Final answer:
The nurse should first turn the patient onto his or her side. This helps prevent aspiration and further complications.
Step-by-step explanation:
The action that the nurse should take first when a patient with a nasogastric tube to low intermittent suction after surgery begins to vomit bright red blood is to turn the patient onto his or her side. This is because turning the patient onto the side can help prevent aspiration and further complications. It allows the vomit to be expelled from the mouth and reduces the risk of choking or aspiration pneumonia.
In this situation, it is important to prioritize airway management to prevent any further complications. Administering oxygen may be necessary to ensure adequate oxygenation, but turning the patient onto the side takes priority as it immediately addresses the risk of aspiration.