Effects of adding low-dose clonidine to a small intrathecal dose of either bupivacaine or ropivacaine on the characteristics of spinal block in elderly patients undergoing primary hip arthroplasty

Background The use of an adjuvant with small doses of local anesthetics is a preferred technique for spinal anesthesia in elderly patients. In our study, we compared the characteristics of spinal block after adding 15 μg clonidine to either 8 mg bupivacaine or 12 mg ropivacaine with regard to the anesthetic efficacy and the incidence of side effects in geriatric patients undergoing lower limb orthopedic surgery. Patients and methods In a prospective, double-blind randomized study, 60 patients of at least 60 years old undergoing primary hip arthroplasty under spinal anesthesia were randomly allocated into one of the two groups. Group BC received 8 mg bupivacaine with 15 μg of clonidine and Group RC received 12 mg of ropivacaine with 15 μg of clonidine. Onset times to reach the peak sensory and motor levels and the duration of sensory and motor blocks were recorded. Hemodynamic changes and side effects including the level of sedation were also recorded. Results The highest levels of sensory blocks were similar (T5) in both groups, but the onset time of sensory block was signifi cantly shorter in Group BC (2.54 ± 0.66 min) than in Group RC (3.19 ± 0.70) (P 0.01).The onset time of motor block (4.80 ± 1.46 min in the BC Group and 4.95 ± 1.04 min in the RC Group), the time to the maximum motor block (11 ± 2.1 min in the BC Group and 11.5 ± 3.2 min in the RC Group),the mean durations of both the sensory block (149 ± 20 min in the BC Group and 148 ± 15 min in the RC Group) and the motor block (165 ± 25 min in the BC Group 164 and ± 20 min in the RC Group) were all comparable between both groups. Differences in the hemodynamic parameters between both groups were insignificant. Conclusion Adding low- dose clonidine (15 μg) to an intrathecal small dose of either bupivacaine (8 mg) or ropivacaine (12 mg) made the difference between both local anesthetics with regard to the motor block and hemodynamic changes insignificant, but did not change the significant difference between them in the onset of sensory block. Either the bupivacaine–clonidine or the ropivacaine–clonidine combination provides sufficient motor and sensory block in elderly patients undergoing major orthopedic surgery without inducing hemodynamic instability.