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. [8] [11]

Candidate brief

You are the senior paediatric clinician in a rural district emergency department. Speak as you would during resuscitation. Treat immediate threats before the diagnosis is certain, 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. [1]

Question 1 — Doorway and the first 60 seconds

Stimulus update. A six-year-old is brought in after being struck by a car at speed. There was a brief loss of consciousness at the scene. Before you touch the child you see a drowsy child who opens their eyes only to pain, makes incomprehensible sounds, and withdraws to pain. Manual in-line cervical stabilisation is in place by the paramedics. Question: What do you say and do now? [1]

Consultant-level model answer. "I am immediately concerned. This child has a Glasgow Coma Scale of 7, which places them in the severe traumatic brain injury band. I call the senior paediatric, resuscitation and retrieval teams now, name a leader, allocate roles, and bring age-appropriate monitoring and equipment. I keep manual in-line cervical stabilisation and begin the neuroprotective primary survey. The primary injury is done; my job is to prevent the secondary injury." [1] [11]

Probing follow-up. "Why is cervical spine control part of the airway assessment?" A strong answer is: "Because every major head injury must be assumed to have a cervical spine injury until cleared. Manual in-line stabilisation continues throughout airway manoeuvres, intubation and transport, because movement of an injured spine can cause cord damage." [8]

Common weak answer. "I will take a history, examine the child fully and order bloods and imaging before deciding." This delays the neuroprotective primary survey for diagnostic completeness in a child with a GCS of 7 who needs a definitive airway now. [1]

Escalation branch. If the candidate calls for help and starts the neuroprotective survey, release the survey data in Question 2. If they anchor on diagnostics, ask which failing system they will protect first. [1]

Question 2 — Airway and ventilation decisions

Stimulus update. The airway is patent but the child is not protecting it. The oxygen saturation is 92 percent on air. The team is ready for rapid sequence intubation. Question: Describe your airway intervention and state the ventilation target. [1]

Consultant-level model answer. "The GCS is 7, which is the threshold for definitive airway protection. I intubate using rapid sequence induction with preoxygenation, a neuro-friendly induction agent that maintains blood pressure, and a muscle relaxant. I confirm tube placement with waveform capnography. My ventilation target is normocapnia: I aim for a partial pressure of carbon dioxide in the normal range, guided by capnography and confirmed by blood gas. I do not hyperventilate prophylactically, because hypocapnia causes cerebral vasoconstriction and ischaemia." [1]

Probing follow-up. "Your colleague suggests using ketamine for induction but is worried it will raise intracranial pressure. What do you say?" A strong answer is: "The historical concern about ketamine raising intracranial pressure has been challenged by multicentre evidence showing no clinically significant acute rise in ventilated children with severe traumatic brain injury. Ketamine is increasingly used because it maintains haemodynamic stability, and maintaining blood pressure is a neuroprotective priority." [5]

Common weak answer. "I will hyperventilate the child to keep the carbon dioxide low and reduce brain swelling." Prophylactic hyperventilation is contraindicated because it causes cerebral vasoconstriction and ischaemia. It is reserved only for impending herniation. [1]

Escalation branch. If the candidate intubates correctly and targets normocapnia, release in Question 3 that the child develops a unilateral dilated pupil. If they hyperventilate, ask what evidence supports a low carbon dioxide target. [1]

Question 3 — Raised intracranial pressure and hyperosmolar therapy

Stimulus update. After intubation, the right pupil becomes dilated and poorly reactive to light. The child is ventilated, normocapnic, and the blood pressure is maintained. Question: Interpret this sign and describe the immediate management. [1]

Consultant-level model answer. "A unilateral dilated, poorly reactive pupil in this context means third nerve compression from ipsilateral uncal herniation until proven otherwise. This is a neurosurgical emergency. I give hyperosmolar therapy now, either 3 percent hypertonic saline as a bolus of 2 to 5 mL per kilogram or mannitol at 0.25 to 0.5 g per kilogram. I ensure the head is 30 degrees up and midline, confirm adequate sedation and paralysis, and arrange urgent CT and neurosurgical referral immediately." [1]

