Page 1989.

Methods	Consecutive patients having elective coronary artery or valvular operations were enrolled in a prospective, randomised controlled trial comparing allogeneic blood consumption between conventional mediastinal drainage and reinfusion of shed mediastinal blood using a hard‐shell cardiotomy reservoir. Method of randomisation and allocation concealment was not described.
Participants	100 consecutive patients undergoing elective coronary artery or valvular operations were randomly allocated to one of two groups: Group 1 (Autotransfusion group): n=48; M/F=38/11; mean (sd) age = 58.3 (8.9) years Group 2 (Control group): n=51; M/F=38/14; mean (sd) age = 56.9 (9.4) years
Interventions	Group 1: 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 50cmH2O was applied. Patients had their shed mediastinal blood reinfused for up to 18 hours post‐operatively. Group 2: 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 25cmH2O. 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 patients transfused allogeneic blood, adverse events, re‐exploration for bleeding.
Notes	Transfusion threshold: allogeneic blood or hetastarch was infused to maintain cardiovascular stability and a haematocrit of 30%.
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 (performance bias and detection bias) All outcomes	High risk