MSFinals-5251

A 25-year-old male patient arrives at the emergency department with agitation, dry mouth, and blurred vision. He has a history of major depression and admits to taking an overdose of amitriptyline two hours ago in an attempt to end his life. Upon examination, his respiratory rate is 18 breaths/min, heart rate is 110 beats/min, and temperature is 37.7°C. What is the primary investigation that should be conducted based on the patient’s clinical presentation?