal disruption. The primary problem relates to gross vessel disruption. Complete separation is rarely if ever a clinical problem, as death is usually instantaneous. Surviving patients manifest vascular injury by the presence of false aneurysms, mediastinal or cervical hematomas, or apical capping. CT scanning has been an excellent screening tool for these injuries. However, unless vessel disruption is demonstrated, arteriography should follow the demonstration of hematomas, as many of these are associated with small vessel disruption that does not require surgery.

Abdominal vascular injuries after penetrating trauma invariably are associated with hemorrhage. Because laparotomy is indicated for almost all gunshot wounds of the lower chest and abdomen and all stab wounds associated with blood loss, the diagnosis of arterial or venous injury is usually made at the time of operation. Because of the relatively protected nature of the abdominal great vessels, blunt traumatic injuries are quite rare, and when present are manifested by weak or absent femoral pulses. For the reasons given previously, special diagnostic studies are rarely necessary when dealing with abdominal vascular trauma. CT scanning is used frequently to assess the source of ongoing hemorrhage but is of greater value in identifying specific organ injury rather than major vascular injury. Notable exceptions that may require arteriography are unstable pelvic fractures with evidence of ongoing bleeding. Arteriography may be indicated to assess the internal iliac vessels and treat the bleeding embolically. There may be a role for CT angiography in patients with unstable pelvic fractures from blunt trauma to identify suspect areas to target for subsequent embolization; often the CT can be obtained while awaiting setup of the angiography suite. Further, additional intra-abdominal and pelvic injuries may be delineated and 3D information obtained regarding the pelvic fracture pattern.

Extremity vascular injuries lend themselves to the diagnostic and screening maneuvers described in the previous sections. These patients fall into three general categories: (1) patients with evidence of pulselessness/ischemia, active bleeding, or a pulsatile hematoma; (2) patients with hard signs and a palpable pulse; and (3) patients with soft signs or an injury known to be associated with vascular injury. Initially, all patients should be adequately resuscitated and undergo reduction and stabilization of associated dislocations and fractures. Perfusion should be reassessed after these initial measures. In some cases, perfusion normalizes, and subsequent workup can proceed more deliberately. Ongoing assessment of patients with suspected extremity vascular injuries is outlined in Figure 1 and in the following discussion.

image

Figure 1 Algorithm: evaluation of extremity trauma.

(Modified from Anderson JT, Blaisdell FW: Diagnosis of vascular trauma. In Rich N, Mattox KL, Hirshberg A, editors: Vascular Trauma, 2nd ed. Philadelphia, Elsevier/Saunders, 2004.)

In the first category, patients with evidence of pulselessness/ischemia, active bleeding, or a pulsatile hematoma, urgent attention is required to prevent exsanguination or tissue necrosis from ischemia. Generally, these patients should be taken promptly to the operating room. If ischemia is complete, such as with a tourniquet, muscle necrosis will result from 4 hours of ischemia; fortunately, there is often some collateral flow that extends this critical time period. In most cases, the location of injury is apparent from the history, physical, and preliminary plain films; operative intervention can proceed accordingly. In other situations, the exact location and degree of injury are not apparent (Table 2). To minimize the duration of warm ischemia, on-table angiography can be performed. In some centers, formal angiography is available in the operating room.

Table 2 Indications for Arteriography: Extremity Trauma

From Anderson JT, Blaisdell FW: Diagnosis of vascular trauma. In Rich N, Mattox KL, Hirshberg A, editors: Vascular Trauma, 2nd ed. Philadelphia, Elsevier/Saunders, 2004.

Patients in the second category manifest hard signs, but do not demonstrate evidence of active bleeding or absence of perfusion. These patients can undergo a more deliberate, albeit expedient, assessment. Often the location and extent of injury is delineated with formal angiography. More recently, enthusiasm for CT angiography has grown. An advantage of formal angiography is the ability to perform therapeutic endovascular interventions such as embolization of muscular bleeders, or to control pseudoaneurysms or AV fistulas. As mentioned, in some cases associated injuries warrant urgent operative intervention before angiography can be obtained. In these cases, on-table angiography or formal angiography in the operating room are viable alternatives.

The final category involves patients with suspected extremity vascular injuries who present with soft signs only. Much of the controversy regarding evaluation of vascular trauma concerns this category. In patients with an injury in proximity to a major artery (although without hard signs), radiologic abnormalities may be present in as many as 10% of patients who undergo arteriography. However, a much smaller proportion of patients require operative intervention—several series indicate a range of 0.6%–4.4% of patients. Dennis and colleagues have made a cogent argument in support of physical examination alone in this patient population.20 They argue that patients requiring operative intervention will be identified from subsequent development of hard signs. Typically, patients are admitted for a short period of observation. Concerns regarding poor patient compliance for follow-up and a push to expeditiously identify significant injuries early (ideally, shortly after presentation to the emergency room to guide appropriate disposition) have led many others to use alternative protocols involving ultrasonography or CT imaging. Ultimately, the choice is often determined by cost, availability of modalities, center volume/resources, and local expertise.

Although injuries to any of the two lower arm or three lower leg vessels can result in bleeding that requires treatment, for the most part, unless clinical symptoms point to the need for intervention, operation is rarely indicated and screening for injury is not indicated. These vessels have abundant collateral flow, so injury that results in occlusion to any one of them is rarely symptomatic, and hemorrhage from a disrupted vessel usually stops spontaneously.

Two scenarios that require mention are patients with a posterior knee dislocation and patients with an injury in the region of the groin or thoracic outlet. Unrecognized popliteal injuries can lead to delayed thrombosis and severe distal ischemia because of poor collateral flow about the knee. For this reason dislocations of the knee and major fractures of the supracondylar and proximal tibial areas should have vascular screening. The minimal comprises duplex assessment and/or vigilant observation/examination, and the more optimal, angiographic imaging. An additional critical area relates to the profunda femoral artery that is buried deep in the thigh, and may be responsible for deep hemorrhage and hematomas that require intervention. When there is any question regarding injury, femoral arteriography is the best screening method and lends itself to embolic treatment of distal bleeding (proximal injuries are best exposed and repaired). In the absence of hard signs of vascular injury, patients with injuries in the region of the groin, thoracic outlet, or neck generally should be evaluated with either formal angiography or CT angiography. Duplex ultrasonography of the subclavian and iliac vessels is generally limited. Prompt evaluation is mandatory, as missed vascular injuries in these regions may lead to exsanguination into the intrapleural or retroperitoneal space.

REFERENCES

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