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] [5]

Candidate brief

You are the senior paediatric clinician in a regional emergency department. Speak as you would during resuscitation. Recognise shock before the blood pressure falls, decide whether the child is bleeding, treat immediate threats, 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. [5]

Question 1 — Doorway and the first fork

Stimulus update. An eight-year-old is carried in after a motor vehicle collision. Before you touch the child you see poor tone, little eye contact, marked recession, and pale mottled limbs. The abdomen looks distended. Question: What do you say and do now? [1] [2]

Consultant-level model answer. "I am immediately concerned. The first impression shows abnormal appearance, increased work of breathing and poor circulation to skin, plus a distended abdomen suggesting concealed intra-abdominal loss. I call the resuscitation and surgical teams now, name a leader, allocate roles, and bring age- and weight-appropriate equipment and the massive transfusion protocol. I begin the hands-on ABCDE primary survey with cervical spine protection and will treat each threat as I find it. My leading fork is bleeding versus not bleeding, and this looks like haemorrhagic shock, so I am preparing to control bleeding and reach for blood products." [1] [5]

Probing follow-up. "How can you be sure this is shock when you have not measured the blood pressure?" A strong answer is: "Shock is a perfusion problem, not a blood-pressure problem. The mottled skin, weak interaction and recession are signs of poor perfusion, and children compensate with tachycardia and vasoconstriction so the blood pressure is preserved until late. I diagnose shock from the whole circulation and treat the direction of change." [2]

Common weak answer. "I will take a full history, examine the child and order a CT abdomen." This delays resuscitation for diagnostic completeness in a visibly critical, bleeding child, and it inverts the order: first impression, then primary survey and bleeding control, then definitive imaging only when stable and escorted. [5]

Escalation branch. If the candidate recognises shock and starts the bleeding pathway, release the survey data in Question 2. If they anchor on imaging first, ask which failing system they will stabilise before the scan. [1] [5]

Question 2 — The survey, access and the massive transfusion trigger

Stimulus update. Airway is patent, voice is weak. Respiratory rate is 36 with good air entry on oxygen. Heart rate is 150, central pulses are weak, capillary refill is 4 seconds, blood pressure is 84/50. The abdomen is tender and distended. Two intravenous cannulae are placed with difficulty. Question: Lead the next ten minutes. When do you activate the massive transfusion protocol? [5]

Consultant-level model answer. "I protect the airway and give high-flow oxygen. I gain two large-bore cannulae, or intraosseous access if I cannot, and I take point-of-care haemoglobin, lactate, coagulation, ionised calcium and glucose, and a group and cross-match. This child is in haemorrhagic shock with likely ongoing concealed intra-abdominal loss, so I activate the massive transfusion protocol now rather than waiting for laboratory confirmation. I request balanced components: red cells, plasma and platelets in a ratio near one to one to one, scaled to weight. I call surgery and critical care in parallel, and I keep crystalloid to the minimum needed to sustain perfusion while blood arrives." [5] [9]

Probing follow-up. "Why not give a 20 mL/kg crystalloid bolus first?" A strong answer is: "In bleeding, large crystalloid volumes dilute clotting factors, worsen acidosis and hypothermia, and drive the lethal triad. Crystalloid is a bridge to blood, not the resuscitation fluid in haemorrhagic shock. I reach for blood products early." [5] [9]

Common weak answer. "I will wait for the haemoglobin and coagulation results before deciding on blood." The massive transfusion protocol is activated on physiological and mechanistic grounds, not on laboratory results; waiting costs the window in which coagulopathy is preventable. [9]

Escalation branch. If the candidate activates the protocol and reaches for blood, release the tranexamic acid question. If they wait for labs, ask what physiological threshold would convince them to transfuse. [5]

Question 3 — Tranexamic acid timing and dose

Stimulus update. The injury occurred 45 minutes ago. The team is about to give tranexamic acid. Question: What dose do you give, and what time window governs its use? [6] [7]

