Many studies have confirmed the analgesic effect of intravenous infusion of lidocaine in abdominal surgery. Transversus abdominis plane (TAP) block is also often recommended for abdominal surgery. Ropivacaine TAP block and intravenous lidocaine infusion are important components of multimodal analgesia for colorectal surgery. However, both of them are the local anesthetics and the safety of combination is unknown, so investigators design the study to explore the safety of the synergistic application of ropivacaine TAP block and intravenous lidocaine infusion in patients undergoing colorectal surgery.

Transversus abdominis plane (TAP) block is often recommended for abdominal surgery. Ropivacaine TAP block and intravenous lidocaine infusion are important components of multimodal analgesia for colorectal surgery. However, both of them are the local anesthetics and the safety of combination is unknown, so investigators design the study to explore the safety of the synergistic application of ropivacaine TAP block and intravenous lidocaine infusion in patients undergoing colorectal surgery.

Inclusion Criteria:

1. Aged between 18 and 65 years;
2. Patients who plan to undergo open/laparoscopic colorectal cancer resection surgery under general anesthesia;
3. American society of Anesthesiologists (ASA) physical status classification system I~II;

Exclusion Criteria:

1. Weight less than 40kg or more than 100kg;
2. Defects in the cardiac conduction system (II or III degree atrioventricular block) or cardiac dysfunction (LVEF<50%);
3. Severe liver dysfunction (ALT, AST, bilirubin 2.5 times higher than normal), renal dysfunction (creatinine clearance rate<60ml/min);
4. Allergies to experimental drugs;
5. Patients who are unable to communicate;
6. Participating in other clinical researchers.