Selective Digestive Decontamination (SDD) – The ICU Book

Lately I’ve been reading The ICU Book by Paul L. Marino.  Everyone in crticial care recommmends this book as standard reading for interns and junior residents, and I have to say it has been quite the read so far.

One of the articles in Marino’s book that has really stuck out to me has to do with selective digestive decontamination (SDD). Marino explains that in the presence of severe chronic illness, the G.I. tract becomes populated with more pathogenic organisms capable of causing invasive infections. He quotes one study that showed that hospitalized patients are often colonized with pathogenic organisms in the G.I. tract most notably aerobic gram-negative bacilli like Pseudomonas. This paper noted that the change in microflora is not environmentally driven, however it is directly related to the severity of illness in ICU patients. Marino recommends selective digestive decontamination for all ICU patients.

One example of this regimen includes a three-step decontamination process.

1. Oral cavity: a paste containing 2% polymyxin, 2% tobramycin, and 2% amphotericin to be applied inside the mouth with a gloved finger every 6 hours.

2. G.I. tract: 10 ml solution containing 100 mg polymyxin, 80 mg tobramycin, and 500 mg amphotericin and given via nasogastric tube every 6 hours.

3. Systemic: intravenous cefuroxime, 1.5 g given every 8 hours for the 1st 4 days of this therapy

Multiple years of randomized controlled trials have shown that ICU acquired infections are dramatically reduced with this kind of regimen. In one study that Marino quotes all 3 types of infections common in ICUs–pneumonia, urinary tract infections, and septicemia septicemia from vascular catheters–were significantly less frequent in patients who received selective digestive decontamination. Many clinical trials are showing a combined 40% relative reduction in the frequency of acquired infections in the ICU.

Marino mentions that over 20 years of experience with selective digestive decontamination and numerous reports of its efficacy clearly show the benefits related to selective digestive decontamination. However there continues to be a debate over the merits of this practice. Marino states two concerns that feed this debate. First the impact of SDD on mortality and also the possibility of the emergence of antibiotic resistant organisms. Marino points out that studies that support the relative reduction in mortality in ICU patients that have received selective digestive decontamination and also he points to studies that show no evidence of antibiotic resistance with use of a standard selective digestive decontamination regimen.

So the question is why don’t hospitals use this regimen in the ICU? I cannot speak for all hospitals, however I can speak for the UC Health. In our ICU we do not use a selective digestive decontamination regimen. I’ve questioned the fellows about this practice, and I usually receive an answer dealing with the concern of the emergence of antibiotic resistant organisms. When I explained that this was a huge part of Dr. Marino’s ICU book the fellows question the studies stating that most of these are over 10 years old. This prompted me to look again at the current data to see if SDD is still the huge benefit that Dr. Marino felt that it once was.

I found an article in the Expert Opinion of Pharmacotherapy, a metanalysis from this year which included 65 randomized controlled trials with over 15,000 enrolled patients, over a 25 year period.  This article concluded:

From an objective, and strictly evidence-based, perspective we conclude that SDD is recommended because there is level 1 evidence to support its use. Moreover, intensivists should be aware that SDD is a life-saving strategy: only 18 patients need to receive the full protocol of SDD to save one life. This makes the ethics of withholding SDD highly questionable.

This was incredibly shocking to me, because I felt that I have stumbled upon something in medicine with evidence so clear and for such a long term period that there seems to be absolutely no debate in the clinical literature.  With evidence this clear and strong, why isn’t SDD a routine in ICUs across the country? Are physicians really that set in their ways?

 

References:

Marino, Paul L. The ICU Book. 2007. Third Ed. Chapter 4 pg 63-80.

Silvestri L, van Saene HK, Petros AJ. Selective digestive tract decontamination in critically ill patients. Expert Opin Pharmacother. 2012 Jun;13(8):1113-29. Epub 2012 Apr 25.