Question

Paramedics transport a 41-year-old male accountant to the emergency department after his wife found him acutely confused and sweating profusely at home. The patient has a long-standing history of major depressive disorder that has been difficult to manage. Five days ago, his outpatient psychiatrist discontinued his fluoxetine and immediately initiated a prescription for phenelzine to target different neurotransmitter receptors. On examination, the patient is visibly shivering, highly agitated, and disoriented to time and place. Vital signs reveal a temperature of $39.5^\circ\text{C}$ ($103.1^\circ\text{F}$), blood pressure of $168/102\text{ mm Hg}$, and a heart rate of $124\text{/min}$. Neurological evaluation demonstrates dilated pupils, marked bilateral hyperreflexia in the lower extremities, and sustained ankle clonus. The medical team promptly discontinues all psychiatric medications and administers intravenous normal saline along with a dose of intravenous lorazepam. Thirty minutes later, the patient remains profoundly agitated, and his hyperthermia and clonus are completely unchanged. Which of the following is the most appropriate next step in management?