In conducting the initial assessment of a preoperative client, the nurse notes that the client's home medications include the monoamine oxidase (MAO) inhibitor phenelzine. Because of this client's medication history, which assessment finding is most important for the nurse to monitor?

A. Urinary output might be important in some contexts but is not the priority related to the use of MAO inhibitors. B. MAO inhibitors like phenelzine can affect blood pressure significantly; monitoring BP is crucial due to the risk of hypertensive crisis when certain foods or medications are taken. C. Respiratory rate might be a consideration in some situations but is not directly affected by MAO inhibitors. D. Temperature is not typically a primary concern related to MAO inhibitor use; blood pressure monitoring is more crucial due to potential interactions.