Selective digestive and oropharyngeal decontamination in medical and surgical ICU patients
Authors: J.C. Hurley
Journal: Clinical Microbiology and Infection (2017)

The recent individual patient data meta-analysis of six studies of selective digestive decontamination (SDD) and selective oropharyngeal decontamination (SOD) by Plantinga et al. [[1]Plantinga N.L. de Smet A.M.G.A. Oostdijk E.A.N. de Jonge E. Camus C. Krueger W.A. et al.Selective digestive and oropharyngeal decontamination in medical and surgical ICU-patients: individual patient data meta-analysis.Clin Microbiol Infect. 2018; 24: 505-513Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar] is of great interest. Their finding is in line with previous estimates in the literature [2Roquilly A. Marret E. Abraham E. Asehnoune K. Pneumonia prevention to decrease mortality in intensive care unit: a systematic review and meta-analysis.Clin Infect Dis. 2014; 60: 64-75Crossref PubMed Scopus (79) Google Scholar, 3Hurley J.C. Prophylaxis with enteral antibiotics in ventilated patients: selective decontamination or selective cross-infection?.Antimicrob Agents Chemother. 1995; 39: 941-947Crossref PubMed Scopus (91) Google Scholar], including a recent meta-analysis of SDD and >20 other intensive care unit (ICU) pneumonia prevention methods by Roquilly et al. [[2]Roquilly A. Marret E. Abraham E. Asehnoune K. Pneumonia prevention to decrease mortality in intensive care unit: a systematic review and meta-analysis.Clin Infect Dis. 2014; 60: 64-75Crossref PubMed Scopus (79) Google Scholar]. Interestingly, for SDD, the adjusted odds ratios for ICU mortality of 0.74 (95% CI 0.65–0.84) found by Plantinga et al. is similar to the risk ratio for ICU death found by Roquilly et al. being 0.84 (95% confidence interval, 0.76–0.92) among 29 randomized studies with over 10 000 patients. There are a range of study designs among the six studies; the largest, with over 9000 patients, has no control group. One has a two-by-two factorial concurrent group design, three achieved observer blinding through the use of topical placebo and three have a nonconcurrent or cluster randomized design without observer blinding. The latter design, Plantinga et al. state, ‘prevents the occurrence of “contamination” (i.e. treated patients protecting control patients from acquired colonization and infection).’ However, is ‘converse contamination’ possible? Might treated patients put at risk concurrent control (or untreated) patients? How much of the impact that Plantinga et al. describe is attributable to factors such as concurrent study design? Is the use of topical placebo without effect in this setting? To address these crucial questions, I extracted the mortality proportions for the control and intervention groups from the six studies. Of note, of more than 17 000 ICU admissions among the six studies, there are only 469 concurrent control group patients, of whom 130 came from one arm of the four-arm study randomized to receive mupirocin and or chlorhexidine versus topical placebos. This figure demonstrates that the mean mortality proportion across these four concurrent control groups is 30% (95% CI 26.4–33.7%) versus 26.3% (95% CI 20.2–33.4%) among three nonconcurrent control groups and versus 20.2% (95% CI 17.5–23.0%) and 21.4% (95% CI 19.2–23.8%) among the groups of SDD and SOD respectively (Fig. 1). The Supplementary Appendix provides details on the data and the method by which Fig. 1 was derived, which includes a derivation of the SDD and SOD effect sizes (unadjusted) and the references. The mean mortalities derived by the meta-analysis differ from the crude ICU mortalities in table 3 of Plantinga et al. Moreover, the mortality percentages in the figure are comparable to those among ten categories of control and intervention groups from 69 studies of SDD and other digestive tract interventions as extracted by Roquilly et al. [2Roquilly A. Marret E. Abraham E. Asehnoune K. Pneumonia prevention to decrease mortality in intensive care unit: a systematic review and meta-analysis.Clin Infect Dis. 2014; 60: 64-75Crossref PubMed Scopus (79) Google Scholar, 4Hurley J.C. Is selective decontamination of the digestive tract safe?.Clin Infect Dis. 2015; 60: 1729-1730Crossref PubMed Scopus (10) Google Scholar]. The median percentage mortality for nine of these ten categories was within six percentage points of 20% mortality. By contrast, the median percentage mortality for the category of concurrent and receiving topical placebo (ten control groups) was highest at 30% [[4]Hurley J.C. Is selective decontamination of the digestive tract safe?.Clin Infect Dis. 2015; 60: 1729-1730Crossref PubMed Scopus (10) Google Scholar]. The apparent effect of SDD and SOD on mortality, as for bacteraemia, candidaemia [[5]Hurley J.C. ICU-acquired candidemia within selective digestive decontamination studies: a meta-analysis.Intens Care Med. 2015; 41: 1877-1885Crossref PubMed Scopus (23) Google Scholar] and ventilator-associated pneumonia incidences, requires a cautious interpretation and consideration of direct versus indirect (contextual) mediations as well as the possible effect of use of topical placebo in this setting. Among >200 studies, the mean ventilator-associated pneumonia, candidaemia and bacteraemia incidences among control groups of concurrent control trials of SDD or SOD are unusually high compared to groups within studies of comparable populations either without any study intervention or studies with interventions other than SDD or SOD. The incidence of ventilator-associated pneumonia is highest among concurrent control groups within studies of SDD who received topical placebo (Supplementary Appendix). Plantinga et al. have demonstrated that SDD outperforms SOD, but I ask them whether SDD and SOD are safe with regard to ‘converse contamination’ of concurrent patients in the ICU not receiving SDD or SOD? This work was supported by the Australian Government Department of Health and Ageing through the Rural Clinical Training and Support (RCTS) program. The author reports no conflicts of interest relevant to this article. The following is the supplementary data related to this article: Download .docx (.05 MB) Help with docx files mmc1 Selective digestive and oropharyngeal decontamination in medical and surgical ICU patients: individual patient data meta-analysisClinical Microbiology and InfectionVol. 24Issue 5PreviewSelective digestive decontamination (SDD) and selective oropharyngeal decontamination (SOD) improved intensive care unit (ICU), hospital and 28-day survival in ICUs with low levels of antibiotic resistance. Yet it is unclear whether the effect differs between medical and surgical ICU patients. Full-Text PDF Open AccessSelective digestive and oropharyngeal decontamination in medical and surgical ICU patients: authors' replyClinical Microbiology and InfectionVol. 24Issue 5PreviewHurley questions whether the use of selective decontamination can have detrimental contextual effects, and he clarified his point by comparing crude estimates of intensive care unit (ICU) mortality among control patients in settings with versus settings without patients that received selective decontamination. These concurrent and nonconcurrent control groups mostly came from studies using different designs, where the first were obtained from individually randomized trials and the latter predominantly from cluster randomized trials [1]. Full-Text PDF Open Archive