Impact of bispectral index monitoring on postoperative delirium in patients undergoing aortic surgery

BACKGROUND Bispectral index monitoring can facilitate anesthesia care. We evaluated the association of Bispectral index with postoperative neurological outcome and delirium in patients undergoing aortic surgery. METHODS From 2006 to 2009, 292 consecutive patients undergoing aortic surgery were retrospectively reviewed. Patients were classified into 5 groups according to Bispectral index reduction: Group I (≤15%), Group II (15-20%), Group III (20-25%), Group IV (25-30%), and Group V (>30%). RESULTS The number of patients in each group was : 52 (17.8%), Group I; 125 (42.8%), Group II;68 (23.3%), Group III; 33 (11.3%), Group IV; 14 (4.8%), Group V. The incidence of delirium and neurological events was higher in Group IV and Group V(90.9% and 18.2% in Group IV, and 71% and 79% in Group V; both p<0.001). Only Group V showed a longer intensive care unit stay compared to Group I (13.5±10.3 vs 5.4±6.6 days; p=0.002), Group II (7.3±8.6 days, p=0.005) and Group III (6.7±6.5 days, p=0.015). Group V also showed a longer intubation time compared to Group I (228±211 vs 73±112 hours; p=0.008) and Group II (105±177 hours, p=0.002). CONCLUSIONS Our data suggest a higher incidence of neurological deficits in patients with a Bispectral index reduction of >25% from baseline. Explanations for these findings are speculative with regard to the underlying mechanisms, and larger studies are warranted to clarify these issues.