Results: Success rate of unilateral anesthesia was 82.9%. In the unilateral group, the sensory block for surgery (above L1) (181.5 ± 18.9 versus 150.0 ± 20.1 min), motor block time (149.3 ± 18.4 versus 121.5 ± 16.4 min) were longer and incidence of hypotension (2.4 versus 29.3%) was lower than those in the bilateral group.