Bedder 1991.

Study characteristics
Methods	Parallel, 24 h
Participants	PCA 20, control 18 Non‐thoracic elective or emergency surgery ‐ ICU environment
Interventions	PCA: morphine. Bolus/lockout/ 4 h limit: 2 mg/10 min/NR Control: IV morphine 2 mg every 10 min prn
Outcomes	Pain intensity, opioid consumption, sedation scores, oxygen saturation
Source of funding	"Supported in part by BARD and Nellcor" (no description of nature of funding groups)
Notes	Oxygen saturation < 90%: 2/20 PCA vs 1/18 No respiratory rate < 10 QS = 3 (R = 2, DB = 0, W = 1)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not blinded
Incomplete outcome data (attrition bias) All outcomes	High risk	Method of analysis and number of participants completing study not described. Figures suggest that several participants in both groups did not complete study
Selective reporting (reporting bias)	Low risk	All outcomes described in Methods section are reported in Results section
Other bias	High risk	Very small sample size