Intra-operative opioids versus opioid-free anesthetic effects on immune function and tumor biology in patients with colorectal cancer undergoing laparoscopic abdominal surgery: a prospective, single-blind, randomized controlled, single-center trial

Interventions: Intra-operative opioids with inhalation anaesthesia group:;Opioid-free with inhalation anaesthesia group:;Intra-operative opioids with total intravenous anaesthesia group:;Opioid-free with total intravenous anaesthesia group: Primary outcome(s): Determination of innate immune function of neutrophils;Citrullinated histone H3, H3Cit Study Design: Cohort study