Due to a quicker onset ( mean standard deviation ( SD ) : 10.1 6.4 vs 18.5 8.3 minutes ; P < 0.0001 ) , the total anesthesia-related time was shorter with the TII technique ( 21.2 7.7 vs 27.7 9.0 minutes ; P = 0.001 ; 95 % confidence interval for the difference of the means : 2.90-10 .08 minutes ) .