The antipathy against SDD explained

With the first paper on Selective Digestive Decontamination in ICU patients published in 1983, this year marks the 35th anniversary of one the fiercest controversies in intensive care medicine, infection prevention and clinical microbiology. To celebrate this, Intensive Care Medicine published 3 editorials called the “Antipathy against SDD is justified”: 1 arguing Pro, 1 Con and 1 wasn’t sure. If the contents of these editorials had been patients, a (good) physician would have called them “diagnostic”. SDD is where clinical epidemiology becomes psychology and sociology.

I trust you all know what SDD is: To protect critically ill patients from ICU-acquired infections they receive topical antibiotics in mouth and stomach to eradicate Gram-negatives, S. aureus and yeasts (while sparing the anaerobic flora) and 4 days of cefotaxime intravenously to treat any yet unnoticed respiratory tract infection. This all comes with microbiological surveillance to monitor eradication (and to intensify topical antibiotics if that fails) and resistance development. So far, SDD is mostly used in Dutch ICUs, where 3 large studies demonstrated patient benefit and multiple studies supported ecological safety (i.e., no increase in antibiotic resistance).

The Antipathy-YES team builds their argument on the global crisis of antibiotic resistance, that is caused by antibiotic use and can only be curtailed by good antibiotic stewardship. “Knowing that resistance is spreading rapidly, that antibiotics may favor this spread, and that oral and digestive antibiotics contain colistin, the antipathy that we should have against SDD is obvious.” This is then supported by 6 studies reporting on resistance and SDD; 4 (!) coming from the Netherlands where SDD is widely considered ecologically safe; 1 study is a post-hoc analysis of 1 bug-drug combination in a large study, 2 are from (uncontrolled) microbiome analyses in 1 and 10 patients, and 1 is from a 5-yr long outbreak with resistant Klebsiella, where discontinuing SDD was one of the many control measures. The 2 non-Dutch papers were case-report like experiences in single units where antibiotic resistance was highly prevalent.

The Antipathy-NO team must have just watched Homeland, as they see a global conspiracy of the Intensive Care mob to exclude SDD from all guidelines, starting with the Survival Sepsis Campaign. They ask the readership: “Which intervention targeted at preventing infection and mortality in critical illness has been evaluated positively in 71 randomised controlled trials over 35 years?” They then provide a 3-page Table and basically say: “we rest our case.”

Apparently, a maximum of 16 references was allowed in these editorials and the funny thing is that the references used by both teams were mutually exclusive. From the massive SDD library they could freely pick their favorites. The only reference used by both is a recently published microbiome study of longitudinal data of 10 patients receiving SDD. The YES team remembered that in these patients SDD was associated with an increase of 4 resistance genes (but forgot that many more, and more relevant, genes went down). The NO team recognized that arguments against SDD are now shifting to the microbiome, and argued that this small study, without a comparison to ICU patients not receiving SDD, was not (or better far from) conclusive.

So, this sounds like a debate between Trump and someone knowledgeable about the topic (pick your choice in who is who). In that case, we ask the United Nations of SDD, that usually take the position “We are not sure”. The unsure team describes the 4 steps leading to “acceptance & diffusion” of research innovations into clinical practice. SDD ticks the first 3 boxes: “valuable rationale”, “clear hypothesis” and “confirming results”, but then fails at “effective communication”. Where tight glucose control and low tidal volume ventilation were widely adopted in ICUs after a single study, the opposite occurred with SDD. One of the explanations they bring forward; glucose levels and tidal volume yield immediate effects (red figures on the patient screen turn black), whereas a 10% reduction in ICU mortality (from 27.5% to 25%) will not be seen in an individual subject. But, wait a minute, screening cultures turn negative rapidly in SDD, improving the quality of life of many intensivists. In addition, they argue that other measures in ICU, such as bundles, may have improved health care such that SDD can no longer provide additional benefit. Yet, wait another minute, that data then has never been communicated.

The large R-GNOSIS study with close to 9,000 patients in 13 non-Dutch ICUs in Europe (currently under review) will deliver more fuel/antipathy for some.  For sure, the debate on SDD continues, and the microbiome will be the new battle field.

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