Methods	A randomised controlled trial was conducted between January 1993 and June 1993 of patients undergoing primary elective coronary artery bypass graft surgery. Patients were randomised on the day before surgery using a computer randomisation programme. Method of allocation concealment was not described
Participants	105 patients undergoing primary elective coronary artery bypass graft surgery were randomised to one of three groups: Group 1 (Autotransfusion group - uncoated circuit): n=36; M//F=30//6; median (range) age = 64 (58-67) years Group 2 (Autotransfusion group - heparin coated circuit): n=35; M//F=31//4; median (range) age = 62 (55-67) years Group 3 (Control group): n=34; M//F=30//4; median (range) age = 63 (58-67) years
Interventions	Group 1: Autotransfusion group (uncoated circuit) had their chest drains connected to a cardiotomy reservoir (CATR 3500) to which suction at 10Kpa was applied. This reservoir contained a 20 micron filter which removed debris and clot from the drained blood. From there blood was carried via an infusion pump which incorporated an air-in-line detector to a peripheral line. Autotransfusion commenced when there was more than 100mls in the cardiotomy reservoir and continued thereafter for 10 hours. Infusion was in hourly pulses according to the previous hours drainage. Group 2: Autotransfusion group (heparin coated circuit) had the autotransfusion circuit bonded with heparin. The heparin-bonded circuit comprised an identical system of drains and tubes except that all surfaces, including the cardiotomy reservoir and connector but excluding the piston chamber of the infusion pump and the intravenous cannula, were coated with heparin by the Duraflow II methodology. Group 3: Control group had their chest drains connected to underwater sealed drainage bottles with suction applied at 10Kpa. Autotransfusion was not performed.
Outcomes	Outcomes reported: amount of blood re-transfused from the cell saver, amount of allogeneic blood transfused, number of patients receiving allogeneic blood, adverse events, re-exploration for bleeding, blood loss, mortality, haematological variables, coagulation variables
Notes	Transfusion threshold: allogeneic blood was transfused to maintain the haematocrit level greater than 25%
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Method used to generate allocation sequences was adequate.
Allocation concealment (selection bias)	Unclear risk	Method used to conceal treatment allocation was unclear.
Blinding (performance bias and detection bias) All outcomes	High risk