Abstract: Objective To observe the impact of low-dose oxycodone-nalbuphine on pain mediator release in patient-controlled intravenous analgesia (PCIA) following laparoscopic radical resection of rectal cancer.Methods 120 patients who underwent laparoscopic radical surgery for colorectal cancer in our hospital from October 2022 to September 2023 were selected and randomly divided into the control group and the experimental group（60 cases in each).PCIA was administered within 48h postoperatively,formulated as 10mg hydromorphone and 40mg nalbuphine diluted in saline to 100ml.No background dose was administered in the control group,and a background dose of 1ml/h was administered in the test group.Compare the number of effective PCIA compressions, the rate of remedial analgesia, the rate of remedial antiemesis, the dosage of analgesic pump, Visual Analogue Scale (VAS), Ramsay sedation score, the release of serum pain mediators and the occurrence of postoperative adverse reactions in patients within ≤24 hours and 24-48 hours.Results VAS Scores:The VAS scores during activity in the experimental group at 24h and 48h after surgery (2.21±0.25,1.78±0.44) were lower than those in the control group (2.58±0.23,2.12±0.27) (both P<0.05).The VAS scores at rest in the experimental group at 12h,24h,and 48h after surgery (2.52±0.28,2.14±0.26,1.75±0.32) were lower than those in the control group (3.17±0.39,2.68±0.33,2.04±0.21) (P<0.05).Pump Usage:The amounts of analgesic pump used in the experimental group at 24h and 48h after surgery [(27.64±0.28)ml,(49.11±0.25)ml] were higher than those in the control group [(12.06±0.33)ml,(20.15±0.36)ml)] (both P<0.001).PCIA Pressing Times:The effective pressing times of PCIA in the experimental group within ≤24h and 24-48h (5.89±0.31,4.73±0.28) were lower than those in the control group (7.28±0.38,6.21±0.37) (both P<0.001).Rescue Analgesia and Antiemesis Rates:The rescue analgesia rate (11.67% vs 28.33%,P=0.023) and rescue antiemesis rate (5.00% vs 18.33%,P=0.023) in the experimental group were both lower than those in the control group.Ramsay Sedation Scores:The Ramsay sedation scores in the experimental group at 12 h,24 h,and 48 h after surgery (2.18±0.31,1.74±0.42,1.46±0.14) were lower than those in the control group (2.43±0.48,2.12±0.32,2.03±0.38) (P<0.001).In the experimental group, substance P [(35.26±5.27)pg/ml, (26.37±4.17)pg/ml], neuropeptide Y[(147.28±27.43)pg/ml, (127.26± 18.49)pg/ml], and prostaglandin E2[(56.48±3.69) at 24 hours and 48 hours after the operation 9) The levels of pg/ml, (42.47±5.35)pg/ml and norepinephrine [(3.12±0.48)ng/ml, (1.57±0.19)ng/ml] were all lower than those of the control group [(41.27±6.48)pg/ml, (34.37±4.86)pg/ml, (35.26± 5.27 pg/ml, (26.37±4.17)pg/ml, (62.47±4.26) pg/ml, (53.95±4.73)pg/ml, (3.64±0.64) ng/ml, (2.16±0.26) ng/ml, (P < 0.001)].Conclusion Low-dose oxycodone-nalbuphine in patient-controlled intravenous analgesia following laparoscopic radical resection of rectal cancer can improve analgesic effects and reduce serum pain mediator release.

Key words: low-dose, oxycodone, nalbuphine, laparoscopic radical resection of rectal cancer, pain mediators