O'Brien 1973.

Study characteristics
Methods	Parallel design (2 arms) Country: New Zealand Follow‐up period: 48 hours
Participants	Randomly assigned: N = 300 Lidocaine group: 51.3% (154/300) Control (5% dextrose solution) group: 48.7% (146/300) Age: not reported Gender (male): not reported Inclusion criterion: proven myocardial infarction Exclusion criteria Known ventricular fibrillation Known ventricular tachycardia Cardiac arrest before admission
Interventions	Lidocaine, 75 mg, first bolus. Infusion 2.5 mg/min in 5% dextrose at 1 mL/min Placebo: 5% dextrose solution Co‐intervention: not reported
Outcomes	Reducing the frequent of ventricular fibrillation and ventricular tachycardia
Notes	Sample size calculation a priori: not reported Sponsor: not reported Trial conduction dates: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"allocation.... by means of random selection" (page 36) Insufficient information about the sequence generation process to permit judgement of ‘low risk’ or ‘high risk’
Allocation concealment (selection bias)	Unclear risk	Insufficient information to permit judgement of ‘low risk’ or ‘high risk’
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient information about the blinding level process to permit judgement of ‘low risk’ or ‘high risk’ Comments: This was described as double blind
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information about the blinding level process to permit judgement of ‘low risk’ or ‘high risk’
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	The report gave the impression that no dropouts or withdrawals had occurred, but this was not specifically stated
Selective reporting (reporting bias)	Low risk	The study protocol is not available, but it is clear that published reports describe all expected outcomes, including those that were pre‐specified (convincing text of this nature may be uncommon)
Other bias	High risk	Design bias (Porta 2008)