Selective digestive tract decontamination in intensive care medicine. Fundamentals and current evaluation

Selective digestive tract decontamination (SDD) is a method where topical non-absorbable antibiotics are applied to the oropharynx and stomach which primarily is aimed at the prevention of ventilator-associated pneumonia. The rationale for SDD is that ventilator associated pneumonia usually originates from the patients'own oropharyngeal microflora. SDD is also used for the prevention of gut-derived infections in acute necrotizing pancreatitis and in liver transplantation. Despite numerous clinical trials and several meta-analyses, SDD is still a controversial topic. It is now commonly accepted that the incidence of pneumonia is reduced,however, the concept of using topical antibiotics has its inherent limitations and the best results have been obtained by combination with a short course of intravenous antibiotics. Several issues surrounding the notorious difficulties in establishing the diagnosis of ventilator-associated pneumonia especially in the presence of antibiotics are an on-going matter of debate.Furthermore, pneumonia is the leading cause of death from nosocomial infections and its prevention was not adequately followed by reduced mortality in most individual trials, however, a benefit was suggested by recalculation of data in meta-analyses.Patients are not well defined by their need for ICU admission and mechanical ventilation and the attributable mortality of infections depends more on the type and severity of the underlying diseases.Recently published trials substantially improved our understanding as to which patients may derive most benefit from SDD.Currently, it seems that an improved survival can be achieved in surgical and trauma patients with severe but salvageable diseases, which might be classified e.g.by calculation of APACHE-II scores on admission.However, the most important drawback of SDD is the development of resistance and an increased selection pressure towards Gram-positive pathogens, especially in institutions with endemic multi-resistant microorganisms.Thus, it appears that "selective" must not only be interpreted as selective suppression of pathogenic bacteria but rather as selection of appropriate groups of patients with respect to underlying diseases and severity of illness. Furthermore, it means selection of ICUs where the endemic resistance patterns might allow the use of SDD at a relatively low risk for selection of resistant microorganisms, which is still the major concern associated with SDD.