A process evaluation of a randomized clinical trial of selective decontamination of the digestive tract in ventilated adults admitted to intensive care: the SuDDICU PE study

The SuDDICU trial evaluated the effectiveness of selective digestive decontamination (SDD), a prophylactic antibiotic regimen comprising oral, gastric and intravenous (IV) components in ventilated adults admitted to intensive care. The trial recruited 9289 participants in 26 clusters across Australia and Canada. There was no difference in the primary outcome of in-hospital mortality, but a reduction in new positive blood cultures and antibiotic organisms. We conducted a concomitant process evaluation in Canadian sites. Our objectives were to quantify participant reach, intervention fidelity and understand drivers of implementation. Multiple methods process evaluation comprising quantitative data on participant reach and intervention fidelity, and qualitative data using key informant interviews and non-participant observation. Analyses were informed by the Consolidated Framework for Implementation Research (CFIR). Of 6317 patients screened in Canadian clusters, 577/3020 (19.1%) screened during the intervention phase were eligible but not included; 47/3297 (1.4%) in the control phase. There were 274/1432 (19.1%) participants without oral or gastric SDD components commenced within 6 h of enrolment; 54/1432 (3.8%) for the IV component. Excluding enrolment and extubation days, the median (IQR) number of ventilator days was 5 (2, 11), with 7438/12,299 (60.5%) ventilator days with 100% SDD oral dose fidelity and 7076/12,299 (57.5%) ventilator days with 100% SDD gastric dose fidelity. Considering all 4 days of IV antibiotic administration, there were 4663/5160 (90.4%) days with 100% fidelity. We interviewed 30 clinical/research team members and conducted 40 h of non-participant observation. Considering CFIR domains, individual, intervention, implementation and contextual influences on fidelity included (1) variable understanding of trial importance/objectives; (2) trial complexity, specifically drug preparation and administration resulting in additional and unanticipated workload, exacerbated at some sites due to physical ICU layout and usual drug preparation/administration practices; (3) concerns about the SDD oral aspect and overall antibiotic side effects; (4) lack of sustained implementation education; (5) lack of research staff availability out-of-hours; and (6) the broader context of running a complex trial during the COVID-19 pandemic. We identified moderate fidelity within the Canadian sites participating in the SuDDICU trial, with important fidelity drivers identified across all CFIR domains. SuDDICU Trial—ClinicalTrials.gov NCT02389036 (registered 03/17/2015); https://clinicaltrials.gov/ct2/show/NCT02389036 .