Selective Digestive Decontamination

Prophylactic enteral administration of non-absorbable antibiotics with the aim of eradicating potentially pathogenic oral and intestinal organisms in order to ↓ nosocomial infection.

Indications

  • Patients at risk of nosocomial infection
  • ICU with low rate of resistance to chosen antimicrobial cocktail

Contraindications

  • Concern of ↑ antimicrobial resistance, although this has not been demonstrated

Demonstrating resistance is difficult however - this may occur over medium-to-long scale timelines, and the efficacy of decontamination and the significance of resistance is plausibly highly dependent on local fauna and biograms.

Principles

In the critically ill:

  • Overgrowth of normal and abnormal flora occurs
  • Gut overgrowth heralds endogenous infections
  • Nosocomial infections are predominantly caused by endogenous flora

Practice

Protocols vary, however the general principle is to cover Gram negatives and fungi with poorly-absorbed agents.

Consider regular:

  • Antimicrobial cocktail
    e.g. Q6H:
    • Colistin 100mg
    • Tobramycin 80mg
    • Nystatin
  • Surveillance cultures

Complications

  • Antimicrobial resistance

Key Studies

Evidence suggests:

  • Possible immediate individual benefit:

    • ↓ Mortality
    • ↓↓ VAP
      By ~70%.
    • No ↑ C. difficile infection

  • Unclear long-term harms

  • Significant variability based on the population studied
    Rates of nosocomial infection and local antimicrobial resistance.

  • SuDDICU (2022)

    • 5982 mechanically ventilated Australian ICU patients
      • Expected to be ventilated >48 hours
      • Imminent death not expected
    • Cross-over cluster RCT (12 month period) with an ecological monitoring window (3 months)
    • Intervention group received 100 mg of colistin, 80 mg of tobramycin, and 125,000 or 2,000,000 IU of nystatin Q6H
      Applied either to oropharynx or via NG/NJ tube; ↑ dose of nystatin was for NG/NJ administration.
    • No frequentist difference in:
      • Mortality (21.2% vs 22.8%)
      • Alive free of ventilation (62 vs 60)
      • C. difficile (0.5 vs 0.9%)
      • Adverse medication events
    • Bayesian mortality analysis suggests benefit
    • Significant frequentist ↓:
      • Antibiotic resistance (20.9% vs 32.5%)
        i.e. Decontamination ↓ resistant organism culture.
      • Positive blood culture (5.6% vs 8.1%)
    • Waiver of consent
    • ~50% of control arm received IV antibiotics
    • Longer term resistance patterns not known

References

  1. The SuDDICU Investigators for the Australian and New Zealand Intensive Care Society Clinical Trials Group. Effect of Selective Decontamination of the Digestive Tract on Hospital Mortality in Critically Ill Patients Receiving Mechanical Ventilation: A Randomized Clinical Trial. JAMA. 2022;328(19):1911-1921.