Effects of baricity of 0.5% or 0.75% levobupivacaine on the onset time of spinal anesthesia: a randomized trial.

Purpose: Levobupivacaine has been extensively evaluated for spinal anesthesia. Its pharmacologic properties are similar to those of bupivacaine, but differences in density between two commercially-available preparations of plain levobupivacaine might lead to different block profiles. We examined the characteristics of spinal anesthesia using the same dose of 0.5% and 0.75% plain levobupivacaine.

Methods: In this randomized, controlled, double-blind clinical trial, 60 ASA I-III patients, scheduled for hip fracture surgery, were randomly allocated to receive spinal anesthesia with 15 mg of either 0.5% (group Levo-0.5), or 0.75% (group Levo-0.75) plain levobupivacaine. Onset time (primary outcome), sensory block height level by pinprick, motor block using a modified Bromage scale, and hemodynamic variables were recorded.

Results: In group Levo-0.5 (n = 29), surgical anesthesia was obtained within 15 (10-20) min, compared to 12 (7-21) min in group Levo-0.75 (n = 31) (p = 0.409). The highest sensory block level was T11 (T6-T12) in group Levo-0.5, and T10 (T8 - T12) in group Levo-0.75 (p = 0.759). Mean duration of anesthesia was 285 (224-303) min in group Levo-0.5, and 318 (243-375) min in group Levo-0.75 (p = 0.117). The groups were similar in regards to the number of failed blocks requiring general anesthesia, and the number of patients requiring vasopressors.

Conclusions: In this population of elderly patients, spinal anesthesia with 15 mg of either 0.5% or 0.75% plain levobupiva-caine resulted in similar onset of pharmacological actions, and outcomes. Potential differences in baricity did not appear to be clinically relevant in this setting.