Table 2.

Randomized trials examining the effect of depth of anaesthesia on postoperative delirium. BIS, bispectral index; CAM-ICU, Confusion Assessment Method for the intensive care unit; DSM, Diagnostic and Statistical Manual; ICU, intesive care unit; MMSE, Mini-Mental State Examination; POCD, postoperative cognitive dysfunction

Authors	Patients	Intervention	Comparison	Outcome	Results	Comment
Sieber and colleagues52	114 patients >65 yr old for hip fracture surgery under spinal anaesthesia	Light sedation (BIS >80) with spinal anaesthesia	Deep sedation (BIS ∼50) with spinal anaesthesia	Delirium was defined by DSM-III criteria using the Confusion Assessment Method	The prevalence of delirium in the light sedation group (19%) was significantly lower than in the deep sedation group (40%; P=0.02)	Patients were extremely vulnerable, with a baseline dementia prevalence of 35%
Radtke and colleagues54	1155 patients >60 yr old with planned elective surgery under general anaesthesia for >60 min	BIS-guided anaesthesia	Usual care. BIS information recorded, but not available to the anaesthetist	Delirium was defined by DSM-IV criteria. Postoperative cognitive change was assessed by a test battery at baseline and 7 days and 3 months after surgery. POCD was defined using reliable change indices	Delirium was lower in the BIS-guided group (16.7%) compared with the usual care group (21.4%; P=0.036). BIS monitoring did not alter the incidence of POCD	BIS protocol was not well defined and was left up to the treating anaesthetist
Chan and colleagues153	921 older adults undergoing major non-cardiac surgery	BIS-guided depth of anaesthesia with target BIS 40–60	Usual care. BIS information recorded, but not available to the anaesthetist	Delirium was assessed using Confusion Assessment Method. Cognition was assessed using a neuropsychological battery at baseline, 1 week and 3 months after surgery. POCD was defined as at least two Z-scores >1.96	The incidence of delirium was lower in the BIS group (15.6%) vs usual care group (24.1%; P=0.01). Patients in the BIS group had a lower rate of POCD at 3 months (10.2%) vs usual care (14%.7%; P=0.025)	Chinese population, with adapted outcome measures
Whitlock and colleagues107	310 patients enrolled in a single-centre substudy of the BAG-RECALL trial	BIS-guided depth of anaesthesia (alarms if BIS <40 or > 60)	End-tidal anaesthetic concentration-guided depth of anaesthesia (alarms if MAC <0.7 or > 1.3)	CAM-ICU twice daily until postoperative day 10 or ICU discharge	The incidence of delirium was 18.8% in the BIS group and 28% in the end-tidal group	No baseline cognitive assessments. CAM-ICU may be insensitive in non-intubated patients