Chan et al. randomized 921 elderly patients undergoing major non-cardiac surgery to receive either anesthesia adjusted to achieve a BIS™ index values from 40 to 60 or standard practice. The standard practice group also received BIS™ brain monitoring that was blinded to the anesthesiologist. Postoperatively patients were screened for delirium. Patients in the BIS™-guided anesthesia group had significantly lower rates of delirium and higher median BIS™ index values.
Elderly total hip arthroplasty patients (N=198) were randomly allocated to receive either general anesthesia without lumbosacral plexus block (routine), BIS™-guided anesthesia (BIS™ index value 40-60) with a lumbosacral plexus block (BIS™ –guided deep), or BIS™-guided sedation (BIS™ index value 60-80) with a lumbrosacral plexus block (BIS™-guided light). Patients were screened for delirium postoperatively. The BIS™ light sedation group had decreased rates of postoperative delirium, propofol consumption, and time to discharge.
Patients (n=1155) aged 60 years or more undergoing elective surgical procedures lasting more than 60 minutes were randomized to receive BIS™-guided anesthesia or standard practice anesthesia.([FOOTNOTE=Radtke FM, Franck M, Lendner J, Kruger S, Wernecke KD, Spies CD. Monitoring depth of anaesthesia in a randomized trial decreases the rate of postoperative delirium but not postoperative cognitive dysfunction. Br J Anaesth. 2013;110 Suppl 1:i98-105.],[ANCHOR=],[LINK=]) The standard practice group received BIS™ brain monitoring that was blinded to the anesthesiologist. Delirium was assessed from day 1 to day 7 postoperatively. The standard practice group had a 28% increase in the rate of delirium. A multivariate analysis confirmed that the % of BIS™ index value < 20 was predictive of delirium (P=0.006)
Elderly patients undergoing hip fracture repair (n=114) under propofol sedation with spinal anesthesia were randomized to receive either deep (BIS™ index value ≈50) or light (BIS™ index value ≥80) sedation.3 Postoperative delirium was assessed after the second day postoperatively. The light sedation group had a 50% reduction in delirium compared to the deep sedation group.
Soehle et al.([FOOTNOTE=Soehle M, Dittmann A, Ellerkmann RK, Baumgarten G, Putensen C, Guenther U. Intraoperative burst suppression is associated with postoperative delirium following cardiac surgery: a prospective, observational study. BMC Anesthesiol. 2015;15:61.],[ANCHOR=],[LINK=]) prospectively recorded pre-, intra, and postoperative EEG variables (BIS™ brain monitoring, EEG asymmetry, and burst suppression) via a bilateral BIS™ monitor in 81 cardiac surgery patients. Postoperatively, patients were screened for delirium via the CAM-ICU. Patients who were identified with delirium had a significantly longer duration of burst suppression.
Santarpino et al.([FOOTNOTE=Santarpino G, Fasol R, Sirch J, Ackermann B, Pfeiffer S, Fischlein T. Impact of bispectral index monitoring on postoperative delirium in patients undergoing aortic surgery. HSR Proc Intensive Care Cardiovasc Anesth. 2011;3(1):47-58.],[ANCHOR=],[LINK=]) retrospectively reviewed the anesthesia records of 292 consecutive patients undergoing aortic surgery. Patients were grouped according the magnitude of intraoperative drop in BIS™ index values from baseline(baseline value-minimum value/ baseline value x 100): Group I (≤15%), Group II (15-20%), Group III (20-25%), Group IV (25-30%), and Group V (>30%). Delirium rates were compared amongst groups. Groups IV and V had significantly higher delirium rates than groups I, II, and III.
