Final answer:
Respiratory depression is the key indication for administering naloxone to a post-op child, as it reverses opioid effects and ensures adequate breathing.
Step-by-step explanation:
The nurse should identify respiratory depression as an indication that naloxone should be administered to a post-op child. Naloxone (Narcan) is an opiate antagonist that is used to reverse the effects of opioids, particularly the life-threatening respiratory depression that can result from opioid overdose.
While crackles in lung bases may indicate a condition such as pneumonia, nausea and vomiting (NV), and tachycardia might be related to different causes and are not direct indications for the administration of naloxone. The primary use of naloxone is to treat opioid-induced respiratory depression, thus ensuring the patient maintains adequate breathing patterns until further emergency medical treatment is available.