Of 310 patients assessed , 28 of 149 ( 18.8 % ) in the BIS group and 45 of 161 ( 28.0 % ) in the end-tidal anesthetic concentration group developed postoperative delirium in the ICU ( odds ratio 0.60 , 95 % confidence interval , 0.35-1 .02 , P = 0.058 ) .