Final answer:
The most appropriate term to use in the medical record when documenting a child who keeps falling asleep after a head injury is 'obtunded'.
Step-by-step explanation:
When documenting a child who keeps falling asleep after a head injury and requires someone to wake them up, the most appropriate term to use in the medical record is obtunded. Obtunded refers to a state of altered consciousness where the child is difficult to rouse and falls asleep easily in the absence of stimulation. This term accurately describes the child's behavior after the head injury.