Methods	Randomised controlled trial of 135 adults undergoing primary cardiac surgery. Method of randomisation and allocation concealment was not described
Participants	135 patients undergoing cardiac surgery were randomised to one of two groups: Group 1 (Autotransfusion group): n=67; M//F=52//15; mean (sd) age = 60 (12) years Group 2 (Control group): n=68; M//F=51//17; mean (sd) age = 61 (10) years
Interventions	Group 1: Autotransfusion group had the cardiotomy reservoir (Dideco 742), after use in extracorporeal circulation, reconfigured to serve as a receptacle for post-operative mediastinal drainage. One of the inlet ports was connected to the tubes draining the mediastinum. In this way the drainage from the chest passed through the 20um filter of the cardiotomy reservoir. The cardiotomy outlet tubing was replaced with an adapter connecting with standard intravenous tubing. A standard infusion pump was used to reinfuse the collected blood. The filtered blood collecting in the reservoir was reinfused at hourly intervals. No blood was reinfused after the 6th post-operative hour. Thereafter the reservoir served only as a receptacle for shed mediastinal blood. Reservoir blood was sampled at 6 hours for bacteriologic study. Group 2: Control group received no autotransfusion.
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, mortality, blood loss
Notes	Transfusion threshold: Transfusion protocol was 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 (performance bias and detection bias) All outcomes	High risk