Skillman 1984.

Methods	Open‐label randomised controlled trial
Participants	Baseline characteristics Number randomised: 60 participants Number analysed: 46 participants Antacids (Mylanta II) Age (years; mean (SD)): 69 (‐) Number of participants (n): 22 Gender (male/female; n): 12/10 Prostaglandin ((15)‐R‐15‐methyl prostaglandin E2) Age (years; mean (SD)): 76 (‐) Number of participants (n): 24 Gender (male/female; n): 13/11 Inclusion criteria Admission to the respiratory surgical ICU Exclusion criteria Improper randomisation Less than 12 hours in the study Protocol not followed properly Repeated patient removal of the NG tube Uncertain Hemoccult test result Receiving food or fluid by mouth Baseline imbalances: no significant differences between the 2 groups in baseline characteristics such as age, sex, and risk factors. Most participants were diagnosed with intra‐abdominal disease (antacids: 7 and prostaglandin: 10)
Interventions	Antacids (Mylanta II) Dose (total/d): varies Duration of treatment (hours): 64 ± 8 Route: NG tube Intervention: Initial dose of 30 mL was instilled into the stomach, if gastric pH was found to be less than 3.5 after an hour; then the dose was doubled until the pH of the subsequent sample aspirated was greater than 3.5 Concomitant medications: ‐ Prostaglandin ((15)‐R‐15‐methyl prostaglandin E2) Dose (total/d): 6 mL Duration of treatment (hours): 39 ± 6 Route: NG tube Intervention: 1 mL through the NG tube washed with 10 mL of water every 4 hours Concomitant medications: ‐ Adherence to regimen: 14 patients were excluded after randomisation for reasons mentioned above under "Exclusion criteria". 11 of the 12 patients in whom prostaglandin E2 prophylaxis failed (upper GI bleeding) were switched to antacid regimen. One of the 11 patients had "double" failure because antacid also failed Duration of trial: October 1980 to August 1982 Duration of follow up: not clearly mentioned in the study report. Probably until death or discharge
Outcomes	Outcomes were not classified as primary or secondary in the study report; however outcomes reported were as follows. Outcomes sought in review and reported in trial Incidence of upper GI bleeding defined as a positive haemoccult test result All‐cause mortality in ICU Outcomes sought but not reported in trial Incidence of ventilator‐associated pneumonia All‐cause mortality in hospital Duration of ICU stay Duration of intubation Participants requiring blood transfusion Units of blood transfused Adverse events of interventions Outcomes reported but not used in review Relationship between underlying risk factors and development of upper GI bleed pH of luminal contents
Notes	Setting: Department of Surgery and Medicine Harvard Medical School and Beth Israel Hospital, Boston, Massachusetts Source of funding: Quote: "This study was supported in part by funds from Upjohn University, Kalamazoo, Michigan and the Charls Diana Research Institures, Beth Israel Hospital, Boston" Conflicts of interest: ‐ Ethics approval: Quote: "The study was approved by the Committee on Clinical Investigation, New Procedures and new Forms of Therapy of the Beth Israel Hospital" Comment: mentioned for only 1 centre Informed consent: ‐ Clinical trials registration: ‐ Sample size calculation: ‐
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “Patients were selected by a table of random numbers” Comment: Method adopted to obtain random sequence generation is clearly mentioned in the study report
Allocation concealment (selection bias)	Unclear risk	Comment: not clearly mentioned in the study report
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: This was not a placebo‐controlled trial, and the different modes of administering study interventions would not have made it possible to blind study personnel and participants
Blinding (detection bias) Clinically important upper GI bleeding	Low risk	Comment: Outcome assessor was not blinded. GI bleeding was an objective outcome detected as per the definition in the study protocol
Blinding (detection bias) Nosocomial pneumonia	Unclear risk	Comment: Study did not address this outcome
Blinding of outcome assessment (detection bias) Adverse reactions of interventions	Low risk	Comment: Outcomes of interest were objective in nature, so the likelihood of detection bias is low
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: 14 patients were excluded from analysis after randomisation for various reasons mentioned in "adherence to the regimen". The interventional arms to which these participants were randomised remain unclear. A per‐protocol analysis was performed, and there appears to be a balance between groups in terms of the number of participants available for final analysis
Selective reporting (reporting bias)	Low risk	Comment: All intended outcomes were analysed and reported
Other bias	Low risk	Comment: This study was supported in part by a research grant from Upjohn University, Kalamazoo, Michigan, and the Charls Diana Research Institures, Beth Israel Hospital. The role of the sponsor in the conduct and reporting of the trial is unclear