Consultant-level model answer. "The child is within the three-hour window, so I give tranexamic acid now: a loading infusion of 15 mg per kilogram, maximum one gram, over about ten minutes, followed by a maintenance infusion of 2 mg per kilogram per hour for at least eight hours, maintenance maximum one gram. The CRASH-2 trial showed reduced mortality when tranexamic acid was given within three hours of injury, with the greatest benefit in the first hour. After three hours the benefit disappears and late administration may be harmful, so I would not give it beyond that window." [6] [7]

Probing follow-up. "If the child had arrived four hours after injury, what would you do?" A strong answer is: "I would not give tranexamic acid beyond three hours, because the CRASH-2 data show loss of benefit and possible harm with late administration. I would still control bleeding, run the massive transfusion protocol and prevent the lethal triad, but antifibrinolysis would be withheld on timing grounds." [6]

Common weak answer. "I will give one gram intravenously regardless of weight and timing." This ignores paediatric weight-based dosing and the critical three-hour window, and the adult one-gram regimen is not weight-scaled for children. [7]

Escalation branch. If the candidate gives the correct dose and window, move to the lethal triad question. [6] [7]

Question 4 — Preventing the lethal triad

Stimulus update. During the massive transfusion the core temperature is 34.8 degrees, the ionised calcium is low, and the international normalised ratio has risen to 1.9. Question: Interpret these findings and describe your damage control resuscitation. [5] [9]

Consultant-level model answer. "This is the lethal triad of trauma: hypothermia, acidosis and coagulopathy. Each worsens the others and deepens the bleeding. My damage control resuscitation warms the child actively with forced-air warming and warmed fluids through a blood warmer, aiming for normothermia; corrects the ionised calcium because citrate in stored blood chelates it and hypocalcaemia depresses the heart and clotting; gives balanced blood products and targeted coagulation correction such as cryoprecipitate or fibrinogen concentrate for the low fibrinogen; and minimises chloride-rich crystalloid to avoid worsening acidosis. I watch the potassium from stored red cells and reassess perfusion, haemoglobin and coagulation after each cycle." [5] [9]

Probing follow-up. "Why does hypothermia worsen bleeding?" A strong answer is: "Hypothermia impairs the coagulation enzyme cascade and platelet function, so clot fails even when factors are present. That is why warming is a resuscitation intervention, not comfort care, in massive transfusion." [9]

Common weak answer. "The temperature and calcium are not urgent; I will correct them after the bleeding stops." The lethal triad must be prevented and corrected in parallel with transfusion, because each limb actively worsens the bleeding. [5]

Escalation branch. If the candidate runs damage control resuscitation correctly, move to the surgery and retrieval question. [5]

Question 5 — Surgery, retrieval and structured handover

Stimulus update. The surgical team is preparing for damage control laparotomy. The regional hospital has paediatric intensive care retrieval available by air, one hour away. Question: Describe your escalation, destination decision and handover. [5]

Consultant-level model answer. "I called retrieval in parallel with resuscitation, before local support was exceeded, because transport must not be the rate-limiting step in definitive control. I agree the destination, the surgical and intensive-care capacity, the treatment to continue, the escort and equipment, the expected deterioration, the plan if transfer is delayed, and the monitoring en route. My structured handover transfers identity and working weight, the mechanism and suspected source, current physiology and trend, timed actions and products given with the tranexamic acid time and dose, the response, local limits, family and safeguarding information, and the next contingency and its named owner. I keep the family informed and document objectively." [5] [9]

Probing follow-up. "What is the one principle you most want the team to carry forward?" A strong answer is: "Recognise shock before the blood pressure falls, control the bleeding, resuscitate with blood not crystalloid, give tranexamic acid within three hours, prevent the lethal triad, and escalate early. The failing system cannot wait for the diagnosis to be complete." [5]

Common weak answer. "I will wait for surgery to finish and then decide on transfer." Retrieval is called in parallel with resuscitation; waiting until surgery is complete can leave the child stranded without intensive-care capacity when deterioration occurs. [5]