Branching cross-examination

This is a MedVellum formative viva. It is not an official RACP, MRCPCH, ABP, ACGME or RCPSC station, mark scheme, duration or pass standard. Release each update only after the candidate states the failing system, the immediate action and the reassessment endpoint. [1] [9]

Candidate brief

You are the senior paediatric clinician in a rural district emergency department. Speak as you would during resuscitation. Secure immediate threats before any decontamination, state the change you expect from each action, and say what you will reassess. This is one continuous case. Each escalation branch leads to the next update. [9]

Question 1 — Doorway and the first 60 seconds

Stimulus update. A parent carries a three-year-old who is drowsy but rousable, forty minutes after swallowing an unknown number of sustained-release tablets from a grandparent's pill organiser. The container is available. Before you touch the child you see a drowsy but pink toddler with mild tachycardia. Question: What do you say and do now? [9]

Consultant-level model answer. "I am concerned. This is a sustained-release ingestion within the intervention window, and the child is already symptomatic. I call the senior paediatric team, confirm the primary survey — airway, breathing, circulation, and a bedside glucose — obtain a working weight, and put the child on continuous monitoring with IV access. I ask the parent to bring the container and remaining tablets. I take the four-question history and call the Poisons Information Centre with the substance, dose, time and weight. Stabilisation and observation run while the toxin is identified." [1] [9]

Probing follow-up. "Why confirm the primary survey before giving charcoal?" A strong answer is: "Because resuscitation precedes decontamination in every poisoned child. An unstable child is harmed, not helped, by charcoal, and the airway must be protected before any dose." [9]

Common weak answer. "I will give charcoal straight away and then take the history." Decontamination before resuscitation and before confirming the toxin is the classic error. [3]

Escalation branch. If the candidate confirms the primary survey and starts the structured history, release in Question 2 the toxidrome and the container detail. If they lead with charcoal, ask which conditions must be met first. [3]

Question 2 — The history, the toxidrome and the charcoal decision

Stimulus update. The container confirms a sustained-release calcium-channel blocker. The child has dilated pupils, a heart rate of 130 and is increasingly drowsy. It is now fifty minutes since ingestion. The airway is protected and the child is not vomiting. Question: How do you decide on activated charcoal? [3] [9]

Consultant-level model answer. "I take the four-question history: what (sustained-release calcium-channel blocker), how much (estimate the maximum missing), when (about fifty minutes ago), and what else (no co-ingestants reported). I read the toxidrome: dilated pupils and tachycardia are not classic, so I keep the differential broad and watch for cardiotoxicity. For charcoal, the conditions are met: we are within the first hour, the airway is protected, the child is not vomiting, and the toxin is adsorbable. I give activated charcoal at 1 g/kg to a maximum of 50 g, after confirming with the Poisons Information Centre that this formulation is adsorbable." [3] [12]

Probing follow-up. "Why does sustained-release change the plan?" A strong answer is: "Sustained-release formulations keep absorbing for many hours, so I extend the observation window and keep decontamination options open, including whole bowel irrigation, because charcoal does not bind everything and absorption is prolonged." [5]

Common weak answer. "It is almost an hour, so charcoal is too late." For sustained-release ingestions the window may be extended and the decision is toxicologist-guided; it is not a hard one-hour cut-off. [3]

Escalation branch. If the candidate gives charcoal correctly and explains the sustained-release implication, release in Question 3 that the child deteriorates with bradycardia and hypotension. If they declare the window closed, ask how sustained-release changes absorption. [5]

Question 3 — Deterioration and whole bowel irrigation

Stimulus update. Two hours after ingestion the child becomes bradycardic and hypotensive, with a falling conscious level. The airway is secured. Question: How do you escalate, and what decontamination method applies now? [5]

Consultant-level model answer. "This is cardiotoxic deterioration from a sustained-release calcium-channel blocker. I resuscitate: secure the airway, give oxygen, support the circulation with fluids and vasoactive support per the toxicology pathway, and treat the specific toxicity with the toxicologist's guidance. Because this is a sustained-release ingestion that continues to absorb, I escalate to whole bowel irrigation with polyethylene glycol via the nasogastric tube, now that the airway is secured, to flush the remaining drug from the gut. I observe in a high-dependency or PICU setting for prolonged and recurrent toxicity." [5] [7]

Probing follow-up. "Why whole bowel irrigation rather than more charcoal?" A strong answer is: "Whole bowel irrigation physically flushes tablets and sustained-release matrices that charcoal cannot bind, and it is specifically indicated for sustained-release, iron, lithium and packet ingestions. It is not a substitute for resuscitation and circulatory support." [7]

Common weak answer. "I will give more charcoal and observe." Repeated charcoal without a recirculation indication, and observation without escalated decontamination for a deteriorating sustained-release ingestion, misses the role of whole bowel irrigation. [7]

Escalation branch. If the candidate escalates to whole bowel irrigation and critical care, move to Question 4 on retrieval and handover. If they only give more charcoal, ask which method removes sustained-release matrices charcoal cannot bind. [7]

Question 4 — Retrieval, safeguarding and structured handover

Stimulus update. The child is stabilised on vasoactive support but needs PICU care and toxicologist-led management unavailable in the rural hospital. Question: Describe your escalation, safeguarding and handover. [9]

Consultant-level model answer. "I called retrieval in parallel with resuscitation, before local support was exceeded. I agree the destination, the treatment to continue, the escort and equipment, the expected deterioration, the plan if transfer is delayed, and the monitoring en route. In parallel I consider safeguarding: this is an unintentional toddler exposure, but I document objectively, check the home safety and storage, and offer poison-prevention advice. My structured handover transfers identity and working weight, the substance and dose and time, the toxidrome and its trend, the timed actions and response, the decontamination given, local limits, family and safeguarding information, and the next contingency and its named owner. I keep the family informed and document objectively." [9]

Probing follow-up. "When would safeguarding escalate beyond prevention advice?" A strong answer is: "If the history is inconsistent with the developmental stage, the substance is unusual, access was unsafe or neglected, or there are repeated presentations, I activate the local safeguarding pathway in parallel with medical care." [9]

Common weak answer. "I will wait for retrieval and then hand over." The child needs ongoing reassessment and stabilisation during the wait, and safeguarding and prevention run in parallel, not after. [9]