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 rare but life-threatening reaction to antipsychotic medications (like haloperidol). The classic triad of symptoms includes hyperpyrexia (very high fever, e.g., 103.4° F), severe muscle rigidity (lead pipe rigidity), and autonomic instability (fluctuating BP, tachycardia). This requires immediate discontinuation of the drug and intensive care. B. Akathisia: Akathisia is an extrapyramidal side effect (EPS) characterized by internal restlessness and an inability to sit still. It does not cause high fever or severe autonomic instability. C. Tardive dyskinesia: This is a long-term side effect of antipsychotics involving involuntary, repetitive movements of the face (lip-smacking, tongue protruding) and limbs. It is not an acute emergency involving fever. D. Agranulocytosis: This is a dangerous drop in white blood cells (neutrophils), commonly associated with Clozapine, not Haloperidol. It presents with signs of infection (sore throat, fever), but not muscle rigidity or hypertension.