A 54-year-old female patient has been admitted to a hospital 12 days after the beginning of acute pancreatitis. Objectively: the patient is in grave condition. The body temperature is hectic. Ps - 112 bpm. The abdomen is swollen. Epigastrium palpation reveals a very painful infiltration falling in the localization of pancreas. Abdominal cavity contains fluid. There is an edema of the left lumbar region. In blood: WBCs -18 × 109/l. What is the required tactics of the patient's treatment?