INTERVENTIONAL RADIOLOGY: DIAGNOSTICS AND THERAPEUTICS

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CHAPTER 22 INTERVENTIONAL RADIOLOGY: DIAGNOSTICS AND THERAPEUTICS

George Maish, Timothy Fabian

Radiology has always been an important component of a Level I trauma center. This relationship has increased over the last two decades such that it is almost impossible to conceive of caring for a trauma patient without the ability to perform trauma imaging. Interventional radiology techniques, including angiography, angioembolization, and stent placement, have evolved from infrequently used adjuncts in the care of trauma patients into pivotal adjuncts in the nonoperative management of solid organ injury and hemorrhage associated with pelvic trauma. Historically, these techniques have only been available in a dedicated angiographic suite that was physically separate from the resuscitation area and operating room. This required that patients were hemodynamically normal so that they could tolerate the transportation to the angiographic suite. In addition, commitment to availability 24 hours a day from angiographic technologists and staff was necessary to ensure that these techniques would be available. This distinction among resuscitation area, operating room, and angiographic suite has been gradually dissolving over the past decade. Many centers have built angiographic suites into or next to their emergency department so that the risk of transportation has been decreased. In addition, the development of better radiolucent operating room tables and portable fluoroscopy machines with digital subtraction capabilities has enabled some interventional radiology techniques to be performed in the operating room. Several institutions have built endovascular suites in their operating room suites for the performance of endovascular techniques by vascular surgeons. This ever increasing fusion of resuscitation area, operating room, and angiographic suite has made interventional radiology techniques available to more trauma patients than ever before.

While the angiography suite has been undergoing an evolution over the past decade, the practitioner who is capable of performing these techniques has been changing as well. Historically, endovascular techniques were the exclusive domain of the interventional radiologist. This has changed. Endovascular techniques are now completely incorporated into the training of vascular surgeons, with many vascular surgeons offering both endovascular and traditional vascular techniques for the management of peripheral vascular disease, aortic aneurysms, and aortic dissections. In addition, interventional cardiologists are placing carotid stents for the management of carotid stenosis. Due to difficulty in obtaining interventional radiology coverage 24 hours a day, 7 days a week, some trauma surgeons have obtained additional training in endovascular techniques so that trauma patients have access to these less invasive techniques.

While interventional radiology techniques have become more accessible for the trauma patients, developments in the technology of computed tomography (CT) scanners, particularly the development of the multidetector CT scanner, have allowed for the development of CT angiography for diagnosis. CT angiography is beginning to challenge conventional angiography as a gold standard in the diagnosis of some injuries. However, for now, angiography remains the gold standard for the diagnosis of most vascular injuries.

In order to make the angiographic suite available to the trauma patient, it is important that the patient is either hemodynamically normal or accompanied by a physician and a nurse to make sure that the patient is being appropriately resuscitated. Good communication between the interventional radiology staff and the trauma team is essential to ensure safe care of the severely injured trauma patient.

INDICATIONS

The indication for using interventional radiology techniques in the care of trauma patient depends on the technique being used and the medical condition of the trauma patient. It is not appropriate to transport a hemodynamically abnormal patient to the angiographic suite for a diagnostic arteriogram. The arteriogram should either be performed in the operating room or delayed until the patient is resuscitated. Alternatively, patients with severe pelvic trauma should undergo relatively prompt arteriography and possible embolization to try to achieve hemostasis. These patients may be hemodynamically abnormal but the interventional radiology techniques are part of their resuscitation. In other injuries, interventional radiology techniques may be used to provide definitive therapy for hemorrhage. The development of intravascular covered stents has allowed for the management of certain injuries, including arterial disruption and arteriovenous fistulas, to move from the operating room to the angiographic suite. Venous injuries including lacerations, thrombosis, and compression can be managed by the placement of uncovered intravascular stents. The decision to use interventional radiology techniques and the timing of these techniques requires that the trauma surgeon understands the indications and limitations of these techniques.

