Selective decontamination of the oral and digestive tract in surgical versus non-surgical patients in intensive care in a cluster-randomized trial

Background: Selective digestive decontamination (SDD) and selective oropharyngeal decontamination (SOD) are effective in improving survival in patients under intensive care. In this study possible differential effects in surgical and non-surgical patients were investigated. Methods: This was a post hoc subgroup analysis of data from a cluster-randomized multicentre trial comparing three groups (SDD, SOD or standard care) to quantify effects among surgical and nonsurgical patients. The primary study outcome was 28-day mortality rate. Duration of mechanical ventilation, duration of intensive care unit (ICU) and hospital length of stay, and bacteraemia rates were secondary outcomes. Results: The subgroup analyses included a total of 2762 surgical and 3165 non-surgical patients. Compared with standard care, adjusted odds ratios (ORs) for mortality were comparable in SDD-treated surgical and non-surgical patients: 0.86 (95 per cent confidence interval 0.69 to 1.09; P = 0.220) and 0.85 (0.70 to 1.03; P = 0.095) respectively. However, duration of mechanical ventilation, ICU stay and hospital stay were significantly reduced in surgical patients who had SDD. SOD did not reduce mortality compared with standard treatment in surgical patients (adjusted OR 0.97, 0.77 to 1.22; P = 0.801); in non-surgical patients it reduced mortality (adjusted OR 0.77, 0.63 to 0.94; P = 0.009) by 16.6 per cent, representing an absolute mortality reduction of 5.5 per cent with number needed to treat of 18. Conclusion: Subgroup analysis found similar effects of SDD in reducing mortality in surgical and nonsurgical ICU patients, whereas SOD reduced mortality only in non-surgical patients. The hypothesis-generating findings mandate investigation into mechanisms between different ICU populations.