Akin to the ultrasound first for appendicitis protocol currently in use, the authors of a recently published study in CHEST propose using ultrasound before CTPA in patients where the diagnosis of pulmonary embolism is being considered.
Their protocol consisted of bedside thoracic and lower extremity ultrasounds to identify either a confirmatory DVT or an alternative diagnosis that would account for the patient’s current presentation. In both the ED and inpatient settings, ICU physicians evaluated this protocol’s performance in 100 patients. The 54 patients who were determined, due to an alternative diagnosis found on ultrasound, not to require further testing, none of them were found to have a pulmonary embolism on confirmatory CT. Of the remaining 40 patients (42%) whose ultrasound revealed no convincing alternative diagnosis or lower extremity DVTs, 12 were found to have pulmonary embolisms on their confirmatory CTPA. The authors conclude that though further studies are needed, an ultrasound first strategy will reduce the number of CTs obtained to rule out pulmonary embolism.
Though I am not opposed to the utilization of ultrasound as a bedside tool, using it to rule out pulmonary embolisms is a flawed paradigm. The proposed protocol is not one which rules out PE, it in fact does just the opposite. This protocol takes advantage of the high specificity of ultrasound for the diagnosis of pneumonia, pulmonary edema, and DVT. It employs the strategy of ruling in an alternative diagnosis or a lower extremity DVT. If no convincing diagnosis is discovered the patient will then move on to the more traditional rule out strategy of CTPA. This study essentially uses bedside ultrasound to address the two most heavily weighted criteria on the Well’s Score, “an alternative diagnosis that is less likely than pulmonary embolism” and “signs and symptoms of deep venous thrombosis”. In no way is this protocol fatally flawed. It has the potential to add a great deal to clinical decision making. Unfortunately it does not address the more serious epidemic in the current management of pulmonary embolisms. That is the egregious over-testing and subsequent over-diagnosis of pulmonary embolism in the ultra low risk patient.
“Ultrasound Assessment of Pulmonary Embolism in Patients Receiving Computerized Tomography Pulmonary Angiography”
journal.publications.chestnet.org/article.aspx?articleid=1763837
journal.publications.chestnet.org/article.aspx?articleid=1763837
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