Final answer:
The symptom most indicative of a complication after a tonsillectomy in a 6-year-old child is Bright red emesis, as it suggests post-operative bleeding.
Step-by-step explanation:
A nurse caring for a 6-year-old child who had a tonsillectomy 2 hours ago should be alert for signs of complications. The symptom most likely related to a complication in this scenario is Bright red emesis. This suggests that the child may be experiencing post-operative bleeding, a known complication after a tonsillectomy. Frequent swallowing can indicate that the child is swallowing blood that is trickling down the back of the throat, which is a more subtle sign of bleeding. Clear breath sounds are a normal finding and increased appetite would be unexpected so soon after surgery and is not suggestive of a complication.