Device-associated and healthcare-associated infection — branching viva

Station status

This is one MedVellum formative branching structured oral. The prompts and performance descriptions are educational feedback tools; they are not an official college examination format, mark allocation, pass score or reproduced station. The viva assesses surveillance definition, recognition, cultures and empiric therapy, the line-removal decision, de-escalation, complication management, and prevention-bundle reasoning. [3] [12]

Stage 1 — Recognition and definition

Examiner. A 9-year-old boy with a long-term tunneled central line for short-bowel syndrome is admitted with fever and rigors during a line flush. He looks unwell but is perfusing normally; the exit site is clean. [1] [3]

What the candidate must do. Recognise suspected central-line-associated bloodstream infection. State the surveillance definition: a laboratory-confirmed bloodstream infection with a central line in place for more than two calendar days and no other attributable source, with onset more than 48 hours after admission qualifying it as healthcare-associated. State clearly that the child is treated on clinical grounds while surveillance is adjudicated. [3] [12]

Examiner branch. "Why do we count these per device-day?" The candidate should explain that rates are expressed per 1000 line-days to make units and time periods comparable, and that the line itself is the dominant modifiable risk factor. [1] [12]

Stage 2 — Investigations, empiric therapy and the line decision

Examiner. "Take me through your first actions." [3]

What the candidate must do. Draw paired blood cultures from a peripheral site and from the line before antibiotics, send inflammatory markers and a lactate, and give empiric antistaphylococcal cover for coagulase-negative staphylococci and Staphylococcus aureus. Because he is stable and the site is clean, immediate removal is not mandated on the first culture, but the candidate must state the removal thresholds: sepsis, tunnel or pocket infection, persisting or relapsing bacteraemia, endocarditis, or a high-risk organism. [3] [12]

Examiner branch on cultures. "How would a short differential time to positivity change your thinking?" The candidate should explain that a line culture turning positive substantially faster than the peripheral culture supports an intraluminal line source and lowers the threshold for removal. [3]

Stage 3 — The organism and de-escalation

Examiner. "Both cultures grow Staphylococcus aureus." [3]

What the candidate must do. Recognise a high-risk organism. Remove the line, arrange echocardiography and targeted imaging to exclude endocarditis and metastatic infection, and extend and guide therapy with infectious diseases. De-escalate to the narrowest effective agent once sensitivities return, and define a duration appropriate to bacteraemia and any seeded focus. [3] [12]

Examiner branch. "He has now had broad antibiotics. He develops watery diarrhoea." The candidate should suspect Clostridioides difficile, stop the inciting antibiotic where possible, send a stool test, and start oral metronidazole or, for severe disease, oral vancomycin or fidaxomicin per current paediatric guidance. [9]

Stage 4 — Prevention and the system

Examiner. "His line was at home. What should have prevented this, and what do you do for the unit?" [12]

What the candidate must do. State the multimodal prevention bundle: hand hygiene at the five moments, maximal sterile barriers at insertion, chlorhexidine preparation, optimal site selection, scrub-the-hub before every access, dressing care, and daily documented review of necessity. Acknowledge that for a home line the family carries out maintenance, so a clear written safety-net for fever is part of discharge. For the unit, explain surveillance, rate feedback, and outbreak review of the failed bundle element. [3] [4] [12]

Examiner branch on equity. "His family lives three hours away and he has complex chronic disease." The candidate should note that complex-chronic and geographically disadvantaged children carry disproportionate device-day exposure and avoidable harm, so clear communication, practical safety-netting, and earlier escalation are justified. [1] [2]

MedVellum formative marking domains

This educational rubric has six domains scored 0–3, giving a MedVellum formative total of 18. Score 0 for omitted or unsafe, 1 for named but incomplete, 2 for clear and safe, and 3 for integrated, prioritised and reassessed. This is not an official board mark or pass standard. [3] [12]

Critical fails

Any item below overrides a reassuring formative total because it creates immediate avoidable risk. [3] [9]

• Delays cultures or antibiotics while awaiting surveillance adjudication.
• Attempts to salvage a line in Staphylococcus aureus bacteraemia.
• Treats catheter-associated asymptomatic bacteriuria, or tests an asymptomatic child for C. difficile without clinical diarrhoea.

Model performance

"This child has suspected central-line-associated bloodstream infection, defined as a laboratory-confirmed bloodstream infection with a line in place for more than two days and no other source, so I treat him on clinical grounds immediately. I take paired peripheral and line cultures before antibiotics, give empiric antistaphylococcal cover, and set removal thresholds for sepsis, tunnel infection, persisting bacteraemia, and high-risk organisms. When both cultures grow Staphylococcus aureus I remove the line, image for endocarditis and metastatic infection, and guide prolonged therapy with infectious diseases. When broad antibiotics are followed by diarrhoea I suspect C. difficile, stop the inciting agent, test stool, and treat appropriately. To prevent the next infection I apply the multimodal bundle — hand hygiene, barriers, chlorhexidine, hub care, and daily review of necessity — and I steward the device and the antimicrobial together, with a clear family safety-net for fever at home." [3] [9] [12]