Risk of bias of the 11 included randomised controlled trials
| Study | Sequence generation | Allocation concealment | Blinding | Incomplete outcome data | Selective reporting | Other biases |
|---|---|---|---|---|---|---|
| Mangano (1996) | Computer generated randomised list | Only pharmacy held the list | All blinded, list held by pharmacy | 2 patients did not complete the study protocol but were analysed as ITT | Only post discharge deaths are mentioned in the primary endpoint. | No |
| Bayliff (1999) | Blocks of 4 | Only one investigator knew the code kept on the patient's health record in a sealed envelope. | Blinded | 1 patient did not undergo major resection and was not continued. 8 patients were withdrawn but were analysed as ITT | No | No |
| POBBLE (2005) | Centrally at Sealedenvelope.com. Blocks of size 2, 4 and 6 within 4 stratification factors (centre, age, sex and planned use of aortic cross clamping) | 4 digit trial number assigned | Anaesthetists were unblinded. All other clinicians and trial coordinators were blinded | 1 death occurred after randomisation in a patient who was too ill to tolerate surgery which is not included | No | No |
| DIPOM (2006) | Computer generated. Blocks of 8 stratified for sex, age, perioperative stress, history of coronary artery disease and malignant disease | Telephone voice response | Blinded | 188 patients did not receive the allocated intervention but were analysed as ITT | No | No |
| MaVS (2006) | Blocks of 4 | Not specified | Blinded | 117 did not complete the study protocol but were analysed as ITT | No | No |
| Neary (2006) | Packs containing medication or placebo were selected at random by the study investigator | Sealed envelope | Allocation was available to the anaesthetic team in an emergency | 19 patients withdrew their consent and were excluded | No | No |
| BBSA (2007) | Block randomisation in a 1 : 1 ratio | Not specified | Blinded design but β-blocker was titrated to heart rate, so likely effective unblinding | 5 patients who could not undergo spinal anaesthesia were excluded | No | No |
| POISE (2008) | Computerised randomisation using block randomisation stratified by centre. Randomisation in a 1 : 1 ratio. | Central phone randomisation | Participants, healthcare providers, data collectors and outcome adjudicators were blinded but analysts were not | 20 patients were lost to follow-up but were analysed as ITT | No | No |
| Yang (2008) | Computer generated random table | Not specified | Yes | No | No | No |
| DECREASE IV (2009) | Non-secure | |||||
| DECREASE I (1999) | Non-secure | |||||
ITT, intention to treat.