The double trocar, also known as “Lai’s double trocar”, was invented by academician Lai Jieshou and is widely used in clinical practice. It consists of two parts: the outer tube and the inner trocar, mostly made of transparent plastic tube, rubber tube and silicone rubber tube. The application of negative pressure drainage of abdominal cavity with double cannulae Continuous negative pressure drainage with double cannulae can drain the fluid and necrotic tissue from the wound cavity in a timely and thorough manner, so that the wound surface and pus cavity can be kept in efficient drainage and the wound cavity can be reduced to promote wound healing. It is used in abdominal surgery for the following diseases: small intestine fistula and colonic fistula, abdominal and soft tissue abscess, subdiaphragmatic abscess, pelvic abscess, deep soft tissue abscess), splenic abscess, deep fluid accumulation in abdominal incision infection, trauma and major surgery such as partial resection and repair of liver, duodenal repair, combined abdominal perineal resection for rectal cancer, drainage of acute severe pancreatitis, radical surgery for pancreatic head cancer, severe multiple injuries and cavity postoperative visceral injury, etc. Double-cannula care Keeping drainage open adopts the method of “one listen, two pinch, three flush and four suction to prevent fracture and blockage. One listen”: listen to the sound in the double cannula, no sound means the lumen is blocked; “two pinch”: squeeze and pinch the jacket tube; “three flush”: flush with saline; “four suction”: flush with saline. ”four suction”: constant negative pressure suction with low-pressure suction device to avoid distortion, folding and pulling of the tube causing poor drainage of the tube.