Final answer:
The nurse should notify the physician when the patient's hourly urine output is less than 50 mL.
Step-by-step explanation:
The nurse should notify the physician when the patient's hourly urine output is less than 50 mL. This is because a minimum volume of urine production is necessary for proper bodily functions and the kidneys must produce a minimum of about 500 mL of urine per day to rid the body of wastes.