Myles 1994.

Study characteristics
Methods	Parallel, 48 h
Participants	PCA 36, control 36 Elective cardiac surgery
Interventions	PCA: morphine. Bolus/lockout/4 h limit: 1 mg/5 min/no limit Control: IV morphine nurse controlled infusion (dose range not specified)
Outcomes	Pain intensity, opioid usage, intensity of nausea, time to extubation, cortisol levels
Source of funding	PCA devices funded by Alfred Hospital Whole‐time Medical Specialists' Private Practice Fund
Notes	Withdrawals: control, n = 3: 2 deaths, 1 cerebrovascular accident QS = 2 (R = 1, DB = 0, W = 1)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not adequately described
Allocation concealment (selection bias)	High risk	Blocked randomization with stratification ‐ study is not blinded, therefore allocation can be established
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not blinded
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Data of 69 participants analyzed: PCA 36 and control 33 (3 withdrawals all in the control group). Data for 16 participants incomplete, due to reasons apparently unrelated to interventions ‐ not clear whether included in analyses. Group assignment and methods of imputation (or completer analysis only) not specified
Selective reporting (reporting bias)	Low risk	All outcomes described in Methods section are reported in Results section
Other bias	Unclear risk	Small sample size