Diagnosis of Posttraumatic Pulmonary Embolism: Is Chest Computed Tomographic Angiography Acceptable?

Abstract

PE frequently occurs soon after injury. The majority of PEs after trauma are found peripherally (in segmental or subsegmental vessels). Right/left pulmonary artery embolisms are likely to be found only later in a trauma patient's course. Any diagnostic study used to diagnose pulmonary embolism in trauma patients must have sufficient resolution capacity to reliably detect segmental and subsegmental clot. A diagnostic modality such as CT scanning that is insensitive to peripheral embolisms may miss a significant number of posttraumatic PEs.

Can We Rely on Computed Tomographic Scanning to Diagnose Pulmonary Embolism in Critically Ill Surgical Patients?

“…In contrast to other populations, the authors have noted that PE occurs early after injury. In a subsequent study, 16 they have confirmed that more than one fourth of the patients had a PE within the first 4 days after admission. Furthermore, they found that three fourths of their patients had PE confined to peripheral vessels.…”

“…Under these conditions, the lack of sensitivity of CTPA to detect peripheral emboli is concerning. The incidence of peripheral PE was 5% in studies with predominantly medical populations 11,17 and over 50% (a 10-fold increase) in studies with predominantly surgical populations 15,16 and in our study. Decreasing the collimation from 3 mm to 2 mm or 1 mm improved the identification of peripheral vessels.…”

“…Some believe that occlusion of small pulmonary vessels does not cause important physiologic alterations. 5 We and others 8,16 believe that peripheral PE may be important for three reasons: multiple peripheral PE may cause a diffuse inflammatory process causing bronchoconstriction and V/Q mismatch; even isolated peripheral PE may upset the delicate respiratory balance of critically ill patient; and peripheral PEs indicate a hypercoagulable state and may be the harbinger of subsequent larger PEs. Under these conditions, the lack of sensitivity of CTPA to detect peripheral emboli is concerning.…”

The (Absence of a) Role of Venous Duplex Scan in the Diagnosis of Pulmonary Embolism after Severe Trauma

“…The prevention, diagnosis, and treatment of PE remain unsettled in trauma. Methods of prevention are ineffective, 22 methods of diagnosis potentially inaccurate, 1,7 and methods of treatment debated. 23 In particular, severely injured patients confuse the picture even further by the multiple confounding factors that complicate their clinical presentation and outcome.…”

“…[2][3][4] Although it has been used successfully in predominantly medical patients, 2-6 the published evidence on its accuracy when used in critically injured patients is far from convincing. 1,7 Transport out of the intensive care unit, even if of shorter duration than for conventional pulmonary angiography, remains a problem with CT. 8,9 Venous ultrasonography and measurement of Ddimer levels have been used as alternative methods to diagnose PE without subjecting the critically injured patient to the risks of transport. Although normal Ddimer levels carry a very high negative predictive value for PE after the 4th day of trauma, 10,11 they are unreliable in earlier periods during which a significant number of thromboembolic events occurs.…”