Murphy 1994.

Study characteristics
Methods	Parallel, 24 h
Participants	PCA 100, control 100 Laparotomy, thoracotomy
Interventions	PCA: meperidine. Bolus/lockout/4 h limit: 20 mg/5 min/NR (titration permitted) Control: IV meperidine nurse controlled infusion, 0 to 40 mg/h with bolus doses of 20 to 40 mg and titration permitted
Outcomes	Pain intensity, opioid consumption, levels of nausea and sedation, incidence of adverse events
Source of funding	Supported by the Dr. John Boyd Craig Bursary of the Australian and New Zealand College of Anaesthetists
Notes	Respiratory depression requiring treatment with naloxone: 1/100 vs 1/100 Withdrawals: previous neurological deficit preventing use of PCA (n = 1) 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 explicitly stated, but appears to be unblinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	Only 1 withdrawal (PCA group), unrelated to intervention
Selective reporting (reporting bias)	Low risk	All outcomes described in Methods section are reported in Results section.
Other bias	Low risk	Adequate sample size