Accuracy of Emergency Medicine Residents Using Point-of-Care Ultrasound (POCUS) to Detect Retained Stingray Barbs.

BACKGROUND: Stingray envenomation is a common presenting complaint for coastal emergency departments in the United States. Currently, radiograph is the gold standard to evaluate for a retained stingray barb, but ultrasound may be a useful tool to detect retained barbs. OBJECTIVE: To determine if emergency medicine residents could use ultrasound to identify stingray barbs embedded in animal tissue models. A secondary objective was to determine if resident experience affected their ability to detect stingray barbs. METHODS: Thirty-two emergency medicine residents participated in the study. After a short didactic session on foreign body identification with ultrasound, they rotated through six simulation stations and were asked to identify whether a stingray barb was present in pig and chicken tissue models. They were given 2 min per model to identify the presence, size, and depth of a stingray barb. Pre- and postexperiment surveys were collected to assess the residents' level of experience and confidence regarding foreign body identification using ultrasound. RESULTS: Residents accurately identified barbs in chicken drumsticks with a sensitivity of 72.92% (95% confidence interval [CI] 63.89-81.48) and a specificity of 64.58% (95% CI 54.16-74.08), and in pig's feet with a sensitivity of 50.00% (95% CI 39.62-60.38) and specificity of 68.75% (95% CI 58.48-77.82). There was no statistically significant difference regarding accuracy for any outcome measured based on experience or level of training. CONCLUSIONS: The use of point-of-care ultrasound by novice sonographers lacks sensitivity to identify retained stingray barbs in animal models and is not significantly impacted by resident experience with point-of-care ultrasound.

Drowning rule-out with novices (DROWN) in ultrasound.

Objectives: Non-fatal drownings confer significant morbidity and mortality in the United States. Chest radiograph (CXR) is typically used as a screening modality for interstitial edema but lacks sensitivity early after submersion. No study has evaluated lung ultrasound in assessing for pulmonary edema after submersion events and we hypothesized that lung point-of-care (POC) ultrasound can identify interstitial edema in patients presenting after non-fatal drownings. Methods: Patients presenting to the emergency department after a submersion event were eligible if a CXR was obtained as part of their care. Emergency medicine residents performed a lung POC ultrasound and provided a "novice" interpretation of "normal" or "abnormal," which was independently reviewed by a blinded expert sonographer. Patients were contacted 2 weeks after presentation to assess for late sequela. Results: A prospective convenience sample of 59 patients included 21 adults (36%) and 38 children (64%) enrolled over 17 months with a median age of 6. Twenty-four (41%) patients had abnormalities on CXR. Of these, 20 patients had a positive ultrasound per novice interpretation. Compared to CXR, ultrasound had an overall sensitivity of 83% and a specificity of 66% for detecting pulmonary edema in non-fatal drownings. Notably, out of 35 subjects with a negative CXR, there were 12 (34%) cases with a positive lung ultrasound, 10 of which required hospital admission. Conclusion: Lung POC ultrasound has a moderate sensitivity and specificity when performed by novice sonographers to detect pulmonary edema presenting to an ED setting after a non-fatal drowning event.

Designed Artificial Protein Heterodimers With Coupled Functions Constructed Using Bio-Orthogonal Chemistry.

The formation of protein complexes is central to biology, with oligomeric proteins more prevalent than monomers. The coupling of functionally and even structurally distinct protein units can lead to new functional properties not accessible by monomeric proteins alone. While such complexes are driven by evolutionally needs in biology, the ability to link normally functionally and structurally disparate proteins can lead to new emergent properties for use in synthetic biology and the nanosciences. Here we demonstrate how two disparate proteins, the haem binding helical bundle protein cytochrome b 562 and the ß-barrel green fluorescent protein can be combined to form a heterodimer linked together by an unnatural triazole linkage. The complex was designed using computational docking approaches to predict compatible interfaces between the two proteins. Models of the complexes where then used to engineer residue coupling sites in each protein to link them together. Genetic code expansion was used to incorporate azide chemistry in cytochrome b 562 and alkyne chemistry in GFP so that a permanent triazole covalent linkage can be made between the two proteins. Two linkage sites with respect to GFP were sampled. Spectral analysis of the new heterodimer revealed that haem binding and fluorescent protein chromophore properties were retained. Functional coupling was confirmed through changes in GFP absorbance and fluorescence, with linkage site determining the extent of communication between the two proteins. We have thus shown here that is possible to design and build heterodimeric proteins that couple structurally and functionally disparate proteins to form a new complex with new functional properties.

Association of Fluorescent Protein Pairs and Its Significant Impact on Fluorescence and Energy Transfer.

Fluorescent proteins (FPs) are commonly used in pairs to monitor dynamic biomolecular events through changes in proximity via distance dependent processes such as Förster resonance energy transfer (FRET). The impact of FP association is assessed by predicting dimerization sites in silico and stabilizing the dimers by bio-orthogonal covalent linkages. In each tested case dimerization changes inherent fluorescence, including FRET. GFP homodimers demonstrate synergistic behavior with the dimer being brighter than the sum of the monomers. The homodimer structure reveals the chromophores are close with favorable transition dipole alignments and a highly solvated interface. Heterodimerization (GFP with Venus) results in a complex with ≈87% FRET efficiency, significantly below the 99.7% efficiency predicted. A similar efficiency is observed when the wild-type FPs are fused to a naturally occurring protein-protein interface system. GFP complexation with mCherry results in loss of mCherry fluorescence. Thus, simple assumptions used when monitoring interactions between proteins via FP FRET may not always hold true, especially under conditions whereby the protein-protein interactions promote FP interaction.