"Children do not have the maturity to understand others' life-and-death decisions about them. I would reach out to the parent and make sure he or she knows the gravity and lethality of the situation. If the parent(s) were to remain adamant against blood, still, I would have hospital counsel place an emergency call to a judge who could issue an order allowing it. Short of that, I'm in no position to force it."

This is a famous dilemma seen in all surgical specialties. By law, a patient can establish a directive that forbids transfusion of any type of blood element, even if it were to mean certain death. Your doing this anyway is considered assault and criminal. The fact that the patient is a child is only there to make the interviewer's question even harder to answer, so it seems to be posed to see how you think on your feet and not necessarily to judge your knowledge of the law. You can never go wrong stating you would follow the law, but an answer that diffuses your responsibility by adding another more authoritative party is always a good call, e.g., Ethics Committee.

"An advanced directive is a legal instrument that must be obeyed. The fact that it is a child means mitigating circumstances, so I would place an emergency consult to the head of the hospital Ethics Committee and defer any decision to him or her."