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Selective Decontamination of the Digestive Tract (SDD)

Sarah Ramsay

Background

  • ICU patients at high risk of acquiring nosocomial infections causing increased mortality, morbidity, length of stay and costs

  • European survey 45% of patients infected of which 21% acquired in ICU

  • Most common are pneumonias, other lower respiratory tract infections, urinary tract infections and blood-stream infections

  • Attributable mortality for VAP: 24-30%

  • Attributable mortality for blood-stream infections 28-35%

  • High risk is the result of multiple factors

    • Severity of underlying disease

    • Frequent and prolonged use of invasive devices

    • Increased exposure to potentially pathogenic organisms

      • From environment

      • From within host
  • In healthy patients indigenous gut and oropharyngeal flora remain very static over time. Overgrowth of potentially pathogenic organisms is prevented by

    • Salivary flow

    • Gastric acidity

    • Bile acids

    • Secretory IgA

    • Peristalsis

    • Colonization resistance  - presence of obligate anaerobic bacteria prevent growth of other potentially pathogenic bacteria

  • In critically ill patients these mechanisms are compromised by the underlying disease process, instrumentation and drugs resulting in

    • Impaired salivary flow

    • Gastric alkalization

    • Cholestasis

    • Intestinal ileus

    Broad spectrum bacteria eradicates indigenous flora and loss of colonization resistance

Within a few days of ICU admission normal flora replaced by potentially pathogenic organisms (in >2/3 of patients) in oropharynx then stomach and gut. Micro-aspiration of contaminated upper GI tract fluid most plausible and demonstrable cause of infection. Translocation through the gut wall is a theoretical possibility which has been demonstrated in animal studies but not convincingly in humans.

Regimes

  • Eradication of potentially pathogenic organisms from the mouth and GIT by local administration of non-absorbable antibiotics

    • Polymyxin E, tobramycin & amphotericin B

      • active against aerobic GNB and yeast

      • limited activity against normal anaerobic flora

  • ± short course of systemic antibiotics for early / incubating respiratory infections

    • Usually cefotaxime, ceftriaxone

    • Given until surveillance cultures show GIT decontamination (usually 4 days)

    • Targets early established infection by community acquired pathogens (e.g. Streptococcus pneumoniae, haemophilus influenzae) which may be aspirated during intubation

    • Temporizes until enteral drugs have decontaminated the GIT

  • Start ASAP on admission, continue enteral drugs until extubated or leave ICU

  • Regular cultures to monitor effectiveness of SSD

  • Optimal hygiene to prevent cross-infection

  • SDD is also used for the prevention of gut-derived infections in acute necrotizing pancreatitis and liver transplantation.

SDD – for and against

  • Many studies with conflicting results.

  • SDD appears to reduce infection rates, especially in critically ill surgical patients (who have a higher rate of nosocomial pneumonia and a higher attributable mortality compared to medical patients)

  • SDD is well accepted in Europe but uptake of the technique has been slow in other countries especially USA despite evidence of improved infection rates and possible improved mortality rates with absence of harm and little increased cost from trials with good design.

  • But …

    • Effect on mortality is less clear – most studies are underpowered and cannot exclude a treatment benefit

    • Select group of patients likely to benefit from SDD not well defined

    • Exact nature of best SDD not well defined: topical alone versus topical plus systemic

    • Concerns about resistance: although good studies have showed little change in resistance patterns, increased colonization (but not infection) with Gram-positive organisms is noted. In some of these studies the incidence of MRSA, and resistant entercocci is very low, and the safety of SDD is questionable in centres where incidence of these potentially more pathogenic organisms is high. Nasal mupirocin may be helpful. Some argue that SDD will add to add to resistance problems, others that it will reduce then by preventing infection and subsequent use of antibiotic.

    • If effect is more marked with systemic antibiotics than topical alone is this simply akin to the peri-operative antibiotics that most surgical patients already receive?

