A 60-year-old man with known peripheral arterial disease presents with sudden onset of a cold, painful, pale left leg starting 3 hours ago. He is unable to weight-bear. On examination, the leg is cool to touch below the knee, femoral pulse is present but popliteal and pedal pulses are absent. Capillary refill time is prolonged (>5 seconds) and sensation is reduced in the foot. What is the most appropriate immediate action?