Final answer:
The nurse should offer 4 ounces of water or juice every hour to a patient who has been NPO since midnight and has completed a diagnostic test at 10:00 AM, to ensure gradual rehydration.
Step-by-step explanation:
After an 85-year-old patient has been held NPO (Nothing by Mouth) for a diagnostic test until 10:00 AM, the appropriate nursing action would be to offer 4 ounces of water or juice every hour. This intervention helps in rehydration and ensures that the patient's fluid intake is gradually restored, avoiding any abrupt changes in fluid balance that could be stressful to the kidneys, which have a reduced capacity in the elderly.
Monitoring urine for the presence of glucose or specific gravity would be important if there were particular concerns about renal function or diabetes, but the primary need after NPO is rehydration. Continuous monitoring of urine might be excessive unless indicated by the patient's condition or doctor's orders.