Spark 1997.

Study characteristics
Methods	Design: RCT, parallel two‐arm, single‐centre study Setting: university teaching hospital, Leeds, Yorkshire, UK Recruitment: recruitment and study dates not reported Maximum follow‐up: duration of hospital stay
Participants	50 participants undergoing elective infrarenal abdominal aortic aneurysm surgery were randomised to one of two groups: Autologous blood (Cell salvage/intervention group): N = 23. M:F 19:4. Median (IQR) age 71 (54 to 78) Homologous blood (Control/no cell salvage group): N = 27. M:F 20:7. Median (IQR) age 68 (54 to 82) There was no imbalance between groups at baseline.
Interventions	Autologous blood (Cell salvage/intervention group): cell salvage group participants received autologous blood via intraoperative autotransfusion (IAT). A COBE Baylor rapid autologous transfusion system was employed for intraoperative cell salvage. Blood was retrieved from the operative site by suctioning into a double lumen catheter at < 150 mmHg, 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 µm removed larger particles of debris. When 500 mL of blood was collected, it was pumped to a spinning centrifuge bowl. The red cells were washed with 0.9% saline, and concentrated to an 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 µm or 40 µm. Homologous blood (Control/no cell salvage group): control group did not receive autotransfusion.
Outcomes	Outcomes reported: amount of allogeneic blood transfused, number of participants transfused allogeneic blood, adverse events, hospital length of stay, blood loss, mortality
Notes	Transfusion protocol: participants were transfused allogeneic blood if the Hct fell below 25%. Prospective registration status: the study was published prior to 2010. Ethical approval: the study protocol was approved by the local ethics committee. Language of publication: English Trial funding: Yorkshire Vascular and Surgical Research Fund Conflicts of interest: not reported
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	Using sealed envelopes (does not state whether they were opaque)
Blinding of participants and personnel (performance bias) Objective outcome: mortality	Low risk	No objective outcomes reported (mortality unlikely to be affected by blinding if reported in future publications)
Blinding of participants and personnel (performance bias) Subjective: transfusion protocol	High risk	No transfusion protocol in place
Blinding of participants and personnel (performance bias) Subjective: all other outcomes	High risk	No mention of blinding; multiple outcomes lack guidelines/diagnostic criteria needed to avoid bias
Blinding of outcome assessment (detection bias) Objective outcomes: mortality and transfusions	Low risk	No objective outcomes reported (mortality unlikely to be affected by blinding if reported in future publications)
Blinding of outcome assessment (detection bias) Subjective outcomes	High risk	No mention of blinding; multiple outcomes lack guidelines/diagnostic criteria needed to avoid bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	ITT analysis
Selective reporting (reporting bias)	Unclear risk	No trial registration or published protocol is available to compare
Other bias	Low risk	No baseline imbalance. Funding reported (non‐pharmaceutical)