Macdougall 1977.

Methods	Open‐label randomised controlled trial
Participants	Baseline characteristics Number randomised: 75 participants Number analysed: 75 participants Antacids Age (years; mean (SD)): ‐ Number of participants (n): 13 Gender (male/female; n):‐ No prophylaxis Age (years; mean (SD)): ‐ Number of participants (n): 12 Gender (male/female; n): ‐ Inclusion criteria Admitted in the paediatric ICU At least 1 of the following criteria: shock, acute cardiac failure, acute respiratory failure, acute liver failure, acute renal failure, sepsis or serious focal infection, coagulopathy, acute nephrologic dysfunction, multiple trauma, severe metabolic acidosis following major surgery Exclusion criteria: ‐ Baseline imbalances: ‐
Interventions	Antacids Dose (total/d): 120 mL Duration of treatment (days): ‐ Route: NG tube Intervention: 20 mL magnesium hydroxide 4‐hourly via nasogastric tube, which was then clamped for 1 hour Concomitant medications: No corticosteroids were administered No prophylaxis Dose (total/d): ‐ Duration of treatment (days): ‐ Route: ‐ Intervention: ‐ Concomitant medications: No corticosteroids were administered Adherence to regimen: The first 25 participants received either antacids or no prophylaxis. The trial was discontinued when H2 receptor antagonists became available. Of the 50 remaining participants, 10 received metiamide and 16 received cimetidine (after case reports of agranulocytosis by metiamide). The remaining 24 got no prophylaxis Duration of trial: January 1975 to July 1976 Duration of follow‐up: ‐
Outcomes	Outcomes sought in review and reported in trial Clinically important upper GI bleeding defined as aspiration of fresh blood via nasogastric tube All‐cause mortality in ICU (data unclear for each interventional arm) Units of blood transfused (only mean provided) Adverse events of interventions (no event recorded) Outcomes sought in review but not reported in trial VAP (data unclear) All‐cause mortality in the hospital Duration of ICU stay Duration of intubation Number of participants requiring blood transfusion Outcomes reported in trial but not used in review Nil
Notes	Setting: Liver Unit, King's College Hospital and Medical School, Denmark Hill, London SES Source of funding: ‐ Conflicts of interest: ‐ Ethics approval: ‐ Clinical trials registration: ‐ Sample size calculation: ‐ Additional notes: Only data for the comparison of antacid with no prophylaxis were extracted for the review, as it was felt that the second part of the trial, which compared H2 receptor antagonist vs no prophylaxis, was not a properly randomised trial
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: not 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 trial was stopped and H2 receptors administered instead of antacids
Blinding (detection bias) Clinically important upper GI bleeding	Low risk	Comment: unclear on blinding of outcome assessors, but the definition for diagnosis of GI bleeding is mentioned in the study report
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: unclear on blinding of outcome assessors, but outcomes of interest were objective in nature
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: All randomised participants were part of the final analysis
Selective reporting (reporting bias)	High risk	Comment: Data are not reported separately for participants who received cimetidine and metiamide. Mortality data are clubbed for both groups of controls (those compared with antacids and H2 receptor antagonists)
Other bias	High risk	Comment: unclear on source of funding and baseline characteristics of participants