Powell 1993.

Methods	Single‐blind randomised controlled trial
Participants	Baseline characteristics Number randomised: 41 participants Number analysed: 41 participants Ranitidine Age (years; mean (SD)): 59.5 (10.1) Number of participants (n): 11 Gender (male/female; n): 8/3 Omeprazole (bolus) Age (years; mean (SD)): 57.7 (6.9) Number of participants (n): 10 Gender (male/female; n): 7/3 Omeprazole (infusion) Age (years; mean (SD)): 55.6 (9.6) Number of participants (n): 10 Gender (male/female; n): 7/3 Placebo Age (years; mean (SD)): 53.3 (10.8) Number of participants (n): 10 Gender (male/female; n): 10/0 Inclusion criteria Participants scheduled for coronary bypass graft surgery Participants who gave their informed consent on the eve of the operation Exclusion criteria Active peptic ulcer diseases Previous definitive acid lowering operation Current treatment with an H2  antagonists or other gastric antisecretory agents History of severe allergy Concomitant renal or liver disease Receiving treatments with warfarin or phenytoin Having received any non licensed drug within the preceding 30 days Baseline imbalances: Quote: "There was no difference between the groups with regard to sex, age, ethnic origin, the presence of droperidol in the premedication and the drugs used after the operation" Comments: The 4 groups of participants who were scheduled for CABG appear to be similar to each other with respect to demographic characteristics and medications given
Interventions	Ranitidine Dose (total/d): 150 mg Duration of treatment (days): not clearly mentioned in the study record. Most probably until discharge Route: IV Intervention: 50 mg IV every 8 hours Concomitant medications: Papaveretum, hyoscine and droperidol, thiopentone, fentanyl, pancuronium, nitrous oxide, droperidol and midazolam, glyceryl trinitrate (GTN), sodium nitroprusside (SNP), pentolinium, phentolamine, atropine (4 participants during surgery and 5 after surgery), heparin, gentamycin and flucloxalline or cefuroxime, potassium chloride Omeprazole (bolus) Dose (total/d): 120 mg Duration of treatment (days): not clearly mentioned in the study record. Most probably until discharge Route: IV bolus Intervention: 80‐mg IV loading dose, then 40 mg every 8 hours by IV bolus Concomitant medications: Papaveretum, hyoscine and droperidol, thiopentone, fentanyl, pancuronium, nitrous oxide, droperidol and midazolam, glyceryl trinitrate (GTN), sodium nitroprusside (SNP), pentolinium, phentolamine, atropine (4 participants during surgery and 5 after surgery), heparin, gentamycin and flucloxalline or cefuroxime, potassium chloride Omeprazole (infusion) Dose (total/d): 120 mg Duration of treatment (days): not clearly mentioned in the study record. Most probably until discharge Route: IV infusion Intervention: 80 mg IV loading dose, then 40 mg every 8 hours by IV infusion Concomitant medications: Papaveretum, hyoscine and droperidol, thiopentone, fentanyl, pancuronium, nitrous oxide, droperidol and midazolam, glyceryl trinitrate (GTN), sodium nitroprusside (SNP), pentolinium, phentolamine, atropine (4 participants during surgery and 5 after surgery), heparin, gentamycin and flucloxalline or cefuroxime, potassium chloride Placebo Dose (total/d): ‐ Duration of treatment (days): not clearly mentioned in the study record. Most probably until discharge Route: IV Intervention: 0.9% (150 mmol/L) saline 20 mL IV every 8 hours Concomitant medications: Papaveretum, hyoscine and droperidol, thiopentone, fentanyl, pancuronium, nitrous oxide, droperidol and midazolam, glyceryl trinitrate (GTN), sodium nitroprusside (SNP), pentolinium, phentolamine, atropine (4 participants during surgery and 5 after surgery), heparin, gentamycin and flucloxalline or cefuroxime, potassium chloride Adherence to regimen: ‐ Duration of trial: ‐ Duration of follow‐up: not clearly mentioned in the study record. Most probably until discharge
Outcomes	Outcomes sought in review and reported in trial (none of these were primary outcomes for this study) Incidence of upper GI bleeding All‐cause mortality in ICU Outcomes sought but not reported in trial Incidence of ventilator‐associated pneumonia All‐cause mortality in the hospital Duration of ICU stay Duration of intubation Number of participants requiring blood transfusions Number of units of blood transfused Adverse events of interventions Outcomes reported but not used in review Gastric pH, 24 hour acid output, total pepsin activity Haematological, urea, creatinine, and electrolyte data
Notes	Setting: Department of Anaesthetics and Department of Surgery, Royal Postgraduate Medical School, Hammersmith Hospital, London W12ONN, UK Source of funding: not clearly mentioned in the study report. However, it is mentioned that Astra Clinical Research Unit, Edinburgh, supplied the drugs and supported the trial Conflicts of interest: ‐ Ethics approval: Quote: "41 patients who were scheduled for CABG were entered into the study, which was approved by the local ethics committee" Informed consent: Quote: "Informed consent was obtained from each patient on the eve of the operation" Clinical trials registration: ‐ Sample size calculation: ‐ Additional notes: The omeprazole arms were combined to form a common interventional arm as the review did not aim to investigate efficacy on the basis of dose or mode of administration of the same drug
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Patients were assigned to one of the four treatment groups from a random list" Comment: Random sequence generation is not clearly mentioned in the study report
Allocation concealment (selection bias)	Unclear risk	Quote: "Patients were assigned to one of the four treatment groups from a random list" Comment: unclear on how allocation was concealed
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "The personnel collecting the aspirates did not know which treatment the patient received" Comment: This was a placebo‐controlled trial. Blinding of personnel was done for the primary outcomes of measuring gastric pH and volume of gastric secretion. The likelihood of performance bias is low
Blinding (detection bias) Clinically important upper GI bleeding	High risk	Comment: not clear whether outcome assessors were blinded. The definition for diagnosing GI bleed, which was an objective outcome, was not clearly 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: not clear whether outcome assessors were blinded. Moreover, the outcome of interest was objective in nature, so the likelihood of detection bias is low
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: All randomised participants were part of the final analysis
Selective reporting (reporting bias)	Low risk	Comment: All intended outcomes were analysed and reported
Other bias	Low risk	Comment: It is mentioned that Astra Clinical Research Unit, Edinburgh, supplied the drugs and supported the trial. But it is unclear whether they had any influence on the results of the trial. No other sources of bias detected