Cholinesterase activity
delirium
Cholinesterase activities were measured in all the whole blood samples drawn from arterial lines or venepuncture at three different points in time: preoperatively (on the evening before surgery or right before anaesthesia induction), 15 min after surgery, and the next morning after surgery at 8 a.m. (± 1 h). We analysed the samples with the portable point-of-care photometry test kit and machine “ChE check mobile” according to the instructions of the manufacture (SECURETEC, Neubiberg, Germany). This test kit applies a modified Ellmann reaction according to Worek et al. to determine the activity of AChE (normalized to haemoglobin U/g Hb) and BChE (U/l). The testing was performed immediately after collecting the blood sample.In order to compare cholinesterase activities between delirium and no delirium, we first adjusted the delirium incidence for our observation period. Patients were classified as delirium positive if they were positively detected with the CAM/CAM-ICU at least once until the first postoperative day.