Brown Ultrasound Tape Review – 9:3:2015
Article #1: Increased ICP via Optic Nerve Sheath Diameter (ONSD)
Amini, et al. (2013). Use of the Sonographic Diameter of Optic Nerve Sheath to Estimate Intracranial Pressure. American Journal of Emergency Medicine 2013; 31: 236–239.
In this 2013 study, Amini et al measured the ONSD of 50 non-traumatized patients undergoing LP and found that an ONSD >5.5mm correlated with an ICP >20mm Hg with a sensitivity and specificity of 100%. While this sounds great, we discussed well known concerns regarding inter-operator reliability and the technical aspects of accurately measuring the ONSD; measuring Optic Disc elevation is an alternative strategy.
The bottom line: while normal ONSD measurements cannot rule out increased ICP, it may be a useful adjunct in patients with low pre-test probability.
Article #2: Proximal Lower Extremity DVT
Crisp, et al. (2010). Compression Ultrasonography of the Lower Extremity with Portable Vascular Ultrasonography Can Accurately Detect Deep Vein Thrombosis in the Emergency Department. Annals of Emergency Medicine 2010; 56 (6): 601-611.
In this 2010 study by Crisp et al, 47 ED physicians performed “2 Point Compression” on the Common Femoral and Popliteal veins in 199 patients, and their results were compared to the “comprehensive” results from the Department of Radiology studies that each patient also received. The physicians took a 10 minutes training session, and the test was “positive” if a thrombus was visualized, or if the vein was non-compressible. When compared to the Radiology results, the ED docs were 100% sensitive and specific for DVTs in these locations. Our discussion centered around whether calf veins (which 2 Point Compression does not search for) are worth searching for (no one knows).
The bottom line: 2-point compression with a D-Dimer (and follow up comprehensive study if positive) may be an acceptable strategy for the management of DVT in the ED.
Special thanks and credit to Jon Thorndike