Bell 1994.

Methods	Parallel‐group randomized controlled trial, conducted in England. Study dates not reported
Participants	39 elective cardiac (coronary artery and/or valve) surgical patients with low cardiac output (defined as cardiac index < 2.5 L/min/m2 and a minimal pulmonary capillary wedge pressure of 7 mmHg) without hepatic or renal impairment
Interventions	Low‐dose opioid, early extubation (fentanyl 15 μg/kg and propofol, extubated within 8 hours) in 20 participants High‐dose opioid, usual care (fentanyl 60 μg/kg and midazolam, extubated after more than 8 hours) in 19 participants Details of weaning protocol and who decided when to extubate were not given.
Outcomes	Time to extubation Length of stay in the ICU
Notes	Median time to extubation and length of stay in the intensive care unit were reported with no interquartile range, thus data were not used in the meta‐analysis. Study authors did not report mortality outcomes or postoperative complications. No power calculation was done. Funding source was J.F. Blades and Zeneca Pharma, Wilmslow, Cheshire. Details of any declarations of conflict of interest among study authors were not provided.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details given
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No details given
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawal from the study during follow‐up
Selective reporting (reporting bias)	High risk	Study authors did not report mortality outcomes or postoperative complications.
Other bias	Low risk	Baseline participant characteristics (age, sex, weight, surface area, duration of surgery, type of surgery) were comparable.