Chang 2004.

Study characteristics
Methods	Parallel, 24 h
Participants	PCA 62, control 63 (142 total agreed to participate, but initial group assignment numbers before withdrawal not described) abdominal gynecologic surgery
Interventions	PCA: morphine. Bolus/lockout/4 h limit: NR/8 to 10 min/NR Control: IM morphine 0.1 to 0.2 mg/kg (max 10 mg every 3 h) prn
Outcomes	Pain intensity, patient satisfaction, cost‐effectiveness, opioid use, side effects
Source of funding	Grant from the Hong Kong Health Services Research Committee
Notes	Method of measurement of respiratory depression not defined 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 mentioned
Blinding of participants and personnel (performance bias) All outcomes	High risk	"Double blinding was not adopted, as there were obvious differences in each method of pain management. However, the research assistant and ward staff were blind to the research hypotheses."
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear how many participants withdrew in each group (17 total). Results reported for completers only
Selective reporting (reporting bias)	Low risk	All outcomes described in Methods section are reported in Results section
Other bias	Unclear risk	Small sample size