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Study characteristics
Methods	Design: RCT, parallel two‐arm, single‐centre study Setting: regional cardiothoracic hospital, Liverpool, Merseyside, UK Recruitment: recruitment and study dates not reported Maximum follow‐up: duration of hospital stay
Participants	100 consecutive participants undergoing elective coronary artery or valvular operations were randomly allocated to one of two groups: Group 2 (reinfusion of shed mediastinal blood) (Cell salvage/intervention group): N = 48. M:F 38:11. Mean (SD) age 58.3 (8.9) Group 1 (conventional mediastinal drainage) (Control/no cell salvage group): N = 51. M:F 38:14. Mean (SD) age 56.9 (9.4) There were no differences between groups at baseline.
Interventions	Group 2 (reinfusion of shed mediastinal blood) (Cell salvage/intervention group): autotransfusion group had a Bentley Catr hard‐shell cardiotomy reservoir (Bentley‐Edwards CVS Division) used during bypass. Both drains were connected to the top of the cardiotomy reservoir, previously used during bypass, and suction of 50 cm H2O was applied. Patients had their shed mediastinal blood reinfused for up to 18 hours postoperatively. Group 1 (conventional mediastinal drainage) (Control/no cell salvage group): control group had a Polystan soft‐shell cardiotomy reservoir (Polystan A/S Walgerholm 8) used during bypass. Blood was drained into conventional drainage bottles with an applied suction of 25 cm H2O. NB: after bypass, any residual blood left in the perfusion circuit was saved and infused through a peripheral vein. Both groups of patients had pericardial and mediastinal drains (Axiom). A variety of both membrane and bubble oxygenators were used in both groups.
Outcomes	Outcomes reported: amount of blood re‐transfused from the cell saver, amount of allogeneic blood transfused, number of participants transfused allogeneic blood, adverse events, re‐exploration for bleeding
Notes	Transfusion protocol: allogeneic blood or hetastarch was infused to maintain cardiovascular stability and a haematocrit of 30%. Prospective registration status: the study was published prior to 2010. Ethical approval: it is not clear whether the study was approved by an ethics committee or institutional review board. Language of publication: English Trial funding: not reported Conflicts of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method used to generate allocation sequences was not described.
Allocation concealment (selection bias)	Unclear risk	Method used to conceal treatment allocation was unclear.
Blinding of participants and personnel (performance bias) Objective outcome: mortality	Low risk	No objective outcomes reported (mortality unlikely to be affected by blinding if reported in future publications)
Blinding of participants and personnel (performance bias) Subjective: transfusion protocol	Low risk	Transfusion protocol in place: "Homologous blood or hetastarch was infused to maintain cardiovascular stability and a hematocrit of 30%"
Blinding of participants and personnel (performance bias) Subjective: all other outcomes	High risk	No blinding in the study and other outcome measures deemed high risk of subjectivity
Blinding of outcome assessment (detection bias) Objective outcomes: mortality and transfusions	Low risk	No objective outcomes reported (mortality unlikely to be affected by blinding if reported in future publications)
Blinding of outcome assessment (detection bias) Subjective outcomes	High risk	No blinding in the study and other outcome measures deemed high risk of subjectivity
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	One participant was excluded from the study following a postoperative complication. 100 people at baseline, unclear N for analysis
Selective reporting (reporting bias)	Unclear risk	No trial registration or published protocol is available to compare
Other bias	Unclear risk	No baseline imbalance. Funding and conflicts not reported