Study	Reason for exclusion
Eldahab 2009	Only abstract available, which does not give complete information. Contact details of study authors not available
Erard 1999	Abstract. Study authors not responding to emails. Outcomes of interest not assessed
Harutjunyan 2005	Participants are not patients with brain tumour undergoing surgery. The study is being conducted in the ICU, not in the operating theatre
Levin 1979	Not an RCT. Participant population is different
Muangman 2005	Probable duplication of data in the Rozet 2007 study
Pausawasdi 1982	Study authors cannot be contacted. Full text could not be retrieved. Failed communication with the Editor of the journal
Smedema 1993	Abstract. Unclear whether it is an RCT. Study authors cannot be contacted. Full text not available

ICU: intensive care unit.

RCT: randomized controlled trial.