A 58-year-old man with a long-standing left inguinal hernia presents to the emergency department with acute onset severe left lower abdominal pain, vomiting, and abdominal distension for 6 hours. On examination, the hernia is tense, tender, and non-reducible. Bowel sounds are absent over the hernia site. His vital signs show BP 98/62 mmHg, HR 118/min, temperature 38.2°C. Laboratory investigations reveal WBC 16,500/μL with left shift, and serum lactate 4.2 mmol/L. What is the most appropriate immediate management?