Final answer:
Blood-tinged saliva needs immediate notification of the registered nurse.
Step-by-step explanation:
The assessment finding that needs immediate notification of the registered nurse when a 3-year-old child has returned to his room following a tonsillectomy is blood-tinged saliva. While an increased heart rate, occasional coughing, and restlessness are common after a tonsillectomy, blood-tinged saliva could indicate bleeding, which requires immediate attention.