Protocol summary and statistical analysis plan for the Selective Decontamination of the Digestive Tract in Intensive Care Unit Patients (SuDDICU) crossover, cluster randomised controlled trial.

Background: It is unclear whether the use of selective decontamination of the digestive tract (SDD) improves outcomes in ventilated patients in intensive care units (ICUs) and whether SDD is associated with the development of antibiotic resistance. Objective: To describe the study protocol and statistical analysis plan for the Selective Decontamination of the Digestive Tract in Intensive Care Unit Patients (SuDDICU) trial. Design, setting, participants and intervention: SuDDICU is an international, crossover, cluster randomised controlled trial of mechanically ventilated patients in ICUs using two 12-month trial periods. For each period, participating ICUs will implement SDD plus standard care or standard care alone. The SuDDICU drug intervention is an oral paste and gastric suspension of three antibiotics combined with a 4-day course of intravenous antibiotics. Observational ecological assessments will be conducted during five surveillance periods. The trial will be conducted in 19 ICUs in Australia and ten ICUs in Canada and the United Kingdom, and will recruit 15 000-17 000 patients. Recruitment commenced in Australia in 2017. Main outcome measures: The primary outcome is all-cause hospital mortality. Secondary outcomes include: duration of ventilation, ICU stay and hospital stay; incidence of new antibiotic-resistant organisms during the index ICU admission; changes in antibiotic-resistant organism rates; incidence of new Clostridioides difficile infections; and total use of antibiotics. Results and conclusions: SuDDICU will determine whether the use of SDD plus standard care is associated with a reduction in hospital mortality in ventilated ICU patients compared with standard care alone. It will also quantify the impact of the use of SDD on the development of antibiotic resistance. Trial registration: Australian New Zealand Clinical Trials Registry (ACTRN12615000411549) and ClinicalTrials.gov (NCT02389036).