A 55-year-old man with a history of diabetes and smoking presents with acute onset of right foot pain and pallor 6 hours after sudden onset. On examination, the foot is cold, pale, and pulseless. Sensory examination reveals loss of light touch and pain sensation in the foot. Motor power is 3/5 in foot dorsiflexion. Femoral pulse is palpable but faint. What is the most appropriate immediate next step?