CXCL8 and depressive symptom measurement: In conclusion, a single sub-anesthetic dose of ketamine (0.3 mg kg−1) by intravenous administration before operation with general anesthesia can reduce the symptoms of depression and anxiety of colorectal cancer patients after operation, reduce the levels of IL-6, IL-8, and TNF-α, and improve the quality of postoperative recovery without obvious adverse reactions.