The 50 % and 95 % effective onset time ( 95 % confidence interval ) values of levobupivacaine were 8.19 minutes ( 7.30-9 .08 ) and 11.17 minutes ( 9.44-12 .91 ) in Group L ( 0.25 ) , 10.16 minutes ( 8.90-11 .41 ) and 15.85 minutes ( 13.14-18 .57 ) in Group L ( 0.20 ) , and 9.91 minutes ( 8.55-11 .28 ) and 16.39 minutes ( 13.32-19 .46 ) in Group LD , respectively .