Whitehead 1980.

Methods	RCT, parallel design
Participants	Total number of randomized participants: 60 Inclusion criteria: scheduled for removal of wisdom teeth under GA Exclusion criteria: cardiac insufficiency, chronic obstructive airway disease, receiving routine medication, diabetes, severe hepatic, renal, or haematological disease Type of surgery: removal of wisdom teeth Baseline characteristics Intervention group (metoprolol) Age, mean: 27 years Control group (placebo) Age, mean: 22 years Country: UK Setting: single centre; hospital
Interventions	Intervention group (metoprolol) Randomized, n = 30; losses = 0; analysed, n = 30 (use of ITT analysis not reported) Details: 2 mg metoprolol, IV, as a single dose before induction of GA Control group (placebo) Randomized, n = 30; losses = 0; analysed, n = 30 Details: normal saline, given same as the intervention group
Outcomes	Outcomes measured/reported by study authors: cardiac arrhythmias (nodal rhythm and ventricular extrasystoles), bradycardia (HR < 50 bpm); hypotension (SBP < 100 mmHg) Outcomes relevant to the review: bradycardia (HR < 50 bpm); hypotension (SBP < 100 mmHg)
Notes	Funding/declarations of interest: study drugs provided by Messrs Ciba‐Geigy Pharmaceuticals Study dates: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not specified
Allocation concealment (selection bias)	Unclear risk	Not specified
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Randomized, placebo‐controlled, double‐blind trial. Ampoules of study drugs were visually similar
Blinding of outcome assessors (detection bias) All outcomes	Low risk	Anaesthesiologist evaluating ECG and haemodynamic parameters was blinded to study group allocation
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses
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	High risk	Short report with baseline characteristics reported with limited detail. Not feasible to assess other risks of bias from this report. In addition, we noted that participants in either group were given metoprolol to manage ventricular dysrrhythmia. This may influence outcome data in the control group