The Effect of Early Postoperative Pain on Postoperative Delirium (POD) in Elderly Patients Undergoing Abdominal Surgery:a Secondary Analysis of Multicenter Prospective Data

Post operative delirium will be diagnosed using the 3D- CAM(Confusion Assessment Method) which tests for four features with a series of questions. The features include 1) acute onset and fluctuating course,2) inattention,3) disorganized thinking and 4) altered level of consciousness. Diagnosis of delirium is made if features 1 and 2 and either 3 or 4 are present. the investigators collected baseline characteristics and demographic data of the patients, including clinical information in the following areas:(1) Baseline characteristics: age, gender, body mass index (BMI), American Society of Anesthesiologists (ASA) physical status score, smoke, alcohol , preoperative history of chronic pain, and comorbidities (hypertension, diabetes mellitus, coronary artery disease, cerebrovascular disease, hepatic insufficiency, and renal insufficiency).(2) Preoperative laboratory tests (the most recent prior to surgery): hemoglobin (Hb), white blood cell count, and serum albumin.(3) Preoperative psychological assessments: anxiety and depression state evaluations.(4) Intraoperative variables: grade of operation, type of surgery, duration of surgery, blood transfusion, blood loss, intraoperative dexmedetomidine and nonsteroidal anti-inflammatory drugs (NSAIDs), drain, and PCIA.In this study, the investigators defined the presence or absence of moderate-to-severe pain on POD1 as the exposure variable, assessed using the Numerical Rating Scale (NRS). An NRS score <4 on POD1 was classified as mild pain, while a score ≥4 indicated moderate-to-severe pain 8. Based on this exposure variable, patients were stratified into two groups: the mild pain group (NRS <4) and the moderate-to-severe pain group (NRS ≥4).The investigators summarized patient characteristics based on the presence or absence of moderate-to-severe pain. Continuous variables were expressed as mean ± standard deviation or median (interquartile range) and compared using t-tests or Mann-Whitney U tests. Categorical variables were presented as frequencies and percentages and compared using chi-square tests. Univariate and multivariate regression models were employed to examine the relationship between early postoperative acute pain and the incidence of POD . Furthermore, propensity score matching and subgroup analyses were conducted to further explore the association between the two.