Boldt 1998.

Study characteristics
Methods	Parallel, 72 h
Participants	PCA 30, control 30 First time elective cardiac surgery
Interventions	PCA: piritramide. Bolus/lockout/1 h limit: 2 mg/10 min/6 doses Control: IV piritramide 5 mg, on demand or as determined by nurse
Outcomes	Pain intensity, sedation, patient satisfaction, pulmonary function, cortisol and troponin levels, O2 saturation, PaO2 and PaCO2, adverse events
Source of funding	Not reported
Notes	See Published notes for details regarding study retraction 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 described
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not blinded
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Number of participants completing study not reported, imputation methods not described
Selective reporting (reporting bias)	Low risk	All outcomes described in Methods section are reported in Results section
Other bias	Unclear risk	Small sample size