A nurse is collecting data from a client who received IV morphine for postoperative pain. The nurse should identify that which of the following findings indicates a therapeutic response to the medication?

A. The client's blood pressure has been reduced: Morphine is an opioid agonist that relieves pain by binding to mu receptors in the central nervous system, thereby decreasing transmission and perception of nociceptive stimuli. Relief of postoperative pain reduces sympathetic nervous system activation and catecholamine release, which can lower blood pressure toward baseline. B. The client exhibits diaphoresis: Diaphoresis is commonly associated with unrelieved pain due to increased sympathetic stimulation and stress hormone release. It may also occur with anxiety, hypoglycemia, or opioid withdrawal, but it is not a desired therapeutic outcome of morphine administration. C. The client is grimacing: Grimacing is a classic nonverbal indicator of pain and ongoing nociceptive stimulation. Effective opioid analgesia should decrease observable pain behaviors such as facial tension, guarding, or restlessness. Continued grimacing indicates that the medication has not sufficiently reduced the client’s pain perception. D. The client has an elevated heart rate: Tachycardia is a physiologic response to pain, anxiety, or hypovolemia, mediated by sympathetic nervous system activation. Adequate morphine administration should decrease sympathetic output by relieving pain, which typically lowers heart rate toward baseline.