To compare the analgesic effect of different concentration of ropivacaine under ultrasound guided transversus abdominal plane block (TAPB) in patients after colorectal cancer surgery.

A total of 165 patients who received laparoscopic radical resection for colorectal cancer at Xi'an Traditional Chinese Medicine Hospital from March 2021 to December 2023 were selected as a research objects, and they were divided into low concentration group, medium concentration group and high concentration group according to random number table method, with 55 cases in each group. All patients were received ultrasound-guided TAPB at the end of the operation, the concentration of ropivacaine was 0.20% in low concentration group, 0.25% in medium concentration group and 0.375% in high concentration group. The perioperative conditions, changes of visual analogue scale (VAS) scores 6 h, 12 h, 24 h and 48 h after surgery were compared among the three groups, and the changes of pain transmitters [substance P (SP), prostaglandin E2 (PGE2)] and stress response [cortisol (Cor) and norepinephrine (NE)] before and 24 h after surgery were compared, the scores of the Mini-Mental State Examination Scale (MMSE) and the Montreal Cognitive Assessment Scale (MoCA) before, 24 h and 72 h after surgery were compared, and the incidence of adverse reactions was compared.

The first postoperative analgesic pump compression time in the low concentration group were shorter than that in the medium and high concentration groups. The number of analgesic pump compression time and the dosage of sufentanil in the low concentration group were higher than those in the medium and high concentration groups. The first postoperative analgesic pump compression time in the medium concentration group was shorter than that in the high concentration group (P<0.05), and there were no statistically significant differences in the number of analgesic pump compression time, the dosage of sufentanil, the time of the first postoperative exhaust and the length of hospital stay between the medium and high concentration groups (P>0.05). The VAS scores at 6 h, 12 h and 24 h after surgery in the low concentration group were higher than those in the medium and high concentration groups, the VAS score at 6 h after surgery in the medium concentration group was higher than that in the high concentration group (P<0.05), and there was no statistically significant difference in the VAS score at 12 h after surgery between the medium and high concentration groups (P>0.05). The levels of SP, PGE2, Cor and NE at 24 h after surgery in the low concentration group were higher than those in the medium and high concentration groups (P<0.05), while the levels of SP, PGE2, Cor and NE at 24 h after surgery in medium and high concentration groups had no statistically significant differences (P>0.05). There were no statistically significant differences in MMSE scores and MoCA scores at 24 h and 72 h after surgery among the three groups (P>0.05). There was no statistically significant difference in the total incidence of adverse reactions among the three groups (P>0.05).

Ultrasound-guided TAPB with 0.25% concentration of ropivacaine has a good effect on postoperative analgesia in patients after colorectal cancer surgery, which can effectively reduce the secretion of pain transmitters and relieve stress response, and has good safety.