A 32-year-old man arrives at the emergency department 45 minutes after a motor vehicle collision with blunt abdominal trauma. FAST examination reveals free fluid in the pelvis. Hemodynamics are unstable (BP 85/50, HR 128). After 2 units of O-negative blood, BP remains 90/55. Exploratory laparotomy is planned. Which agent is the drug of choice for rapid sequence intubation in this haemodynamically unstable trauma patient?