Marcus Schultz | Chief Investigator
Sabrine Hemmes | Coordinator
Intraoperative Ventilation Strategies and Patient Outcomes Following Surgery: an International Observational Study (LAS VEGAS)
The LAS VEGAS Investigators for PROVE Network*, and the Clinical Trial Network of the European Society of Anaesthesiology
*PROVE Network: the PROtective VEntilation Network (www.provenet.eu)
Postoperative pulmonary complications (PPCs) are an important contributor to morbidity and mortality of surgical patients.1,2 Recent trials suggest that the ventilation strategy used during general anaesthesia may affect the incidence of PPCs.3-6 As ventilation practice during surgery is unknown, the ”Local Assessment of Ventilatory Management During General Anaesthesia for Surgery and effects on Postoperative Pulmonary Complications” (LAS VEGAS) study collected data to describe current practice of intraoperative ventilation, and determined associations between ventilator settings and development of postoperative pulmonary complications. We hypothesized that use of low tidal volumes and positive end–expiratory pressure (PEEP), as currently proposed,7 are associated with lower incidence of PPCs.
We performed an international prospective observational cohort study of consecutive adult patients requiring invasive ventilation during general anaesthesia for surgery over a seven–day period in 146 hospitals across 29 countries throughout Europe and the America’s in early 2013. In total 10,523 patients were recruited, of which 8,241 patients entered the primary analysis. The primary outcome measure was PPC development in the first five days, defined as a composite endpoint of unexpected need for oxygen or postoperative ventilation, respiratory failure, acute respiratory distress syndrome, pneumonia or pneumothorax.
Part of the statistical analysis plan was published previously.8 Patients with incomplete data in main intraoperative ventilation settings were censored. The remaining cohort thus included only complete data of main ventilation settings and the primary endpoint. A multivariate model was built to quantify the net effect of intraoperative ventilation characteristics on the occurrence of PPCs, while controlling for other known perioperative risk factors for PPCs. This model was adjusted for multi-level clustering of the data by conducting a generalized linear mixed model. Additionally, a propensity-matched analysis was performed to investigate and correct for potential selection bias, confounding factors, and differences between groups. Finally, the large number of included patients allowed us to perform post hoc analyses on several subgroups of patients: patients with body mass index (BMI) < 35 versus ≥ 35 kg/m2, patients undergoing laparoscopic versus non–laparoscopic surgery, and patients with low versus high risk for PPCs, according to the Assess Respiratory Risk in Surgical Patients in Catalonia risk score (ARISCAT < 26 versus ≥ 26, resp.).9
As the LAS VEGAS study is currently under review, unfortunately we cannot unveil any details on the results.
The LAS VEGAS study was performed by a large number of anaesthesiologists who all understood its importance, and therefor participated enthusiastically in this project. Consequently, the LAS VEGAS study is the largest investigation of the association between intraoperative ventilation strategies and PPCs conducted to date and very representative of current practice.
Other strengths of our study are the robust prospective design, and statistical analyses. The prospective design not only improved the completeness of data collection, but also avoided any effect of time. The models were designed to include intraoperative mechanical ventilator settings and other determinants, which can be influenced by the anaesthesiologist. Finally, its international character makes it representative for many countries.
We want to thank all participating centres for their hard work, and for delivering excellent data. We want to give a special thanks to the ESA team (Brigitte, Sandrine, Benoit), for their endless and tremendous support and effort, and for keeping close contact with all centres during the study and data cleaning.
The Clinical Trial Network of the European Society of Anaesthesiology generously supported the study.
1. Mazo V, Sabate S, Canet J et al. Prospective external validation of a predictive score for postoperative pulmonary complications. Anesthesiology 2014, 121(2):219-231.
2. Serpa Neto A, Hemmes SN, Barbas CS et al. Incidence of mortality and morbidity related to postoperative lung injury in patients who have undergone abdominal or thoracic surgery: a systematic review and meta-analysis. The Lancet Respiratory Medicine 2014, 2(12):1007-1015.
3. Severgnini P, Selmo G, Lanza C et al. Protective mechanical ventilation during general anesthesia for open abdominal surgery improves postoperative pulmonary function. Anesthesiology 2013, 118(6):1307-1321.
4. Futier E, Constantin JM, Paugam-Burtz C et al. A trial of intraoperative low-tidal-volume ventilation in abdominal surgery. N Engl J Med 2013, 369(5):428-437.
5. Ge Y, Yuan L, Jiang X, Wang X, Xu R, Ma W. Effect of lung protection mechanical ventilation on respiratory function in the elderly undergoing spinal fusion. Zhong Nan Da Xue Xue Bao Yi Xue Ban 2013, 38(1):81-85.
6. PROVEnet, Hemmes SN, Gama de Abreu M, Pelosi P, Schultz MJ. High versus low positive end-expiratory pressure during general anaesthesia for open abdominal surgery (PROVHILO trial): a multicentre randomised controlled trial. Lancet 2014, 384(9942):495-503.
7. Slutsky AS, Ranieri VM. Ventilator-induced lung injury. N Engl J Med 2014, 370(10):980.
8. Hemmes SN, de Abreu MG, Pelosi P, Schultz MJ. LAS VEGAS – Local Assessment of Ventilatory Management during General Anaesthesia for Surgery and its effects on Postoperative Pulmonary Complications: a prospective, observational, international, multicentre cohort study. European journal of anaesthesiology 2013, 30(5):205-207.
9. Canet J, Gallart L, Gomar C, et al. for the ARISCAT Group. Prediction of postoperative pulmonary complications in a population-based surgical cohort. Anesthesiology 2010, 113(6):1338-50.