Table 1.

Characteristics of included studies

Study	N	Age			Strategy of blood transfusion				Units of RBC transfusion or transfusion rate
		Restrictive	Control	Setting	Restrictive		Control		Restrictive	Control
					Triggered Hb	Observed Hb	Triggered Hb	Observed Hb
Bracey et al.1999 [12]	428	61 ± 11	62 ± 11	Elective CABG	Hb < 8 g/dl	9.1 g/dl	Hb < 9 g/dl	9.7 g/dl	0.9 ± 1.5	1.4 ± 1.8
Murphy et al. 2007 [16]	321	NS	NS	Elective or urgent cardiac surgery	Hb < 7 g/dl	NS	Hb < 8 g/dl	NS	NS	NS
Hajjar et al. 2010 [13]	502	58.6 ± 12.5	60.7 ± 12.5	Elective cardiac surgery	Hct < 24%	9.6 g/dl	Hct < 30%	10.7 g/dl	0 (0–2)	2 (1–3)
Shehata et al. 2012 [15]	50	67.2 ± 11.2	68.8 ± 9.2	Cardiac surgery with CARE score of 3 or 4	Hb < 7.5 g/dl	9.1 g/dl	Hb < 10 g/dl	10.7 g/dl	11 (44)	17 (68)
Murphy et al. 2015 [14]	2003	69.9(63.1 –76.0)	70.8(64.1–76.7)	Elective or urgent cardiac surgery	Hb < 7.5 g/dl	9.0 g/dl	Hb < 9 g/dl	9.8 g/dl	1 (0–2)	2 (1–3)
Koch et al. 2017 [10]	717	59 ± 15	60 ± 13	Elective CABG or HVR	Hct < 24%	28%	Hct < 28%	30%	195 (54)	265 (75)
Mazer et al. 2017 [9]	4860	72 ± 10	72 ± 10	Cardiac surgery with a EuroSCORE I of 6 or more	Hb < 7.5 g/dl	Hb < 8.5 g/dl	Hb < 9.5 g/dl	10.5 g/dl?	2 (1–4)	3 (2–5)

CABG coronary artery bypass grafting, Hb hemoglobin, Hct hemotocrit, HVR heart valve replacement, NS normal saline