A 32-year-old male farmer presents to the emergency department with excessive salivation, difficulty breathing, and confusion. He reports spraying pesticides on his field earlier in the day. Approximately one hour after exposure, he began experiencing profuse sweating, tearing, nausea, and abdominal cramping. Over time, he developed significant muscle weakness and respiratory distress. On examination, he is diaphoretic, confused, and in respiratory distress. Vital signs show BP: 90/60 mmHg, HR: 50 bpm, RR: 30/min, and SpO₂: 88% on room air. Physical examination reveals miosis, excessive salivation, wheezing with frothy secretions, bradycardia, hyperactive bowel sounds, and muscle fasciculations. What is the most appropriate treatment to reverse the underlying pathophysiological mechanism of his condition?
