Magnusson 1986.

Methods	RCT, parallel design
Participants	Total number of randomized participants: 30 Inclusion criteria: scheduled for cholecystectomy, herniorrhaphy, with hypertension Exclusion criteria: obstructive lung disease, previous MI, congestive heart failure, 2nd‐ or 3rd‐degree atrioventricular block Type of surgery: cholecystectomy, herniorrhaphy Baseline characteristics Intervention group (metoprolol) Age, mean (SD): 56 (± 9) years Gender, M/F: 3/10 Preoperative use of beta‐blockers, n: 11 Control group (placebo) Age, mean (SD): 59 (± 7) years Gender, M/F: 7/7 Preoperative use of beta‐blockers, n: 3 Country: Sweden Setting: single centre; hospital
Interventions	Intervention group (metoprolol) Randomized, n = 15; losses = 2 (due to cancellation of surgery because of: chest pain in 1 participant, and appearance of new T wave on ECG in another); analysed, n = 13 (use of ITT analysis not used) Details: 200 mg metoprolol (in slow‐release form) once daily for at least 2 weeks up to and including the morning of surgery; IV infusion of metoprolol 15 mg before induction of GA Control group (placebo) Randomized, n = 15; losses = 1 (due to dizziness leading to discontinuation of medication); analysed, n = 14 Details: placebo, given same as the intervention group
Outcomes	Outcomes measured/reported by study authors: multiple haemodynamic parameters, heart failure, ventricular extrasystoles, bradycardia (HR < 40 bpm), hypotension (SAP < 70 mmHg) Outcomes relevant to the review: bradycardia, hypotension
Notes	Funding/declarations of interest: supported by university funding Study dates: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomization was not specified. We noted a difference between groups in the number of participants who were previously taking anti‐hypertensive treatment (which included beta‐blockers); we could not be certain whether this difference was caused by insufficient randomization
Allocation concealment (selection bias)	Unclear risk	Not specified
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Randomized, double‐blind, placebo‐controlled trial
Blinding of outcome assessors (detection bias) All outcomes	Unclear risk	Not specified
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Two patients in the treatment group and one patient in the placebo group were subsequently excluded because of complications during treatment". Comment: loss of < 10%
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