Probing follow-up. "What does the recent evidence say about hypertonic saline versus mannitol?" A strong answer is: "The JAMA Network Open comparison found that both agents reduce intracranial pressure, with hypertonic saline showing a numerically greater reduction. A 2025 outcome study found no statistically significant difference in mortality, and a systematic review confirmed comparable efficacy. Either agent is acceptable based on local protocol." [2] [3]

Common weak answer. "I will wait for the CT before giving any treatment for the pupil." A unilateral dilated pupil in severe TBI is impending herniation and demands immediate hyperosmolar therapy while the CT and neurosurgical referral proceed, not after. [1]

Escalation branch. If the candidate treats the herniation sign correctly, release in Question 4 that the CT shows an extradural haematoma and the hospital has no neurosurgery. [2]

Question 4 — Cerebral perfusion pressure and blood pressure

Stimulus update. During transfer to CT, the child's systolic blood pressure drops. Question: Explain why hypotension is dangerous in this child and what cerebral perfusion pressure means. [7]

Consultant-level model answer. "Cerebral perfusion pressure equals mean arterial pressure minus intracranial pressure. This child has a raised intracranial pressure from the haematoma and herniation, so the driving pressure is already under threat. A drop in blood pressure reduces it further from the other side. After traumatic brain injury, cerebral autoregulation is often impaired, so cerebral blood flow is passively dependent on systemic blood pressure with no safety margin. Even a single episode of hypotension after severe TBI is associated with a doubling of mortality, so I maintain an age-appropriate blood pressure with isotonic fluid and, if needed, vasoactive support." [7] [9]

Probing follow-up. "Why is cerebral autoregulation relevant here?" A strong answer is: "When autoregulation is intact, the brain maintains constant blood flow across a range of blood pressures. After traumatic brain injury, autoregulation is often lost, so cerebral blood flow becomes passively dependent on systemic pressure. In that state, hypotension translates directly into cerebral hypoperfusion." [9]

Common weak answer. "A slightly low blood pressure is fine in a child; they compensate well." Children do compensate, but in traumatic brain injury the compensation is already consumed by the raised intracranial pressure. Waiting for hypotension is the classic dangerous error. [7]

Escalation branch. If the candidate protects the blood pressure correctly, move to Question 5 on retrieval and handover. [7]

Question 5 — Neurosurgical escalation and retrieval

Stimulus update. The CT confirms an extradural haematoma with midline shift. The rural hospital has no neurosurgical service. Question: Describe your escalation and retrieval plan. [8]

Consultant-level model answer. "I called neurosurgery and retrieval at the point of recognising severe traumatic brain injury, in parallel with resuscitation, not after the CT. I discuss the child's physiology, the CT findings, the treatment underway, the expected response, the escort and equipment, the transport time and weather, the safest destination for neurosurgical evacuation, and the contingency if transfer is delayed. The neuroprotection bundle continues throughout transfer: normocapnia, normotension, head 30 degrees up, adequate sedation, seizure prophylaxis, and continuous monitoring with a named escalation owner. My structured handover transfers identity and weight, current physiology and trend, timed actions and response, the CT findings and pending tests, local limits, family and safeguarding information, and the next contingency." [8] [11]

Probing follow-up. "What is the one principle you most want the team to carry forward?" A strong answer is: "The primary injury is fixed, but the secondary injury is preventable. Every minute of hypoxia, hypotension or raised intracranial pressure worsens outcome. Protect the brain from the first moment, and escalate before local support is exceeded." [1]

Common weak answer. "I will wait for the retrieval team to arrive before doing anything else." The child needs ongoing neuroprotection during the wait, with continuous monitoring and a contingency for further deterioration, including maintaining normocapnia, normotension and readiness to repeat hyperosmolar therapy. [8]