What is the low-cost test to order for a ventilated patient who becomes confused with arm edema?

Ordering an ultrasound is a prudent choice in the case of a ventilated patient who presents with confusion and arm edema. This imaging modality is non-invasive and can quickly assess for a variety of potential underlying issues, such as deep vein thrombosis (DVT) or other vascular concerns that may not be immediately apparent through a physical exam, especially in a patient who may be confused or unable to cooperate fully.

Given that the confusion and edema could indicate a significant complication, such as a thrombus affecting blood flow or causing discomfort, an ultrasound provides real-time visual information about blood flow and tissue status. It allows for immediate assessment of any vascular abnormalities that may require urgent intervention.

While other options such as D-dimer testing can provide information regarding clotting tendencies, they are not as direct and immediate in assessing the physical condition of the patient as an ultrasound. Similarly, while a VQ scan could evaluate for pulmonary embolism, it is more complex and expensive, making it less appropriate as an initial test in this scenario. The ankle-brachial index, while useful for assessing peripheral artery disease, would not provide relevant information regarding arm edema and confusion in this context.