PERISCOPE study: predicting post-operative pulmonary complications in Europe

Introduction Post-operative pulmonary complications (PPCs) account for a substantial proportion of risk related to surgery and anaesthesia and are a major cause of post-operative morbidity, mortality and longer hospital stays.1,2 The incidence is between 2 and 40%, depending on the type of patients and surgery.3 The American College of Physicians issued guidelines for reducing PPC in patients undergoing non-cardiac surgery and identified risk factors according to the level of evidence. However, the systematic review on which the guidelines are based found that many studies were subject to bias, with limitations such as small sample size, narrow selection of patients and operations, retrospective or unblinded outcome assessment and inconsistencies in PPC definition. Two studies analysed data from the National Veterans Affairs Quality Improvement Program in order to derive indices for predicting risk of pneumonia4 and respiratory failure5 after non-cardiac surgery. Although these studies included the largest recorded samples on PPC, the patients were mostly male veterans who were far from representative of a general European surgical population. In 2006, in Catalonia (Spain), a prospective study on post-operative outcome in a representative general surgical population [Assessment of Respiratory Risk in Surgical patients in CATalonia (ARISCAT) study] found a 5% incidence of PPC. The 30-day mortality of patients with PPC was 20%. The ARISCAT also identified seven independent risk factors for PPC (age, low pre-operative SpO2, acute respiratory infection during the previous month, pre-operative anaemia, upper abdominal or intrathoracic surgery, surgical duration ≥2 h and emergency surgery). The C-statistic was 0.91. A simplified risk score was derived from the β coefficient for each variable.6 Currently, no definitive study provides a simple and useful score for predicting PPC that is widely applicable. The hypothesis is that it is possible to use a simple pre-operative score, built up from a clinical set of variables, to predict PPC in a variety of settings. The incidence of PPC can vary depending on factors related to geographic, economical status or clinical practices across Europe. Research questions Might the ARISCAT score for predicting PPC be applicable across Europe? What is the incidence of PPC in a general surgical population in Europe? Study design This international multicentre observational study will recruit a random-sample cohort of patients undergoing a non-obstetric in-hospital surgical procedure under general or regional anaesthesia during a 7-day period of recruitment. Inclusion and exclusion criteria Patients undergoing a non-obstetric in-hospital surgical procedure, elective or emergent, under general or regional (neuraxial or plexus) anaesthesia will be recruited. Exclusion criteria are age less than 18 years; obstetric procedures or any procedure during pregnancy; procedures in which only local or peripheral nerve anaesthesia will be used; procedures outside the operating room; procedures related to a previous post-operative complication; transplantation; patients with pre-operatively intubated trachea; and outpatient procedures, defined as those requiring less than 1 day's stay for a patient alive at discharge. Participating centres All centres in Europe will be welcome to participate in the study. Each applicant centre must estimate the number of surgical procedures and patients available for recruitment in a single week. The estimated minimum number of centres is 150. A responsible investigator must be designated in each centre. Ethical considerations Due to the nature of the study, no ethical concerns exist. All patients will receive routine care; no research-related intervention will be introduced. Institutional permission to collect observational clinical information will be required in each participating centre. Data collection and dataset Each local research team will fill in a structured questionnaire and identify the PPC outcomes recorded in the charts. An Internet-based electronic case record form will be used. The patients will be followed up until hospital discharge. The following information will be collected for each patient in order to calculate the score: administrative (date of surgery and date and status – alive or dead – at hospital discharge), general (sex, birth date, height and weight), pre-operative [pre-operative SpO2 breathing air in supine position, respiratory infection in the last month, pre-operative haemoglobin, cough test, chronic pulmonary disease, smoking status and the American Society of Anesthesiologists (ASA) class], intra-operative (surgical incision, surgical duration in hours, type of surgery – scheduled or emergency, description of the surgical procedure, surgical specialty and anaesthetic technique), and post-operative outcome (PPCs, standardised according to the definitions previously set out). Outcome measures The main outcome, defined as a PPC, will be a composite of the in-hospital fatal or non-fatal post-operative events. This composite will include, among others respiratory infection, respiratory failure (mild, severe, or acute lung injury/adult respiratory distress syndrome) bronchospasm, atelectasis, pleural effusion, pneumothorax or aspiration pneumonitis. The investigators will not modify a centre's customary management of patients. Patients with PPC will be identified by consulting medical records and looking for events that fulfil any PPC definition. The secondary outcomes will be post-operative length of stay and in-hospital mortality rate. Sample size calculation According to the ARISCAT study, the PPC incidence was 5%. We need at least 100 PPC for a decrease in C-statistics of 0.1. Then, the minimum sample size required will be around 2000 individuals. These figures have an 80% power to detect substantial differences in model performance. To find differences among countries or geographical areas, we need 2000 individuals for each one. Statistics The PPC and mortality incidence and their 95% confidence intervals (CIs) will be calculated. Individual risk score will be calculated for each patient. Risk factors will be evaluated for their bivariable association with the PPC, based on t-test (continuous variables) and Fisher's exact test or the χ2 test (categorical variables). Bivariable odds ratios for PPC and 95% CIs will be also estimated. The discriminative power of the risk score will be assessed using the area under the receiver operating characteristic (ROC) curve (C-statistic). In a ROC curve, the true positive rate (Sensitivity) is plotted as a function of the false positive rate (1-Specificity) for different cut-off points of a risk index. We will compare ROC curves among countries or geographical areas using the method of Delong et al.7 implemented in Medcalc software (version 11.1.0.0; Medcalc Software, Mariakerke, Belgium). Statistical analysis will be performed using the computer software SPSS (version 18.0; SPSS Inc., Chicago, Illinois, USA). Organisation The research team will consist of a steering committee, and nationally and locally responsible investigators on behalf of the European Society of Anaesthesiology (ESA). General and local training sessions will be held to instruct the investigators on how to fill in the structured questionnaire and how to identify the PPC outcomes recorded in the charts. They will supervise data collection and ensure all local regulatory approvals. Funding The Prospective Evaluation of a RIsk Score for postoperative pulmonary COmPlications in Europe (PERISCOPE) study is funded and supported by the ESA through the ESA Clinical Research Network.