Methods	A prospective, randomised study was conducted to determine if cell-salvaged autologous blood can serve as an alternative to allogeneic blood in patients undergoing elective infra-renal abdominal aortic surgery. Method of randomisation not described. Allocation concealment was by sealed envelopes
Participants	50 patients undergoing elective infrarenal abdominal aortic aneurysm surgery were randomised to one of two groups: Group 1 (Autotransfusion group): n=23; M//F=19//4; median (IQR) age = 71 (54-78) years Group 2 (Control group): n=27; M//F=20//7; median (IQR) age = 68 (54-82) years
Interventions	Group 1: Autotransfusion group patients received autologous blood via intraoperative autotransfusion (IAT). A COBE Baylor rapid autologous transfusion system was employed for intra-operative cell salvage. Blood was retrieved from the operative site by suctioning into a double lumen catheter at less than 150mmHg, to minimise haemolysis. Blood was anticoagulated with heparin (30,000 units/1 litre 0.9% saline). The salvaged blood was then collected in a reservoir where a macrofilter of 150 microns removed larger particles of debris. When 500mls of blood was collected, it was pumped to a spinning centrifuge bowl. The red cells were washed with 0.9% saline, and concentrated to a Hct above 50%. The effluent containing plasma fractions, platelets, leukocytes, free haemoglobin, anticoagulant and saline was discarded. The washed red cells, suspended in saline were pumped from the centrifuge to the patient through a microfilter of either 20 or 40 microns. Group 2: Control group did not receive autotransfusion.
Outcomes	Outcomes reported: amount of allogeneic blood transfused, number of patients transfused allogeneic blood, adverse events, hospital length of stay, blood loss, mortality
Notes	Transfusion threshold: patients were transfused allogeneic blood if the Hct fell below 25%
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 used to conceal treatment allocation was inadequate.
Blinding (performance bias and detection bias) All outcomes	High risk