Møller 2019.

Study characteristics
Methods	Design: RCT, single‐site, 2‐arm parallel trial Setting: "vascular unit servicing a population of 820,000"; Denmark Recruitment: 2015 to 2017 Maximum follow‐up: 90 days
Participants	58 participants over 40 years of age undergoing elective open infrarenal abdominal aortic aneurysm repair or lower limb bypass surgery or femoro‐femoral cross‐over surgery Liberal group: n = 29; mean (SD) age = 73.7 (7.3.) years Restrictive group: n = 29; mean (SD) age = 71.3 (9.4) years
Interventions	Liberal group: transfused to maintain Hb > 9.7 g/dL Restrictive group: transfused when Hb < 8.0 g/dL to maintain Hb ≥ 8.0 g/dL
Outcomes	Primary outcome: mean postoperative Hb between days 0 and 15 Secondary outcomes: units of RBCs transfused, randomisation rate, proportions of patients with protocol suspensions, adherence to Hb concentrations used for transfusion triggers, intraoperative tissue oxygenation determined by near‐infrared spectroscopy, severe adverse events within 30 days of surgery
Notes	Trial title: Transfusion in Vascular surgery (TV) trial Trial registration: NCT02465125 Trial funding: Local Research Fund of Region Zealand, Næstved, Slagelse, Ringsted Hospital (2015‐01‐26) (A. Møller), and Region Sjaelland Health Research Fund (Denmark). The funders of this trial were reported to be public organisations with no role in trial design, collection, management, analysis, and interpretation of data, writing of the report, or the decision to submit the report for publication COI statement by investigators: "the authors declare no competing financial interests" (Møller 2019 p 2648)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The allocation sequence was computer generated in a 1:1 ratio with fixed block sizes of 6 stratified for type of surgery: open abdominal aortic aneurism operation vs lower limb bypass
Allocation concealment (selection bias)	Low risk	External, centralised, web‐based system
Blinding of participants and personnel (performance bias) Objective outcomes	Low risk	Blinding of personnel for this intervention is not feasible, but in our view, for objective outcomes such as mortality (the primary outcome used within this review), we graded risk of bias as 'low' Patients, statisticians, and outcome assessor were blinded to group assignment
Blinding of outcome assessment (detection bias) Objective measures	Low risk	Blinding of mortality (the primary outcome used within this review) is not relevant, and we graded risk of bias as 'low' Outcome assessors were blinded to group assignment
Blinding of outcome assessment (detection bias) Subjective measures	Low risk	No data from subjective outcomes (e.g. function) Near‐infrared spectroscopy done by blinded assessors
Incomplete outcome data (attrition bias) All outcomes	Low risk	58 participants randomised. There were 8 protocol suspensions in the restrictive group and 4 in the liberal group. 10 participants in the restrictive group 'avoided' RBC transfusion; none did in the liberal group All participants were included in an intention‐to‐treat analysis
Selective reporting (reporting bias)	Low risk	Trial reports 90 days' mortality, not 30 days (as stated on Clinicaltrials.gov) 30‐Day outcomes were presented (e.g. laboratory values) and data on mortality were presented in a supplement (1 death both arms) prepublished protocol was reported
Other bias	Unclear risk	Protocol suspensions for RBC transfusion were recorded, but there was a good discussion about the definitions of protocol adherence, and this would be expected as an issue for trials in this patient population. Overall rates of non‐adherence were 28% and 34% of patients in the 2 arms, which seems quite high