Boldt 2001.

Methods	Randomised controlled trial. Volume therapy was done by doctors who did not know the aim of the study
Participants	75 patients undergoing major abdominal surgery Volume was administered to keep the CVP between 8 mmHg and 12 mmHg
Interventions	1) 6% HES (n = 25) 2) 6% HES (n = 25) 3) 4% MFG (n = 25) All groups also received 500 mL of RL for each hour of surgery
Outcomes	Death Haemodynamic variables Blood loss Blood units transfused
Notes	There were no deaths in the study period (until first follow‐up on first postoperative day. Deaths until discharge
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Low risk	Adequate. 'Closed envelope system'