    • Inconvenience of additional drugs and surveillance culturing

    • Possible increased drug costs

The Evidence:

Meta-analyses:

D'Amico R et al

  • 5727 patients from 33 trials

  • Combination of systemic and topical Rx reduced respiratory infection rates and overall mortality

  • VAP: odds ratio 0.35 (0.29-0.41)

  • Mortality: odds ratio 0.8 (0.69-0.93)

  • Reduction in mortality = 6% (30 to 24%)

Nathens AB and Marshall JC

  • Analysed predominantly surgical or medical patients separately

  • Mortality was reduced for surgical patients (odds ratio 0.7 [0.52-0.93]) while no such affect was demonstrated for medical patients (odds ratio 0.91 [0.71-1.18])

  • Greatest effect was seen in topical and systemic therapy combined.

  • Pneumonia was reduced in both subsets, although bacteraemia was only reduced in surgical patients.

van Nieuwenhoven CA et al

Investigated the methodological quality of SDD trials and found an inverse relationship between trial quality and benefit of SDD on incidence of pneumonia, and no relationship between trial quality and mortality rates. May have resulted in over optimistic estimates of the effect of SDD in meta-analyses.

Recent trials

Kruerger WA et al 2002

Well-designed trial showed in 527 mainly surgical and trauma patients showing reduced infection rates and reduced organ failures but not ICU mortality in patients given combined topical and systemic SDD. In a predefined subgroup of patients with mid-range APACHE scores (20-29) ICU, hospital and one year mortality was significantly reduced. Surveillance cultures showed no change in resistance patterns although there was increased colonization (but not infection) by Gram-positive organisms.

Sánchez García M et al 1998

271 mainly medical patients reduced pneumonia rates but not ICU mortality in patients given combined topical and systemic SDD.

Bergmans DCJJ et al 2001

Oropharyngeal decontamination without GIT decontamination or systemic therapy reduced rates of VAP in 227 critically ill patients, underpowered to show a survival benefit.

Additional reading

D'Amico R, Pifferi S, Leonetti C, Torri V, Tinazzi A, Liberati A. Effectiveness of antibiotic prophylaxis in critically ill adult patients: a systematic review of randomised controlled trials. BMJ 1998;316:1275–1285.

Nathens AB, Marshall JC. Selective decontamination of the digestive tract in surgical patients. Arch Surg 1999;134:170–176.

Bergmans DCJJ, Bonten MJM, Gaillard CA, Paling JC, Van der Geest S, Van Tiel FH, Beysens AJ, de Leeuw PW, Stobberingh EE. Prevention of ventilator-associated pneumonia by oral decontamination. Am J Respir Crit Care Med 2001;164:382–388.

Wolfgang A. Krueger, Franz-Peter Lenhart, Gertraud Neeser, Gotthart Ruckdeschel, Heidi Schreckhase, Hans-Joachim Eissner, Helmuth Forst, Joachim Eckart, Klaus Peter, and Klaus E. Unertl. Influence of Combined Intravenous and Topical Antibiotic Prophylaxis on the Incidence of Infections, Organ Dysfunctions, and Mortality in Critically Ill Surgical Patients: A Prospective, Stratified, Randomized, Double-Blind, Placebo-controlled Clinical Trial Am. J. Respir. Crit. Care Med. 2002 166: 1029-1037.

Miguel Sánchez García, José A. Cambronero Galache, Julia López Diaz, Enrique Cerdá Cerdá, José Rubio Blasco, Miguel A. Gómez Aguinaga, Antonio Núñez Reiz, Santiago Rogero Marín, Juan J. Oñoro Cañaveral, And José A. Sacristán Del Castillo. Effectiveness and Cost of Selective Decontamination of the Digestive Tract in Critically Ill Intubated Patients . A Randomized, Double-blind, Placebo-controlled, Multicenter Trial. Am. J. Respir. Crit. Care Med. 1998 158: 908-916. 

Christianne A. van Nieuwenhoven; Erik Buskens; Frank H. van Tiel; Marc J. M. Bonten Relationship Between Methodological Trial Quality and the Effects of Selective Digestive Decontamination on Pneumonia and Mortality in Critically Ill Patients. JAMA. 2001;286:335-340

© Sarah Ramsay February 2003


©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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