Plot the level, respect the time — paediatric paracetamol poisoning

Station status

This is one MedVellum formative structured clinical encounter. The scoring, prompts and performance descriptions are educational feedback tools. They are not an official college station, timing, mark allocation, pass score or reproduced examination format. The encounter assesses first-impression recognition, taking a precise ingestion history, applying the Rumack-Matthew nomogram at four hours, giving activated charcoal early, starting intravenous N-acetylcysteine on or above the treatment line, managing an anaphylactoid reaction, tracking the ALT and INR trend, communication, escalation, and a structured handover. [1] [11]

Candidate instructions

You are the paediatric registrar called to the acute assessment room. Assess the child from the doorway and say aloud what you see. Take a precise ingestion history: the formulation, the amount, the time of ingestion, whether it was single or staggered, and any co-ingestants. Apply the Rumack-Matthew nomogram correctly for a single acute ingestion with a known time, draw the four-hour level, give activated charcoal within the window, and start intravenous N-acetylcysteine on or above the treatment line. Speak directly to the child and parent. Reassess after every action. Call the poisons information centre and senior or toxicology support early. Finish with a structured handover and disposition plan. Say what you would assess or do; do not perform painful or distressing manoeuvres on the actor. [1]

Room setup and observable starting state

The encounter. Leo is eight and is sitting on the assessment trolley beside a parent. The parent holds an open bottle of paracetamol tablets and says, "He's taken some of these about two hours ago." Leo is alert, pale and mildly nauseated, with no distress. The candidate should describe the scene objectively, declare the suspected paracetamol ingestion, establish the ingestion pattern and time, and recognise that the four-hour level cannot yet be interpreted. [11]

Simulation safety. Leo remains on the trolley and is never forcibly positioned. Cards or the assessor supply vital signs, monitor readings and laboratory values. The parent does not obstruct urgent care. [1]

Actor cues

Parent actor

• Begin with "He's taken some of these about two hours ago." If asked what has changed, answer: "Leo found the bottle in the kitchen drawer. He says he swallowed about ten tablets around then. He's been sick once." [1]

Child actor

• Respond to questions appropriately early in the encounter; remain stable and alert unless the assessor's cue card specifies a change. [1]

Assessor cues and clinical data

Release findings as the candidate reaches each step. Reward a precise ingestion history, correct use of the nomogram, early charcoal, and antidote started on or above the line; penalise plotting a level before four hours or treating a staggered or unknown-time ingestion on the nomogram. [1]

A and B — Airway and breathing

Airway is patent. Respiratory rate 20, oxygen saturation 99% on air, no recession. Expected strong behaviour: confirm a safe airway and adequate breathing; note that this is not a cardiorespiratory emergency yet, so the focus moves to the ingestion history and the timed level. [1]

Decontamination — activated charcoal

The ingestion was a single acute ingestion about two hours ago of a significant dose. Expected strong behaviour: state that the child is within the charcoal window after a significant ingestion and give activated charcoal at 1 gram per kilogram (maximum 50 grams) by mouth, weighing benefit against the vomiting and airway risk; explain that charcoal reduces absorption and complements, but does not replace, the nomogram decision. [1] [4]

The four-hour level and the nomogram decision

The four-hour paracetamol level is 180 milligrams per litre; ALT and INR are normal. Expected strong behaviour: state that for a single acute ingestion with a known time the level is plotted on the Rumack-Matthew nomogram using the 150 milligrams per litre treatment line; a level of 180 milligrams per litre is above the line, so start intravenous N-acetylcysteine. Confirm the exact regimen and treatment line with the poisons information centre. [1]

Escalation event — an anaphylactoid reaction to NAC

During the loading dose Leo develops flushing, an itchy urticarial rash and mild wheeze. Expected strong behaviour: recognise an anaphylactoid (non-IgE) reaction; slow or briefly pause the infusion and give an antihistamine, then resume; explain that this is not a reason to abandon the antidote. [9]

Escalation event — rising hepatotoxicity

At twenty-one hours the ALT is 1200 units per litre and the INR is 3.2, while the paracetamol level is now negligible. Expected strong behaviour: recognise that a falling paracetamol level with a rising ALT and INR is evolving hepatotoxicity, not recovery; extend the N-acetylcysteine and track the prothrombin time trend; escalate the level of care. [10]

King's College criteria and retrieval

If the INR climbs above 6.5 with a creatinine above 300 micromoles per litre and grade three to four encephalopathy, or the arterial pH falls below 7.3 after resuscitation, the King's College criteria are met. Expected strong behaviour: contact the regional liver transplant centre immediately, continue NAC and supportive care, and arrange transfer with a structured handover. [10]

Marking domains

Debrief prompts

• What made you confident the nomogram was valid here, and when would it not have been?
• Why is the prothrombin time trend more important than the paracetamol level after the nomogram phase?
• How would your management have differed if the ingestion had been staggered or of unknown time?
• What safeguarding and mental health response runs in parallel, and when?