What is the recommended selective gastric decontamination (SGD) protocol—including drug composition, dosing, frequency, and duration—for a mechanically ventilated critically ill patient in the ICU?

Selective Digestive Decontamination Protocol for Mechanically Ventilated ICU Patients

In ICUs where multidrug-resistant bacteria prevalence is below 20%, implement selective digestive decontamination (SDD) using topical polymyxin E (colistin), tobramycin, and amphotericin B applied to the oropharynx and administered enterally four times daily, combined with intravenous cefotaxime for a maximum of 5 days, to reduce mortality by approximately 35 deaths per 1000 patients treated. 1, 2

Drug Composition and Administration

Topical Antibiotic Components

• Polymyxin E (colistin), tobramycin, and amphotericin B constitute the standard topical regimen 1, 2
• Apply as a paste to the oropharynx 1
• Administer enterally through a nasogastric tube to the stomach 1

Systemic Antibiotic Component

• Intravenous cefotaxime for the first 4-5 days only 2
• This short-course systemic antibiotic targets early primary endogenous infections 3

Dosing and Frequency

• Topical antibiotics (polymyxin E, tobramycin, amphotericin B): four times daily 2
• Continue topical application throughout the entire ICU stay until discharge 2, 3
• Systemic antibiotic (cefotaxime): maximum 5 days to prevent emergence of multidrug-resistant bacteria 1, 2

Critical Patient Selection Criteria

When SDD Should Be Used

• Only in ICUs with multidrug-resistant bacteria prevalence <20% 1, 2
• Patients with expected intubation duration >48 hours or expected ICU stay >72 hours 1
• Greatest mortality benefit occurs in patients with higher baseline mortality risk (more critically ill patients) 1

Absolute Contraindication

• Do not implement SDD in units where multidrug-resistant bacteria prevalence is ≥20% 1, 2
• The major trials demonstrating SDD efficacy were conducted exclusively in low-resistance environments 1

Evidence for Mortality Benefit

The mortality reduction with SDD is substantial and well-established:

• Adjusted odds ratio of 28-day mortality: 0.83 (translating to 35 fewer deaths per 1000 patients treated) 1
• Relative risk reduction in mortality: 0.75 across 17 RCTs involving 4045 patients 1
• Network meta-analysis of 15 RCTs (7839 patients) confirmed mortality reduction with OR 0.73 1
• Number needed to treat: 12 patients to prevent one death 4

Additional Clinical Benefits

Beyond mortality reduction, SDD provides:

• 65% reduction in lower airway infections (RR 0.27 for VAP) 1, 3
• Decreased duration of mechanical ventilation 1
• Reduced ICU bacteremia and candidemia, particularly from S. aureus and glucose-nonfermenting Gram-negative species 1
• Number needed to treat: 5 patients to prevent one pneumonia 4

Antimicrobial Resistance Considerations

The evidence regarding resistance is reassuring but requires vigilance:

• Meta-analyses and RCTs comparing SDD to standard care showed no link between SDD and development of bacterial resistance 1
• SDD was associated with a decrease in acquisition of multidrug-resistant bacteria in subgroup analysis 1
• No significant difference in prevalence of MRSA (OR 1.46) or vancomycin-resistant enterococci (OR 0.63) 1
• Trend toward reduction in Gram-negative resistance to tested antibiotics 1
• Over 10 years of studies failed to detect emergence of resistance or associated superinfections 3

Implementation Requirements

Surveillance and Monitoring

• Obtain throat and rectum surveillance samples to monitor compliance, efficacy, and detect early resistance emergence 3
• Regular monitoring of local bacterial ecology is essential when using SDD 1, 2
• Track institutional antibiotic resistance patterns continuously 2

Hygiene Standards

• Maintain a high standard of hygiene to prevent exogenous infections throughout ICU stay 3
• This is the third component of the four-part SDD protocol 3

Common Pitfalls to Avoid

• Never extend systemic antibiotics beyond 5 days - prolonged therapy leads to multidrug-resistant bacteria emergence 1, 2
• Never implement SDD without first confirming local resistance patterns are <20% - efficacy disappears in high-resistance environments 1, 2
• Never use topical antibiotics alone without the systemic component - mortality benefit requires both topical and systemic antibiotics 1
• Never discontinue surveillance - early detection of resistance emergence is critical for patient safety 3
• Never apply SDD universally - reserve for mechanically ventilated patients with expected prolonged intubation 1

Comparison with Selective Oropharyngeal Decontamination (SOD)

SOD uses the same topical antibiotics but oropharynx only (no gastric administration, no IV antibiotics):

• SOD showed adjusted OR of 28-day mortality: 0.86 (29 fewer deaths per 1000 patients) 1
• SOD is less effective than full SDD but still reduces mortality compared to usual care 1
• Consider SOD when systemic antibiotics are contraindicated or in settings where full SDD implementation is not feasible 1