Final answer:
The priority action by the nurse is to assess hourly urine.
Step-by-step explanation:
The priority action by the nurse is to assess hourly urine.
Infusing parenteral nutrition (PN) can affect the renal function of the patient. By assessing the urine output hourly, the nurse can monitor for any signs of impaired renal function, such as decreased urine output or abnormal urine characteristics. This allows for early detection and intervention if necessary.
Assessing vital signs every 4 hours, evaluating serum protein, and evaluating AST tests are important aspects of patient care, but in this scenario, assessing hourly urine is the priority action.