Laboratory Studies
The arterial pressure index is useful in detecting patients with major vascular injury and pulses that appear normal. Systolic blood pressure in the affected extremity is divided by systolic pressure in the contralateral normal extremity. A value of less than 90% is considered abnormal.
The sensitivity of the arterial pressure index for injuries requiring intervention ranges from 75 to 95%, depending on the circumstances. The arterial pressure index is highly sensitive in ruling out popliteal artery injury in patients with knee dislocation. Most injuries that present with an arterial pressure index greater than 90% heal spontaneously. [21, 22]
The ankle-brachial index is equivalent to the arterial pressure index and may be used when multiple extremity injuries are present. This is calculated by dividing the higher of the systolic dorsalis pedis or posterior tibial artery pressure by the ipsilateral brachial artery pressure.
The Allen test is useful for detecting injuries distal to the brachial artery bifurcation. Persistence of pallor of the hand when the radial artery is manually compressed suggests occlusion of the ulnar artery and vice versa.
Imaging Studies
Conventional angiography remains the criterion standard for evaluation of vascular injuries in trauma patients. [23, 24] The disadvantages include cost, significant time delay in preparation for the test, and a 0.6% major complication rate. Contrast dye load and renal function are important pre-study considerations. Only 1-1.5% of proximity angiograms performed in patients lacking "hard" signs of vascular injury reveal injuries that require intervention. Duplex ultrasonography is a noninvasive technique used to investigate injuries with a high-risk mechanism or location but without "hard" signs or obvious indications for surgical management. [2]
Small, prospective studies suggest that the sensitivity of ultrasonography is 95-100% for diagnosing vascular injuries that lack "hard" signs but require intervention. [25] These results were obtained by highly qualified teams that maintain a high clinical index of suspicion. [26] Color-flow duplex ultrasonography has been found to be a low-yield strategy for predicting therapeutic intervention. [7] The examination is highly operator dependent, and the negative predictive value has been as low as 50% in some series. Duplex ultrasonography is of limited use in the evaluation of poorly accessible vessels, such as the subclavian, profunda femoris, and profunda brachii arteries. Duplex ultrasonography can play a role in the evaluation of patients presenting with "soft" signs of injury; however, its use has largely been supplanted by multidetector CT angiography.
Multidetector helical CT (MDCT) angiography is a sensitive method of diagnosing arterial injuries when compared with conventional angiography and surgical exploration. [27] Studies using 4- and 16-slice MDCT angiography have demonstrated a sensitivity of 90-95% for significant arterial injuries. [28, 29, 30] . A study by Seamon et al demonstrated a sensitivity and specificity of 100% for clinically significant injury using 16-slice and 64-slice technology. [31]
Compared to conventional angiography, MDCT angiography is considerably faster, is less expensive and less invasive, and does not require the involvement of interventional radiology. Studies support MDCT angiography as the diagnostic study of choice for blunt and penetrating vascular trauma patients who do not have obvious indications for immediate operative intervention. [10]
In a retrospective evaluation of 51 patients with penetrating neck injury, MDCT angiography as initial evaluation was found to help guide management decisions if an external carotid artery injury was detected. Sensitivity of CTA for detecting arterial injuries ranged from 75.7% to 82.2%, and specificity ranged from 96.4% to 98.4%. However, according to the authors, negative findings should not preclude close clinical follow-up, repeat CTA evaluation, or, in the presence of high suspicion of arterial injury due to clinical findings or wound trajectory, evaluation with digital subtraction angiography. [32, 33]
In a study of 150 patients with soft signs of vascular injury, Doppler had a sensitivity of 94% and specificity of 82.5% for the diagnosis of vascular injury. [34]
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Pseudoaneurysm of the axillary artery.
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Arteriovenous fistula between common femoral artery and vein.
