Reducing the Risk of Postoperative Delirium

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.⁵  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.⁶ 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.⁷ 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.