Passchier 1993.

Study characteristics
Methods	Parallel, outcomes assessed through 96 h (unclear how long PCA or control administered)
Participants	PCA 21, control 19 Elective upper abdominal surgery (cholecystectomy, intestinal resection)
Interventions	PCA: morphine. Bolus/lockout/1 h limit: 1 mg/5 min/10 mg Control: IM morphine 10 mg prn (no schedule specified)
Outcomes	Pain intensity and relief, opioid consumption, state anxiety, patient satisfaction, distress, Profile of Mood State questionnaire, locus of control
Source of funding	Support from Bard, the Netherlands
Notes	Withdrawals: PCA vs control (n): refused to continue postoperatively: 4 vs 5 (not included in analyses) 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	Withdrawals balanced between groups and apparently unrelated to interventions
Selective reporting (reporting bias)	Unclear risk	All outcomes described in Methods section are reported in Results section. No adverse events assessed or reported
Other bias	High risk	Very small sample size