Which adverse effect of gabapentin is of greatest concern for the 85-year-old patient?

The physician writes an order for diphenhydramine 250 mg PRN for sleep. Which part of the order does the nurse question?

The nurse is caring for a 57-year-old woman who is intubated and sedated in the post-anesthesia care unit following a radical hysterectomy. The patient remained stable throughout the 6 hour surgery during which she experienced a 2 L blood loss. The nurse has emptied the patient’s indwelling catheter every hour for the 3 hours the patient has been in the PACU with the following volumes: 54 mL, 23 mL, 12 mL, and 5 mL. Her heart rate is 112 bpm, oxygen saturation is 99%, and blood pressure is 82/54mmHg. The patient received maintenance fluids during the procedure and no blood transfusions. How many liters of isotonic fluid does the nurse anticipate administering to the patient during the postoperative period? Enter your response using a whole number.