Skiba 2013.

Methods	RCT, parallel design
Participants	Total number of randomized participants: 148 Inclusion criteria: > 18 years of age; in normal sinus rhythm preoperatively; scheduled for cardiac surgery: ejection fraction > 30%; not in NYHA class IV heart failure Exclusion criteria: thyroid disease; elevated serum aspartate aminotransferase or alanine aminotransferase, or gastrointestinal disorders, which may interfere with drug absorption Type of surgery: cardiac surgery (CABG, valve, or both) Baseline characteristics Intervention group (metoprolol) Age, mean (SD): 67.5 (± 1.8) years Gender, M/F: 56/19 History of MI, %: 28 History of hypertension, %: 57 Preoperative use of beta‐blockers, n: 13 Control group (standard therapy) Age, mean (SD): 63.3 (± 1.2) years Gender, M/F: 60/13 History of MI, %: 26 History of hypertension, %: 60 Preoperative use of beta‐blockers, n: 4 Country: Australia Setting: single centre; hospital
Interventions	Intervention group (metoprolol) Randomized, n = 75; losses = 48 (did not receive allocated treatment); analysed, n = 27 (per‐protocol); 75 (ITT) Details: started during surgery IV infusion of 5 mg/kg metoprolol over 5 min, then 3 subsequent doses in next 24 h. Dose adjusted according to haemodynamic parameters; then oral administration 25‐50 mg metoprolol 3 times daily (nasogastric administration if necessary, until oral therapy could be tolerated), adjusted according to haemodynamic parameters. At hospital discharge, metoprolol continued at the final discharge dose until follow‐up Control group (standard therapy) Randomized, n = 73; losses = 0; analysed, n = 73 Details: standard therapy
Outcomes	Outcomes measured/reported by study authors: AF, length of hospital stay; mortality (time point not specified) Outcomes relevant to the review: AF, length of hospital stay; mortality
Notes	Funding/declarations of interest: not reported Study dates: not reported Note: study included an additional group (metoprolol plus amiodarone), which we did not include in the review study authors reported a large number of losses in the metoprolol group due to treatment not being given. Study authors reported ITT analysis and per‐protocol analysis. Because the losses were so many, we used the per‐protocol data in analysis. Study authors report baseline imbalances between groups in per‐protocol analysis which influenced data for AF we did not combine data for length of hospital stay because these were reported as median (IQR) values. Intervention group 6 (5‐7) days; control group 6 (5‐7) days
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not specified
Allocation concealment (selection bias)	Unclear risk	Use of sealed envelopes, opened in theatre. No additional details
Blinding of participants and personnel (performance bias) All outcomes	High risk	Open‐label
Blinding of outcome assessors (detection bias) All outcomes	High risk	Open‐label
Incomplete outcome data (attrition bias) All outcomes	High risk	Study authors reported a large number of losses due to treatment not being given at each time point. However, because doses were given according to haemodynamic parameters, the loss of participants may relate to haemodynamic stability.
Selective reporting (reporting bias)	Unclear risk	Study authors did not report prospective clinical trial registration or publication of a protocol. It was not feasible to effectively assess risk of reporting bias
Other bias	Low risk	Not detected