BLUNT CEREBROVASCULAR INJURY

Over the past decade, there has been an increased awareness of blunt cerebrovascular injury (BCVI), which includes carotid artery injuries (CAI) and vertebral artery injuries (VAI). Several studies have identified an incidence of 1.5%–2% for BCVI among blunt trauma victims. Historically, blunt carotid artery injuries had been diagnosed by onset of neurologic symptoms. The outcomes for this injury were poor. Blunt carotid injuries had an associated mortality rate of 31% and a stroke rate of 43%. Blunt carotid injuries have been shown to have worse outcomes compared to penetrating carotid injuries. Seventy-eight percent of patients with penetrating carotid injuries have been found to be independent with locomotion at the time of discharge compared to 37% of those with blunt carotid injuries. Blunt carotid injuries also have a worse outcome compared to the overall blunt trauma population. Fifty-five percent of blunt trauma patients are able to be fully independent at the time of discharge compared to 33% of patients with blunt carotid injury. VAI occurs in 0.53% of blunt trauma patients, and has an associated stroke rate of 25%. Screening protocols using four-vessel angiography have been used to successfully identify these injuries prior to the development of neurologic symptoms. The institution of early treatment with anticoagulation or antiplatelet therapy in VAI has been shown to decrease the stroke rate from 14% to 0%. When anticoagulation or antiplatelet therapy is used in the management of blunt carotid injuries, the stroke rate decreases from 60% to less than 10%. It is clear that there is significant morbidity and mortality when BCVI is missed. However, they occur relatively infrequently, such that it is not practical to screen all blunt trauma patients.

Several screening triggers have been suggested in the literature including cervical spine fracture, neurologic findings not explained by radiographic findings, Horner’s syndrome, LeFort II or III facial fractures, skull base fractures involving the foramen lacerum, and neck soft tissue injury. A good screening test should be relatively inexpensive, have a low morbidity rate, and a high sensitivity rate. It should find all the true positive results with some false positives and no false negatives. In a comparison of magnetic resonance angiography (MRA), computed tomographic angiography (CTA), and four-vessel cerebral angiography between 2000 and 2002, the sensitivity of MRA and CTA for BCVI was 47%–53%. These rates are too low for a test to be an effective screening modality. Four-vessel cerebral angiography has been identified as the gold standard for the diagnosis of BCVI. However, its cost and major complication rate of 1%–3% in large series make it a less than ideal screening test. The development of the multidetector CT scanner has increased the resolution of the CT scanner. Two recent studies demonstrated that CTA performed on multidetector CT scanners has dramatically improved ability to diagnose these injuries. A head-to-head comparison of CTA with multidetector CT scanners and four-vessel cerebral angiography has yet to be done. As a result, four-vessel cerebral angiography remains the gold standard for diagnosis and screening of these injuries. It will be important to continue to monitor improvements in CTA, MRA, and possibly even ultrasound technologies for less invasive, cheaper, and safer screening modalities for BCVI.

Blunt cerebrovascular injuries have been effectively managed by anticoagulation or antiplatelet therapy in patients with contraindications to anticoagulation. With the development of endovascular technologies including balloons, coils, and stents, there have been several single-institution, small series that have demonstrated good efficacy in the treatment of traumatic pseudoaneurysms of the carotid artery with good short-term follow-up. However, one large series with 46 patients over an 8-year period demonstrated a 21% complication rate and 45% occlusion rate for patients treated with endovascular stents. Patients who had received antithrombotic agents alone only had a 5% occlusion rate. This study concluded that antithrombotic therapy was the recommended therapy for blunt carotid injuries, and that the role of stents remains undefined. The indications for the use of endovascular techniques in the management of BCVI remain unclear and their long-term results are unproven. Clearly, further study of these techniques is warranted.

BRACHIOCEPHALIC TRAUMA

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