Introduction- Hospital acquired infections (HAI) are a major cause of morbidity and mortality and increase health care costs. Critically ill patients are particularly susceptible to these infections and have an even higher mortality. One intervention that has gained much interest in the medical literature for reducing infection rates and deaths from HAIs is selective decontamination of the digestive tract (SDD). SDD involves the application of antibiotic paste to the mouth, throat, stomach and a short course of intravenous antibiotics. The evidence supporting the use of SDD for saving lives and preventing infections is actually quite strong. However, health care professionals in many parts of the world have refrained from using SDD due to fears of the effects of overuse of antibiotics on the frequency of infections with resistant bacteria such as multi-resistant Gram negative organisms, MRSA and Clostridium difficile.

SuDDICU is a cross-over, cluster randomised trial comparing the effect of using selective decontamination of the digestive tract (SDD) plus standard care, to standard care alone on hospital mortality in patients receiving mechanical ventilation in the intensive care unit (ICU).

Secondary outcomes include an ecological assessment and a long-term health economic analysis.

Design- international, multicentre, crossover, cluster randomised controlled trial (x-cRCT) of eligible patients in participating ICUs using two 12-month interventional trial periods separated by a 3-month inter-period gap.

An observational ecological assessment will be conducted in all ICU patients during one week of each month during the 3-month surveillance period before the first intervention period; in all trial eligible patients during the two 12-month intervention periods; in all ICU patients during one week of each month of the final 3-months of the two intervention periods; in all ICU patients during one week of each month during the 3-month inter-period and post-trial periods.

Participants- General ICUs that admit mechanically ventilated patients will be randomised in the first 12-month period to either implement the SDD protocol in addition to standard care or to continue standard care without SDD, and then to cross over to the other arm during the second 12-month period.

Eligible patients are defined as:

1. All patients who are mechanically ventilated via an endotracheal tube on admission to the ICU and who are predicted to remain ventilated beyond the end of the calendar day after the day of ICU admission, or
2. All patients who become mechanically ventilated via an endotracheal tube during their ICU stay and who are predicted to remain ventilated beyond the end of the calendar day after the day they are first ventilated, or
3. All patients who not already recruited but are receiving mechanical ventilation via an endotracheal tube and are expected to receive ongoing ventilation for a further 48-hours or more despite an earlier prediction that ventilation would be discontinued earlier.

All patients eligible for the intervention will receive the following in addition to the usual infection control measures:

1. 1. A six-hourly topical application of 0.5g paste, containing colistin 10mg, tobramycin 10mg and nystatin 125,000 IU, to the buccal mucosa and oropharynx
2. A six-hourly administration of 10 mL of a suspension containing 100 mg colistin, 80 mg tobramycin and 2 x 106 IU nystatin, to the gastrointestinal tract via a gastric/post-pyloric tube
3. A four-day course of an IV antibiotic. Patients not already receiving a therapeutic antibiotic will be prescribed cefotaxime 1g six-hourly or ceftriaxone 1g daily, with dose adjusted as appropriate for organ dysfunction. Ciprofloxacin (400mg 12-hourly) may be used as an alternative if there is a contraindication to cephalosporins (e.g. allergy). Patients already receiving an alternative IV antibiotic to treat infection will not receive this additional IV antibiotic, but will continue the prescribed antibiotic for the usual duration of therapy.

Statistical considerations and sample size- SuDDICU will recruit 10 000 to 15 000 patients from 29 ICUs and will have 80% power to detect an absolute reduction in hospital mortality of 3-5% from a baseline mortality of 29%, depending on the precise number of clusters.

Inclusion Criteria:

Site inclusion for cluster study- A general ICU or complex of ICUs (medical, surgical, mixed) capable of treating mechanically ventilated critically ill adult patients.

Patient inclusion criteria

1. All patients who are mechanically ventilated via an endotracheal tube on admission to ICU and who are predicted to remain ventilated beyond the end of the calendar day after the day of ICU admission, or
2. All patients who become mechanically ventilated via an endotracheal tube during their ICU stay and who are predicted to remain ventilated beyond the end of the calendar day after the day they are first ventilated, or
3. All patients not already recruited who are receiving mechanical ventilation via an endotracheal tube and are expected to receive ongoing ventilation for a further 48 hours or more despite an earlier prediction that ventilation would be discontinued earlier.

Site exclusion criteria for cluster study-

1. Unwilling or unable to follow trial protocols.
2. Unable to capture the minimum data set required for the study.
3. Isolated specialty ICUs not co-located with a general ICU, such as solely cardiac, neurological/neurosurgical and burns ICUs, but such specialty patients cared for in general ICUs will be included
4. Specialty paediatric ICUs

Exclusion Criteria:

Patient exclusion criteria

1. Patients enrolled in a trial that would interact with the intervention
2. Patients with a known allergy, sensitivity or interaction to trial topical intervention drugs
3. Patients who are known or suspected to be pregnant
4. Patients who are moribund and not expected to survive the next 12 hours
5. Patients less than 16 years of age will not be enrolled in the UK

The protocol and statistical analysis plan were made public in 2020. The participant level dataset will not be publicly available immediately but will be available to collaborative researchers after consultation and negotiation with the SuDDICU Investigators.

The SuDDICU Protocol V4.0 and SAP V1.1 are available on the open science framework in pre print.

Public access, no access criteria to view the SuDDICU Protocol V4.0 and SAP V1.1