Comparison 1. Active warming vs control (no active warming).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Surgical site infection and complications	3	589	Risk Ratio (M‐H, Random, 95% CI)	0.36 [0.20, 0.66]
2 All‐cause mortality	2	500	Risk Ratio (M‐H, Random, 95% CI)	1.01 [0.26, 4.00]
3 Blood transfusions during surgery and up to 48 hours post‐surgery (ml)	8	779	Mean Difference (IV, Random, 95% CI)	‐54.58 [‐92.57, ‐16.58]
4 Participants transfused	8	621	Risk Ratio (M‐H, Random, 95% CI)	0.79 [0.50, 1.23]
5 Blood loss (ml)	20	1372	Mean Difference (IV, Random, 95% CI)	‐46.17 [‐82.74, ‐9.59]
5.1 Forced‐air warming	18	1103	Mean Difference (IV, Random, 95% CI)	‐50.77 [‐88.43, ‐13.10]
5.2 Foam warming pad	1	153	Mean Difference (IV, Random, 95% CI)	5.09 [‐64.78, 74.96]
5.3 Warm water mattress	1	116	Mean Difference (IV, Random, 95% CI)	‐100.0 [‐389.17, 189.17]
6 Fluids infused (ml)	24	1491	Mean Difference (IV, Random, 95% CI)	‐144.49 [‐221.57, ‐67.40]
6.1 Forced‐air warming	21	1337	Mean Difference (IV, Random, 95% CI)	‐139.83 [‐220.17, ‐59.48]
6.2 Electric blanket	2	38	Mean Difference (IV, Random, 95% CI)	‐243.00 [‐732.80, 246.80]
6.3 Warm Water mattress	1	116	Mean Difference (IV, Random, 95% CI)	0.0 [‐239.12, 239.12]
7 Participant's thermal comfort (higher values mean higher comfort)	4	364	Std. Mean Difference (IV, Random, 95% CI)	0.76 [0.29, 1.24]
8 Participant's thermal sensation (higher values mean 'insufferably hot')	6	336	Mean Difference (IV, Random, 95% CI)	1.13 [‐0.61, 2.87]
9 Pain < 12 hours	7	624	Mean Difference (IV, Random, 95% CI)	‐0.24 [‐1.12, 0.64]
10 Chills/shivering	29	1922	Risk Ratio (M‐H, Random, 95% CI)	0.39 [0.28, 0.54]
10.1 Forced‐air warming	26	1866	Risk Ratio (M‐H, Random, 95% CI)	0.43 [0.31, 0.59]
10.2 Electric blanket	3	56	Risk Ratio (M‐H, Random, 95% CI)	0.12 [0.03, 0.39]