Wong 2007.

Methods	Design: RCT Operative phase: pre‐, intra‐ and postoperative Withdrawals: 2/103 Setting: 1 centre (UK) Sample size: 103 Funding: not stated
Participants	Age (mean range): 60.5 ‐ 63.0 years Gender (M/F): 53/50 ASA grade: I ‐ III Surgery type: elective (major open abdominal surgery) Surgery duration (mean): > 2 hrs (3.0/3.5 hrs theatre time) Anaesthesia type: general
Interventions	Intervention (ABSW periop + co‐FAW intraop): n = 47 Conductive carbon polymer mattress (Inditherm® warming mattress, Rotherham, UK) 2 hrs before transfer from the ward to the operating theatre, during surgery and up to 2 hrs after surgery Temperature: set at 40°C Theatre time (mean): 3.0 hrs Body area covered: not stated Control (co‐FAW intraop): n = 56 In the control group, the mattresses were switched off Theatre time (mean): 3.5 hrs Body area covered: not stated Co‐interventions: all the participants in this study were warmed during surgery ("It was standard practice to deliver systemic warming during all major surgery using a forced‐air warming device (Bair Hugger; Arizant Healthcare, Eden Prairie, Minnesota, USA) set at 40°C and with a fluid warmer") Room temperature: not stated
Outcomes	Blood loss Need for blood transfusion Postoperative complications (surgical site infection, chest infections, ileus, urinary tract infections, pelvic collection, cardiac complications, Clostridium difficile diarrhoea, and pressure ulcers) Length of hospital stay
Notes	Comparison 3
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random numbers
Allocation concealment (selection bias)	Low risk	Sealed, opaque envelopes
Blinding of participants and personnel (performance bias) All outcomes	Low risk	In the control group, the mattresses were switched off
Blinding of outcome assessment (detection bias) All outcomes	Low risk	An independent observer unaware of the participants’ group assignment, evaluated the participants’ surgical wounds, postoperative variables and complications daily during hospitalization and again at 6 – 8 weeks after surgery. The senior surgeons, who were unaware of the participants’ group assignment and core temperatures, decided when to begin feeding after surgery, remove sutures and discharge from hospital
Baseline comparability of groups	Low risk	To a high extent according to Table 1
Co‐interventions equal between groups	Low risk	Yes
Incomplete outcome data (attrition bias) All outcomes	Low risk	1 participant In the control group was warmed preoperatively. 1 participant In the intervention group was not warmed preoperatively. These participants, however, were included in the ITT analysis
Selective reporting (reporting bias)	Unclear risk	We did not have access to the protocol, therefore we cannot exclude risk of selective reporting with the information provided
Other bias	Low risk