Basso 1981.

Methods	Single‐blind randomised controlled trial
Participants	Baseline characteristics Number randomised: 168 participants Number analysed: 168 participants Cimetidine Age (years; mean (SD)): ‐ Number of participants (n): 60 Gender (male/female; n): ‐ Antacids (Maalox) Age (years; mean (SD)): ‐ Number of participants (n): 52 Gender (male/female; n): ‐ No prophylaxis Age (years; mean (SD)): ‐ Number of participants (n): 56 Gender (male/female; n): ‐ Inclusion criteria Patient admitted to the ICU Exclusion criteria Evidence of gross upper GI bleeding before or during the 12 hours after start of the trial Gastric or oesophageal operations Age < 12 years Having coagulopathies Baseline imbalances: Risk categories and risk factors in the 3 groups were comparable
Interventions	Cimetidine Dose (total/d): 800 mg Duration of treatment (days): min 10 Route: IV or PO Intervention: 200 mg every 6 hours IV or orally Concomitant medications: ‐ Antacids (Maalox) Dose (total/d): 2400 mL Duration of treatment (days): min 10 Route: NG tube or PO Intervention: 10 mL/h by NG tube or orally Concomitant medications: ‐ No prophylaxis Dose (total/d): ‐ Duration of treatment (days): min 10 Route: ‐ Intervention: ‐ Concomitant medications: ‐ Adherence to regimen: 16 participants died, 6 did not comply with therapy, and 9 were transferred to other institutions. Therefore, 31 participants did not complete 10 days of the trial Duration of trial: March 1978 to April 1979 Duration of follow‐up: not clearly mentioned in trial report
Outcomes	Outcomes sought in review and reported in trial Clinically important GI bleeding diagnosed by clinical signs of haematemesis, melena, blood in NG tube or stool, or change in haematocrit All‐cause mortality in ICU (not reported separately for each arm) Number of units of blood transfused (not mentioned separately for each arm) Outcomes sought but not reported in trial VAP All‐cause mortality in hospital Duration of ICU stay Duration of intubation Participants requiring blood transfusion Adverse events of interventions Outcomes reported but not used in review Nil
Notes	Setting: ICU, University of Rome Source of funding: ‐ Ethics approval: ‐ Informed consent: Quote: "Informed consent was obtained from either the participant or their closest relative" Clinical trials registration: not provided Sample size calculation: ‐
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: “The study was done in a single blind manner, assigning the treatment according to a list of randomised values” Comment: not enough information reported on method of sequence generation
Allocation concealment (selection bias)	Unclear risk	Comment: not enough information reported on method of allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: This was not a placebo‐controlled trial and personnel were not blinded
Blinding (detection bias) Clinically important upper GI bleeding	Low risk	Quote: "The observer assessing the occurrence of gastrointestinal bleeding did not know the type of prophylactic measures the patient was receiving"
Blinding (detection bias) Nosocomial pneumonia	Unclear risk	Comment: The trial did not address this outcome
Blinding of outcome assessment (detection bias) Adverse reactions of interventions	Unclear risk	Comment: Unclear whether outcome assessors were blinded for other outcomes
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: All randomised participants were part of the final analysis
Selective reporting (reporting bias)	Unclear risk	Comment: All‐cause mortality in ICU and units of blood transfused were not mentioned separately for each interventional arm. Unclear whether this contributed to reporting bias
Other bias	Unclear risk	Comment: source of funding and baseline characteristics unclear