Allocation and randomization of the study participants
BLIND
Random allocation into sevoflurane and desflurane study arms was performed using a pool of sealed opaque envelopes containing an equal number of sevoflurane and desflurane codes. In the operating room just before the induction of anesthesia the attending anesthesiologist was asked to draw one envelope and unsealed it without disclosing the code to the researcher. The anesthesiologist did not belong to the research team and did not have access to cognitive scoring results. The attending anesthesiologist was also asked to enter the code of volatile anesthetic into the intraoperative data collection sheet.Both the patient and the researchers responsible for allocation and cognitive testing were blind to group allocation results. To avoid unblinding, assessment of baseline cognitive tests, postoperative retesting and collection of intraoperative data were assigned to separate members of the research team.