Epidemiology Of Chronic Post-surgical Pain And The Development And Validation Of Its Predictive Model In General Surgical Popilation

Objective Chronic post-surgical pain (CPSP) has been defined by theInternational Association for the Study of Pain (IASP) as persistentcontinuously or intermittently for more than3months after surgery anddifferent from the preoperative pain. Unfortunately, CPSP remains a majorclinical problem, the development of which is a complex and poorlyunderstood process. It is a serious complication of surgery with potentialimpacts not only on quality of daily life for the individual patient, but alsoon the subsequent costs to the health care and social support systems of oursocieties. Therefore, we performed the present study to assess theprevalence and characteristics of chronic pain after surgery, as well as theeffect of CPSP in terms of interfere with daily living, psychologicalwell-being, and health-related quality of life at the6months’ follow-up in alarge population of surgical patients. At the same time, we also aimed toidentify the risk factors that predict CPSP by analyzing variousperioperative factors. Subsequently, we will use these data to develop and validate an easily applicable prognostic model for the occurrence of CPSP.Methods After study approved by the ethics committee at ourinstitution, the consecutive patients who had undergone a scheduledsurgery between Jun1,2012and Sept30,2012at our hospital six monthsearlier were connected to conduct a telephone questionnaire surveyregardless of the type of anesthesia and operation. All patients wereinformed and gave oral informed consent. Those who were aged below18years, patients who were unable to be contacted or express themselvesverbally or refused to participate in the telephone questionnaire survey andwho found it difficult to complete the questionnaire over the phone wereexcluded from the study. The first section of the survey questionnairemeasured the presence of CPSP. Those who responded positively to thequestion were subsequently asked systematically to specify pain accordingto intensity, site, and characteristics. They were asked to rate the maximumand average pain intensity with a numeric rating scale (NRS) at rest and onmovement. The presence of neuropathic pain were screened by DN4(Douleur Neuropathique4) questionnaire. The quality of life was evaluatedwith Brief Pain Inventory (BPI). Occurrence of anxiety or depression wasinvestigated by the Hospital and Depression Scale Depression Scale(HADS). Relevant medical-surgical data were retrieved from the patients’hospital records. The patients’ sex, age, BMI, occupation, education degree,previous chronic pain at both surgical site and other site, surgical history, abuse of smoking or alcohol, history of diabetes mellitus, hypertension andcardiovascular disease, American Society of Anesthesiology (ASA) score,anesthesia method, type of operation and the time it required, the mean andhighest values of NRS scores at rest and on movement during postoperative48hours, incision infection, and length of hospital stay after surgery werealso recorded. Data were divided into evaluation set and validation set. Theevaluation set was subjected to stepwise backward logistic regressionanalysis using the maximum likelihood function. The factors included inthe final model were used to calculate the probability of CPSP for eachpatient of the validation dataset. The discriminating properties of apredictive model were assessed by calculating the area under curve (AUC)of a receiver operating characteristic curve (ROC).Results The complete data from surgery and CPSP questionnaire wereobtained from3110participants. The overall incidence of CPSP of6months post-surgery was29.6%. The prevalence of CPSP differedconsiderably between the anatomical locations of surgery, ranging from45.7%to19.6%. When compared with other type of surgery, CPSP wasmore common occurred in patients underwent joint replacement procedure,thoracotomy or spinal surgery. Among patients reported CPSP,71.3%hadmild pain,24.6%had moderate pain, and4.1%had severe pain.Thoracotomy was associated with most severe pain at rest, whereas jointreplacement surgery was associated with most severe pain on movement. Twenty-one percent of the patients with CPSP had taken analgesic painmedication. Patients with CPSP perceived their health related quality of lifeas more compromised than those without CPSP. The significantly higherlevels of anxiety and depression were also found in patients with CPSP.Multivariate logistic regression analysis revealed that independent riskfactors for CPSP were younger (OR0.847), female (OR0.560), highervalue of BMI (OR1.393), single (OR1.363), history of smoking (OR1.668), history of alcohol abuse (OR1.605), preoperative pain at surgicalsite (OR2.018), inguinal hernia repair procedure (OR2.040), longerduration of operation (OR1.609), intensity of acute postoperative pain atrest (OR1.324) and on movement (OR1.444), incision infection (OR2.234) and longer postoperative hospital stay (OR1.233). The areas underthe ROC curve were all larger than0.70in evaluation dataset (0.748，with95％CI0.725-0.771) and in validation dataset (0.767，with95％CI0.733-0.801).Conclusion The incidence of CPSP of6months post-surgery is highfor various common operations. About one third patients with CPSPexperienced moderate to severe pain. CPSP impairs both patients’ qualityof life and mental wellbeing. Independent risk factors for CPSP wereyounger, female, higher value of BMI, single, history of smoking, historyof alcohol abuse, preoperative pain at surgical site, inguinal hernia repairprocedure, longer duration of operation, intensity of acute postoperative pain, incision infection and longer length of postoperative hospital stay.