THE DIAGNOSIS OF VASCULAR TRAUMA

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CHAPTER 63 THE DIAGNOSIS OF VASCULAR TRAUMA

John T. Anderson, F. William Blaisdell

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 colleagues ¹ 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

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