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Background Overdiagnosis of ventilator associated pneumonia (VAP) is common and may be due, in part, to excessive culturing of the respiratory tract in ventilated patients. We sought to evaluate the appropriateness of these cultures based on clinical characteristics leading to culture acquisition, and the relationship with antibiotic use. Methods We included mechanically ventilated adult patients in the Neuroscience and Cardiac Surgery Intensive Care Units at an academic medical center in Baltimore, MD, who had respiratory tract cultures obtained from March 1 to June 30, 2021. The appropriateness of respiratory cultures was evaluated by chart review in a standardized manner using a published algorithm (Figure 1). Clinical characteristics of patients with appropriate vs. inappropriate cultures were compared using Fisher’s exact test. Results 98 respiratory tract cultures (58 endotracheal aspirates, 25 mini bronchoalveolar lavages (BAL), 13 BALs, and 2 bronchial washings) were evaluated. Of these, 19 (19%) were deemed appropriate and 79 (81%) were inappropriate. Compared to patients with inappropriate cultures, those with appropriate cultures were more likely to demonstrate worsening oxygenation, new or increasing infiltrate on chest x-ray, or hemodynamic instability. The groups did not significantly differ with respect to fever or changes in WBC count (Figure 2). Of 79 inappropriate cultures, 31 (39%) received a clinical diagnosis of VAP from their provider. In 23 (29%) instances, antibiotics were started or changed based on culture results, and 9 (11%) were on empiric therapy for VAP that was continued unchanged. An additional 24 (30%) continued antibiotics not directed toward VAP. Excluding those on antibiotics not directed towards index respiratory culture results, patients received a median of 6 (IQR 2.5, 7) days of therapy. Conclusion A large majority of lower respiratory tract cultures in mechanically ventilated patients are potentially inappropriate and associated with overdiagnosis of VAP and unnecessary antibiotic exposure. Incorporating respiratory tract specific attributes into clinical decision making rather than “pan-culturing” for fever or leukocytosis may be an opportunity for diagnostic stewardship in this setting. Disclosures Kimberly C. Claeys, PharmD, BioFire Diagnostics: Honoraria.

Background: Cardiovascular implantable electronic device (CIED) implant sites usually heal with hypovascular fibrotic capsule formation which can lead to complications including device movement, infection risk and reoperative challenges. An ECM CIED envelope at implant may promote stabilization, constructive tissue remodeling, reduced fibrosis and increased vascularity. Methods: Ten rabbits received single-chamber pacemakers (PMs) (St. Jude Medical) in ECM envelopes (CanGaroo® Envelope, Aziyo Biologics, Silver Spring, MD) and 10 received identical PMs without envelopes. One PM+ECM animal was evaluated at week 2, and remaining animals were evaluated at either week 13 or 26. Implant site tissues were analyzed by gross observation and histopathology. Results: PM+ECM animals had a 5-fold reduction in PM subcutaneous movement (migration or device flipping) compared to the PM only group. Histology showed progressive ECM envelope resorption by 13 and 26 weeks, with increased vascularization over time compared to PM only group at 13 and 26 weeks (Fig 1). PM+ECM animals had a lower average capsule thickness compared to PM only group -mean of 349 ± 165µm (mean ± SD) versus 417 ± 152µm at 13 weeks and a mean of 427 ± 141µm versus 439 ± 91µm at 26 weeks. Neovascularization score (blinded pathologist, 0-4 point scale) demonstrated a significantly higher PM+ECM group average score vs. PM only (2.1 vs 1.7, p<.05, Student's t-test). Conclusion: Porcine small intestinal submucosa ECM envelopes promoted PM implant stabilization with implant site healing remarkable for reduced capsule thickness and increased vascularity, compared to PMs without envelopes in a preclinical model. ECM envelopes may provide meaningful clinical benefits for CIED implant pockets and warrant further investigation. Figure 1: Representative gross images of the subcutaneous pocket. 1A) Images demonstrating remodeling of the ECM envelope over time at 2, 13, and 26 weeks with increasing levels of vascularization. 1B) Comparison images from PMs without envelope implant at 13 and 26 weeks show lower vascularization levels and a flipped device at 26 weeks.

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Patient: Male, 35-year-old Final Diagnosis: Thrombosis Symptoms: Pain Medication: — Clinical Procedure: — Specialty: Infectious Diseases • Medicine, General and Internal • Psychiatry Objective: Unusual clinical course Background: A predictable consequence of long-term injection drug use is the destruction of the native venous system; as a consequence, people who inject drugs may eventually move to injection into skin and subcutaneous tissue, wounds, muscles, and arteries. These practices put people who inject drugs at risk for injection-related soft-tissue infection, vascular damage, ischemia, and compartment syndrome, all of which have overlapping presenting symptoms. Case Report: A 35-year-old man who injects drugs presented with foot swelling and discoloration initially concerning for necrotizing fasciitis or compartment syndrome. After progression despite appropriate antimicrobial and surgical treatment for soft-tissue infection, he was diagnosed with arterial insufficiency and resultant distal ischemia. This diagnosis was discovered only after obtaining additional history of the patient’s drug use practices. Just prior to his symptoms, he had unintentionally injected a formed thrombus into his dorsalis pedis artery. Conclusions: Intra-arterial injection of drugs can cause ischemia through a variety of mechanisms, including direct vessel trauma, arterial spasm, toxicity from the drug of abuse or an adulterant, embolism of particulate matter, and as proposed here, direct injection of preformed thrombus. Medical providers should be aware of the steps of injection drug use and their associated risks so that they can ask appropriate questions to focus their differential diagnosis, increase their understanding of common or current local injection practices, and develop rapport with the patient. Patient education on safe injection techniques may also reduce the risk of serious complications.