A 48-year-old man with a history of hypertension and type 2 diabetes presents to the emergency department with a perforated duodenal ulcer. He is hemodynamically stable (BP 132/88 mmHg, HR 102/min) but in severe pain. He last ate 4 hours ago. On examination, he has a rigid, board-like abdomen with rebound tenderness. He requires emergency laparotomy under general anesthesia. Which of the following is the MOST appropriate muscle relaxant to use during rapid sequence intubation in this patient?