[Summary] The neuropeptides orexin A and orexin B are involved in numerous central regulation processes such as energy homeostasis,sleeping behaviour,and neuroendocrine activities.Orexin receptors are expressed in a variety of tissues besides the brain,adrenal gland for example.The article reviews the effect of orexin on adrenal gland function.

Objective:To assess the value of preoperative salivary cortisol morning/night secretion ratio (AM/PM ratio) in predicting acute postoperative pain in patients.Methods:This was a prospective cohort study. A total of 120 patients, aged 18-64 yr, of American Society of Anesthesiologists Physical Status classification Ⅰ or Ⅱ, with body mass index of 18-28 kg/m 2, undergoing elective single-port laparoscopic hysterectomy from January to October 2023 in Subei People′s Hospital of Jiangsu Province, were selected, and their anxiety and depression status was evaluated by using the Hospital Anxiety and Depression Mood Measurement Scale (HADS) before surgery. Saliva samples were collected in the morning and evening 1 day before operation, and the cortisol concentration was determined by enzyme-linked immunosorbent assay. The ratio of morning cortisol concentration to night cortisol concentration before operation was calculated (cortisol AM/PM ratio). The patients were divided into two groups according to the highest numerical rating scale (NRS) score within 48 h after surgery: no or mild pain group with the highest NRS score ≤3 and moderate to severe pain group with the highest NRS score ≥ 4. Multivariate logistic regression was used to identify the risk factors of moderate to severe acute pain after surgery, and the receiver operating characteristic curve was plotted to evaluate the predictive value. Results:Multivariate logistic regression analysis showed that age, preoperative HADS anxiety score, preoperative HADS depression score and preoperative cortisol AM/PM ratio were independent risk factors for moderate to severe acute pain after surgery ( P<0.05). The results of the receiver operating characteristic curve showed that the area under the curve of preoperative cortisol AM/PM ratio in predicting moderate to severe acute postoperative pain was 0.803 (95% confidence interval 0.708-0.898, P<0.001), the optimal cut-off value was 3.46, the sensitivity was 71.1%, and the specificity was 87.7%. Conclusions:Preoperative salivary cortisol morning/night secretion ratio can predict the occurrence of acute postoperative pain in patients.