Methods	A prospective, randomised study to assess the impact of cell salvage autotransfusion on the requirements for allogeneic blood in patients undergoing a total knee replacement was conducted. Patients were allocated to groups according to a computer generated randomisation schedule. Method of allocation concealment was not described
Participants	100 consecutive patients undergoing total knee replacement were randomised to one of two groups: Group 1 (Autotransfusion group): n=50; M//F=21//29; mean age males = 70.4 years (range 47-78 years); mean age females = 69.3 years (range 52-81 years) Group 2 (Control group): n=50; M//F=24//26; mean age males = 67.9 years (range 51-82 years); mean age females = 70.8 years (range 46-88)
Interventions	Group 1: Autotransfusion group patients had post-operative drainage blood processed by a Haemonetics Cell Saver 3. Blood was collected via the wound drains following the release of the tourniquet. The collected blood was anticoagulated with heparinised saline. The machine aspirated the wound drainage into the centrifuge bowl via roller pumps. The blood underwent accelerated sedimentation, being spun at 5600 revs/per/minute. The supernatant was discarded and the resulting red cells washed and resuspended in normal saline. The machines produced a product with a haematocrit of over 55% and a volume of 250mls. Group 2: Control group did not receive autotransfusion.
Outcomes	Outcomes reported: amount of blood collected by the cell saver, amount of allogeneic blood transfused, number of patients transfused allogeneic blood, adverse events, hospital length of stay
Notes	Transfusion threshold: allogeneic blood was given in the post-operative period when the haemoglobin fell below 9.0g/dL. Routine procedure of crossmatching two units of packed cells was performed for all patients in the study
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