Mercer 2004.

Methods	This was a single‐centre randomised clinical trial of intra‐operative autotransfusion (IAT) in surgery for abdominal aortic aneurysm (AAA). Patients were randomised using sealed envelopes. Patients were blinded to the transfusion group allocation. Members of the operating surgical team were responsible for the continuing care of patients, decision to use blood transfusion and investigation of post‐operative complications. They were independent of the research team, but were not blinded to the use of IAT.
Participants	81 patients undergoing elective repair of infrarenal abdominal aortic aneurysm were randomised to one of two groups: Group 1 (Autotransfusion group): n=40; M/F=34/6; median (interquartile range) age = 72 (69‐76) years.] Group 2 (Control group): n=41; M/F=29/2; median (interquartile range) age = 73 (67‐78) years.]
Interventions	Group 1: Autotransfusion group (Haemonetics Cell Saver) had their shed blood collected and processed by the autologous blood recovery system. Processed blood was returned to the patient as soon as haemostasis had been achieved. Group 2: Control group received standard care without autotransfusion.
Outcomes	Outcomes reported: number of patients transfused allogeneic blood, amount of allogeneic blood transfused, blood loss, adverse events, mortality, hospital length of stay.
Notes	Transfusion threshold: patients received allogeneic blood transfusion to maintain haemoglobin levels above 8.0g/dL.
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)	High risk	Method of allocation concealment was inadequate.
Blinding (performance bias and detection bias) All outcomes	High risk	Single‐blind.