To investigate the effect and safety of subanesthetic-dose esketamine combined with subcostal transversus abdominis plane block (STAPB) on postoperative delirium in patients undergoing radical resection for colorectal cancer (CRC).

Patients scheduled for radical CRC resection were divided into control group and treatment group according to the anesthetic regimen. The control group received conventional anesthesia, while the treatment group was intravenously administered 0.2 mg·kg^-1 esketamine hydrochloride injection before endotracheal intubation on the basis of the conventional anesthesia protocol. Both groups underwent STAPB after intubation and before skin incision. The excellent and good rate of anesthesia, surgical parameters, hemodynamic indices, postoperative recovery quality-related indicators, incidence of delirium, analgesic efficacy parameters, and adverse reactions were compared between the two groups.

A total of 52 patients were enrolled in the control group and 48 in the treatment group. The excellent/good rates of anesthesia of treatment group and control group were 91.67% (44 cases/48 cases) and 88.46% (46 cases/52 cases), respectively (P>0.05). The fluid infusion volume of treatment group and control group were (1 412.69±38.27) and (1 428.63±35.47) mL, respectively; the heart rates at T3 were (76.19±8.56) and (80.69±9.14)beats·min^-1, respectively; systolic blood pressure at T3 were (131.08±10.39) and (138.52±13.78) mmHg, respectively; diastolic blood pressure at T3 were (79.94±7.27) and (82.35±8.25) mmHg, respectively; the extubation time were (16.75±2.71) and (15.54±2.42) min, respectively; the recovery time were (18.63±2.81) and (20.40±2.86) min, respectively; the Quality of Recovery-40 (QoR-40) scores on postoperative day 2 were (160.79±18.70) and (154.35±20.56) points, respectively; the lower Hospital Anxiety and Depression Scale-Anxiety subscale (HADS-A) on postoperative day 7 were (6.25±1.76) and (7.10±2.05) points, respectively; the Depression subscale (HADS-D) on postoperative day were (6.13±1.82) and (7.15±1.95) points, respectively; the total incidences of delirium were 10.42% (5 cases/48 cases) and 26.92% (14 cases/52 cases), respectively; the Numerical Rating Scale (NRS) scores for resting pain were (2.00±0.41) and (2.17±0.47), respectively; the dynamic pain at 48 h postoperatively were 2.60±0.54 and 2.81±0.60), respectively; the differences of above indicators between two groups were all statistically significant (P<0.05, P<0.01, P<0.001). The main adverse drug reactions included dizziness, tachycardia, bucking, nausea and vomiting in the control group, and dizziness, tachycardia, hypertension, nausea and vomiting in the treatment group. The total incidence of adverse drug reactions was 9.62% (6 cases/52 cases) in the control group and 12.50% (6 cases/48 cases) in the treatment group, with no statistically significant difference (P>0.05).

Subanesthetic-dose esketamine combined with STAPB for patients undergoing radical CRC resection can reduce intraoperative fluid requirements, stabilize perioperative blood pressure and heart rate fluctuations, improve postoperative recovery quality, alleviate postoperative anxiety and depression, and decrease the incidence of postoperative delirium. This combined regimen also yields definite postoperative analgesic effects and does not increase the risk of adverse reactions, thus exhibiting favorable clinical safety and tolerability.