Preoperative Carriage of Respiratory Viruses and Acute Respiratory Distress Syndrome After Cardiac Surgery: Protocol for the VIRUS-ATTAC Prospective Cohort Study.

Background: Cardiac surgery patients are at particular risk of postoperative acute respiratory distress syndrome (ARDS), with an estimated incidence of 5% to 10%. Cardiopulmonary bypass (CPB), ischemia-reperfusion injury, and blood product transfusions are well-recognized contributing factors. Asymptomatic carriage of respiratory viruses has been hypothesized to prime the lungs and potentiate ARDS development when combined with the pulmonary insults of cardiac surgery. However, no study has directly assessed the relationship between preoperative asymptomatic viral carriage and postoperative ARDS. Objective: The VIRUS-ATTAC study aims to determine whether asymptomatic carriage of influenza or other respiratory viruses is independently associated with postoperative ARDS following elective cardiac surgery under CPB. Methods: VIRUS-ATTAC is a prospective, multicenter, low-interventional clinical study conducted across 5 French university hospitals and sponsored by Rennes University Hospital. Adult patients scheduled for elective cardiac surgery under CPB are eligible. A nasopharyngeal flocked swab is collected at anesthesia induction and tested using a multiplex reverse transcription polymerase chain reaction assay detecting 16 respiratory viruses. Results are kept blinded to the clinical team. The primary outcome is ARDS within 7 postoperative days, defined using the Berlin criteria and adjudicated by an independent blinded committee. Secondary outcomes include reintubation, postoperative pulmonary complications, pneumonia, ventilator-free days, intensive care unit-free days, hospital-free days, and 28-day mortality. The primary analysis uses a causal inference framework with a directed acyclic graph for confounder selection and g-computation to estimate the average treatment effect of viral carriage on ARDS risk. A sample size of 1250 patients (including 250 asymptomatic influenza carriers) provides 80% power to detect a 5% absolute risk increase in ARDS (2-sided α=.05). Results: The VIRUS-ATTAC study received ethics approval from the Comité de Protection des Personnes Sud-Est VI, and recruitment was initiated in February 2021 across 5 French university hospitals. Data collection was completed on March 10, 2023. Of the 1258 patients assessed as eligible, 1204 provided written informed consent and were enrolled. The study database was locked on April 9, 2026. Statistical analysis began after database lock, and the results are expected to be reported in a separate publication in 2027. Conclusions: VIRUS-ATTAC is the first prospective multicenter study to directly evaluate the association between preoperative asymptomatic respiratory viral carriage and postoperative ARDS in cardiac surgery patients. If confirmed, this association would provide a rationale for evaluating preventive strategies, such as systematic preoperative vaccination or postponement of elective surgery in carriers, in future interventional studies aiming to reduce postoperative respiratory complications.