A 58-year-old man with a 20-year history of heavy alcohol consumption presents to the emergency department with acute onset epigastric pain, vomiting, and elevated serum amylase (850 U/L). Abdominal ultrasound shows pancreatic edema and peripancreatic fluid collection. On histopathology of a pancreatic biopsy obtained during endoscopic ultrasound, acinar cells show loss of cell membrane integrity, cytoplasmic swelling, and inflammatory cell infiltration. What is the most appropriate immediate next step in management?