A 52-year-old man with a 10-year history of duodenal ulcer disease presents with acute epigastric pain and haematemesis. He denies NSAID use and is H. pylori-negative on serology. On examination, he is haemodynamically stable with mild epigastric tenderness. Upper GI endoscopy reveals a 2 cm duodenal ulcer with a visible vessel at the base. What is the most appropriate immediate next step in management?