The hidden reservoir of SDD users

A next little piece of evidence on the effectiveness of Selective Digestive Decontamination (SDD). Nienke Plantinga pooled all data from the 16,528 patients that had been enrolled in a randomized evaluation of SDD since 25 years, in an Individual Patient Data meta-analysis, see. Not surprisingly SDD was associated with better survival in intensive care unit (ICU), as it was in most of the individual studies. Yet, the pooled etsimates also provide more certainty (and precision) on the beneficical effects of SDD on hospital survival and failed to confirm previous suggestions that SDD was more effective in surgical than in medical patients.

If you’re not Dutch: SDD is the application of topical antibiotics (they don’t reach the bloodstream) in the oropharnx and stomach in ICU patients. The antibiotics kill potentially harmful bugs (dead bacteria cannot invade) and subsequently prevent carriage. To protect the patient during the first days in ICU they also receive IV antibiotics (usually a cephalosporin), even if a clinical suspicion of infection doesn’t exist.

For most of us that built a carreer on antibiotic resistance this is the last thing on earth you would like your intensivists to do. In my country they do this since the 1980s. For years, though, a simple reminder on the fundaments of evidence-based medicine was sufficient to kill their arguments. Well , it looks as if that time has passed. Now they ask the question where the evidence is that SDD doesn’t improve outcome and that it increases antibiotic resistance.

What is the effect? When admitted to ICU, with an expected length of stay of at least 48 hours, the likelihood of leaving the hospital alive increases with 13%. As hospital mortality among untreated patients was 32.4%, this reduction reflects an absolute risk difference of 4% and you need to treat 24 patients to have 1 patient extra surviving hospital stay. This is what the data tell us: nothing more, nothing less.

The last foothhold against this evidence is the lack of generalizibility. The ICUs in which SDD was tested differ from others, mainly in that antibiotic resistance is less prevalent. Let’s not argue on what is the “chicken and egg”, but let’s try to quantify that difference. And could someone propose a cut-off for something that marks the end of generalizibility; if bacterium X is above Y%, the ICU is different, and we cannot extrapolate findings. Happy to hear suggestions.

I do know, from hidden and open sources, that SDD is used in other countries. In a survey among 232 ICUs in 2012, SDD was used in 17% of Western European ICUs (mostly Netherlands and Germany) and in only a few Non-Western European ICUs, see. But there is more. I know of ICUs in Spain (only 2 with SDD in survey). Spain? The shared gene pool created by 80 years of occupation may have resulted in a common acceptance gene (cag-gene) for the concept. And I know of other countries, where physicians do, but rather not speak of it, isn’t it Jon?

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