Methods	Between June 1988 and August 1989, 103 patients who gave informed consent to participate in the study underwent cardiopulmonary bypass. Of the initial 103 patients, 71 were excluded from the study. Method of randomisation and allocation concealment was not described
Participants	32 patients undergoing cardiac surgery requiring cardiopulmonary bypass were randomised to one of two groups: Group 1 (Autologous retransfusion group): n=16; mean (sd) age = 60 (8.0) years Group 2 (Control group): n=16; mean (sd) age = 61 (8.0) years
Interventions	Group 1: Autologous retransfusion group (Pleur-evac Autotransfusion System - A-5005-ATS) had their mediastinal shed blood collected in a polyvinyl chloride blood bag containing an inline 200um nylon mesh filter by means of a closed system with - 20cmH2O suction applied. This collection system contained no anticoagulant and none was added. Mediastinal shed blood was transfused without washing by detaching the autotransfusion replacement bag and reinfusing the blood through a standard 40um screen blood filter (Pall SQ40S) via a peripheral intravenous line. Group 2: Control group received either autologous packed cells if available or allogeneic packed red blood cells (standard citrate-phosphate-dextrose ADSOL-preserved cross-matched packed RBCs units stored at 4 degrees celsius for up to 42 days).
Outcomes	Outcomes reported: amount of allogeneic blood transfused, amount of autologous blood transfused, number of patients transfused autologous and/or allogeneic blood, complications, bleeding times, plasma protein variables, post transfusion febrile reactions
Notes	Transfusion threshold: the decision to transfuse a patient post-operatively was made by the clinician who was responsible for the patient’s post-operative care, and who was not involved in the study. The clinical criteria used to determine the need for transfusion consisted of the following: systolic BP less than 80mmHg; mean arterial pressure less than 50mmHg; central venous pressure (CVP) less than 5mmHg; pulmonary capillary wedge pressure (PCWP) less than 5mmHg; cardiac index (CI) less than 2.0L/min/m2; evidence of inadequate end-organ perfusion (ie: urine output less than 20ml/hr), or anaemia (Hct less than 25%). Any patient who bled more than 400ml in the first 4 hours post-operatively and who met any of these criteria underwent transfusion
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 concealment treatment allocation was unclear.
Blinding (performance bias and detection bias) All outcomes	High risk