A nurse in an emergency department is assessing a client who has been taking haloperidol for 3 months. The client has a temperature of 39.5° C (103.4° F), blood pressure of 150/110 mm Hg, and muscle rigidity. Which of the following complications should the nurse suspect?

A. Neuroleptic malignant syndrome (NMS) is a potentially life-threatening condition that can occur in clients taking antipsychotic medications like haloperidol. Symptoms include hyperthermia (high fever), autonomic dysregulation (elevated blood pressure), and muscle rigidity. These symptoms are consistent with the client's presentation, making NMS the most likely diagnosis. B. Agranulocytosis is a serious side effect of antipsychotic medications, particularly clozapine, but it is not typically associated with elevated temperature, blood pressure, and muscle rigidity. It usually presents with signs of infection, such as fever, sore throat, and low white blood cell count. C. Akathisia is characterized by restlessness, fidgeting, and an inability to sit still, but it does not typically involve high fever, elevated blood pressure, or muscle rigidity. D. Tardive dyskinesia is a chronic condition that results in involuntary, repetitive movements, often involving the face and limbs. It is not associated with the acute symptoms of fever, high blood pressure, and muscle rigidity seen in this client.