Dahl 1987.

Study characteristics
Methods	Parallel, 16 h
Participants	PCA 18, control 18 Lower abdominal surgery (hysterectomy, hysterosalpingo‐oophorectomy, oophorectomy, second look)
Interventions	PCA: morphine. Bolus/lockout/4 h limit: 2.5 mg/10 min/NR Control: scheduled IM morphine (7.5 to 12.5 mg depending on body weight), with IV morphine 2.5 mg as required
Outcomes	Pain intensity and relief, opioid consumption, vital signs, nausea/vomiting, consciousness
Source of funding	Not mentioned
Notes	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	Low risk	All participants completed the study
Selective reporting (reporting bias)	Low risk	All outcomes described in Methods section are reported in Results section, although consciousness only reported at 4 h
Other bias	High risk	Very small sample size